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I had a little spill after stupidly riding in the dark through a park (my light had just broke the same day), and I didn't have enough time to react, leading to a head on collision at about 27km/h with a small wooden post - I ended up ok, but my bike had some noticable problems like the brakes being in the wrong places afterwards. Ok, no problem, easily readjusted with my trusty allen keys. But then I noticed that my front fork had seemingly been bent backwards.

Before : http://i.imgur.com/NkpbNGO.jpg After : http://i.imgur.com/uxieZAz.jpg

Noticable that the front tire has been bent back - anything I can do about this, or is this a case for a mechanic?

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Did a little Googling and found out that this is a steel fork which is good because steel can often be bent back to its original position without compromising the integrity of the component, unlike aluminium which is usually trash once it has been bent. And of course, carbon can't be bent. Yours looks pretty bent though. So its hard to say if it would be a good idea to try this. –  Kibbee Feb 24 '13 at 13:26
    
I knew a guy who ran into a parked car (in broad daylight!) and similarly bent his fork. The tire didn't quite touch the downtube (a few mm clearance). He rode it like that for months -- dunno what he eventually did. –  Daniel R Hicks Feb 24 '13 at 13:54
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I find it amazing how often you'll see accidents like this where the fork is bent out of shape but the front wheel is pretty much unharmed. –  Kibbee Feb 24 '13 at 14:46
    
@Kibbee - Yep, the standard spoked bike wheel is remarkably strong. –  Daniel R Hicks Feb 25 '13 at 0:26
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4 Answers

I had a somewhat similar accident this summer, and the steerer of my fork was bent and I assume this is also the case for you. I decided to go for a new fork, as it was quite inexpensive (sub $30) and bending it back would have been troublesome and awkward, even with a lathe (which I happen to have access to). One of the problems would be that you'd need to bend it back such that the headset bearings are (near) perfectly aligned, otherwise you'd end up more or less than normal play in the headset bearings when steering. If the steerer is not damaged, you'd have to align the blades of the fork to their old position, without knowing this old position (at least not exactly). Other than worry about the fork, I would suggest checking all the parts of the steering mechanism, as well as the frame and the front wheel for cracks/bends to avoid surprises, I you haven't done so yet.

P.S.: If you really want to fix the existing fork, I'd suggest removing it from the bike, putting it into a lathe at the steerer above the bend and try to bend it back. You'd have to be careful however, if you feel that the material is giving in, you've likely already gone to far with the bending.

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I don't see the point in using a lathe. You would want to pad the post when you put it in a vise, though. –  Daniel R Hicks Feb 25 '13 at 0:25
    
You can use a dial gage when putting it into a lathe to check if the steerer is rotationally symmetric, as well as check the blade ends for symmetry, Turning the thing by hand, in a switched off state that is. –  Andreas Fitzinger Feb 25 '13 at 8:16
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I don't think anyone can give you a valid answer from a photo. Is there a fine crack there? Who knows? Certainly, no one can tell from a photo. Are the forks bent unevenly or beyond their design specs, leading to handling problems? Again, who knows?

Personally, I would replace it without further ado. It's steel, so although that does mean it can possibly be straightened, it also means it shouldn't be very expensive to replace. A fork is an awfully safety-critical component to gamble with, so I would just replace it. I want my forks in unquestionably perfect condition. But if money is a serious constraint, I would, at an absolute minimum, have it inspected by a bike mechanic and take their advice.

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That's very true. It won't help the OP if we say it's safe riding it and suddenly it breaks. –  Uooo Apr 24 '13 at 4:25
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I have bended steel fork like you did, maybe even more. Since I was not able to find a cheap one at that time, my LBS straightened out the bended one. I was not watching him do it, but he told me that steel has a memory, and that it would snap back to the position it had before bending.

I was driving about half a year with repaired fork, it worked ok with following exceptions:

  • adjusting front V brake not to squeak in wet weather was next to impossible. Installing break booster did reduce squeaking but did not eliminate it. I guess fork was still a little misaligned.
  • It seems that my headset was also dented in the hit, and it was kind of "indexed" in straight possition.

So when I finally found cheap replacement fork, I have replaced it together with new headset.

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One piece of advice I would add to the answers here:

If you hesitate to have your bike looked at by a mechanic / continue to ride on the bent fork, be wary of any new squeaks or rattles you hear while riding. These may indicate a break in the fork (or elsewhere on the frame).

I once crashed and broke my fork right above the axle and never noticed the break. Two days of riding later I found the source of the seemingly insignificant rattling noise. My front wheel was holding on just one side of the fork; very dangerous.

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