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"Carbon would have bounced back"

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

"Carbon would have bounced back"

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Old 01-09-19, 07:53 PM
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Originally Posted by redlude97 View Post
Did you mean carbon fiber hybrids?
I think they were probably cyclocross carbon fiber wheels used in the Road Bike Party clips. A few crashes that didn't make it into the films. The wheels certainly took a lot of abuse, but apparently didn't fail. There is a summary somewhere.

I presume steel spokes, with 100% Carbon Fiber resin rims.

Of course, hitting a pothole or road crack at high speeds can put extreme stresses on a a wheel that might not be the same as the jumps they were doing in the Road Bike Party clips, usually landing on flat surfaces that would distribute the weight better than the sharp edge of a hole, and in the OP's case, apparently he collapsed the tire causing a pinch flat.
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Old 01-09-19, 08:11 PM
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I'd opine that who knows.. Every brand, every design, and every type of alloy composition or carbon layup method used in making a rim affects what *would* happen if hitting a pothole. Likewise if the width of said rim perhaps affecting the PSI you've chosen to inflate X brand of tire to, certainly all bets are off, and asserting any opinion of whether another rim made out a, b, or c material is kinda pointless.
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Old 01-09-19, 08:19 PM
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Originally Posted by CliffordK View Post
I think they were probably cyclocross carbon fiber wheels used in the Road Bike Party clips. A few crashes that didn't make it into the films. The wheels certainly took a lot of abuse, but apparently didn't fail. There is a summary somewhere.

I presume steel spokes, with 100% Carbon Fiber resin rims.

Of course, hitting a pothole or road crack at high speeds can put extreme stresses on a a wheel that might not be the same as the jumps they were doing in the Road Bike Party clips, usually landing on flat surfaces that would distribute the weight better than the sharp edge of a hole, and in the OP's case, apparently he collapsed the tire causing a pinch flat.
you can see the aluminum brake tracks
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Old 01-09-19, 09:16 PM
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Originally Posted by Marcus_Ti View Post
There was also that incident at Tirreno Adriatico's TTT....where Team Sky's TTT train hit a pothole...and there was lots of broken carbon fiber wheels. Shimano traced the error back to out-of-spec tubular being used IIRC...

Wheel failures decimate Team Sky's Tirreno-Adriatico ambitions | Cyclingnews.com

https://road.cc/content/news/218799-...-broken-wheels
Remshaw was riding in next to Cav in the pack on a straight road and dropped into a huge whole.
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Old 01-09-19, 09:30 PM
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Originally Posted by redlude97 View Post
Yes, but generally with a carbon rim that level of cushioning is enough to protect the carbon which is susceptible to impact damage but deforms elastically. You'll snakebite but the rim will generally be fine. Carbon rims hardly ever need to be trued
​​​​​​Years ago I had a set of carbon hoops from a smaller wheel builder. They were too light for me, so I had to have them trued occasionally. Every time, which was rare, they would come back to perfectly 100% true. Because the rim never bent out of shape. It would take an impact and a spoke would unwind and the wheel wouldn't role properly, it was never the rim. Until "the" pothole.

I wish I could get a carbon brake rotor for the same reason, it would never be out of true.
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Old 01-10-19, 03:03 PM
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Originally Posted by Seattle Forrest View Post
​​​​​​Years ago I had a set of carbon hoops from a smaller wheel builder. They were too light for me, so I had to have them trued occasionally. Every time, which was rare, they would come back to perfectly 100% true. Because the rim never bent out of shape. It would take an impact and a spoke would unwind and the wheel wouldn't role properly, it was never the rim. Until "the" pothole.

I wish I could get a carbon brake rotor for the same reason, it would never be out of true.
I tried working with a group that is/was doing carbon rotors. At the end - just easier running good Shimano rotors. They will become more prevalent as the years go by though for sure.

Yeah - carbon doesn't "bend". Not sure why anyone is still discussing it. It stays...then breaks. those are the only options in essence.

