How do I check to see if my frame is bent?
08-29-08, 08:51 PM
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How do I check to see if my frame is bent?
I recently had a crash that bent my front fork and rim. Other than just looking, is there some way to know if my frame is still ok? Maybe some where to check for a likely area of damage? I hit a large dog at about 25mph.
08-29-08, 10:02 PM
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I'd be looking at the underside of the top and down tubes, right behind the headtube. Damage will show up as cracked paint or a ripple in the tube. A frontal impact will not always throw a frame off side-to-side.
Here's an extreme example, taken from the Yellow Jersey site:
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08-29-08, 10:13 PM
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+1 on what Jeff said... You didn't mention what material your frame is made of. That can make a big difference on how obvious the damage will be to spot. If you have ANY doubts about its post-crash condition take it to a reputable shop.
What happened to you in the crash, by the way? How about Fido?
What happened to you in the crash, by the way? How about Fido?
08-30-08, 12:00 AM
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I hope you weren't trying to recreate what happened in two stages of the Tour de France last year.
08-30-08, 06:50 PM
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Look here under "Checking Alignment" for a method to check some things using a string wrapped around the headtube.
https://www.sheldonbrown.com/frame-spacing.html
https://www.sheldonbrown.com/frame-spacing.html
08-30-08, 07:35 PM
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try riding the bike without any hands...
08-31-08, 08:00 AM
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Thanks all. That Sheldon Brown article looks like what I'm looking for.
I ended up getting surgery for a broken collarbone. The (neighbor's) dog dissappeared for a day but has come back with psychological problems. He doesn't trust anyone.
I ended up getting surgery for a broken collarbone. The (neighbor's) dog dissappeared for a day but has come back with psychological problems. He doesn't trust anyone.
08-31-08, 11:24 AM
#9
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The string deal will work for the rear stays but to check the steering head tube you'll need to get a little more imaginative. I'm thinking two long builder's levels shimed so they sit level. Lay the seat tube on one using some packing with matching lift to set the seat tube parallel to the first level. Then use the second level at the head tube and measure to the lips on each end. They should match to within a fairly small tolerance. Flip it over and check again.
It would be even better if you could arrange a tube that sits locked into the bearings so you're checking the true steering axis but that would require some fancy playing around to make up jigging device to do the job.
For the head angle you'll want the frame geometry. Using a pendulum angle finder from a hardware store set the frame up so the seat tube angle matches the spec table for your frame. Then measure the head tube.
If the measurements match closely then you're fine. For the first test you're looking for a difference bigger than something like a 1/64 inch (.015 inches). For the angle if you're within 2 degrees you should be fine since those angle finders are just so-so to read from the small scale.
It would be even better if you could arrange a tube that sits locked into the bearings so you're checking the true steering axis but that would require some fancy playing around to make up jigging device to do the job.
For the head angle you'll want the frame geometry. Using a pendulum angle finder from a hardware store set the frame up so the seat tube angle matches the spec table for your frame. Then measure the head tube.
If the measurements match closely then you're fine. For the first test you're looking for a difference bigger than something like a 1/64 inch (.015 inches). For the angle if you're within 2 degrees you should be fine since those angle finders are just so-so to read from the small scale.
