Road Bike, Cycling Forums banner

1 - 20 of 62 Posts

·
Registered
Joined
·
103 Posts
Discussion Starter · #1 ·
So I crashed my bike and cracked the frame (top tube). At first I thought it was superficial/paint, but I was suspicious it may be more and that was confirmed by the store. Two actually. They specifically said that although the carbon fiber was cracked it was only a couple layers and wasn't broken all the way through. The crack is mid-top tube, about a half a centimeter wide and 2 centimeters long, or at least that's the size of it that I can see.

Now I know the official answer is that I shouldn't ride it (and that's the bike shop's stance), but I'm wondering what others' thoughts are. How much force/weight is really transmitted across the top tube anyway? Does it matter that the crack isn't the full thickness of the tubing? I already rode the bike home, about 10 miles at 20+ mph, after the crash and crack occurred (no cell phone service) with no problems.

I intend to replace it eventually but would rather wait till I can afford to spend more on a quality frame than spend what is still a decent amount on a frame I don't love. Yeah yeah yeah don't ride a bike you can't afford to replace. Shut it.

So assuming no races or sprinting or anything too crazy, would you ride it?
 

·
Adorable Furry Hombre
Joined
·
30,793 Posts
Time to get a new bike. Or make sure you have a great insurance policy.
 

·
'brifter' is f'ing stupid
Joined
·
15,446 Posts
just for starters, there is NO way any one...shop employee or otherwise, can tell you whether your frame is cracked to the point of being unsafe to ride or not by looking at it. the ONLY way to do this is to cut it open and look. that being said...it's not a good idea to ride it, especially if it feels 'soft' when you push on it. but it's your call...good luck.
 

·
Sucker for carbon
Joined
·
266 Posts
bds3 said:
How much force/weight is really transmitted across the top tube anyway?
The top tube experiences a lot of force actually. Especially while braking hard, going over potholes, and in-the-saddle pedaling. I'll leave it up to you decide if you want to keep riding it.
 

·
Registered
Joined
·
469 Posts
Did you buy it new (warranty?) Otherwise get it repaired profesionaly and ride it ,or repair it yourself at home for materials cost, till you ditch it for something else. Is the damage where the Handlebars would swing around and hit it ?
 

·
Registered
Joined
·
2,078 Posts
wim said:
The middle of the top tube isn't stressed very much at all, which is why it's so thin there and cracks easily. Being a cheapskate and having some boat-building experience, I'd repair it with fiberglass and resin. Here's how: http://www.sheldonbrown.com/rinard/carbonqa.htm
+1

When butted tubes are drawn the center is also the thinnest point of the tube as it is also the least stressed.
 

·
Registered
Joined
·
2,597 Posts
I for one would love to see some pictures of the bike. Sure, there is no way to tell if the frame will hold other than the xray machine. Where's the pics?
 

·
Registered
Joined
·
11,474 Posts
Hooben said:
I for one would love to see some pictures of the bike. Sure, there is no way to tell if the frame will hold other than the xray machine. Where's the pics?
With the area fiberglass + resin reinforced, it doesn't matter. No need for complicated diagnostic procedures with an unloved frame soon to be disposed of anyway. Just bandage and ride.
 

·
Registered
Joined
·
610 Posts
What will the company do to determine if there is actually a crack when it cannot be determined if it's a crack or a blemish under the clearcoat? Let's say there's a line running out from under the clamp and it hasn't changed for about 800 miles (no movement or growth of the line). Could be a scratch under the clearcoat or could be a crack from too much torque on the clamp. How can this be determined?
 

·
Registered
Joined
·
5,613 Posts
it's a bad idea to ride a frame you know is compromised and no one on a forum can provide any general recommendation worth following sight unseen. Crashes happen - the best option is to have a back up frame you can stick the parts on while you either replace or repair the frame. Lots around for cheap on ebay, pricepoint etc.
 

·
Registered
Joined
·
16 Posts
I had a gash in a seat stay after a crash. I did some research and was going to send it to Calfee for repair. That was going to run me about $400. With shipping and bike dismantling, the total would have been closer to $700 with 4-6 weeks of wait time. Still cheaper than $2500 for a new frame.

I took some time to look around at CF fabrication sites and other industries that use CF. Think of it this way, airplanes and speedboats use CF. If they get a break, they fix it. If they had to buy a new boat or airplane every time it got a rupture in the fabric, then that would be pretty stupid. I talked to a fabricator and got some good advise as well as some nice CF weave (12K) and industrial quality epoxy resin from a small shop.

When I scarfed the gouge I was able to get to smooth CF without going very deep. I put on two layers of the repair weave with three layers of epoxy resin (there are youtube videos on how to do it). I let it set up for 48 hours, sanded it to match the existing tube and then did a clear coat and light buffing with polishing compound. Over the period of one weekend the seat stay is like new and looks like a lot of the shots I see from Calfee. There is nothing magic here - it is like repairing fiberglass. That said, if the gouge had cut all the way through, there might be an alignment issue, but it could still be repaired, it would just take a bit more time and the need to put a block in the hollow part of the tube.

