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Straightening out a badly bent wheel

gt-arrowheadgt-arrowhead Posts: 2,507
edited October 2013 in MTB workshop & tech
Hi, today on the way back from my ride it started chucking it down with rain, and i was on the pavement and i tried going round a corner. I grabbed my rear brake a little too hard and the back just stepped out. Usually when releasing the rear brake the bike straightens out again, but for whatever reason the rear just kept on going even though the angle of the slide wasn't too extreme. Then the front started sliding as well and the rear wheel whacked into a lamp post on my right, and straight after my handlebar got stuck in the fence on the left and i flew off.

As a result of this my rear wheel is badly bent, and it isnt just one bend, its bent at two different points around the wheel. After a quick inspection thats all that appears to be wrong. Everything else is fine. I have a spoke wrench, but my dad usually does the straightening of the wheels as he is really good at it. My dad is really pissed off at me and said he is not going to mend it for me, before i even i asked :lol: So ive gotta have a go at it.

I am going to start looking at tutorials and stuff on youtube too, wondering if anyone on here has any good ideas or tips on how to do it properly. All i know is that to get the wheel in the center if its bent to the right, you have to tighten up the spokes on the left around where the bend is to sort of pull it back. And tighten the right if the left is out.

Posts

  • jimothy78jimothy78 Posts: 1,407
    How bad is the bend? - Can you measure how far from "normal" the rim has been bent?
    Have you broken any spokes/nipples?
  • gt-arrowheadgt-arrowhead Posts: 2,507
    Thanks for your reply.

    I will have a measure tomorrow morning and post back here.

    Im almost certain that the spokes and nipples are all completely fine. I didnt have a proper look over but from just a quick glance after the crash and arriving at home, all seems fine apart from the bend.
  • Interesting article that actually makes sense.http://sheldonbrown.com/on-road-wheel-repairs.
    Note the advice not go straight to a spoke wrench unless you have broken spokes . You may be able to get the wheel back into reasonable shape using the method shown.
  • gt-arrowheadgt-arrowhead Posts: 2,507
    Isnt on road wheel repairs essentially bodging it enough to see you home? After a quick ish scan of that link i noticed it said this:

    "The spokes will be same tension if the wheel is bent" Then....how can adjusting spoke tensions straighten the wheel out, as mentioned by Sheldon Brown on his "wheel truing" link which i have fully read.

    Im not too sure about what exactly i have to do :/ Ive looked in different places and they all say different things. I think i am going to have a massive headache on my hands. :/
  • Chunkers1980Chunkers1980 Posts: 8,035
    I think rather than wheel in that statement, it should say rim.
  • njee20njee20 Posts: 9,613
    If your wheel is bent to the left you tighten the spokes on the RH side of the wheel - thus pulling it back to the right.

    That's more or less all there is to it! What you're likely to find if you've bent it enough though is that the spokes on the LH side (continuing the example) are rather slack, and you'll struggle to get it straight, or that you develop a large flat spot (vertical trueness) in the rim because of all the adjustment, it's a balancing act, but once you've put a big hop in a rim it's hard to get it back to where it was.
  • gt-arrowheadgt-arrowhead Posts: 2,507
    njee20 wrote:
    What you're likely to find if you've bent it enough though is that the spokes on the LH side (continuing the example) are rather slack, and you'll struggle to get it straight,

    Wouldnt retightening those left hand spokes bit by bit and spinning the wheel after every turn to make sure they are straight eliminate this problem?
    njee20 wrote:
    or that you develop a large flat spot (vertical trueness) in the rim because of all the adjustment, it's a balancing act, but once you've put a big hop in a rim it's hard to get it back to where it was.

    My bend is fairly bad from what i can see. If i can get a video of the wheel spinning, would you be able to say how easy it would be to fix it? Ill get the measurement of how badly out of average it is aswell.

