misaligned wheel - could this cause problems?

Question

Last summer I was on tour with my Trek 520 when my rear rim cracked. I found a bike shop, and they rebuilt the wheel with a new rim.

Recently I noticed the wheel was off center relative to the frame by about 1cm. I did some basic measurements with a string to confirm the frame wasn't bent, and inserting the wheel backwards confirmed it was the wheel.

I brought it to a bike shop and they attempted to redish it. When I picked it up the guy told me the spokes had to be adjusted unusually tight, and he was only able to correct it by so much (it's still slightly off center, but hardly noticeable). He guessed the wheel may have been built incorrectly last year (i.e., left spokes on the right side and vice-versa), although I don't see how that's possible since the spokes weren't removed from the hub when it was rebuilt.

My question in all of this is: Was the bike shop guy talking BS and could the off center wheel or tight spokes cause problems?

Answer 1

The bike shop that replaced your rim replaced it either incorrectly or with the incorrect part, I suspect. At least some of the 2007-2008 Trek 520 shipped with Bontrager Maverick rims, featuring an offset spoke bed. If they did in fact use the same spokes, and if they replaced it with a normal rim of appropriate ERD, the wheel will end up dished incorrectly the amount of the offset. Similarly, if they laced the rim backwards, the wheel will end up dished incorrectly double the amount of offset. The former is more likely, especially if you didn't get your wheel rebuilt by a mechanic who routinely works on Trek/Bontrager bicycles.

An off-center wheel will cause some odd handling characteristics, almost certainly not noticeable in normal riding conditions but you'll be able to tell that your wheels are not tracking in a straight line in low-traction scenarios, such as ice or wet grated roadways. The more extreme the offset, the more noticeable this will be.

Otherwise, moz is absolutely correct about the rationale behind dishing and the ramifications of running spokes in too high of tension. I'd probably ride the wheel locally until failure but I would recommend getting a properly dished and tensioned wheel built (possibly just rebuilding this wheel with the correct spokes) before going on another tour of significant distance.

Answer 2

Short answer: probably not. It may make your brakes harder to set up but that's all.

Dishing is having shorter, tighter spokes on one side of the wheel to move the rim towards that side relative to the midpoint between the flanges (where the spokes attach on the hub). The frame and wheel are still built symmetrically for historical reasons, but dishing allows the flanges to be assymetric so you have more space to fit cogs in.

The bike shop guy is probably right if he used a spoke tensiometer (if he didn't you need to find a better bike shop). There's a limit on how tight the spokes can be, usually set by the rim but sometimes by the hub (or with aluminium spokes, the spokes). If you overtension the spokes something will give way, usually nipples start pulling through your rim.

If he has wound the spokes up as tight as he can and the dishing is still not right, you are indeed stuck. Since it seems to work like that, I say accept it and move on. Expect the wheel to be a little more fragile than before, more likely to buckle and it will fail earlier than it should. But since it should last a lifetime, that doesn't mean it won't last until the braking surface wears away.

If the new rim is the same or only slightly different from the old one it's possible they used the old spokes, but that's penny wise and pound foolish. Spokes stretch slightly and settle into position when the wheel is built for the first time, and trying to do that a second time rarely works well - spokes are more likely to break in the future. Much better to pay the $20 or so for new spokes and be done with it. The wheelbuild labour cost is so much greater than the spoke cost that it's foolish not to just buy new spokes.

One cheat that can give you a millimetre each way is to play with the spacers and locknuts on your axle. There are thin locknuts and fat locknuts, as well as a variety of spacers. With most wheels you can swap bits around to shuffle the whole thing a little bit sideways. This changes the chainline and can mean the chain hits the frame in the smallest cog, so it needs to be done cautiously. But if you are really worried about that last millimetre that should fix it.

Answer 3

On a geared bicycle the rear wheel is dished to accommadate the cassette depending on the number of cogs on the cassette. This is to set the correct chain-line. The chain-line is very important for the adjustment and operation of your gears. Your wheel rim should be off center to the hub when you look at it from the rear. Hope that helps.