But there's more to it than just numbers on paper, and there's more to biking than just riding in a straight line from point A to point B. Carbon fiber frames aren't just about saving weight. The Carbon Fiber has different flexibility and damping properties that result in a different feel, for example.
My engineer friends make fun of me for spending $1K on a set of carbon fiber wheels, until I let them ride the bike. It only takes a few pedal strokes to feel how the reduced rotational inertia translates to faster acceleration. The advantages are even more significant when jumping or throwing the bike around, because the bike's moment of inertia is reduced significantly.
Carbon fiber handlebars don't save much weight, but the damping properties make for a minor reduction in fatigue. Carbon fiber Derailleur arms will again only save a few grams, but they're more likely to spring back from impacts than metal pieces that will simply bend. More expensive shifters have better bearings and cables that make for more precise shifts, meaning less fiddling over time and less mental effort to make sure I'm only changing 2 gears instead of 3.
The list goes on and on. Casual observers think we're just being silly and fooling ourselves with expensive parts. Meanwhile, I'm still buying the expensive stuff, enjoying it, and having zero regrets. At this point I just don't talk about it with any non-bikers because so many of them think they've got it all figured out.
Bikes are all about diminishing returns.
If you spend $500, you get a bike that's probably twice as good as a $250 department store bike.
Spend $1000, and you get a bike that's half again as good as that $500 bike.
Drop 2 large and you get a bike that's 25% better than the $1k bike.
etc etc until you are paying $15,000 for a bike that's 0.5% better than a $10,000 bike.
We all find what part of the curve we want to participate in.
Personally, I think $4500 for a really nice looking eBike with some fantastic add-ons is a decent deal.
Pretty much everything is about diminishing returns though, so nothing special about bikes.
For instance I can (and have) build a Miata race car for $5K to do good laptimes at the race track. Or I can spend over $100K on a car to go a handful seconds faster per lap.
Mostly truth. Some things more than others.
if you do a blind experiment, where you don’t know the wheels under you, or a third party adds weights to the rim you can demonstrate this. be sure to use the same tires, at the same pressure, as tires and pressures make massive differences in comfort feel and efficiency.
source: me, long time triathlete, cat3 bike racer, coach of a professional cyclist and state tt record holder, gear nerd who has done lots of power meter experiments and spreadsheets
This is exactly what I was talking about. People like to assume that a simple math equation tells the whole story, while ignoring the fact that bikers do more than just exist as rigid attachments to a bike that travels in straight lines.
I can do the math, but I can also swap wheels in a matter of minutes and feel the very obvious difference.
I'm talking about 29" mountain bike wheels, where the mass and moment of inertia is significantly more than what you see on 26" road bikes. It's palpable.
Maneuvering the bike in the air is another place where the mass difference is noticeable. Dropping 500g doesn't sound like much when you think about holding 500g in your hand, but it's a different story when that mass is on the ends of a 48" long wheelbase and you're trying to maneuver it in the 0.5s that you're in the air.
If you're just riding something like your tri bike in a straight line down a smooth asphalt road at a constant velocity then it obviously doesn't matter, though.
You’re not necessarily wrong, but I will point out that high end audiophiles will often say the same thing about their absurdly priced equipment, and then refuse to participate in a double blind test.
You also probably won't see this in your PM data unless you're getting data on partial pedal strokes.
More steady power stuff like on the road, climbing fast, etc? I agree that lower wheel weight just isn't something you'll notice. (Very good evidence for this is riding a fatbike on a fast rolling dirt road ride vs. climbing very steep fire roads.)
This is only true if you measure only along the forward/reverse axis.
Cyclists stand up, and rocking the bike sideways is easier with lighter wheels.
On mountain bikes there are even more cases.
- Carbon fiber is a worse conductor of heat than aluminum. Use some carbon fiber bars, foam grips, and either carbon brake levers or aluminum ones with heatshrink tape over them and your hands will stay warmer in the cold. When it's REALLY cold and you're using pogies (grip area covers) this is particularly important as it means less heat wicking away from your hands.
- In my experience the sidewalls on carbon rims are a LOT stronger than aluminum. Sure, it's possible to break carbon, but it takes a lot more force than it does to dent or crease aluminum. I've ridden carbon rims hard on seriously rough trails, hitting rims on things which have dented my aluminum rims, and the rims are just fine.
