Maybe Not Carbon Fiber

Tom Butler: 0:04

This is the Cycling Over 60 Podcast, season 2, episode 30, maybe not carbon fiber and I'm your host, tom Butler. In a few days I will be turning 61 years old. I am coming up on a year since I started out my cycling over 60 journey with a 60-mile ride on my 60th birthday. That led to many awesome moments of cycling last year, including the Cascade Bicycle Club Seattle to Portland ride. I am celebrating my birthday again with a ride. This time it is only 33 miles, but with more climbing. The beautiful ride we did last year had about a thousand feet of climbing and this year I will be doing the chilly, hilly ride that has twice the elevation and half the miles. I like that a lot because hills are a real struggle for me. So I feel like, even though this is a short route, it is a bigger challenge over last year's ride. That is one of the things that I would love to demonstrate with my cycling over 60 journey. I want to show that I can still get stronger and take on bigger challenges as I get older. At some point I will slow down, I know, but I bet I'm a long way from that, so this is a new perspective for me.

Tom Butler: 1:23

In the last year. I wish I had my wife on with me because she could testify to the fact that a few years ago I started seeing my life as winding down. I was facing health issues that I had seen heavily impact my father and his siblings, and I was losing hope that I would continue to have quality of life. So it is a big deal for me to see how much stronger and healthier I am now Because of the gains I've made this last year. I have no doubt that I will be able to handle the hills on this ride. I might have to step off on the steepest climb, but I will definitely be able to get back on and finish. Another difference over last year is that I will be celebrating my birthday this year with a ride both with my son-in-law and with my daughter. Next year, I'm committed to include my wife as well. My vision is that my birthday weekend will become a family cycling trip. The biggest obstacle is the fact that my wife has only a year to figure out how she can dress in a way that she will enjoy biking in February in the wet and cold Pacific Northwest. It is possible that we might need to travel south if she's going to join in, but that doesn't sound too bad.

Tom Butler: 2:34

I registered my email with the Washington State Department of Transportation to get updates on when Washington Pass will be cleared of snow. That is the pass on Highway 20, the North Cascades Highway, which is also US Bike Route 10. This is the route that I planned to ride across Washington State in September. I'm excited because there is a short period of time between when they clear the pass of snow and when they open it up for cars, so you can bike up to the pass on one of the most scenic routes in all of the US without worrying about any cars. In addition to just a great cycling adventure, I will also be experiencing a very challenging section of the ride I want to do in September. The route is about 69 miles round trip, with 67,000 feet of climbing For 30 miles. It is almost a constant 2-6% grade. Yes, this will be a big test, but is the best way to see what kind of challenge it will be for me to go over the Cascades in September.

Tom Butler: 3:35

A quick note on my health progress. I think I'm going to have to start wearing the continuous glucose monitor again. I find that I'm slacking off way too often without the feedback of the CGM. I'm still maintaining the majority of the habits I developed when I wore it before, but I'm just not as compliant as I should be. I'm very proud of my son-in-law, garan, for a lot of things. One of them is that he excels at his job as a mechanical engineer. I have been thinking a lot about bike frame materials lately and I asked Garan to join me for a conversation about the benefits of the different materials. Here is our discussion. I'm here again with Garan Myler. Thanks for coming on, garan.

Garren Miler: 4:22

Yeah, thanks for having me.

Tom Butler: 4:23

Garan is the official mechanical engineer for the Cycling Over 60 podcast, also my son-in-law, so he pretty much has to come on, but I do think you enjoy talking about bike tech, is that right?

Garren Miler: 4:35

Oh, absolutely yeah. I think it's a really great application of engineering and it's a lot of fascinating ways to look at it.

Tom Butler: 4:41

McKenna, your wife, my daughter, just got a new bike and so we were looking at bikes again, which it seems like we're finding plenty of excuses to look at bikes. There's always a reason. Yes, that's right. It got me thinking about bike frame materials again. I wanted to have you come on. I've spent about a year now that you've been looking at bikes, have been dealing with bikes. As an engineer, I know that you've been thinking about bikes in that part of your brain and that part of your life. I thought it would be good to bring up some things about frames that I'm interested in and just have a dialogue To give some framing to this discussion. I'd like to first have you talk about some terms that, as an engineer, you would have in mind when you're evaluating a bicycle frame. Could you do that?

Garren Miler: 5:39

Yeah, definitely. My flavor of engineering that I do at my job is marine engineering, so I work a lot on boats. So material selection is at the forefront of a lot of what we do, because we're not just combating the strength and the durability of the material, but we're also combating corrosion and other factors like that. Combating my materials is something that I'm more than happy to dive into. If I'm choosing a material and I'm especially in the context of a bike frame the first thing you want to know is the weight to strength ratio. That's going to be determined by the density of the material, which is directly proportional to its weight, but also by the tensile strength and the yield strength of the material.

Garren Miler: 6:17

Tensile strength and yield strength are both measurements of the overall strength of a material, but they mean very different things From the perspective of design. You have to understand the difference in order to know just where you can push your product to where the limits are. So the tensile strength of an item is the absolute overall strength, the maximum amount of force that you can put on it before it breaks. The yield strength is how much force you can put on something before it starts to deform, and this is really important when you're deciding between a ductile material like an alloy or a brittle material like carbon fiber. The tensile strength of a material is not actually super relevant to engineers in day-to-day life because we always design things based on their yield strength. Yielding is really important because it lets you know that the metal is about to break. If you're in a building and you see that a metal beam is sagging, then you know that it's under more stress than it should be under and you need to have mitigating support for it.

