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Paint crack or frame crack

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Paint crack or frame crack

Old 02-06-12, 04:03 AM
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Technology
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Paint crack or frame crack

Hi, My first post in BF.

I noticed a strange nerve developing in left fork end of my bike and it seems to grow. I can feel the little lump when touching. See the attached pictures.

Is this a paint or a frame crack?

Thanks.
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Old 02-06-12, 06:15 AM
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The only kind of paint I'm personally familiar with that would crack with that signature is laquer, which isn't commonly used on bikes anymore. But it also originates from a pressure relieve hole in the fork which would also be from where cracks in the fork material are likely to propagate so I would't dismiss it as just a paint crack either. Better to take it to a shop and gave someone look at it.
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Old 02-06-12, 07:19 AM
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Sand it, polish it and will be gone.

Steel bikes like that one don't crack that way And not in that area either
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Old 02-06-12, 09:33 AM
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The "crack" seems to continue over the vent hole in the blade which should be covered only with paint and with no metal under it. Clean the paint out of the hole and inspect the edges of the hole to see if the metal is cracked there. That should tell you if it's structural or just cosmetic.
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Old 02-06-12, 03:00 PM
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Is that a brazing vent hole covered up with pain on the left side of the pic??
If it is, the "tendril" you see that might be growing could be corrosion stating to get under the paint caused by moisture in the tube and going out the vent hole then between the paint and the steel.
Just my theory......

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Old 02-06-12, 04:10 PM
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Thanks for replying.

The "crack" appears to start from the welded drop-out which you can see on the left end of the image.I've made the marking with a random Google image. Check the attached.

Taking it to my LBS and get this "Certified" from the manufacturer will be my last resort.
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Old 02-06-12, 04:19 PM
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That looks like it started in the unfilled weld crater. It is a very poor weld. I would talk to the manufacturer or shop about it.
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Old 02-06-12, 05:42 PM
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Originally Posted by Technology View Post
Hi, My first post in BF.

I noticed a strange nerve developing in left fork end of my bike and it seems to grow. I can feel the little lump when touching. See the attached pictures.

Is this a paint or a frame crack?

Thanks.
It looks more like a paint run than a crack. It also looks like it propagated under the paint which suggests water or solvent forced out of the weep hole during drying and it moved under the paint. Hillrider's suggestion is probably the least damaging of many alternatives to investigating the problem.
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Old 02-07-12, 01:15 AM
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Originally Posted by davidad View Post
That looks like it started in the unfilled weld crater. It is a very poor weld. I would talk to the manufacturer or shop about it.
I agree. It's a sloppy weld, and the "tendril" is probably a thermal crack in the fork blade rather than corrosion. The DO may have been forced too tightly into the blade prior to welding or the blade may have been defective to begin with. You'll need to sand the paint down to bare metal and inspect the metal itself. Does the fork have an open weep hole, or was it filled in with brazing metal?
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Old 02-07-12, 11:56 AM
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Go to an automotive machine shop and have them magnaflux it.It will show a crack through the paint.Cost you about $10.Takes all of the guessing fun out of it though.....

If you have access to a compressor,pressurize the fork blade through the vent hole and squirt soapy water on the "crack" and see if it leaks.

No need to screw up the paint yet......
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