how do you unbend a mountain bike rim?

Answer 1

As a bike mechanic in college I had the opportunity to fix many badly bent wheels, but before you do anything, make sure there isn't a broken spoke. One broken spoke or nipple can let a wheel go more than one inch out of true. If that's the problem, then get a new spoke (a shop can measure and replace it for you as they come in 1mm increments).

If there aren't any broken spokes, is it out veritcally or horizontally?

As mentioned before, if it's got a flat spot (vertically out of true) there's not much you can do without disassembling the wheel and using a mallet!

If it's bent sideways more than about an inch, and the spokes on the side of the wheel opposite the direction of the bend are loose, you'll just need to tighten them up to pull it back into true. If those spokes opposite the bend are tight, then you'll most likely need to straighten the rim before adjusting the spokes. I've had the most luck in straightening the rim by whacking the wheel on the ground in the direction you want it to go. Make sure you have a tire mounted and filled with plenty of air before doing this and make sure you're hitting the right spot! It will take more force than you expect, so without having the feel for it, I wouldn't expect great success on your first try. Once you've gotten the wheel relatively straight and the spokes on each side of the wheel are at about the same tension, you can adjust the spoke nipples to get things straighter.

Keep in mind, this is at best, a band-aid fix. If you can't afford a new wheel (starving college student), or need to get back out of the woods in an emergency, this works great. Long term, however, the wheel has likely suffered enough damage to weaken it substantially. Most shops won't fix wheels like this because of the liability, so go talk to an experienced mechanic and see what they say.

Answer 2

First of all we would need just a little more info on the type of bend. If it's a bend sideways, a minor one, then you can adjust the spokes to make it true again, but I would not do this unless you were already experienced at it. If it's what's called a flat spot then you're out of luck, in fact I'm dealing with this right now and I will have to get rid of this rim. If it has tacoed, meaning an extreme sideways bend then most people say the rim is gone also. The problem is if you're able to restore the rim to a semblance of true then there is a very good chance that it will happen again as soon as you hit another bump on the trail. Here's what you do to fix the taco, lay the wheel down on its side and place your feet at oposite sides of the wheel where the bend is the worst and you stomp down on the side that's still sticking up. If that doesn't work then you will have to jump and stomp. Now my wheel has not tacoed again since I did this, but the wheel has never been the same it has a weird wobble that all the spoke wrenching I do cannot fix. So you get what you pay for, maybe I shouldn't tell you to do this. Good luck!

Answer 3

if its too badly bent it cant be un bent but if its bent a little then go get whats called a spoke wrench bike shops will know what you want if u want to go through that much trouble i would just get a new rim some times you tighten the spokes and sometimes you loosen you gotta play with it a little its not hard to figure out if you are doing it right or wrong i would leave it on the bike while your doing that spin the rim after you made an adjustment

Answer 4

You cant. Once they are bent, they are bent. You might be able to tighten some of the spokes on the side that will bring it back true but that's defiantly best left to a bike shop if you didn't have the tools or know what your doing.

Answer 5

Have to agree with the 3 posters above. I think that unless you paid a lot for your rim e.g. Mavic or Shimano or ZIPP or something, it's not worth saving.

A new one will be stronger.