Garren Miler: 7:17

So along with those two items is something called the modulus of elasticity. That's a bit of a deep dive if you want to know exactly where that number is derived from. There's quite a bit of theory behind it and it's kind of almost an entire semester of engineering schools devoted towards relating the modulus of elasticity to the tensile strength and to the yield strength of different materials. But overall it measures the stiffness of a material. It's a measurement of that material's ability to bend and then bounce back to its original shape. In alloys, the modulus of elasticity is relatively high. Modules can take quite a bit of force before they start to bend, and if they do bend they'll kind of boing back into shape, which is why you make springs out of them and things like that. Carbon fiber has an excellent modulus of elasticity, but it's a lot higher. It can bend, but when it gets to its breaking point it will break catastrophically. It's not going to stretch itself into a spaghetti noodle like a piece of metal would before it snaps. It's just going to break with no warning.

Tom Butler: 8:15

Now, when you talk about yield strength, it seems like there are materials out there you know, just talking about material properties in general where you actually wouldn't be able to see some bending of that material before it would snap.

Garren Miler: 8:31

Absolutely. That's what we would call a brittle material, a material whose primary mode of failure is catastrophic at the first sign of damage. So in that material the tensile strength and the yield strength are going to be almost the same number, because it breaks just as soon as it starts bending. But with things like aluminum, for example, the yield strength is far below the ultimate strength and you can stretch aluminum out quite a bit because it's quite a ductile material. So those numbers are quite a bit different.

Garren Miler: 8:59

Fatigue resistance is another thing we look at with materials, but it's actually quite disconnected from yield strength and tensile strength and it varies a lot depending on the exact composition of your alloy, because not all aluminum are created equal and we can dive into that a little more later. But the fatigue resistance is all about the ability of the metal to be loaded and unloaded repeatedly over time. So if you have a cyclic loading on something where the load is applied and then unapplied which obviously in bicycles is exactly what you're doing you're cycling hits in the name. A cyclic loading pattern is going to lead to a decreased overall strength and an increased amount of brittleness and in aluminum, for example, that might look like fracturing or cracking in the metal far before it's yielded, and it can greatly reduce the overall tensile strength of the material over time. There's really not a lot of mitigations for that, aside from just making sure that you have done, of course, your homework and done a lot of product testing, but also making sure that you've designed your product to be well below the threshold and there are numerical thresholds that you can calculate based on empirical data to know that your product is not going to build up too much fatigue over time over its lifespan.

Garren Miler: 10:10

The thing that we think about maybe the most as marine engineers is corrosion resistance. Of course, the first thing you think of when you think of corrosion is rust, and rust happens to ferrous metals, which is steel. Any metal that has iron in it is going to rust when exposed to air and water. Things that make rust worse is salt, including the salt that they put on the roads. That can easily rust your bike out. That being said, steel won't rust if it has a proper coating on it, it was painted well, or if it has a nice finish. Stainless steel won't corrode either, but it's an expensive material and probably isn't one you'd see.

Garren Miler: 10:46

A bike frame made out of Stainless steel is also very difficult to weld. Aluminum does not rust, but that does not mean that it is free from the effects of corrosion. Aluminum will build an oxide layer on it. It looks like a white kind of powdery layer that can build up on the aluminum. Rust can be just as bad as rust is for steel. Over time the oxide layer will eventually eat into the material and will create a very brittle aluminum that will break on you without you realizing that it's gotten to that point, until the bike is in half below you. Additionally, here in Seattle we have a particular risk to aluminum bikes. That's that the chemical that they use to deice the roads in Seattle, which I've been told is unique to the Seattle area, is especially aggressive towards aluminum itself.

Tom Butler: 11:32

That's handy, it's very convenient.

Garren Miler: 11:35

So people in Seattle oftentimes report that their spokes eventually, after riding in bad weather, their spokes will just pull right out of their wheels, and that's due to the really aggressive chemical that they use here. Of course it's better for the cars, which are mostly steel, but it's not better if you're a cyclist. The way to mitigate that risk in particular is to just make sure you're rinsing your bike down after any ride in really bad weather.

Tom Butler: 11:56

Well, I think that's a great overview of properties that you would look at when evaluating materials. Let's talk about common bike materials. I'm going to go through these in a way that I was exposed to them. So the first bike I ever had, and several bikes that I had as growing up, were made out of steel. Let's talk about the properties of steel that make it from these principles, these engineering principles. What is it about steel that makes it a typical bike material?

Garren Miler: 12:37

So steel is really easy to work with and it's the reason that most of our buildings are made out of steel and that cars are made out of steel and overall, steel is easy to weld, it's very durable, it is very strong and it's actually quite cheap. In fact, it's probably the cheapest material we're gonna look at. So there's a reason that most bikes start off in the low end as steel frames. Of course, the downside of steel is that it's quite dense, quite a bit denser than aluminum. So even though it has twice the strength, it has quite a bit more weight to it.

Tom Butler: 13:10

When you're looking at weight, then I think it's fair to say that there's an element of the alloy that is used.

Garren Miler: 13:18

Oh, absolutely Within steel. There's many different flavors of steel. Each one's gonna have their advantages and disadvantages, but really the two most common is gonna be carbon steel, which is what you might think of as plain steel or regular steel, and then there's stainless steel. Stainless steel is gonna be a bit more brittle and have a bit less strength, but it has a very good corrosion resistance. However, that does come with a bit of a weight cost as well. It's also not as easy to work with, it's not quite as ductile and it's much more difficult to weld than regular steel is, and that makes it a bit less attractive of an option for building a bike. You might look back at the DeLorean or even the new Tesla Cybertruck that are made completely out of stainless steel, and none of those cars are successful because stainless steel is very hard to work with. There are disadvantages quickly outpaced its advantages when you scale stainless steel up to a larger assembly.

Tom Butler: 14:15

So what is the term chromoly refer to?

Garren Miler: 14:19

Chromoly is an alloy of steel that it's a particularly attractive flavor of steel because it has a lot of the advantages of regular steel, like its affordability and its ease of welding, but it also has much better corrosion resistance due to the chromium infused in it.

Tom Butler: 14:39

What I have here is ranges for a 56-centimeter bicycle frame that's made of steel is 2.2 to 3 kilograms. Again, there's this corrosion element to steel that you have to take care of it. I mean, I know as a kid like my bike rusted as a kid, just specifically because I really didn't think that much about taking care of my bike when I was a kid. If the paint gets scratched, gets chipped off or whatever, then that can lead to an issue.