When carbon wheels go out of true it's because something affected the tension balance in the spokes. This can happen, and most often happens, because the spokes weren't fully "relieved" during building allowing some residual ability to stretch under load or for the nipple orientation to change (stored wind-up).

In all wheels the spokes only are there to support the rim and allow it to do what it does based on it's strength and stiffness (mass and or area moment of inertia). When loads exceed the rims ability then the spokes try and take up the slack so to speak. If a carbon wheel moves around under the rider a lot it's because the rim is not adequately supported with the correct spoke count. The tension doesn't really do much. The thickness of the spokes don't really do much. It's the count and in turn the corresponding spacing along the rim, that will or will not support the rim adequately.

So when the loads exceed the rims ability to stand and there are not enough spokes to adequately support it then they take the brunt. It will either unload them, or slightly overload them. Spokes fail through fatigue. When you increase the load cycle you decrease the fatigue life. So in a properly built wheel - even when you exceed the limits of the rim you only really unload or overload the spokes. This shortens their lives. That's pretty much it. As long as the spoke hasn't gotten physically longer or shorter and the rim hasn't physically bent (as in alloy) then it will return that rim to the same relative position in space. Meaning it will remain true.

If I am explaining this well enough then it should be easier to see that the only way a carbon wheel can really come out of true is if it is overloaded in a way that causes the overall spoke length to change or if the spoke orientation changes (like being bent at the flange). Again this physically can only happen if during the building of the wheel the spokes were not subjected to enough of a load during "relieving". Relieving basically eliminates the spokes stretch through the load cycle it should see in use. it also aligns the spoke lines, sets the heads and nipples into the flanges and rims.....or in other words takes the slack out. If you truly do it well then the wheel in essence never moves through normal use even after a deflecting load. Just goes right back to where it's supposed to be.

Sorry for the long explanation and it's not really directed at you Seattle Forrest - you just supplied the story from which I could build the explanation. It's these things that even many in the world of wheel building don't actually truly understand. As a result there is a ton of misinformation and a lot of incorrect assumptions. If one can truly visualize what's happening through use on a wheel then they can really understand root causes of issues when they arise and fix things a heck of a lot quicker and permanently.
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Old 01-10-19, 09:52 PM
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Thanks for the excellent and detailed explanation. I'm sure I'm not the only one who appreciates it.
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Old 01-11-19, 09:58 AM
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Well, I hit another pot hole last night, which begs the question of why I'm hitting so many. Pot holes are not native to Atlanta but we seem to have an infestation. Anyway....

32 spoke aluminum 29'er wheels with 40 mm tubeless gravel tires at 35 PSI. This hole was deep and I thought the bottom bracket shell was going to hit. The tire compressed all the way on the lip at the exit of the hole and the rim definitely bottomed out, hard. I stopped the bike, took a deep breath and prepared myself mentally...

American Classic 29 Race wheels didn't even flinch. Took the hit like a minivan carries groceries.

So yeah, just felt like saying that.

@Psimet2001 , I also appreciate your explanation. It means a lot that you took the time to write that up.


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Old 01-11-19, 12:12 PM
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Cav's wheel folded nearly in half then bounced back.

Before and after pics here
https://www.telegraph.co.uk/sport/ot...itzerland.html

Video
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Old 01-11-19, 02:31 PM
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Originally Posted by TimothyH View Post
Well, I hit another pot hole last night, .

American Classic 29 Race wheels didn't even flinch.
I spoke too soon. Didn't see this last night in the dark and rode 16 miles including rough singletrack on this. It is going to Pro Wheel Builder to get the rim replaced next week.


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Old 01-11-19, 03:07 PM
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Originally Posted by TimothyH View Post
I spoke too soon. Didn't see this last night in the dark and rode 16 miles including rough singletrack on this. It is going to Pro Wheel Builder to get the rim replaced next week.


