Why carbon rims?

[Likes2ridefar]

Originally Posted by MikeD

How many of us race? Stability in crosswinds and lightness are more important to me. I used to use aerobars. They are more aero than wheels. I don't use them any more.

It almost seems like trolling now, if that word is still used. Kick off the post referencing a guy who races and no mention of what’s valued for more accurate insight.

[Mark McM]

Originally Posted by MikeD

Breaking spokes and truing doesn't have much to do with the rim. The quality of the spokes and the wheel build are what's important.

The quality of the spokes and the wheel build are certainly important, but in terms of wheel design the rim is often the most important parameter. Spokes fail from fatigue, and fatigue is the result of cyclic loading. A deeper, stiffer rim better distributes loads across the spokes, reducing peak loading, and reducing spoke failures. Likewise, wheels go out of true when a component (usually the rim) is deformed/damaged - since deeper rims are less likely to dent, wheels with deeper rims are less likely to go out of true.

[NHAero]

Originally Posted by Mark McM

I've also noticed that among aluminum rims, the deeper the rim the less likely it is to go out of true. Which is probably not surprising, as increasing the depth of a rim increases its strength and stiffness (out of proportion with its weight).
I've got several sets of 30+ mm deep aluminum rims that have never had to be trued after many years of hard use. Carbon rims tend to be deeper than aluminum rims, so I wonder if robustness is more closely tied to depth or material.

We're both engineers so we probably notice the same things
I've not had deep section aluminum rims so no data, but yes, as a rim cross section gets a higher moment of inertia it's got to be stiffer, just like larger diameter (or cross section) frame tubes.

My deepest carbon rim however is 35mm. On Martha's Vineyard and at 140 pounds getting blown around matters to me more than the other aspects.

[Mark McM]

Originally Posted by benb

How do you do the math to get to 10W average over the course of the race if the wind tunnels says 10W at 25mph with no one around you (or no rider on the bike, or the wheel is not even on the bike) but it turns out in the race you are drafting someone 80% of the time?

If you're tall enough to have your head stick it up it would seem the helmet is the thing that is relevant in all situations.

I would love to see any aero data that tested rider A behind rider B or in a group of 10 riders. We know the rider nestled in the pack could be saving way over 100w, it probably makes most of the equipment choices irrelevant till that rider is exposed to the wind. I know from my own racing experience there was tons of time I was in like zone 1 in the pack doing 30mph on the flats. It's a HUGE effect.

I am not saying this stuff doesn't matter in a race. But to someone going "I don't get dropped out of the pack in a recreational ride" that effect of drafting negating all this is probably highly relevant.

One thing I do get is a ton of the marketing is about convincing people who don't race that their needs are exactly the same as people who do race. I like to go fast even though I am 100% done with racing and have no real desire to do it again, but there are all kinds of things where the cost or PITA of something that matters for racing is a step too far if you don't race. Especially when you're time crunched and/or spending time on those things has to come out of your riding time. (Not saying any particular wheel is a time suck, but other things are.)

I hear what you are saying about drafting in the pack. Drafting can save a huge amount of power, and the skill of a rider to ride the draft can make a big difference. But on the flip side of the coin, better aerodynamics can reduce the power needed to ride in the draft (although of course the difference isn't as much as when riding solo). And yes, the hills are usually where one gets dropped - but if one gets dropped on the hills, better aerodynamics can help one catch back up with the pack (and keep in mind that a chasing rider has to go faster than the group in order to catch them). There have been multiple times in races where I lost contact with the back of the group on an uphill, only to catch them again going down the other side.

[bikinchris]

Originally Posted by MikeD

Carbon fiber is not a ductile material. If you exceed its yield strength, it does not bend, it fractures.

What's so great about carbon rims over aluminum? Maybe a little weight savings? They don't work all that well with rim brakes either, and can deform from braking heat. They suck in wet weather too.

Different companies build to different specs. Here Danny MacAskill spends some time testing and trying to break Santa Cruz Reserve rims:

https://youtu.be/VfjjiHGuHoc?si=WUmcXb_UOZG_t6WD://

[Likes2ridefar]

Originally Posted by benb

How do you do the math to get to 10W average over the course of the race if the wind tunnels says 10W at 25mph with no one around you (or no rider on the bike, or the wheel is not even on the bike) but it turns out in the race you are drafting someone 80% of the time?

If you're tall enough to have your head stick it up it would seem the helmet is the thing that is relevant in all situations.

I would love to see any aero data that tested rider A behind rider B or in a group of 10 riders. We know the rider nestled in the pack could be saving way over 100w, it probably makes most of the equipment choices irrelevant till that rider is exposed to the wind. I know from my own racing experience there was tons of time I was in like zone 1 in the pack doing 30mph on the flats. It's a HUGE effect.

I am not saying this stuff doesn't matter in a race. But to someone going "I don't get dropped out of the pack in a recreational ride" that effect of drafting negating all this is probably highly relevant.

One thing I do get is a ton of the marketing is about convincing people who don't race that their needs are exactly the same as people who do race. I like to go fast even though I am 100% done with racing and have no real desire to do it again, but there are all kinds of things where the cost or PITA of something that matters for racing is a step too far if you don't race. Especially when you're time crunched and/or spending time on those things has to come out of your riding time. (Not saying any particular wheel is a time suck, but other things are.)