    Ive read about people just buying a new rim, strapping it to the wheel, then transfering the spokes across one by one. Then tensioning the spokes up. Doesnt sound like a bad shout really. But then again i can buy a whole new rear wheel, the exact same as what ive got right now for £30 as its on a 44% off sale at the moment. (They are Alexrims DH22 if that helps)
  • OuijaOuija Posts: 1,386
    You have to remember that tightening the right hand side spokes (for instance) doesn't just pull the rim to the right, it also pulls it towards the hub so that the distance from hub to rim is shorter, leading to a non circular wheel (albeit, a straight one). Best of with new rims and a new build. Or a new wheel.
  • njee20njee20 Posts: 9,613
    My bend is fairly bad from what i can see. If i can get a video of the wheel spinning, would you be able to say how easy it would be to fix it? Ill get the measurement of how badly out of average it is aswell.

    Ive read about people just buying a new rim, strapping it to the wheel, then transfering the spokes across one by one. Then tensioning the spokes up. Doesnt sound like a bad shout really. But then again i can buy a whole new rear wheel, the exact same as what ive got right now for £30 as its on a 44% off sale at the moment. (They are Alexrims DH22 if that helps)

    Can give you a vague idea if it's totally beyond hope, little else.

    For £30 I'd definitely just buy a new one if it can't be saved, the time and effort (not to mention the cost) of replacing just a rim isn't worth it in that instance.
  • The RookieThe Rookie Posts: 27,802
    +1.....if the rim is bent (rather than just out of shape) it's scrap.
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • jimothy78jimothy78 Posts: 1,407
    Actually, that's not half as bad as I was expecting, and should be fixable. Take the tyre off the wheel and rig up some sort of marker that will allow you to see where the rim deviates from the central position (my favourite method is frame upside down on workbench, with masking tape stretched between chainstays - you can then mark on the tape where the edge of the rim should be) and then work round from the valve hole all the way round the rim tightening spokes as needed to even out the worst of the wobble, then go round again to fine tune it. Just be careful not to overdo it on your first attempt and remember that tightening one spoke affects the rim over quite a large area (at least as far as the next spokes on the same side).
  • gt-arrowheadgt-arrowhead Posts: 2,507
    Thats good news then :)

    I was thinking to take a wheel off one of my V brake bikes, and using the pads as the reference point. And as it turns it will touch the pads, and thats the bit i would need to work on. But your idea sounds pretty clever, i might give that a try.

    Ill take it easy the first time round. I had a feel of the spokes, and some feel looser than others where the bend is. Ill post back with my progress.

    Thanks for your help :)
  • jimothy78jimothy78 Posts: 1,407
    I was thinking to take a wheel off one of my V brake bikes, and using the pads as the reference point. And as it turns it will touch the pads, and thats the bit i would need to work on.

    Yep, that would work, too - you could then use a zip tie to pull in the brake lever bit by bit as you worked, so as the rim got straighter you could bring the pads closer to it.
  • Chunkers1980Chunkers1980 Posts: 8,035
    That vid was done in your shite phone right.

    Looks not too bad, may not go back perfect but only a couple of kinks to iron out. Just take it slowly and never more than 1/2 a turn at a time.
  • gt-arrowheadgt-arrowhead Posts: 2,507
    Yes it was.That background noise was cars by the wayt :lol:

    Yeah, as long as its very nearly straight its not a problem.
  • njee20njee20 Posts: 9,613
    you could then use a zip tie to pull in the brake lever bit by bit as you worked, so as the rim got straighter you could bring the pads closer to it.

    Barrel adjuster... Only issue with using v-brakes is that if they're not centre you'll end up pulling the whole wheel off to one side if you're not careful.
  • photonic69photonic69 Posts: 1,828
    Use a long pencil/dowel and an elastic band to hold the pencil across the chain stays (assuming bike upside down or seat stays if in a stand) Then get two ordinary clothes pegs and set them on the pencil at right angles so they just touch the rim (tyre off) spin the wheel. Rim touches peg when wobbles to that side or the other. Cheap, simple and effective. You can also do it with the tyre on if you can get the pegs to stay at and angle.

    HTH
  • The RookieThe Rookie Posts: 27,802
    I just bl;uetack a ruler across the rear stays, work out total gap, less rim width and therefore the measurement the rim needs to be at on each side, really simple!
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
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