Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 35 Post(s)
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It really depends on the rigidity of the rim, the severity of the hop, how local it is, and your skill.
Before starting consider that the rim is a hoop, and that any section of it acts like an arch. That means that flattening the arch would lengthen it, and raising would shorten it. That's what makes taking hops out so difficult, the rim has to flow along the length. High spots are fairly easy to resolve by simply tightening the spokes locally, and slightly loosening the spokes for about 60 degrees of arc to either side.
Low spots are trickier, If the rim is fairly pliable as many light rims are, you can loosen the spokes in the low area, and it'll rise a bit, and/or you might have to tighten the rest of the wheel very slightly. For a more sever low spot, loosen the spokes in the immediate area until they're fully slack, then slightly loosen the spokes to either side. Then take of your shoes, put center your foot over the low spot, and lift the wheel/push the area out. Push it slightly beyond the original radius, then you'll true it back later on.
Once you've resolved the worst of it, you true, and retension the wheel looking for the best balance between even tension and good trueness. You won't get both, so you'll have to use your judgement and look for the best balance.
This kind or alignment work was SOP many years ago, and any decent wheel mechanic could and would do it. Nowadays it's less commonly done, partly because of the current attitude toward "rescue" work, but also because modern rims are heavier and stiffer, making them hold the set or bend more that rims did in the past.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
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