Forum home Road cycling forum Workshop

Wheel Building for Beginners

BobbinogsBobbinogs Posts: 4,841
edited February 2011 in Workshop
Folks,

Any idea how to get rid of a lump in the rim?

I rebuilt some OEM wheels at the end of last year to use as winter wheels. The lateral setup is fine (when checked against the brake blocks) but if I stick a ruler across the forks the rim is fairly level until there is a noticeable bump (as in it rises away from the hub). I figured that it made sense to tighten the nipples in the area and loosen off the others but it hasn't made anything like enough of a difference. In fact, I have now managed to completely max out the tension of the nipples/spokes near the rise and mashed the nice nipple edges to boot.

I was hoping to sort this out over the next 6 months before next winter but I ended up riding my nice RS80s through 3 hours of a monsoon yesterday (literally rivers in the roads as the Cotswold hills maxed out on absorbancy). I know my nice new wheels won't melt but it seems nonsensical to use nice wheels in stupidly heavy rain.

Thanks in advance.

Posts

  • deswellerdesweller Posts: 5,175
    Are you stressing the spokes after making a change? You may also need to back off the spokes in the low spots so the wheel can move.

    If you're rounding off nipples, check you are using the right size spoke key.

    For a complete guide, spend a tenner on Roger Musson's book. You won't regret it.
    - - - - - - - - - -
    On Strava.{/url}
  • BobbinogsBobbinogs Posts: 4,841
    Thanks Des, I do have the right key but the rounding off is a symptom of the amount of pressure applied to try and get the lump down. I have backed off the other areas which I figured would work but the lump is still there.

    I am trying to ignore the option which says start again (with a few new nipples needed) but wondered if the rim was the problem? I strongly suspect user error btw.
  • Monty DogMonty Dog Posts: 20,614
    Any 'hop' deviation is down to assembly - you need to think about moving the rim relative to the hub in particular the group of spokes diametrically opposite. If you're rounding brass nipples, then you are reaching the limit of tension or using the wrong size key. I would slacken off every spoke a turn or two and then try and get radial and lateral truth correct - no need to start again.
    Make mine an Italian, with Campagnolo on the side..
  • Monty Dog wrote:
    Any 'hop' deviation is down to assembly - you need to think about moving the rim relative to the hub in particular the group of spokes diametrically opposite. If you're rounding brass nipples, then you are reaching the limit of tension or using the wrong size key. I would slacken off every spoke a turn or two and then try and get radial and lateral truth correct - no need to start again.

    +1

    You should also be aware that it's likely that you have affected the "dish" of the rear wheel and the lack of dish on the front, by your efforts to achieve roundness. Best to check on this with both wheels. Uneven spoke tension is also something to look out for.
    Sorry to be a bit negative.
  • BobbinogsBobbinogs Posts: 4,841
    Thanks chaps, so a free hour or two and a comfy chair required by the sound it. I suspected as much.
  • 1+ for Roger Mussons book.

    If you are rounding off the spoke nipples you might have run out of thread on the spokes which might mean they are too long.
    You need to make sure that everything is round and true before putting tension into the spokes, and you need to stress the spokes often. If the wheel starts true and you tighten by the same amount all round you should end up with a round true wheel.
    It could be that your OEM wheels were not very round when you started. Did you replace the rim or the spokes? or did you just reassemble them?
  • BobbinogsBobbinogs Posts: 4,841
    Hi there Stig, the rims did get a real bashing over the year but it was the freehub was knackered. Hence, bought a new Shimano hub (105, I think) which was a pretty close match on the Spesh one it replaced. Thanks for the tip about starting round. When building I did get a bit diverted (I think I underestimated the time and adding a beer or two was probably not a good move looking back). The rim was all over he place at one point.

    The wheel is rideable but having been spoilt with nice wheels I figured replacing them with a round wheel is the least I can do.
  • rakerake Posts: 3,204
    it might not be the spokes opposite to the hump that are the problem as that would make that point low while the other is high. it could be to each side of the hump pulling in causing the hump between. think of an arch being compressed horizontally it will rise upwards in the middle. jusy a thought.
Sign In or Register to comment.