Worried I damaged my fork fitting crown race

Question

I'm an idiot. I've been working on building up a Surly LHT frame and was all going fine until I got to fitting the crown race.

I couldn't get it to fit properly and instead of making a cup of tea and watching some how-to videos like I normally would, I fitted a metal pipe on the crown and a bit of PVC pipe above that and rested the forks on some carpet and smacked the pipe really hard with a metal bar. When I stopped I'd gone through the carpet and put a small (1mm) dent in the bottom of one of the dropouts (not deformed them). After that I went to my LBS and they milled the fork down a bit and fitted the race.

I've inspected the fork really carefully - no visible damage or bending. Is there any chance hitting it that hard could have damaged it somehow? I just don't know enough about steel as a material.

Answer 1

Nobody is going to be able to tell you 100% that its integrity hasn't been compromised from this. Steel can fatigue, brazed dropout joints are strong but not infinitely strong, etc. We all know it's a tough dropout and in all likelihood it's totally fine. But there's always a level of distant hypothetical risk that gets created when things like this happen to bike parts, and nobody can tell you just how distant.

Were a slightly more developed guess to be made, the first steps in getting there would be check dropout alignment (with dropout alignment tools), check the size and parallelism of the dropout slot with a caliper, and ideally check the fork alignment. The detail that's lost in time here, especially from an outside perspective, is exactly how hard it got hit.

Answer 2

I am not a framebuilder but I seriously doubt you did any damage. The main type of failure of a fork is that the fork tangs pull away from the fork crown. You can look for wrinkling in the paint around the fork crown - if there it would run parallel to the floor and/or shoreline of the fork crown shoreline(s). This would indicate some compression damage to the fork blades.

Steel forks are unbelievably over-engineered, which is why they weigh ~850 grams (see : http://www.ece.ubc.ca/~gillies/raleigh/weights.txt for my fork weights) unlike carbon forks which weigh 300-500 grams, I wouldn't worry.

I have bent the same steel fork 3 times in head-on collision(s) but that fork never broke (however on the 3rd bending I purchased a new chromed fork to replace it since the original fork was clearly getting used to the bending and might crack or snap the next time I bent it).

Most of the time steel fails in a very slow-motion way over a number of miles of riding and will do things (like make weird noises or start to pull to on side or another) to let you know that a stress crack is growing. Carbon and Aluminum tend to fail in really catastrophic ways with no warning, which is why Steel is still an extremely popular material for bicycle frames.

Answer 3

OK just an update. In the end I decided to take the hit and get a new fork. Just didn't seem worth the worry not too. It's a lesson learned and part of getting to know more about my bike.

When the new fork arrived it came with a manual which specifically said not to to hit the fork when resting it on the floor. I think the chance of damage is very slight, but still, it's there.

From now on I only gently tap stuff on my bike and make sure it's very well suspended from sharp impacts.