Wow...and no loss of pressure? Sorry about the rim. Good PSA for tubelessness though. Been mulling it over for a while...might get a tubeless wheelset to run GP5ks on during the summer, then tubeless CX tires in the winter.
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Old 01-12-19, 05:33 PM
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I guess we could say if you're not breaking your rim, you're not riding hard enough.
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Old 01-13-19, 12:40 PM
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Originally Posted by Psimet2001 View Post
in a word - yes. Alloy bends when it hits obstacles. There's really no fixing it. I do a lot of rim swaps for that reason. Doesn't happen with carbon. Really one of the big features in my world when in many cases the carbon and alloy rims are near same weight. I deal with a lot of racers and racers hit things - especially in cross. Carbon does way better.

That said when you exceed carbon it just breaks. Rest assured that the same impact would have destroyed an alloy wheel as well.
"There's really no fixing it."
Dented and flatspotted rims can frequently be repaired. It takes some time and the result is often not predictable. But it can be done. I've had several badly damaged "hopeless" rims that were fixed and went on to live long lives. Right now am riding a Fiamme Red with the standing pins that has to be at least 60 years old. It was in the trash can. Would not take a chance riding such a thing except I know I'm not taking a chance.

Most aluminum rims are made from second rate aluminum and the extrusions are not even accurate. Cut up a cracked alloy rim and see how wildly the wall thickness varies. Any who have worked with the old Mavic S.S.C. rims know how strong they are. My brother is riding one that was dented by falling machinery. I needed a six pound sledge hammer to move that rim back to shape. He's been riding it for years since then. The double heat treating process Mavic used was expensive and few have troubled to imitate that. Still way cheaper than fabbing carbon. Carbon rims are a fashion more than an engineering choice. Until more high quality aluminum rims are made we don't even know how strong they are. We know how alloy rims that are cheap to bring to market perform and that's about all we know.
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Old 01-14-19, 08:15 AM
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Originally Posted by 63rickert View Post
"There's really no fixing it."
Dented and flatspotted rims can frequently be repaired. It takes some time and the result is often not predictable. But it can be done. I've had several badly damaged "hopeless" rims that were fixed and went on to live long lives. Right now am riding a Fiamme Red with the standing pins that has to be at least 60 years old. It was in the trash can. Would not take a chance riding such a thing except I know I'm not taking a chance.

Most aluminum rims are made from second rate aluminum and the extrusions are not even accurate. Cut up a cracked alloy rim and see how wildly the wall thickness varies. Any who have worked with the old Mavic S.S.C. rims know how strong they are. My brother is riding one that was dented by falling machinery. I needed a six pound sledge hammer to move that rim back to shape. He's been riding it for years since then. The double heat treating process Mavic used was expensive and few have troubled to imitate that. Still way cheaper than fabbing carbon. Carbon rims are a fashion more than an engineering choice. Until more high quality aluminum rims are made we don't even know how strong they are. We know how alloy rims that are cheap to bring to market perform and that's about all we know.
I'm as much of a curmudgeon as many folks here, but I don't agree here. I haven't cut up aluminum rims, but I've noticed the recently made rims are more balanced than old ones, they are shaped more consistently, and they true up with greater tolerances than the old ones. Carbon rims haven't been around a long time, so it's too soon to say if we will still regard them well in the future. They are strong enough for racers, which is not to say they are perfect for general use. Price may keep them off commuter bikes but not necessarily durability and reliability. And for some background, I have never owned a carbon fiber frame or wheel.
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Old 01-14-19, 11:27 AM
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Originally Posted by 63rickert View Post
"There's really no fixing it."
Dented and flatspotted rims can frequently be repaired. It takes some time and the result is often not predictable. But it can be done. I've had several badly damaged "hopeless" rims that were fixed and went on to live long lives. Right now am riding a Fiamme Red with the standing pins that has to be at least 60 years old. It was in the trash can. Would not take a chance riding such a thing except I know I'm not taking a chance.