I do not dismiss any incremental gains so why not get them if you can if after every advantage? I’d imagine every bit counts but i am with you that as a former racer using power I’ve always wondered how much a difference marginal aero gains truly makes in most scenarios. I definitely don’t think saving 10w will make or break the legs. Mine anyways.

[MikeD]

Originally Posted by Likes2ridefar

It almost seems like trolling now, if that word is still used. Kick off the post referencing a guy who races and no mention of what’s valued for more accurate insight.

I think you're the one trolling. I never said that. To the racer, aero has benefits. To the non-racer, not so much.

[Likes2ridefar]

Originally Posted by MikeD

I think you're the one trolling. I never said that. To the racer, aero has benefits. To the non-racer, not so much.

I’d copy and paste the first post to prove otherwise but it is predicted to be wasted effort. (Just like this)

[benb]

Originally Posted by Likes2ridefar

I do not dismiss any incremental gains so why not get them if you can if after every advantage? I’d imagine every bit counts but i am with you that as a former racer using power I’ve always wondered how much a difference marginal aero gains truly makes in most scenarios. I definitely don’t think saving 10w will make or break the legs. Mine anyways.

Probably depends on how long your race is.

I think I still wait for a disc bike for this. But for some of the non-race endurance stuff I've done since racing I think these aero things actually make more sense cause they are longer events than racing and you're more likely to end up riding alone because of the way waves start and the way you could easily get mixed up in a group faster than you belong in and then spit out. Especially compared to a race where your category dictates you can't really get mixed up in a much faster group. Also when I did those types of things I generally didn't actually have a group I entered with where we were all in the same target speed range. When I raced I was in the right field and I'm not sure I ever entered a race without a teammate/club member.

Also these long endurance events I feel like you're less likely to get caught in a crash and destroy stuff. The "cost is no object" approach to recreational riding & amateur racing is not what I was used to when I did race. Nearly everyone I raced with was very conscious of "only buy what you can afford to throw away after the big crash". I could afford to throw this stuff away now, but I couldn't really then. Even my current alloy wheels are more expensive than anything I raced. I haven't gone to a race in quite some time but I'd be fascinated if a Cat 4/5 field is full of $5-10k bikes now, cause I'm sure they still crash just as often.

[Turkle]

The Cycling Independent had a nice article on aero benefits today.

https://cyclingindependent.com/do-ae...ge-road-rider/

This section really spoke to me:

Also, with respect to group rides, those aero gains can mean being comfortable on front when otherwise you might not have been up front. Or, if you’ve gotten dropped in one particular section, aero equipment could mean maintaining contact with the group.

Every time I put my Zipp 404s on my bike it was with the knowledge that I was going to come home destroyed because they would help me get to the front of the ride and take longer, harder pulls.

This feels exactly right to me. As a recreational rider that likes to hang with the fast group, the aero benefits of my bike absolutely allow me to take long pulls at the front where I might not be able to on my other bikes. And if you're trying to catch back up to the group in a headwind, 10W savings can be a super big deal!

[Likes2ridefar]

It’s not a super big deal though. 10w is maybe .5mph? Or less? That is not going to make or break catching most pelotons that should be going much faster than a single rider can hope to hold for more than a few minutes.

[benb]

Yah it's been a while but I would expect in a fast group ride, not even a Cat 5 race you are talking more like at least 100-150W difference (maybe 200W?) between in the pack and taking a pull. There were certainly a lot of times I did catch back on to a group on a downhill or flat though.

That article makes good points though. Helmets and clothes should not be ignored cause they have almost no extra cost and have a really high value. I have a lot of jerseys that have lasted forever.. I just got some new ones and they are clearly cut to be more aero, even in a non race fit. And they weren't even expensive. I am too fat to wear my actual race fit ones right now. But 20 years ago our race fit jerseys fit looser and flapped more in the wind than the "non race" ones do today. All the jerseys back then were basically "comfort fit" compared to today.

I rode an aero helmet the last 5 years but bought a non-aero one last year. The non-aero is clearly better on a really hot day, but ignoring the aero benefits the aero one is better on a cold day.

Almost all the wind tunnel numbers claim the helmet is as good as the wheels, and the helmet loses less of it's benefit in the pack, especially if you're tall.

[djdj]

Why carbon rims? Because I think they look better!

[flying]

Originally Posted by El Chaba

I understand that my findings are in contradiction to what the industry and its adherents are pushing. .

Honestly that is all that matters

There have been videos that show how much the industry plays with yaw etc in wind tunnels till they get the talking point they want.

Whereas your data is factual & personally validated for you & that is what matters IMHO

[callmeishmael]

I haven't raced on the road (aside from a club 10) in a decade, but our Tuesday night chaingangs are pretty spirited, and can pull in a national standard junior, a couple of ex pros, and a current semi-pro female.

The route is lumpy, but when I get dropped - and I always do! - it's not usually on one of the two main risers: it's when people kick hard out of the corners for the nth time, establish a gap, and I just don't have the legs for another acceleration and can't get back on. Yes, positioning plays a part, but it's continually going from 35-45kph that kills me.

I also notice that if the group is pulling hard down the long, false flat downhill section, if you're careless/lazy/tired when you pull off the front and ease off too much, you get spat out the back pretty quickly, and at those speeds your odds of getting back on again (at least with my watts - ymmv) are zero, at least not without absolutely burying yourself.

To my mind, it's those surges at already fairly high speed that create splits in most fast rides, be they races or not, and that's also where aero gains most come into play.