- When building bicycle wheels one of the usual steps is truing the wheel, or adjusting the tension on each spoke to pull the rim into being straight and eliminating wobble. This is not a thing with carbon rims. With carbon rims they are SO stiff that instead you bring all the spokes up in tension evenly and then maintain this even tension and ensure the wheel is straight (no radial or lateral wobble). Unlike aluminum rims, changing the tension on just one, or even a handful, of spokes won't pull that part of the rim in whatever direction. The rims are just that stiff, and a well-built even-tensioned carbon wheel will last a long time.
- It's also possible to do far more complicated forming with carbon fiber than one can do with metal, particularly at reasonable weights. Having a very low stand-over height (good for technical mountain biking) with carbon is no big deal; just some engineering. With aluminum it requires a lot more material, which can add pounds (noticeable amounts) of weight.
I've been riding on carbon rims on both hard tail XC bikes and my full suspension trail bike for six years. I've also had aluminum rims on my single speed and hard tail trail bike. I can't count the number of times I've hit the carbon rim and had it be just fine, but all of my aluminum rims have some degree of denting from much lesser riding.
Between the bikes with carbon wheels there's about 12,000 miles of trail riding and they've been just fine.
After I dented the rim on the I9s and had a spoke break I decided a good winter project would be rebuilding the wheels to carbon rims because my previous experiences with them have been so good.
I think the primary benefits of carbon are stronger sidewalls (less likely to dent) and that they cannot be bent and thus can't go out of true (unless the wheel is built wrong). Yes, they can be broken, but it takes a LOT more than it would for a comparable aluminum rim.
(For reference, the rims I've beat on so hard are Light Bicycle RM29C07 and I'm replacing the stock rims on the I9 wheels with AM930.)
You can watch Danny macAskill try to destroy bare carbon wheels (no tires) on concrete here: https://www.youtube.com/watch?v=VfjjiHGuHoc
I assume some of the horror stories come from people buying cheap carbon wheels or early models before they had layups and molds figured out.
If you're really concerned, add something like a cushcore to the inside of the tire for additional damping.
Your complaints are common, though. I've all but given on up trying to discuss carbon wheels with people in person because there are so many preconceived notions out there. It was the same way 5-10 years ago with everyone avoiding carbon handlebars for one reason or another.
Look for "Danny MacAskill Tests Santa Cruz Reserve Carbon Wheels": he really tries to destroy those rims, and it takes him doing ridiculous things to do so. Aluminum rims would have cracked/ bent much earlier.
\aside why not smaller (radius) wheels? Use higher gearing, and accept the bumpiness.
Though for touring aot commuting, there's something pleasant about higher inertia.
Bumpiness isn't just a comfort issue. Your body ends up absorbing a lot of the up and down motion, which drains your forward momentum.
So, biking audiophilia.
You might be interested in what we're up to [0], get in touch if it interests you.
Are you going all out with triaxial load in the seat post, or uniaxial (posterior)?
Seatpost is actually one of the simpler sensors, without giving too much away it's sensing force in 4 different directions.
Your post is what theory looks like when people forget the difference. Your theory leaves out tons of variables, including the condition of the road, and the differences in how materials deform under pressure. I've seen the stats you're referring to, and that's what it looks like in a lab with perfect conditions.
Go ride a $400 bike and a nice carbon fiber bike. The difference is much more substantial than 15 seconds per 4 hours. It's less fatiguing, the pedals feel stiffer (cheap bikes feel mushy in the pedals), my speedometer has a higher average speed, it's easier to climb hills (flat surfaces like in the lab are rare on real world streets--flat roads are almost never 0% grade), etc.
Sometimes you need to put down excel and actually do the thing you're theorizing about.
In particular, when you are bonking and trying to keep up with a group or get up a mountain, you become PAINFULLY aware of the deficiencies in your equipment. An extra pound on your bike when trying to keep up with your group up a 8% grade will feel like you're carrying an anvil.
A semi-professional once told me how crazy it is that people with a beer belly spend a huge amout of money on their bike, just to get a few grams off. A proper diet could save them a few kilos for free.
aero equipment and position and training are all orthogonal so it isn’t a question of picking just one.
I'm a fluid dynamics researcher, and I'll tell you the money these people spend on "aero" and "weight saving" and "higher drivetrain efficiency" stuff is 99.9% snake oil. Unless you are among the top 1000 road bike racers in the world.
Increasing your exercise load by half an hour per week, or spending a little time understanding and implementing aerodynamically efficient body posture or other forms of technique, will both yield improvements that are several orders of magnitude higher than the marginal improvements achieved by spending $$$ on "aero" and carbon fiber.
I've seen detailed calculations of rider performance that indicate a 500 g saving in frame weight (which is huge), over the course of a 120 km race with 1200 m climb, will save you a whopping total of 15 seconds on ~4 hours of race time.