Most aluminum rims are made from second rate aluminum and the extrusions are not even accurate. Cut up a cracked alloy rim and see how wildly the wall thickness varies. Any who have worked with the old Mavic S.S.C. rims know how strong they are. My brother is riding one that was dented by falling machinery. I needed a six pound sledge hammer to move that rim back to shape. He's been riding it for years since then. The double heat treating process Mavic used was expensive and few have troubled to imitate that. Still way cheaper than fabbing carbon. Carbon rims are a fashion more than an engineering choice. Until more high quality aluminum rims are made we don't even know how strong they are. We know how alloy rims that are cheap to bring to market perform and that's about all we know.
Alas this is unilaterally incorrect but nostalgic for sure.

Indeed back in the days of wagon wheels, horseless carriages and 3M Fastack it was very common to pry and pound a rim back into shape.

Today the alloys have changed dramatically - even in the last 19 years. The extrusion consistency is nowhere near as off as you claim. In fact small variance in thickness have led to massive returns in multiple cases (Velocity Major Tom, Velocity A23, Pacenti SL23 off the top of my head). The rims we've used for the last 20+ years have performed amazingly well. The one thing these alloys don't like though is bending. Especially along the hook like what was posted in the picture a few posts back. Back in the day you'd put an adjustable wrench on it and bend it back. Today the rim will snap/crack where you bent it back. The heat trating used today far exceeds anything mavic did long ago in the past and if anything was most likely spearheaded by mavic.

You can get over your love of mavic. Back in the day they were great. Today there are a big company that is as lost as anyone else with massive declining sales. They bought ENVE a few years back for $50M. Roughly 10 years ago they purposely stopped supporting small independent builders by eliminating aftermarket sales of rims. They continued with the Open Pro though and some still built with it even though that rim's time was passed.

Top everything off with the fact that today most riders are riding with tubeless setups and it quickly becomes apparent that damage to the clincher hook or rim bed is not acceptable or "repairable" - less the tire fly off while riding.

I suggest you save your knowledge and experience and pass it on in the "Classic and Vintage" forum where it is still timely and of use.
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Old 01-14-19, 04:10 PM
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Originally Posted by Psimet2001 View Post
Alas this is unilaterally incorrect but nostalgic for sure.

Indeed back in the days of wagon wheels, horseless carriages and 3M Fastack it was very common to pry and pound a rim back into shape.

Today the alloys have changed dramatically - even in the last 19 years. The extrusion consistency is nowhere near as off as you claim. In fact small variance in thickness have led to massive returns in multiple cases (Velocity Major Tom, Velocity A23, Pacenti SL23 off the top of my head). The rims we've used for the last 20+ years have performed amazingly well. The one thing these alloys don't like though is bending. Especially along the hook like what was posted in the picture a few posts back. Back in the day you'd put an adjustable wrench on it and bend it back. Today the rim will snap/crack where you bent it back. The heat trating used today far exceeds anything mavic did long ago in the past and if anything was most likely spearheaded by mavic.

You can get over your love of mavic. Back in the day they were great. Today there are a big company that is as lost as anyone else with massive declining sales. They bought ENVE a few years back for $50M. Roughly 10 years ago they purposely stopped supporting small independent builders by eliminating aftermarket sales of rims. They continued with the Open Pro though and some still built with it even though that rim's time was passed.

Top everything off with the fact that today most riders are riding with tubeless setups and it quickly becomes apparent that damage to the clincher hook or rim bed is not acceptable or "repairable" - less the tire fly off while riding.

I suggest you save your knowledge and experience and pass it on in the "Classic and Vintage" forum where it is still timely and of use.

Having personally broken 4 Velocity rims, cut them, measured them, color me unimpressed. Mavic made one good rim. For that they get credit. Not love. Any who have ever worked with those rims know what I am talking about. If you haven't you don't.

Is anyone else heat treating rims after they are hooped? A few have, the performance of those rims was impressive. Heat treating extrusions before they are hooped is largely a waste. Manipulate that heat treated metal to a hoop and what's left? Were the heat treating as astounding as claimed the extrusions could not be hooped.

