Rim replacement - Bike Magic

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Rim replacement

Bike wheels are remarkable things. A well-built wheel will last for a long time. In fact, unless you hit it spectacularly hard, a wheel will last until the rim wears out. Wears out? Yep. There’s only so much material in a rim sidewall, and eventually the brake pads will wear them so thin that the rim’s not strong enough to take the force exerted by an inflated tyre. At this point a loud bang occurs and a length of aluminium alloy peels off the wheel. This is likely to be inconvenient at best, so ideally you’ll keep an eye out for this happening and catch it before it does. A simple clue is the shape of the rim. Generally the sidewalls are flat and straight when new. If yours are noticeably concave or have curious lips, edges or grooves in the surface, they’re probably on the way out. The other, more aggressively entertaining, way of checking is with the infamous “BANG – sh*t” test. Simply get a track pump and inflate the tyre until something gives way. If the rim was a bit tired, it’ll go first. Stand well back…

Fear not, though, for replacing a rim is pretty straightforward, particularly if you’ve already got to grips with basic wheel truing. Note that this method works great for worn out or excessively dented rims, but if you’ve had a proper stack and bent the wheel a lot, chances are that the spokes aren’t really worth reusing. Just take the thing apart and re-use the hub – we’ll show you how soon.

1. Your tools du jour today are the spoke key, some tape and a flat-bladed screwdriver. You’ll also need some sort of wheel truing stand, either a proper one or a cunning assemblage of bike frames, pointers and rubber bands.

2. Here’s our tragically-burst rim. This is why you should check them regularly, otherwise this happens at some inconvenient moment. Like, ooh, a 3am lap at the Red Bull 24hr for example. Guess where this happened? Mm. Anyway, an exploded rim is easy to spot, and equally easy to snigger at in a schoolboy fashion. But we’re way above that. Really.

3. If you haven’t already, take the tyre and tube off the wheel. Then find the end of the rim tape and peel that off too. If it’s a stretchy plastic or proper cloth tape you’ll be able to use it again if you like, so take it off carefully. If it’s just a bodge job with insulating tape then just pull it off and chuck it away.

4. Next get your new rim. Ideally you want one just like the old one but new. Failing that, the two critical things are that it has the same number of spoke holes as the old one. Yes, it’s obvious, but we don’t mind admitting that we’ve got a fair way into lacing 32 hole rims onto 36 hole hubs before noticing. The other requirement is that the rim is the same depth as the old one. If it’s wildly different you’ll need different length spokes which makes this a somewhat more involved job. In fact it makes it a different job altogether. Thing is, if the old rim died from wear then it was a good rim, so you might as well get another one the same and make life easier.

5. Now comes the clever bit. Lay the new rim on top of the old wheel and line up the valve holes on the two rims. Then check the orientation of the spoke holes. They’re staggered left and right, make sure both rims have the holes staggering the same way.

6. Grab some tape and tape the two rims together. Don’t go mad, you’re not trying to preserve them for their journey to the afterlife, just to hold them together reasonably firmly.

7. Time for the fiddly bit. You need to work your way around the wheel undoing a spoke at a time and moving it over to the equivalent hole on the new rim. You may find this easier if you loosen all the spokes first. To speed things up you can use a screwdriver on the back of the nipples. Take care not to drop any nipples inside the rim, and put a dab of oil (chain lube is fine) on each one before you wind it back on. Put each nipple onto the spoke two turns at first. If any nipples are extremely hard to turn or rounded off, replace them.

8. Once all the nipples are in place, you can take the old rim off and put it in the pile of things to take to the tip. Now go around the wheel taking the slack out of the spokes. Tighten them all by the same amount – aim for two threads showing under the nipples. The exact amount isn’t vital, what matters is that they’re even all the way around.

Now’s a good time to refit the rim tape, as it’ll be there to catch any spokes that decide that, actually, they’ve had enough thank you very much and would quite like to break now as you tighten them up.

9. With all the spokes taut (but not tight), it’s time for final tensioning and truing. Follow the instructions in our wheel truing article, but until the spokes are actually tight correct errors just by tightening spokes. This way the total tension will gradually increase. If they all get tight and it’s not quite straight, you’ll need to start loosening and tightening spokes equally. How tight is tight enough? Gauge by plucking or squeezing spokes and compare with a known good wheel. If you don’t have one, keep going until the nipples are hard to turn or the wheel suddenly takes on a dramatic wave shape and then loosen them a bit…

More maintenance

There’s hundreds of top maintenance tips in the BM archive.


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