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Fixing A Bike Wheel

  1. Jul 23, 2012 #1
    I recently took a curb harder than I should've and my bike's rear tire now has a flat spot. Since my tools are currently all elsewhere I can't fix it myself. When I took it into the local bike shop the tech said that it was too badly bent to fix by simply adjusting the spokes (I agree with that), and that it would be cheaper to get a new rim than to have them fix it.

    I've attached an image of the rim. The walls of the rim have also bent inward, that made getting the tire off a little interesting.

    I'm thinking that if I pull all of the spokes out I can beat the flat spot out with a rubber mallet. My concern with this however is that working the metal like that will weaken it to the point where it will randomly break one day while I'm riding. I'm probably going to get a new rim anyways because I need this bike operational as soon as possible. However is this rim safe to fix, or should I just put it in the recycling?
     

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  3. Jul 23, 2012 #2

    Astronuc

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    You'd have to beat that one out to near the original diameter (radius). It might be OK, but you probably should think about replacing the rim.

    I've repaired some pretty twisted rims, but more from lateral deformation than radial. I presume one uses tubeless tires.
     
  4. Jul 23, 2012 #3
    It's a tube tire. My main issue is that I'm not sure how accurately I could re-form the curvature.

    I came up with an idea for a device that could do the job. Two wheels, with one fixed on a threaded shaft. Turn the rim around them, while spreading the wheels and hopefully that would re-form the rim. Problem is that would be a bit expensive to build...
     
  5. Jul 23, 2012 #4
    I suspect your solution won't work easily. In trying to return metal objects to the intended shape before, I've generally found the metal will attempt to return to its new bent shape (memory), unless I over-bend it trying to get it back to the initial shape. Additionally, the metal may be somewhat stretched, making a return to anything like factory spec unlikely. I'd get the new rim. Unless it's a performance bike, in which case you wouldn't use a damaged rim anyway, I can't image it would be too expensive. Factor in the man-hours you’d spend trying to fix the rim, buying a new one may still be “cheaper”.
     
  6. Jul 23, 2012 #5
    I'm getting a new rim regardless because with school right now I don't have the time to fix it. I guess I might as well just salvage the useful components like the spokes and hub from it, then put it in the recycling.

    Although, I wonder if heating the metal while running it through the machine would help it adjust to the new shape.
     
  7. Jul 23, 2012 #6

    Astronuc

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    Heating the metal would help regarding deformation, but then then section of the rim may have slightly different strength properties that the rest. I'm not up on whether or not rims are annealed or not.

    If one reuses the spokes and hub, just make sure you have photographs of the hub and spoke patterns, and perhaps number the spokes and spot on the hub and rim.
     
  8. Jul 23, 2012 #7

    Chi Meson

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    Assuming that is an aluminum rim, that rim is toast. Your bike shop is correct, it can't be fixed into a dependable wheel ever again. Toast!

    Buying a new rim is an option, but not a great on unless that's a real expensive hub you've got there. And you don't want to reuse spoke (unless you like broken spokes in the middle of your rides).

    Having the bike shop rebuild a wheel would cost almost the same as a factory built basic wheel anyway.

    20 years ago I would have charged you $30 just for the labor of building a 32 or 36 spoke wheel; it's likely more now. It's a very skill-and-equipment intensive job.

    I'm assuming that's a 26" (mtb) wheel. You would be looking at around $50 for a decent factory built replacement (not great, but are you competing with it? or just getting around town?). Make sure that the wheel is compatible with your rear gear cluster (they mostly are, following the Shimano pattern).
     
    Last edited: Jul 23, 2012
  9. Jul 23, 2012 #8

    BobG

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    As Chi Meson noted, rebuilding the wheel with a new rim probably isn't cost effective, but it can be worth it anyway if you enjoy that sort of thing.

    When I was in high school, one of the bike shops had the $1 part boxes that were always fun to go through. For one thing, you were pleasantly surprised with a perfectly good quality derailleur sitting in the box for no good reason at all more often than you would think. And, even if I did find a perfectly good part, I would still go through the rest of the box looking for about 3 damaged derailleurs that, between them, had enough good parts to build one good derailleur.

    Of course, the challenge was that you could always find damaged parts in the good quality range; but it was really hard to find top quality damaged parts. And when you did find one and bought it for $1 just out of principle, you'd never find another that matched it no matter how long you looked and could never get the missing pieces to rebuild it.

    It was still a fun hobby.
     
  10. Jul 23, 2012 #9

    Monique

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    Around here it would be hard to find a bicycle wheel without a dent or kink in it.. I used to just bend it back in shape and it was fine again. If it's a long-distance high-performance hi-speed bicycle buying a new wheel and being a bit more careful with the curbs would make sense :smile:
     
  11. Jul 23, 2012 #10
    Well I'm not sure what I could re-use the hub in. I know some people have tried using them in home-brew jet engines. Maybe I could do that.
     
  12. Jul 23, 2012 #11

    BobG

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    Put wooden handles on the axles and give the entire tire to a physics teacher.
     
  13. Jul 23, 2012 #12
    I wonder how much of a profit I could turn from that...
     
  14. Jul 23, 2012 #13

    BobG

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  15. Jul 23, 2012 #14

    Chi Meson

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    I strongly recommend learning the skill of building wheels, but it's just not worth the effort if the parts aren't at least mid-level quality. Do you know exactly what hub it is?
     
  16. Jul 24, 2012 #15
    Years ago I retreaded a tire with the grip from another glue and thread and needle and it worked some some time and was quite thrilled with the job. I really cannot remember why except for probably being extremely cheap.
     
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