Pacenti makes good rims. Like them a lot.

Knowing something about old parts has purpose. You don't have to figuratively re-invent the wheel constantly. Or in this case not so figuratively. The industry behaves as if they and we were all born yesterday. They sell a born yesterday attitude which mechanics unfortunately adopt.

That rim that Cavendish collapsed in a video posted above bounced back. Gee whiz. It's in original geometric shape but it's delaminated. Unsafe and unusable. What happens when there is a less spectacular carbon rim failure and there is no video recording it, no audience replaying it to see what happened?
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Old 01-14-19, 04:38 PM
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Originally Posted by noglider View Post
I'm as much of a curmudgeon as many folks here, but I don't agree here. I haven't cut up aluminum rims, but I've noticed the recently made rims are more balanced than old ones, they are shaped more consistently, and they true up with greater tolerances than the old ones. Carbon rims haven't been around a long time, so it's too soon to say if we will still regard them well in the future. They are strong enough for racers, which is not to say they are perfect for general use. Price may keep them off commuter bikes but not necessarily durability and reliability. And for some background, I have never owned a carbon fiber frame or wheel.
I've noticed the same balance phenomena with H+Son, with Pacenti, with HED. And it's easy to get them very straight. Others not to be named, not so much. Am very hopeful the good rims will set a standard others have to meet. I could name a long list of vintage rims head and shoulders above prevailing standards, what they all have in common is there weren't many of them. Mavic S.S.C. is the best known by far and those were scarce. Remember when they were new racers would do crazy things to get to the head of the line and try to be top of food chain. Prices paid were 5 and 10 times what ordinary rims claimed. In rough service, like racing, they lasted at least five times longer than ordinary rims.

Carbon rims are a big part of why we are being herded towards disc brakes. I would not be one bit surprised if there are carbon rims that are next to immortal. Which ones though? Advertising claims and LBS scuttlebutt are no clue. Until discs are much much less hassle I am on rim brakes and there are no carbon rims for me.
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Old 01-17-19, 11:25 AM
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Originally Posted by Psimet2001 View Post
in a word - yes. Alloy bends when it hits obstacles. There's really no fixing it. I do a lot of rim swaps for that reason. Doesn't happen with carbon. Really one of the big features in my world when in many cases the carbon and alloy rims are near same weight. I deal with a lot of racers and racers hit things - especially in cross. Carbon does way better.

That said when you exceed carbon it just breaks. Rest assured that the same impact would have destroyed an alloy wheel as well.
I don't think the bolded portion is stated enough on here. People seem to forget this. I loved my aluminum CAADX I built up as the ultimate commuter/rando bike. Then I hit a gate that was half open. Frame was toast. Carbon would have for sure assploded, but the aluminum was damaged beyond repair as well.
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Old 01-17-19, 12:37 PM
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Originally Posted by 63rickert View Post
Carbon rims are a big part of why we are being herded towards disc brakes.
This is nonsense. Looking out my office window, I can see the reason for disc brakes. You're being "herded" toward them, meaning more bikes are becoming available with them, because people want them.
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Old 01-17-19, 03:12 PM
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Originally Posted by WalksOn2Wheels View Post
I don't think the bolded portion is stated enough on here. People seem to forget this. I loved my aluminum CAADX I built up as the ultimate commuter/rando bike. Then I hit a gate that was half open. Frame was toast. Carbon would have for sure assploded, but the aluminum was damaged beyond repair as well.
In today's reality carbon is fair more readily repairable as well (frames). There are many options for quick, accurate and effective carbon repair. Not so much with aluminum.

