rosefarts

I'm probably going to get a new bike this winter. Primarily to get substantial weight savings and for a smoother/faster bike.

I did a gravel race yesterday that had a massive (miles long) descent through washboards. I love that stuff and do very well at it. For guys in my class (slow), nobody beats me downhill.

It's a lot of fast riding and hard hits. I have all the confidence in the world on my steel frame and steel fork old ass bike. It makes me wonder about a new carbon everything bike and longevity. To be sure, nearly everyone else in the field had a carbon everything bike, and there weren't any failures yesterday.

But what about a bunch of rides like that every year, for several years. I don't want to buy a new frame or fork every season or two. I especially don't want to deal with the crash that tells me I need a new frame or fork.

TLDR, carbon everything, fast bumpy descents, longevity?

terrymorse 

Carbon is stronger and longer lasting than steel or aluminum.

Carbon's weak spot: it doesn't like to be smacked with hard objects or have its tubing crushed.

HarborBandS

Exactly.

Or another way to put it is that carbon fiber doesn't weaken due to fatigue cycles like steel and aluminum. But it does not do well with impacts or crushing that permanently break the adhesion of the fibers to one another.

rosefarts

I've had entire rides where I hear my frame getting pelted by shale from below. It's a major concern for a carbon upgrade actually. Do manufactures lay it on thicker on the underside?

Define stronger? Tensile? cycles to failure? I could see it's compliance potentially increasing longevity.


Another little thing that's been bugging me. I have a steel fork with rim brakes. Think about where the forces would come from and how that would load the fork (barely at all). Now think about discs, it clamps, quite hard at nearly the end of the fork applying a much higher load (something like shear but not quite) at the smaller part of the blades. I know everyone does it and I haven't heard of failures or recalls, so it's probably fine. Just another thing in my mind.

mstateglfr 

1- get some clear protective tape and cover the underside of the downtube if you are concerned about rocks hitting the frame. Add it to the stays and fork too, if that helps you sleep better.
2- disc brakes do transmit a lot more twisting force to a point far from the flucrum(up at the head tube). The twisting is on one side of the fork too, vs evenly distributed. But this is designed for with steel and carbon forks(i assume aluminum too). Steel forks are typically thicker on the left blade to compensate for the twisting force. Carbon forks are designed sometimes with more material, sometimes different material layup, and sometimes both.

redlude97

My carbon cyclocross bike has probably been crashed a hundred times by now. They are a lot tougher than people make them out to be.

chas58

Carbon is fine. Like I say, I have a 30 year old carbon mountain bike I ride the crap out of. It flew off my car at 80mph about 10 years ago. Destroyed the aluminum fork (no front wheel on it) and rear wheel, but the frame is fine.

Carbon does not like abrasion (i.e. trunk bike rack) or sharp point loads (carbon forks loses in a sword fight to steel forks), but its pretty tough.

Steel is good (in some eyes) because it can be repaired.

Mountain bikers have all kinds of tape to prevent it from getting chipped in high abrasion areas...

as for front forks - they all used to be J curved. With disks they are all (mostly) straight blades. You are right, the torque (and lever arm) is much different with disks.

chas58

Some tape info:

Pinkbike: 7 Protective Frame Tapes Ridden & Rated

Canker

https://www.amazon.com/3M-Scotch-Tape/dp/B0772YNDF4
and for areas that really take a heavy beating

grolby

Frame protectors will prevent damage to the paint. You don’t need to worry about thrown gravel causing more than cosmetic damage to your frame. It’s designed to take it.

ab_antiquo

This is simply not true.

p.s. Also, carbon-composite is used to make great baseball bats.

OP doesn't need to worry.

Seattle Forrest

The descent from Loup Loop Pass was 15 or 20 miles. Steep in places. I hit washboards at speed, could barely see until I slowed down. I do stuff like this a lot. I'm probably jinxing myself here, but never a problem from the carbon. Same thing with disc brakes, a clear improvement. I bet I weigh more than you.

Koyote

It's 2019. I think we need to get over the asploding cf myths.

rosefarts

I'm not talking myths. I rode American Classic tubulars a full 10 years before carbon took over. Even my steel road road bike has a China bomb fork on it that I'm completely confident in over 50mph.

You should see the carbon fiber surgical equipment I deal with daily. Smacked around with hammers, repeatedly sterilized, and abused by staff. It doesn't wear out.

The question was simply one of longevity. I like buying nice stuff but I don't want to do it often. This has helped confirm what I pretty much already knew.

Fwiw, the only carbon failure I had was a fork came unbonded from a steerer tube that was aluminum. I probably could have epoxied it back in and been fine but I made a lamp out of it.

The only frames I've seen broken were Al but were wrecked. Probably a function of how common aluminum was when I was racing.

Flip Flop Rider

hmm, now I'm thinking about buying a carbon bike seriously