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Frame crack...give it to me straight doc

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,099
6,036
borcester rhymes
My frame is cracked. On the outside not the inside. I took the fork out and confirmed the crack does not go all the way through. It appears to be in the epoxy top coat only, but I can feel it with my fingernail. There is a ton of carbon on the inside of where the crack is. I believe it happened when I was assembling the bike by whacking it with a wrench, but I'm not sure. Doesn't appear to be any other evidence of an impact.

Sand it and see how deep it is?
Leave it and keep an eye on it?
Replace it with another main frame?



 

Kiwintas

Chimp
Oct 22, 2018
93
56
If you like the bike and want to keep riding it, find someone who does carbon repair.
Had a similar crack in my carbon Rocky Mountain. Found a guy who fixed carbon road bikes and row boats. He fixed the crack and repainted it.
Have risen that bike hard for the last 18-24 months and it’s still going strong.
If you are going to go this way make sure you use someone good to do the repair work.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,099
6,036
borcester rhymes
Is there any warranty on the frame?
Zero, it's an eBay special but it was wicked cheap. When it's gone, it's gone, but that will be ok

Oh that's right!

I forgot you bought a BMC, a name synonymous with high performance mountain bikes, respected for their MTB specific investments across decades.

How's that working out?
Hey I got it for one tenth retail expecting it to crack at some point, just not under my feeble ridership
 

Jm_

sled dog's bollocks
Jan 14, 2002
19,031
9,687
AK
I'd leave it and keep an eye on it. Paint over the crack with clear nail polish to see if it is spreading over time.
Um...I'd just use a silver permanent marker to make a dot at the end of the cracks.


Sand that bitch down and re-carbon it.
 

Westy

the teste
Nov 22, 2002
54,511
20,310
Sleazattle
Cracks fail in tension, just make sure that part of the frame is in compression by wrapping it with rubber bands, hose clamps and electrical tape.





You could also drill holes on either side of it and thread some zip ties in there real tight.
 

Udi

RM Chief Ornithologist
Mar 14, 2005
4,915
1,200
For a BMC, the go-to brand that every mountainbiker associates with the most extreme riding demands.
Could be worse, at least he didn't get a Transition...

The only thing worse than being a punter brand is actually associating yourself with "extreme riding demands" then making frames that break repeatedly and consistently under said demands.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,099
6,036
borcester rhymes
mmm thanks for the help, about exactly what I expected...snark from kidwoo, something about zip ties, and a few helpful answers

I sanded down the crack with a little emory cloth last night. I can't get all the way through as the clear coat is incredibly fucking thick...there's like 2mm of clearcoat to get through before hitting carbon. I wasn't able to clear the crack, but I can shine my flashlight parallel to it and see that it's pretty clearly not to the carbon, just the candy shell. The clear coat is pretty weak on the frame, having put a few dings in it simply building the fucker up. Either way, i put a bid on the replacement mainframe for peace of mind and to help with resale value if I ever try to move it. Seems like it wouldn't hurt to have a few replacements hanging around.

As far as replacements, I have my eye on an Orange, because why would I ride anything normal?
 

dan-o

Turbo Monkey
Jun 30, 2004
6,499
2,805
When I’m looking for a bike that cracks I stick with brands with MTB street cred. Turners, Pivots, Evils and the like. They’re meant to be ridden hard so cracks are a badge of honor.
 
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Sandwich

Pig my fish!
Staff member
May 23, 2002
21,099
6,036
borcester rhymes
all this talk about cracks and nobody has suggested a yeti? yeesh come on people

I bought the replacement mainframe. I'll keep an eye on the crack and seal it with a little clearcoat. If it gets worse I'll swap frames. Or just sell the whole lot and buy a Cannondale
 

Toshi

Harbinger of Doom
Oct 23, 2001
38,420
7,804
When I’m looking for a bike that cracks I stick with brands with MTB street cred. Turners, Pivots, Evils and the like. They’re meant to be ridden hard so cracks are a badge of honor.
I’m proud of my crack!




Wait, that doesn’t sound right on a few levels there.
 

toodles

ridiculously corgi proportioned
Aug 24, 2004
5,533
4,805
Australia
When I’m looking for a bike that cracks I stick with brands with MTB street cred. Turners, Pivots, Evils and the like. They’re meant to be ridden hard so cracks are a badge of honor.
Geez you forgot Intense.

all this talk about cracks and nobody has suggested a yeti? yeesh come on people
In my experience, Yetis don't crack. Its more of a snap or explosion.

We should have started a thread on what bike you'd ride if the goal was to break it as soon as possible.
 

toodles

ridiculously corgi proportioned
Aug 24, 2004
5,533
4,805
Australia
gary fisher. those sugars were cracktacular!
I had one buddy break FIVE Giant Anthems. FIVE. All warrantied.

I've personally broken Mongoose, Norco, Turner, Transition and Avanti frames. And bent one chromoly Giant BMX. One day I'll learn to bend my knees when I land.