Garren Miler: 15:16

So I actually have a steel-framed bike. My Rad bike is steel-framed and I used to take my Rad bike every single day on a ferry when I was queuing to work across the sound and on that ferry it was sprayed with saltwater repeatedly every morning, which is just pretty much the worst environment you can possibly imagine for corrosion. A steel bike being sprayed with saltwater and the frame itself actually wasn't the biggest risk factor. The paint chipped off in a few places and you'd get some surface rust, but it was nothing Nothing you couldn't just wipe off with some WD-40 or some other solvent and then retouch up.

Garren Miler: 15:50

The really difficult part is the little tiny bits and pieces that are inside of your different components. I had my brakes go out multiple times on that bike because the little springs and the levers inside the handles were not functioning properly because the little tiny pieces were rusting out. The frame itself is so big it's easy to take care of. It's really the nooks and crannies where things go wrong and engineering. One thing we focus on is the avoidance of what we call faying surfaces or two surfaces that are really really close together, when you have two pieces of steel that are basically sitting on top of each other but aren't actually adhered. That's a faying surface in that crevice and that is just a treasure trove for rust to get in there and eat your metal from the outside in, and you won't realize until it's too late.

Tom Butler: 16:35

Interesting I ended up which I think is the main reason why aluminum frames came about is that I ended up wanting a lighter bike and so when I bought my Trek 1500, we talked about it a couple of times on the podcast when I got that on that frame and so I'm thinking this is about 90, 89, someone there I should probably figure out when that is but right on the frame it says in bold letters aluminum. You know they were really at that time still promoting aluminum as a new frame material and again, I believe it was because it was a lighter frame material. Can you talk a little bit about aluminum as a frame material?

Garren Miler: 17:23

So aluminum is kind of the next obvious choice from steel. It has about half the strength, but it's also substantially lighter, and it's pretty obvious to tell. If you have items in your house that you know are steel, you know are aluminum, you can pick them up and it's quite jarring the difference. Aluminum also can be formed through a couple of different methods, although it is more difficult to form than steel is, it's not quite as ductile and, like we said earlier, aluminum has an excellent resistance to corrosion, which makes it yet another drop in the bucket for why you'd want to switch over.

Garren Miler: 17:54

When you're comparing something, say, steel to aluminum, one of the things you're looking at really the only thing you're looking at is the strength to weight ratio, or you could look at that as the yield strength to density ratio, because a steel bike, for example, even though steel itself is heavier, you can get away with less steel because it has more strength, whereas you're going to need more aluminum to have the same amount of strength, but it is also lighter. So you have to look at the ratio of its density to its strength in order to really know which material you're going to want to use. That being said, aluminum is quite a bit more expensive than steel and it does come in a lot of different flavors In the marine industry. Aluminum is they're picking the right. Aluminum is vital to making sure that your craft is going to build a function in all weather conditions and in all environments. Aluminum does change its properties substantially with temperature. It doesn't do as well in really cold temperatures and it has a lower melting point. But hopefully your bike isn't being subjected to that.

Tom Butler: 18:54

Yeah, I think I'm going to be stopping biking before I get to that point.

Garren Miler: 18:58

Yeah, but in really cold temperatures you will notice that aluminum can become brittle.

Tom Butler: 19:04

Now, how cold is cold.

Garren Miler: 19:05

That depends on the flavor, but cold within reasonable riding conditions for winter time in the northern hemisphere.

Tom Butler: 19:13

Really, that's interesting.

Garren Miler: 19:14

Yeah, I mean I would say if it's below freezing in general you're running a bit higher risk for having a brittle failure of aluminum.

Tom Butler: 19:22

OK, when I was looking at different frames, there are these alloys, just like with steel, and so there's a 6061 alloy and a 7005 alloy. I have no idea what those mean, but again, I think that when they're building aluminum frames, they're taking account that these alloys are more suited for the stresses that a bicycle frame would have.

Garren Miler: 19:51

Yeah, absolutely so. With steel, steel is, steel is steel, and you can weld it, you can heat it up and, for the most part, its properties are pretty constant. With aluminum, that is absolutely not the case, and so, moreover, more so than just your alloy, you have to pay very close attention to the heat treatment of the aluminum, and the quality of the welds plays an enormous role in the strength of the structure.

Tom Butler: 20:14

Now, when you're talking about welding aluminum, what's that look like as opposed to welding steel?

Garren Miler: 20:20

So when you weld aluminum you obviously have to heat up the metal quite a bit and, like I said, heating up aluminum changes its properties pretty drastically compared to steel. So when you weld aluminum you're going to create localized areas within the frame that are going to have different material properties than other areas of the frames that were cold instead of being welded. So that means you have to factor those sorts of stress concentrations into your design to know that you're not going to hit a failure point due to the extra heat that was added during the welding process.

Tom Butler: 20:54

Do you know if there's other ways to bond aluminum together that's not heat related?

Garren Miler: 21:00

There are some ways to do that. One of the common ones you see on old bikes and in fact on that first bike that you had, the Trek 1500, you'll see it used on the fork and that's a socket fit. So they would take the aluminum and they would fit it into a socket of another aluminum. That would. So essentially a tube would slide inside of a slightly larger tube and then they would either they could use epoxy to put that joint together and that's what they did on the fork. Because when you heat up aluminum it also expands and contracts a lot more than steel does when steel is heated up. So when you weld, say, a fork, you're much more likely to bring that fork out of true and have misalignments. So when they're assembling aluminum forks in particular, they tend to use socket connections at the top to ensure that they're not putting any heat into that aluminum and not warping that fork. So they use an epoxy joint inside of a socket to connect sensitive elements like a fork or with maybe the rear section of your frame together.

Tom Butler: 21:59

What is TIG welding?

