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I'm about 3500 miles into a long tour, and the other day we noticed a few of the wheels between my own bike and some other guy's were starting to warp pretty noticable. With the help of someone more versed in maintenance we tightened some spokes to true them against the brake pads and gave them all 1/8 turn on the advice they were a little loose. Another few days riding revealed in the course of this fix we warped the rim a little from circular (radially untrue?) so I did my best fixing that a little. My only worry is in somehow making the bike unsafe to ride since I'm new to truing wheels. On the road and without a means of measuring spoke tension, does it seem excessively risky to eyeball the tensions like this? My main worry, reasonable or (hopefully) not, is I'm somehow crippling the wheel and it will give out catastrophically at high speed or something. Is this fear founded at all? I'm curious how the wheel would fail if I'd messed it up.

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    I would guess that about 90% of the time when spokes are adjusted a tension meter is not used. (I know I've never used one.) And on the road ya gotta do what ya gotta do. The problems with adjusting on the road are 1) there is a slight increase in a broken spoke in the first 100 miles or so after doing an adjustment (whether on the shoulder or in the shop), and 2) on the road you're slightly more likely to rush through or be a hair careless, and hence a rounded nipple or over-tensioned spoke or some such is a bit more likely. – Daniel R Hicks Jul 29 '18 at 0:51
  • Do you carry spare spokes and nipples in your loadout ? – Criggie Jul 29 '18 at 9:55
  • You're braver than I am. I wouldn't mess with this at the roadside; I would (and did) ride straight to the nearest wheel truing stand. – Michael Hampton Jul 29 '18 at 13:13
  • I don't understand why you'd have to do that. My bike has done about 20 or 30,000 km I'd guess over about 7 years, had a change of bottom bracket, but never had to change the wheels or touch the spokes. Perhaps you (with your touring gear) are too heavy for the wheels, or something like that. – ChrisW Jul 29 '18 at 13:52
  • I have three times had a spoke break while far enough out on the road that simply limping home was not practical. The first step is to use your spoke wrench to detension other spokes so that the wheel stops dragging, then you get to a spot of relative comfort to complete the repair. If you're lucky there's a repair truck on the tour with you (happened once), but otherwise you must do the repair yourself (in one case after borrowing a pipe wrench to remove the freewheel). It's just what you do. – Daniel R Hicks Jul 29 '18 at 21:38
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Unfortunately there's not many aspects to truing wheels this question doesn't touch. Also unfortunately, figuring out what's going on with a given heavily used wheel with issues and then making it as good as possible are both beyond-the-basics wheel work skills.

Yes, it's possible to set yourself up for a bad situation here. The main ways you would do that are by allowing some spokes to be too loose (making them prone to go all the way slack, which both allows the nipples to unscrew and makes the wheel less strong/stable), having them all too loose (making the whole thing weak and prone to going out of true), or having some or all of them too tight, which can cause fatigue cracking.

It is critically important you understand and are able to spot the difference between truing a rim that's in good condition (would be flat and round if it were a bare rim with no forces acting on it) and truing a damaged rim (would be not perfectly round or flat instead). In the former case you're equalizing spoke tension on each side to make the wheel true. In the latter case you're creating intentional tension disparities to make the wheel look true and limp along having a greater or lesser degree of the above mentioned issues with too-tight or too-loose spots, and it usually won't stay true under touring conditions if there's very much of this going on at all. (Although conversely, wheels can handle some amount of this without incident.) Making this distinction empirically is one of the few things tensiometers are reallly good for. Doing it without one is fine too, but generally takes some experience to be confident about.

It's worth noting here that it's common for even rims in good condition to force you to have a little bit of tension disparity and/or out-of-round at the seam.

It's also worth noting that in the case of a rim with some radial damage only (flat but not very round), if you must keep going with that wheel, it can be reasonable to make the spoke tensions equal on each side and just accept it's not going to be very round, which you'll probably feel while riding and will require rim brakes to either be backed off or adjusted around the warbling tire, and never let the pads touch the tire. There are a lot of wheels running around the world with minor versions of this problem.

Wheels that are sufficiently overtensioned and/or unevenly tensioned can in fact give out under high speeds or from side loads, and a loaded up touring bike is a very probably venue for this to happen.

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    If the option is doing something or doing nothing, does doing nothing expose you to a higher or lower risk of failure? – mattnz Jul 29 '18 at 2:27
  • Thanks so much for the answer. I'd also love to hear your thoughts on mattnz's question. In addition, when it comes to your critical question of identifying whether the rim is in good shape or damaged, are there canaries to watch for? We got the bikes for the tour, but it's also been a pretty bruising 3900 miles in terms of terrain. I'd love to give the rims a good inspection somehow if there are common signs that could tip us off to a rim in dangerous condition. – fedora Jul 30 '18 at 15:16
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    @mattnz Unfortunately I think the answer to that depends on many factors if one is applying the question to all wheels period. If you started out with well-built wheels, they've generally held up well, and now you've got a little side-to-side warble, then yes, making some adjustments is prudent there. But it should be on the order of a handful of 1/4-ish turn tightening adjustments. If there are more significant problems with many or most spokes seeming slack, it's a difficult choice because that's a wheel that could fail on you, but it's also easy to get in over your head with limited skills. – Nathan Knutson Jul 30 '18 at 18:09
  • @fedora The big, reliable, easy to explain one is that if you're truing the wheel, paying all normal attention to both radial and lateral true, and you find a spot where to get the rim to move in the direction you want you have to either loosen spokes that are already getting too loose or tighten ones that are already getting too tight. Once I make that observation, damage to the rim is something I think about. The next step is to make the tension balance in those areas on the rim as good as possible, because it's possible it was off for other reasons and if so it can throw off your judgment. – Nathan Knutson Jul 30 '18 at 18:15
  • I use a tensiometer on every spoke for all those steps to help quantify what I'm seeing or the judgments I'm making. It's perfectly reasonable to do it without a tensiometer, but despite tensiometers being kind of a fancy and intimidating tool, it's actually a more advanced skill to do this stuff without them, as what they let you do is observe the tension without your wrench feel being tricked by thread or nipple friction, or your grip of the spokes by how strong your hand is feeling or your memory of what you should compare against, or your ears by different harmonic ranges or whatever, etc. – Nathan Knutson Jul 30 '18 at 18:20
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For a normal wheel with 32 or more spokes and a metal rim, I'd say you are pretty safe. Even if one or two spokes ended up breaking, there is enough redundancy to avoid catastrophic failure. Myself I'd probably continue riding even if one spoke broke.

However, if you have one of those super-light 16 spoke wheels or a carbon fiber rim, be more careful as they have been optimized for the minimum necessary strength and have less margin for unbalanced tension.

To roughly balance the tension, you can pluck the spokes after adjustments and listen to the sound. You can hear if a spoke is very loose (low sound) or very tight (high-pitched sound).

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