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I broke a spoke on my rear wheel, and ended up messing with it a bit too much - I may need to get it re-dished.

If it's a common market model bike, can I simply take the wheel into my bike shop, instead of the whole bike? Will it work when I bring it back home?

The problem is I can't ride it in because the disc brake is scraping on the caliper.

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Yep, unless it's something exotic the rim is centered between the lock nuts on the axle, both front and rear. No need to have the bike to center the wheel. However, it's not clear how being off-center would affect a disk brake. –  Daniel R Hicks Jun 3 '13 at 0:10
    
@DanielRHicks You're right - that could just be because the pads are off center, so adjusting the calipers I end up with the disc pressing against it. Hmm. Sounds like a separate question. :S –  Jono Jun 3 '13 at 9:42

1 Answer 1

up vote 4 down vote accepted

Yes, a dished wheel can be built or re-dished without a frame handy.

In order to get the wheel to revolve, the rim must be equidistant between the insides of the stays/fork. The reason why most rear wheels/front wheels with disk brakes are dished is because the hub flanges aren't centered between the ends of the axle. This is to accommodate the width of a cassette on a rear wheel and the space taken up by a disk on a front wheel.

To accomplish the desired dish, a mechanic will lace a hub to a rim using spokes that will result in the correct rim placement. There are all sorts of calculators out there to correct for the offset from the hub flange. The spokes on opposite sides of the wheel will be at different tensions and lengths, as opposed to a dishless wheel which has spokes at the same tension and length on both sides. People commonly break spokes on the drive side of their rear wheel - this is because those spokes are generally at a higher tension than those opposite it. Ideally, a wheel is dishless so as to evenly distribute the stress on all spokes. To achieve this, there are many offset rims which compensate for some of the hub flange offset.

However, none of that will effect the disc or caliper function unless you've misplaced some shims reinstalling the disk or moved the caliper. If you have hydraulic brakes and pulled the brake lever without the wheel installed, the brake pads will probably just need to be pushed back into the caliper housing with something flat and blunt.

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Should I revert to regular brakes for the sake of simplicity? Hell, now I understand the attraction of single speeds. Or maybe just a 3-speed. –  Jono Jun 3 '13 at 9:43
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@Jono - There are several advantages to rim brakes, and you've found one. But converting a bike to rim brakes would be more trouble than fixing the disk brakes, if they're halfway decent to begin with. (Dishing a wheel, by itself, is no big deal, once you know what you're doing.) –  Daniel R Hicks Jun 3 '13 at 11:05
    
@DanielRHicks Actually, I think my frame supports rim brakes (There's holes where the brakes would be mounted), so it should be doable, but I'm happy with the setup. I'll definitely take it into account on my next bike! That said, I asked at the bike shop, and I think with a truing stand and a dishing tool I could be ok doing it by hand. They'd pay themselves off in about 6-7 spokes! –  Jono Jun 3 '13 at 13:10
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@Jono Part of the beauty of disc brakes is that the wheel doesn't need to be perfectly true. With rim brakes all it takes is an 8 mm wobble and you have to disconnect your brakes to roll at all. –  WTHarper Jun 3 '13 at 17:42

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