Garren Miler: 22:01

So TIG welding is the type of welding that's more common in exotic metals is how you're going to connect titanium pieces together. In my industry we use a lot of copper and nickel pieces, and those are connected together with TIG welding and it's a lot more difficult to carry out, but in the end it creates a much better end product. Tig welding can also fuse non-homogeneous metals together. For example, you can theoretically weld aluminum to steel using TIG welding, even though you couldn't do that with other forms, and it introduces a third type of metal, tungsten, into the mix, and that creates a bond that's stronger and lighter than if you were to just use traditional welding methods.

Tom Butler: 22:39

Interesting. So, looking at a comparison again, what I have here is a comparison on a 56 centimeter bicycle frame, and this source was talking about that. Aluminum is 1.8 to 2.5 kilograms as a range, as opposed to steel being 2.2 to 3 kilogram. You can see the difference between 3 kilogram and 1.8 kilogram. That's a decent difference in weight.

Garren Miler: 23:09

That's a very significant difference in weight in the bike world, but weight actually isn't the only factor that might influence you to switch from steel to aluminum. The increased ability to form aluminum is really a strong motivator pushing people into the aluminum realm. What I mean by that is steel. Bikes are almost always made out of tubes, and tubes actually are not great at carrying loads, especially in bending. So the top tube of your bike all it wants to do is bend when you sit on the bike right, and tubes aren't particularly good at taking that.

Garren Miler: 23:41

Really, you want a different shape, and what that shape is? There's no one right answer, and many bike companies have very differently shaped top tubes. And not only that, but your top tube versus your down tube versus your seat post are all going to be loaded in completely different patterns from the way you sit and pedal the bike. And steel just being limited to tube construction means that you're going to have a less efficient shape than if you were to have a material like aluminum that can be molded into different shapes that are more efficient to carry the load through that particular member of the bike. Does that make sense?

Tom Butler: 24:13

Yes, it does, and I want to talk a little bit more about that later on.

Garren Miler: 24:19

So the advantage of aluminum isn't just its strength to weight ratio, but it's also the ability for aluminum to be created into more efficient shapes that carry the load with less material overall.

Tom Butler: 24:30

Gotcha.

Garren Miler: 24:32

And, of course, that advantage is what would bring you straight into the world of carbon fiber.

Tom Butler: 24:37

And when I was looking at getting a road bike, then I started looking at a carbon fiber frame, which I hadn't before, and I really wasn't considering a carbon fiber frame. Frankly, if I could look at the weights again with my 56 centimeter frame comparison, carbon fiber is 0.8 to 1.5 kilograms for the frame. If you're talking about the lightest aluminum frame at 1.8 kilograms versus a carbon fiber frame, that is 1.5 kilograms. To me that is not a big enough difference to make a difference for me and my cycling ability. I really wasn't looking at carbon fiber before, but I have to say that when I got the bike it just felt really good. So let's talk about carbon fiber as a frame material.

Garren Miler: 25:35

Absolutely. To understand the advantages and disadvantages of carbon fiber, you first have to understand exactly what it is, and in simple terms, it's carbon fibers, and maybe the name is misleading, because it's really not just carbon fiber. It's carbon fiber suspended in a resin base, and so you might hear it called composite or a polymer, and it is all of those things, but the actual fibers themselves are little tiny strands that are suspended in a matrix of epoxy resin around them. So the fibers are where the strength comes from. Now, carbon fiber is essentially like making your bike out of a million tiny ropes, and so they act really really good in tension.

Garren Miler: 26:19

You can pull on them all you want, but you can't push on a rope, so the epoxy matrix is what resists compression in a carbon fiber material.

Garren Miler: 26:28

So you have the little carbon ropes that are holding the tension and you have the matrix of epoxy that's holding the compression. That being said, if you had all your ropes lined up in the same direction and you started pulling on them in that direction, they'd be very strong. But if you started pulling them apart, side to side, you would find out that the ropes would just give way immediately, which is why, in carbon fiber, they have to weave the fibers in every direction to make sure that you're always pulling the ropes end to end. That being said, the quality of carbon fiber doesn't just depend on the very fact that it is carbon fiber, but it depends on how it was laid out, how it was designed and how it's loaded relative to the direction of all the fibers. So a well-designed carbon fiber bike will have the fibers facing in strategically advantageous ways to make sure that they're best equipped to handle whatever loads are going through the frame.

Tom Butler: 27:21

I think that that was something that really happened in bicycle manufacturing at one point was that they got serious about really researching and developing how to lay the fibers down in a way that, as a bicycle is being pedaled over and over again, the stresses that you get with the pedal stroke when you're standing up and climbing, the stresses you would get that would be different from just pedaling along on a flat hitting bumps, the different stresses that the bike would have. They started getting serious about how to lay fibers down to what you said create a matrix that can withstand force in a lot of different directions.

Garren Miler: 28:08

That's why there's a massive quality gap from the lowest carbon fibers to the highest and ones, and why you keep seeing manufacturers each year come out with the latest and greatest carbon fiber, because they're further and further optimizing their formula. It's not like metal where you can just pick an alloy and make your bike out of it and really you're fine. Tuning with an alloy is really trivial things like its shape and its form and its welds whereas with carbon fiber you can improve the actual properties of the material itself over time without changing other design factors. The biggest advantage of carbon fiber over alloys is the very fact that you can make the bike entirely out of a solid chunk of it. You don't have to have any welds or seams or connections, and that greatly opens up the design space for how you can actually design your frame if you want it to be more aerodynamic or you want to have it be loaded in a certain way. One thing we do in engineering, for example, is we avoid having sharp corners. That's why airplane windows are round and you'll see a lot of it and on boats all the doors are round, because square corners actually build stress concentrations and can create a failure point and can create cracking On bikes. If you can have your top tube flow into your down tube and flow into your seat post, then having big radiuses and swooping curves on your bike isn't just aesthetic, it's actually helping to distribute the load more evenly throughout the whole frame.

