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No it's not normal to crack the seatstays in fairly minor crashes. The pic below is from my Hightower LT tumbling down Windrock. It looks bad but structurally fine. If you're talking about two bikes
of the same brand/model then I think that's more likely the cause than the material. Some bikes are built more stout (and heavier) than others.
View attachment 1910425

That does not look fine. It looks like there has been some gauging into the carbon. If this is so then you should get it repaired. The good news is that carbon is easy to repair.
 

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Discussion Starter #26
Yep exactly. I would have words with the manufacturer. Sounds like it’s a weakness in the frame in the same spot.

I would definitely change brands.
Well, I wouldn't necessarily say I'm non-aggressive. :LOL: I'm pretty hard on stuff. I rode about 8,000 miles this past year on those 2 bikes around Colorado and Utah.

Working with the manufacturer, but the shop doesn't think it's likely since it was crash damage. The first bike I was able to replace the rear seat stay portion only and the bike has been fine since (other than destroying the crank-also carbon- but that is another thread!!) And yeah, finding a new bike or frame in this market is going to be tough!!
 

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To the OP. Some brands are stronger than others. Its sounds like a time for a change of brand is required. Post up some pictures of the failures and we can inspect and give an indication of what went wrong.

What type of carbon bike is it? Is it a no expense spared super light xc racer or is it trail/enduro?

If super light xc racer then you need to accept that its build for a fast time not a long time. There are carbon bikes all the way along the spectrum from super light to super strong.
 

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Discussion Starter #28
Carbon has two weaknesses. Abrasives and sharp rocks. Unless you're riding on sandpaper, you don't have to worry much about the first (fun fact, you can hand sand a carbon steerer tube down in no time). The second...roll of the dice. Carbon usually does okay. Usually.
Yeah, lots of rocks where I live. I think I have perfected the "bail crash" where I lean the bike down and skid out. Good for me, not good for the bike. The crashes with both bikes where I'm pretty sure the damage occurred was the same type of crash, a big side slide. Probably the frame made contact with the perfect rock at the perfect spot.
 

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Discussion Starter #29
To the OP. Some brands are stronger than others. Its sounds like a time for a change of brand is required. Post up some pictures of the failures and we can inspect and give an indication of what went wrong.

What type of carbon bike is it? Is it a no expense spared super light xc racer or is it trail/enduro?

If super light xc racer then you need to accept that its build for a fast time not a long time. There are carbon bikes all the way along the spectrum from super light to super strong.
Yep, both were purchased through a race team with the purpose of racing. One a 100mm travel all the specials rocket, the recent one was my 120mm trail bike but still quite light. I had been using it for burly Colorado bikepacking trips and also my Moab fun bike. My plan is to revive it and use it for the CTR next year going for a fast time. We'll see.
 

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Discussion Starter #30
So...you only have one black bike left? Can we get a name change over here?

sorry for your loss
:alien:
LOL. Yeah, old name from a long time ago. All 3 of those bikes are long gone, I've been digging colors recently, though I do have 1 black bike still. Black/Blue/Purple/OrangeBikes doesn't exactly roll off the tongue though. :p:LOL:
 

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Yep, both were purchased through a race team with the purpose of racing. One a 100mm travel all the specials rocket, the recent one was my 120mm trail bike but still quite light. I had been using it for burly Colorado bikepacking trips and also my Moab fun bike. My plan is to revive it and use it for the CTR next year going for a fast time. We'll see.
With the milage and racing that you are doing it probably equates to 3 to 4 years worth of riding for an average person. You probably have to accept that if you keep this level of racing and riding up you are going to blow through gear on a regular basis.

If the bikes are super light then they are optimized for performance not longevity. You can't have both. Add some weight and get a stronger frame. It will last longer. But you will loose some performance.
 

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Time to get a titanium frame...
Um...perhaps you should google titanium frame and "crack"...Ti tends to crack a lot, since the welds are so difficult to do properly and it's a brittle material.
 

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Um...perhaps you should google titanium frame and "crack"...Ti tends to crack a lot, since the welds are so difficult to do properly and it's a brittle material.
Hmmm... not arguing here 'cuz I'm no metallurgist. But I always thought ti was comparatively elastic.

That said, I do understand the challenges of welding it. But if the welding is done to perfection? Please enlighten me, Jayem. Thx
=sParty
 

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You can't say for sure if that carbon is structurally sound unless you X-Ray it.