I've put 200 miles on the bike since then and it is fine.

One word of caution. Don't use superglue or some other sealant to fix this. You need to use epoxy resin after prepping the crack. The resin will form a permanent bond. Everythign else will eventually deteriorate. You do not want to get water or contaminants in the CF - it will degrade and then you'll have real trouble.

Just to clarify,most people talk about a ding in the clear coat, but remember that clear coat is like a coat of paint. If you see a ding that is more than the thickness of saran wrap, you've chipped the resin.

I felt comfortable doing this, since I am mechanical and have done some fiberglass work in the past. If I can get a link set up I'll post a before and after shot. I really like my bike, so I figured I'd give it a shot and could always send it out if I failed. It cost me about 4 hours of total work over 3 days and $45.
 

·
Registered
Joined
·
78 Posts
I crashed my carbon frame 2 years ago, as someone else mentioned its typically cheaper to fix the frame then replace it. Yes, fixing it isn't cheap but still cheaper and as someone else mentioned when carbon cracks it cracks - no warning, better to be safe then sorry in my opinion. I went through RR Velo, not as popular as Calfee but over 5,000 miles later I have complete confidence in it - most people can't see where it was repaired.
 

·
Registered
Joined
·
7,290 Posts
DO NOT RIDE IT!!!!! It could fail suddenly without warning causing harm to you.

Depending on the value of the bike, you can either replace just the frame and transfer your components to it, or have the folks a Calfee examine it to see if it can be fixed and for how much if it's an expensive frame to replace; see: http://www.calfeedesign.com/howtosendrepair.htm There is a $50 exam fee plus the cost of shipping. This is the only place for the time being that has had extensive and successful repairs with CF.

Home repairs can be especially dangerous unless you have extensive knowledge about CF repair. Riding it repaired by yourself could end up with a sudden collapse of the frame hurting you or worse.
 

·
Rub it............
Joined
·
3,833 Posts
latman said:
Did you buy it new (warranty?)

There is no warranty on crashed stuff. Why does everyone automatically say warranty with broken stuff due to a crash?:mad2:

Thats like taking your car to the dealer for warranty after you hit a brick wall. They will just point and laugh at you.


You have a couple of options.

1. Send it out for repair. Either Calfee or RRVelo

2. Contact your LBS and ask about a crash replacement frame. It will be offered at a reduced price.

3. Ride it till it breaks - not recommended and strongly advise against it, but you are an adult - a stupid one if going this route and I hope natural selection comes into play if you go this route - hope you have good insurance.
 

·
Registered
Joined
·
21,544 Posts
Tap test

Weav said:
What will the company do to determine if there is actually a crack when it cannot be determined if it's a crack or a blemish under the clearcoat? Let's say there's a line running out from under the clamp and it hasn't changed for about 800 miles (no movement or growth of the line). Could be a scratch under the clearcoat or could be a crack from too much torque on the clamp. How can this be determined?
One good way to do this is to tap the affected area with a coin or small metal tool. If the sound of the tapping doesn't change as you work your way back and forth across the "crack" then it probably is just a paint crack. A sound change suggests partial failure in the layered structure. Another obvious test is to press firmly on the area and see if it deflects more easily than the rest of that tube. If yes, then you have more serious damage.

As others have noted, the repair is not that hard, though getting a professional look is a lot more challenging. Considering the value of a cracked frame, you have nothing to lose by attempting a repair. The upside is very favorable.
 

·
Registered
Joined
·
1,186 Posts
bds3 said:
So I crashed my bike and cracked the frame (top tube). At first I thought it was superficial/paint, but I was suspicious it may be more and that was confirmed by the store. Two actually. They specifically said that although the carbon fiber was cracked it was only a couple layers and wasn't broken all the way through. The crack is mid-top tube, about a half a centimeter wide and 2 centimeters long, or at least that's the size of it that I can see.

Now I know the official answer is that I shouldn't ride it (and that's the bike shop's stance), but I'm wondering what others' thoughts are. How much force/weight is really transmitted across the top tube anyway? Does it matter that the crack isn't the full thickness of the tubing? I already rode the bike home, about 10 miles at 20+ mph, after the crash and crack occurred (no cell phone service) with no problems.

I intend to replace it eventually but would rather wait till I can afford to spend more on a quality frame than spend what is still a decent amount on a frame I don't love. Yeah yeah yeah don't ride a bike you can't afford to replace. Shut it.

So assuming no races or sprinting or anything too crazy, would you ride it?
I normally do not chime in on posts not related to us
BUT THIS ONE SCREAMS OUT FOR RESPONE

DO NOT RIDE THE FRAME; that is my advise

If you can not afford to replace a CF frame that you damage; try a metal frame. With AL, Steel, or Ti it is much more clear if your frame is safe after an impact
 
1 - 20 of 62 Posts
Top