Garren Miler: 29:36

The way that manufacturers approach this is by using a method called finite element analysis. That's a really fancy way of saying. It's a computer process that breaks your frame down into little, tiny elements. It discretizes it and then it sees how each little part would react and it adds it all up. You've probably seen pictures of a finite element analysis performed. A lot of companies use them to taut their R and D division. These 3D CAD models usually have a rainbow-looking color on them, where one part's really red and one part's green, the red denoting really high stresses. The advantage of finite element analysis is that you can follow the path that stress takes through your bike. Something we talk about a lot as engineers is the load path.

Garren Miler: 30:22

When you sit on your bike, you're sitting on the seat post and you're putting all your weight through the seat post, but then, when it gets down to the actual frame, it's being distributed into the down tube and on the top tube.

Garren Miler: 30:34

You have to know how much of the force is getting distributed into the top tube versus the down tube, how much of it's going back to your rear tire and how things are distributing. That's a very complicated process, which is why we have these programs that are able to just compute a massive amount of data at once to follow that stress through your bike, to see where your weight and your cranks and your hands on your handlebars, to see where all that force actually ends up in the frame. Sometimes you might find that if there's an area of your frame that's all good and all green and it's not really experiencing any of the force, well, get rid of it. You want to make your bike as light as you can. Eventually, you start to cut away portions of your frame that aren't experiencing much load, while bolstering the parts that are. You have a frame that's completely optimized for the way that people are going to ride these bikes.

Tom Butler: 31:23

When we were looking at the Roubaix. You ended up getting a roubaix and then you evangelized me and I ended up getting a roubaix. One of the things that I liked about the roubaix and the frame that we got was that we did not get a high-end roubaix. I don't know if you would even consider what we got to be middle of the road roubaix. It depends on if you're going to look at the S-Works roubaix as part of the roubaix family.

Garren Miler: 32:00

I don't think they had the S-Works roubaix when I bought mine.

Tom Butler: 32:03

Oh, is that right Okay?

Garren Miler: 32:05

I think that they released that just after I bought mine.

Tom Butler: 32:08

Okay, Well, I think. Actually the S-Works roubaix was $14,000 when it was released. When you compare the different carbon frame sets that Specialized is using, the FACT-10R is what's used on our bike, which is, I think, a reasonably priced entry level. It's got 105 group set. It's a reasonably priced entry level carbon fiber frame, but that same frame is used all the way up through their $8,000 Specialized roubaix. You have to get into the S-Works roubaix before you get what they call the FACT-12R, which is a higher form of carbon fiber. Now I don't know exactly what that difference is, but I think that you're again you're starting to look at maybe higher grade modulus fibers. What do you think about that? And maybe you even looked at this? But if you were just going to theorize the difference between a FACT-10R and a FACT-12R carbon fiber frame set, what would you theorize, the difference being?

Garren Miler: 33:12

I think the difference between those is probably very, very small and I'm guessing closely guarded differences in their formulas for their resin and in their the way that their fiber matrix is woven inside of it. It also could have to do with the way that it's laid up, because with carbon fiber it's not just the design of the material, it's how that material is actually put together, how it's laid up in the shape of a bike, and by changing the manufacturing process you change the end product pretty substantially. So it's not just that the FACT-12 might just not be a better material. It might just be. It might also just be that it's manufactured in a more efficient way.

Garren Miler: 33:48

That being said, the way that these companies name their materials is all completely proprietary. It's their invention. They invented that type of carbon fiber. They can call it whatever they want, and so some other company can invent something very similar and call it some other fancy word that they made up for it, and what that does is it makes it. So it's really hard to compare apples to apples across different companies and say, with aluminum, you know that a 6061 bike is the same if you bought it from this manufacturer versus that manufacturer. It's always going to be the same alloy, aluminum, whereas when you're comparing the word that specialized and made up for their aluminum, for their carbon fiber, versus the word that giant made up for their carbon fiber, you don't actually know what those minute differences are and if they're relevant to what you're looking for.

Tom Butler: 34:36

You know, I felt pretty confident that whatever FACT-12R is, that it wasn't going to make a $14,000 difference as far as you know my bike is concerned. So that was the way that I judged those properties.

Garren Miler: 34:53

I would completely agree with that. I think that the whole carbon fiber versus carbon fiber discussion is a bit more in the clouds than the average cyclist really needs to worry about. Something my dad just made me as a kid was that even the worst NFL quarterback is still an NFL quarterback and even the worst carbon fiber is still carbon fiber, assuming there's no defects or errors in its design or manufacturing. The carbon fiber is carbon fiber and the advantages of carbon fiber are always going to be there. You're going to have the ability to make a complex frame shape. You're going to have that great strength to weight ratio, you're going to have the really really light outcome and you're going to have the really really nice flexibility that you get when you're riding a carbon bike the shock absorption that you don't quite get from an alloy frame.

Tom Butler: 35:40

So I want to talk about comfort with frames. I find the Roubaix to be very comfortable. A couple episodes ago, I interviewed Eddie Holmes, who is the president of the Gulf Coast Bicycle Club and has been cycling a long time, and Eddie talked about the Roubaix being the most comfortable bike he'd ever ridden. And there is a property of carbon fiber that creates a comfortable bike. Can you talk about that a bit?

Garren Miler: 36:09

Carbon fiber has a great ability to absorb shock and you'll notice that immediately when you start riding a carbon fiber bike. The primary places that you're going to feel this shock absorption is going to be in your seat post and in your front fork, because those are the areas where your weight is getting transferred down into the tires. Most manufacturers produce a D shaped seat post these days out of carbon fiber, and it allows it to bend really well in the aft direction but still have a lot of rigidity in the forward and downwards directions. What this does is it essentially puts you on a giant leaf spring where the road shocks are being absorbed simply through the carbon fiber material and the shape of the seat post. Similarly, front forks are designed so that their shape allows them to bend and absorb shocks when your front wheel hits a bump, and that eliminates the load coming up to your hands through the handlebars.

Tom Butler: 36:59

And when you're talking about bend, you're talking about a pretty minute bend.