The problem with carbon is not that it fails suddenly without warning, it doesn't. The problem is that, lots of times, you can't see the damage without specialized means, and carbon can fail in a multitude of ways that can't be seen wothout specialized equipment: delamination can be internal, bad epoxy, bubbles under the surface... most frames don't have significant defects from the factory, but can develop them after impacts.

And impacts happen everyday on a mountain bike without even having to fall: your tire can throw rocks at various parts of the frame, for example.

That doesn't usually happen with aluminium. You can easily see if it's dented or cracking if you bother inspect the frame. Moreover, dents don't make the frame fail suddenly if they're small. Most of the time they'll be fine, and when they're not, they'll probably develop a crack that grows slowly.

Most sudden failures on aluminium frame happen at welds because of welding defects, but that's quite unusual, and most of the times you can see the crack grow before failure anyway.
Realistically, no one is going to catch a corrosion pit or weld flaw usually until too late either, where the crack progresses with each fatigue cycle and where there's eventually a more catastrophic failure as the part can no longer support the load. Sometimes people catch it before failure, but it's not really all that different. Delamination can often be seen and can be tested for with tap-test, yes, not perfect by any means, but people aren't going over aluminum frames every day to look at each weld and depending on the mode of failure, it may not be readily apparent in an alloy frame until the damage is much further along.

What CF is awesome for is repairing. If it's a non-complex shape, like the middle of a tube, the repair is pretty simple. Messy, but pretty simple to do. If it's a more complicated part involving bonding, there are still several places that will fix it, but in general, it's still easier to fix than aluminum, which requires very delicate welds and then heat-treatment. In both cases, re-painting, although you'll probably get away with less re-painting with the CF frame, due to not having to remove the paint and heat treat the entire frame.
 
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Hmmm... not arguing here 'cuz I'm no metallurgist. But I always thought ti was comparatively elastic.

That said, I do understand the challenges of welding it. But if the welding is done to perfection? Please enlighten me, Jayem. Thx
=sParty
Ti is brittle, it has a great fatigue life if it can be kept within it's limits, but it's extremely difficult to weld correctly. While there are lots of really nice Ti frames, you'll also see with a few searches that Ti cracks are a pretty significant thing. Far more than Alu in my opinion, just based on the number of hits.
 

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I cracked the seat-stay on my carbon RFX accidentally with a rake (think: leverage) during trailwork. I repaired it. I've ridden and raced it hard since.
013b2bf2dc8d2aa4934b511e12d9326e9121ffc771.jpg
 

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Ti is brittle, it has a great fatigue life if it can be kept within it's limits, but it's extremely difficult to weld correctly. While there are lots of really nice Ti frames, you'll also see with a few searches that Ti cracks are a pretty significant thing. Far more than Alu in my opinion, just based on the number of hits.
I agree -- I've had several friends over the years with ti frames that have cracked. But I was often unsure if the failures were due to inadequate wall thickness at the point of failure, bad welds, or exactly what. That's why my question included the words, "...if the welding was done to perfection..."
=sParty
 

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I agree -- I've had several friends over the years with ti frames that have cracked. But I was often unsure if the failures were due to inadequate wall thickness at the point of failure, bad welds, or exactly what. That's why my question included the words, "...if the welding was done to perfection..."
=sParty
Welding seems to be the issue:

The techniques and equipment used in welding titanium are similar to those required for other high-performance materials, such as stainless steels or nickel-base alloys. Titanium, however, demands greater attention to cleanliness and to the use of auxiliary inert gas shielding than these materials. Molten titanium weld metal must be totally protected from contamination by air. Also, hot heat-affected zones and root side of titanium welds must be shielded until temperatures drop below 800°F (427°C).
This is done AFAIK by using an inert gas during the welding process...but gas is gas and it's not going to completely fill an area unless that area is completely sealed off. This is what makes it so challenging. Most welding processes AFAIK basically "spray" the inert gas at the same time, but it's difficult to do this right and maintain no contamination.
 

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seems like Guerrilla Gravity has a good thing going on with their carbon frames. at the moment, if I wanted to buy a carbon fiber frame (I don't, but hypothetically), it's one of the few I would trust.
I own a Revved GG Shred Dogg. The Revved carbon is thiiiiiiiick! I cannot see many scenarios that you will crack this frame. Now I’m not saying it’s indestructible or impervious to damage, but just the frame weighs 6.5 pounds NO shock. My other carbon frame is 5.4 pounds WITH shock.
Keep in mind the GG uses alloy rear triangle. Revved carbon bikes are not for “bike weight” conscience riders. GG was known for overbuilt alloy models, they are doing the same with their carbon.
 
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