Originally Posted by Seattle Forrest View Post
This is nonsense. Looking out my office window, I can see the reason for disc brakes. You're being "herded" toward them, meaning more bikes are becoming available with them, because people want them.
Semi-agreed. The industry is heading that way. Sometimes because they want to reduce the complexity of parts variants and design needs. The lines between bike types are uses are starting to blur with the endurance/adventure/gravel/cross/road style bikes that can run 4 different dropouts and 2 or 3 wheel sizes and widths, etc. Some of it is just simply that the larger market is really geared towards mtb offerings and they are all disc. Some of it is also liability. Braking on carbon has been an issue of sorts since day one. It isn't arguably a major issue today like it once was but it's still an issue. Without rim brakes you are free to do a whole lot more with the rim design and the odds of failing are greatly reduced. Couple that with tubeless usage demands - disc.

What you're going to notice though is that none of those reasons is rider or customer driven. That bothers me a lot, but there's nothing I can actually do about it. That is also the reason so many riders are actually against it.

Just like how silver parts became black parts, became logo less parts, and are now silver parts again I feel that rim brake bikes will come back around at a point int eh future as people look for that old school, light and cool feeling ride. Roll your eyes but explain fixie culture.
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Old 01-19-19, 05:18 AM
  #46  
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Well thank you psimet. That is part of what I was thinking. But back to carbon wheels bouncing back.

For those who haven't watched the Cavendish video what it shows is the bottom third of his carbon wheel folding under. A big section of rim simply lays flat on the pavement. This makes Cav fall. When Cav's weight is no,longer on the wheel, the wheel snaps back into original shape. But of course once the glue bonds have broken the rim is now useless.

What is interesting to me is that this is precisely how sprinters used to fold aluminum rims. Except of course once folded the alloy rims stayed folded. And the alloy rims they once folded weighed perhaps 350 grams and were box shaped, 20mm wide and perhaps 12mm tall. When tall aero alloy rims came around that sort of foldover stopped happening. Tall triangles are stronger than small rectangles. But evidently what is issued to the big sprinters at TdF is no stronger than what track sprinters used fifty years ago. With identical failure mode.

In days of yore when a sprinter folded a rim the old racers would conference with him. Maybe a better wheel build was necessary. Or maybe that sprinter needed special sprinter parts. There was always a little world of special parts for those who broke things. What happens now? How do you even think through the problem when the first response to anything is a blizzard of marketing speak?
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Old 01-19-19, 09:03 AM
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Originally Posted by WalksOn2Wheels View Post
I don't think the bolded portion is stated enough on here. People seem to forget this. I loved my aluminum CAADX I built up as the ultimate commuter/rando bike. Then I hit a gate that was half open. Frame was toast. Carbon would have for sure assploded, but the aluminum was damaged beyond repair as well.
Interesting assumption on your part. I too hit a gate (closed in my case, at ~17 mph - long story) and my carbon frame was not toast. I rode it back home. It needs to be repaired but it certainly didn't assplode as you imagine it should have.
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Old 01-19-19, 09:05 AM
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Originally Posted by noglider View Post
Carbon rims haven't been around a long time, so it's too soon to say if we will still regard them well in the future. They are strong enough for racers, which is not to say they are perfect for general use. Price may keep them off commuter bikes but not necessarily durability and reliability. And for some background, I have never owned a carbon fiber frame or wheel.
This is much of BF encapsulated in a just a few sentences.
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Old 01-19-19, 09:05 AM
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Originally Posted by balut bandit View Post
Interesting assumption on your part. I too hit a gate (closed in my case, at ~17 mph - long story) and my carbon frame was not toast. I rode it back home. It needs to be repaired but it certainly didn't assplode as you imagine it should have.
I know this is crazy talk, but is it possible that he was referring to his crash specifically and not making sweeping generalizations about gate collisions in general?
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Old 01-19-19, 09:06 AM
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Originally Posted by Seattle Forrest View Post
This is nonsense. Looking out my office window, I can see the reason for disc brakes. You're being "herded" toward them, meaning more bikes are becoming available with them, because people want them.
Not to mention all of us who were choosing discs long before carbon rims were even contemplated or available.
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