Garren Miler: 37:03

I'm talking about an almost imperceptible bend. This isn't something you're going to take with your bare hands and bend into a rubber. I mean, this is something that is measured on the level of thousands of inches.

Tom Butler: 37:14

Right. At one point I thought I'm never going to get a carbon fiber frame. And now I have a carbon fiber frame. Right now my mind I'm thinking I'm never going to get a titanium frame. I don't know. What do you think about that? Do you think someday you might end up with a titanium frame?

Garren Miler: 37:28

I don't think titanium frames offered a distinct enough advantage over other alloy frames or over carbon fiber to really be too big of a market share at any point. For starters, titanium is an incredibly expensive material. It's one of the most expensive metals that you're going to find in day to day life. It's hard to even get your hands on enough titanium to make a bike and by the time you do it's going to be quite expensive. Titanium is very difficult to work with, very difficult to weld. It also suffers from the same property changes due to heat that aluminum does, where when you weld it it changes the local properties of the metal near the weld.

Tom Butler: 38:03

When I'm looking at this chart again that I have for this 56 centimeter bike frame, it actually says titanium is heavier than carbon fiber.

Garren Miler: 38:14

That probably depends on the carbon fiber. I think that they're pretty well neck and neck, but I don't have specific numbers, I guess. But in general, I would expect carbon fiber to be lighter than titanium. Is the thing that titanium really doesn't solve, that aluminum didn't solve and that seal didn't solve and titanium still doesn't solve is the issue of the shape of your bike being limited to tubes and limited to pieces that are fit together by joinery, be that a weld, a resin joint, sockets or whatever. The advantage of a carbon fiber bike being a single laid piece that you can shape into whatever shape you want is still a shortcoming that titanium can't overcome. There will still be welded joints, no matter how good the weld is, and that limits how you can design your bike. Carbon fiber does not have those limitations, Even if it is heavier. Being able to more accurately tailor your bike to the loading pattern that it's subjected to is still enough of an advantage to go with a carbon fiber bike over an alloy solution of any kind.

Tom Butler: 39:14

There's an element here of the shaping that, among all these frames, it sounds like the carbon fiber frame can be laid out in a way that makes it more aerodynamic. I've heard you talk about before that a round shape is not a very aerodynamic shape and I'd like you to talk about why that is again. But then it seems like with a carbon fiber frame you would have the ability to lay it out in a way that you can make it more aerodynamic.

Garren Miler: 39:53

Yeah, obviously aerodynamics is a big topic in the bike world. When you're talking about the aerodynamics of your frame itself, your frame is such a small amount of cross-sectional area compared to you on top of the bike. You're probably 90% of the cross-sectional area and your bike is only about 10. So when you're talking about your bike being more and more streamlined, that's really not an advantage you're going to feel unless you're really pushing the boundaries, which I think most people on bikes on the weekends are absolutely not. So aerodynamics really isn't a huge concern. The ability to shape your frame into different, into more accurate and more creative shapes actually has more to do with making sure that your load is being distributed evenly throughout your material, allowing you to shave off any excess material that you don't need and lighten up your bike. That's really the advantage of it is that you can shape your bike into a more efficient shape from a mechanical perspective.

Tom Butler: 40:49

Well, yes, I understand what you're saying and I totally agree that when I said on a bike seat, the aerodynamics of the frame are just lost. But that being said, I'm still thinking that you can create a more aerodynamic frame, regardless of whether or not that transitions into any meaningful performance advantage. You're still able to shape a bike frame into a more aerodynamic shape with carpet fiber. Is that fair?

Garren Miler: 41:18

Yeah, carpet fiber certainly allows you to make a lot more creative shapes. That includes some real cool airfoil looking bikes. You might see them on some of the indoor velodrome races where aerodynamics is key. It looks like a big flying wing out there and that's certainly something you wouldn't get away with on an alloy bike. That you have to have the malleability of carpet fiber and the customizability of the layup in order to create a bike that can have anything close to that kind of shape.

Tom Butler: 41:46

So now I want to come to a point where I talk about where my mindset is now. At one point I said I'm never going to have a carpet fiber bike. Now I have one, but in this process of looking at McKenna's bike, there are a few things that I looked at that made me question having a carpet fiber bike, and so the first of those things that I will talk about is this element of hydroforming. Can you talk about hydroforming?

Garren Miler: 42:27

Yeah, hydroforming is a way to have aluminum sort of catch up to carpet fiber in the shape world. You can take a tube of aluminum and you can fill it with water and press it into a mold to create whatever shape you'd like. So on McKenna's bike you'll see that the top tube does have a more carbon fiber-esque sort of oval shape to it. It's not just a tube, and that's because they're able to take the aluminum and form it using water pressure in a mold, Similarly to how you would have injection molded plastic parts. They can hydroform the aluminum into a much better shape that's more efficient and more aerodynamic.

Tom Butler: 43:05

McKenna's bike is a live bike which is made by Giant. They call their aluminum frame I think it's pronounced Alex, but it's A-L-U-X-X and so they call it their Alex grade aluminum frame. To me again, what you just said was they're able to replicate some of the advantages of a carbon fiber frame.

Garren Miler: 43:34

The advantages that we see from carbon fiber bikes are not limited just to full carbon frames, and that's what's really nice about the middle ground that we're able to strike in today's bike industry.

Garren Miler: 43:44

To use a good analogy, in the car industry you have supercars that only a handful of people in the world own, but the innovations that come from the development of those supercars eventually trickle down into daily drivers.

Garren Miler: 43:57

For example, conseg, created at one point, was very near the world's fastest car and it had a very unique transmission system inside of it, and that transmission system was then adopted by other European manufacturers and it trickled down into the transmissions of everyday cars, and I think that's what we're seeing with carbon bikes now. The advantages that carbon fiber bikes were able to bring about in the world of aerodynamics and frame shapes are now being transferred to aluminum frames through hydroforming to create more aerodynamic and more efficiently shaped aluminum frames. And the ability of carbon fiber to absorb shock can also be included on aluminum frame bikes by just making the seat post and the fork carbon fiber, which is a common configuration you'll see these days and it's the configuration that's on McKenna's bike the fork and the seat post isolate you from the bike and the ground in order to have all the benefits of the shock absorption the carbon fiber offers, without needing to pay the premium price tag that comes with buying a full carbon fiber bike.

Tom Butler: 45:00

Yeah, and McKenna's bike was I don't know half the price of our bike. And again, I think that you know, if I was getting into a new bike, I'm really happy with my bike, but if I was looking at getting a different bike, I think I would look at an aluminum frame. I think I'd want it to be the latest design principles as far as aluminum frames are concerned and I would want to have a carbon fiber seat, post and carbon fiber forks. By the time you do that, if you can save $1,000 or whatever, at my level as a cyclist, it seems like that wouldn't be a bad choice for me.

Garren Miler: 45:38

I completely agree with you. Our Rubais size 56, weigh 19.1 pounds. Her live, which isn't sized in the same system but it's a size medium weighs 20.7 pounds. The weight difference for an average cyclist is completely negligible. In fact you'd be hard-pressed until the difference just by picking them up, I think. Bottom line a carbon fiber bike is better than an aluminum bike, but for the weekend warrior it's really hard to justify an almost doubling of the price for a product that's only marginally better.

Tom Butler: 46:15

And if McKenna can get you to carry the bike tool, the tubes, you know, there's not many things that she would need to convince you to carry on. Your bike rides together and you're riding pretty much the same weight of bike, right exactly.

Garren Miler: 46:35

I think it just depends on how much water is in your water bottle. I mean, it's really, it's such a minute difference. It's been so many cliff bars I eat at the stop. I think that the carbon fiber can be utilized in the areas where it's most needed, without the extra cost of making the entire bike out of carbon fiber. Aluminum will do just fine for someone who is just getting out on the weekends getting some exercise or commuting.

Tom Butler: 46:59

Okay, so I want to talk about a different frame material, and this is a frame material that I would really like to have the extra money to just go out and buy this frame and that is a frame made out of bamboo. Have you ever seen a bike with a frame made out of bamboo?

Garren Miler: 47:18

I've certainly never seen a frame made out of bamboo. I think the first thing that comes to mind is how much of a nightmare quality assurance would be on that, making sure that you have consistency and that you know that your bamboo is not going to fail. One thing that's difficult with materials like bamboo is that each plant is completely unique. You can't say, just because plant A broke it, this amount of strength means that plant B is going to break it, that amount of strength. The only way to know the breaking strength of a plant is to break it. It's a chicken and egg problem where you can't break the thing you're making your bike out of to test it, but then you don't know when your bike is going to break.

Tom Butler: 47:57

The interesting thing about it is that the 56 centimeter bamboo frame they're saying weighs 1.8 to 2.5 kilograms. So comparing to steel 2.2 to 3 kilograms it's actually a lighter frame material than steel. And about the range of aluminum frames, I think that's very interesting. But again what you're talking about, it seems like there's so much variability even in that in what the weight would be.

Garren Miler: 48:32

Absolutely. I think it depends on everything from the water content of the tree to the soil it was growing in. I don't think that's really you can control very tightly.

Tom Butler: 48:41

Right, how much sun there was that year. Whatever, right.

Garren Miler: 48:45

I think that the most obvious advantage of a bamboo bike is the inherent sustainability of it. I think if we're trying to bring bicycling to the masses, that's certainly a direction you might want to take it. Our rubes are literally and essentially made out of plastic, and they'll be here long after we're done riding them, be that in the ground or in our kids' hands. But a bamboo bike is not only biodegradable at the end of its lifespan and hopefully no sooner but bamboo is also a really good carbon sink. When it grows, it sucks a surprisingly large amount of carbon out of the area compared to other plants. So growing bamboo in and of itself is also a more sustainable practice.

Tom Butler: 49:24

I want you to go to Ampro bikes and just look at the bike and give me your impression looking at it.

Garren Miler: 49:33

I got to say that is a pretty awesome looking bike. It definitely would catch some attention and turn some heads cruising that thing down the street. I want to say if I saw it in person I'd probably have to get real close to it before I'd believe that it was actually bamboo. But they don't try to hide it. I just wouldn't believe that someone would ride a bike around and just made out of bamboo. But it's pretty awesome.

Tom Butler: 49:56

Yeah, I think you'd be like is that a really innovative paint job, or is that actually in bamboo?

Garren Miler: 50:03

Exactly. I think it's a. Really I love the juxtaposition of the really high-tech group set and everything on it with a really just naturalistic bamboo that looks like it just got picked out of the woods and slotted with a coat of lacquer.

Tom Butler: 50:17

They show a frame set by itself and it's a $600 frame set, which isn't that expensive of a frame, and I think they're probably using carbon fiber to join the different bamboo together to make the frame set. They have a commuter frame set, they have a gravel frame set. They have some electric bikes. I find it to be a really fascinating thing and I hope to someday run in these bikes again. If something happens, I end up with a bunch of extra money, I think I'll buy a frame set and build it up, because I think that would just be fantastic.

Garren Miler: 50:56

Yeah, for sure.

Tom Butler: 50:58

If you were going to yes, okay, I'm putting you on the spot here. What frame material do you think has the largest market share in bicycling?

Garren Miler: 51:08

I think it's aluminum.

Tom Butler: 51:09

Okay, what would you put second?

Garren Miler: 51:11

Probably steel.

Tom Butler: 51:12

Okay, and what would?

Garren Miler: 51:13

you put, and then only carbon.

Tom Butler: 51:14

Okay, these are the numbers that I have and this is from a variety of sources. Aluminum is number one largest market share at 35 to 45%. Carbon fiber is gaining ground rapidly it said the report that I read and it's at 30 to 35%. So steel is 15 to 25%. I found that to be interesting because I would have thought for sure that steel was at least 50% of the market.

Garren Miler: 51:45

Yeah, and you also have to wonder how much of a role e-bikes play in these numbers as well, because a lot of e-bikes are made out of steel. Because it's increased strength, it makes it a lot easier to strap a battery to it and not have it break, and so I wonder how much of the steel market is e-bikes as well and what kind of an impact that would have.

Tom Butler: 52:02

I think that's a really good question. And then kids' bikes. I would think that steel is still the predominant material in kids' bikes, right? So I thought that was pretty interesting. They estimate around 5% to 10% titanium, and then bamboo is so small that they don't even estimate it.

Tom Butler: 52:20

I did want to touch on one thing and I wanted to get your comment on it. There was an article that I found and I sent over to you, and it was an outside magazine, so this is a pretty significant source of information as far as outdoor sports are concerned, including cycling, and the title of the article is there's no Good Reason to Buy a Carbon Bike. Again, we've said here that we both would really consider aluminum frame in the future, given the carbon fiber seat post and the carbon fiber forks, you know, counting in as far as part of aluminum frame. But one of the things that this person pointed out Eben Weiss, I believe, is their name is that carbon fiber bikes. And I'm just going to read this section of this article, and this was published in the January 27th online. I don't know it's online, so it was published January 27th of this year and then it was, since it was updated in January 30th. I'm not sure what they updated. There's the statement here Probably the biggest drawback to carbon fiber bikes is that they're like eggs.

Tom Butler: 53:36

You know how eggs are almost impossible to break if you squeeze them from the pointy ends, but if you squeeze them any other way, you'll quickly wind up with a handful of yolk. Similarly, while carbon bikes are quite strong when used as designed, what they're designed for is racing. They're not designed for crashing, falling off a hitch rack, getting knocked over in the garage by your young children or any other little mishaps that befall normal people's bicycles as part of the messy business of day-to-day living. So what I heard this person saying is that they're so fragile that it doesn't make sense for people to have them, unless they're professional racers where they're constantly given new bikes. I sent that over to you. I know that you've had some time to think about it. What do you think about that?

Garren Miler: 54:24

I think the article brings up some good points, but I also do think that it exaggerates the fragility of a carbon bike. I mean, they certainly are designing these bikes with factors of safety against, for example, side loads or crashing, and they're doing crash tests on these bikes. You've got to be sure of it, that they're making sure that these bikes aren't just going to explode if it falls over your garage, for example. I mean, that's maybe a bit of a catastrophized approach to the issue, but it is definitely a concern, and one way that manufacturers mitigate this is when you buy a carbon bike new and you register with a manufacturer, you get a lifetime warranty on the frame, and that's given the fact that carbon fiber is going to be different layup to layup.

Garren Miler: 55:04

Not all bikes are created equal. In fact, you can see that on your bike where it has the unfinished paint job, you can see the carbon layup, and if you were to take another bike with that same unfinished look, it would have a completely different pattern on it because the carbon fiber was laid up differently. And so it's very possible that you do get a carbon fiber bike that has a weak point in it because something went wrong on the layup and one day you're leaning on it against a post and your top tube cracks, and that's when specialized and giant and Trek will take those bikes back. And it's industry standard to give a lifetime warranty on carbon bikes and that's one of the advantages, of course, of buying a new bike and that's one of the ways that they help to mitigate the concern of an overly fragile carbon bike.

Tom Butler: 55:49

I haven't seen people writing about I'm never getting carbon fiber bike again. I bought this carbon fiber bike and it cracked and they replaced it, but it cracked again I'm just not reading about that and it seems like they were as fragile as falling off a hitch rack or getting knocked over in the garage by your young children. If a carbon fiber frame was that fragile, you would get people saying, hey, I had a carbon fiber bike, but it just kept getting cracked over and over again, and so I just dumped it and got a limited frame.

Garren Miler: 56:27

It would be hard to imagine carbon bikes having what was it? A 30% market share if people were to get a carbon fiber bike. So we're going to be breaking them and having to buy new ones frequently.

Tom Butler: 56:37

But we look at giant producing frames for quite a long time now. They've had a lot of years to look at carbon fiber frames and they've not been selling those frames to only racers. They're selling that to normal people like you and me, obviously. And so, yeah, I just carbon fiber would have got popular, popular, popular, and then it would have died off.

Garren Miler: 57:03

I'd agree.

Tom Butler: 57:04

Well, Garen, thank you so much for coming on. We talk about bikes a lot. I find it to be really fun and I really appreciate your perspective on it. I don't know if you have anything else that you're looking forward to or thinking about as far as frames.

Garren Miler: 57:22

No, I'm always happy to talk about this kind of thing. Like I said, I do this for work and I think about it all day long, and it's fun to get home and think about it some more.

Tom Butler: 57:29

And you also have some engineer classmates that are cyclists as well, I think.

Garren Miler: 57:35

Yeah, I had some classmates present senior projects on different bike related problems that they had solved. Pretty interesting stuff. It's kind of a tragic job if you're a mechanical engineer.

Tom Butler: 57:44

Yeah, so that's very cool. And again, thanks a lot and we'll be riding together soon.

Garren Miler: 57:50

Yeah, thank you, and I'll see you then.

Tom Butler: 57:52

All right, bye now Bye. I certainly don't regret that I got a carbon frame bike, and it is likely that I would have always wondered what I was missing if I'd gotten an aluminum bike instead, but I do think I will make a different choice if I get another bike in the future. What I really want to purchase next is a bamboo frame bike, and not because I need it or I would even ride it very often, just because there are certain rides that would be really fun to show up on a bamboo bike Now I just have to figure out a way to justify it.

Tom Butler: 58:31

If you have a bamboo bike, I would really love to hear from you, and if you have some thoughts on carbon fiber as a bike material, please share. You can find my email and the podcast, instagram and the show notes. Whatever frame you are riding on, I hope you are experiencing some beautiful scenery and some wonderful fresh air, and remember age is just a gear change.