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My mountain commuter (2008 Schwinn High Timber) has picked up a vibration in the front wheel under braking. I'm worried that this is a sign that the rim is end of life. I checked the V-brakes and they do have some slight play front to back (about a 1 mm at the top of the brake arms), but the bolts for them are still tight. I have found a few spots on the wheel that looks like a pit, or possibly environmental damage, but not enough of them to justify the vibration.

Is it possible that a rim will warp into a wavy pattern (I highly doubt it)?

This rim does not have a wear indicator when new, but will they put something in the rim that will be exposed when worn?

It is a Alex "X101" (best geuss) Rim single wall alloy, but since it is a BSO OEM, it isn't listed on the website. I have put 15000 km on it with 2/3 of it being daily commuting. My commute home involves braking from speeds of 50 kph for red lights and a turn on a 3.5 km stretch. I have to ride the brakes for a short but steep downhill section while escorting the kids home. The wheel is still true and the bearings are in good shape. I'm on my 3rd set of brake pads (oem, over the counter bike shop, and now KoolStop dual compounds used for 2000km). I'm a all weather rider, but I keep the bike clean. I don't get to ride in nasty slushy snow, but roads are heavily salted here that will linger for weeks.

I'm planning on changing the wheels out anyways here in a few months for other reasons, but I just want to make sure I'm not going to kill myself in the mean time.

  • I'm thinking that the title question can be better worded. Perhaps "Cause of braking vibrations"? – BPugh Sep 15 '15 at 16:55
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    Its a front wheel - and they're symmetrical. As a test, try flipping the whole thing. Your brakes should line up with the rim okay, but your tyre tread may be sub-optimal if its a directional pattern. That won't matter for a short test in dry conditions though, and if it helps then you can flip the tyre on the rim later. Also consider the wear on your brakepads - if they're getting worn then that can oscillate under braking. You may need to move the pads closer to the rim, or adjust the barrel adjuster at the brake hand lever. – Criggie Sep 15 '15 at 23:53
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    So I fixed the vibration in this case, and it wasn't serious. However please submit answers that might help others. I'll post my answer after some photo editing. – BPugh Sep 16 '15 at 2:09
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Is there any kind of wobble or unevenness in the rim? There shouldn’t be more than about 1mm of wobble. If there is a noticeable wobble the wheel might simply need truing.

Are the brake pads properly aligned? They should wear evenly over the whole surface.

You can measure rim wall thickness with a caliper gauge. A sign for rim wear is also if you can measure a deformation (change in rim width) between zero and maximum tire pressure.

  • I know using calipers to check the thickness is useful, but I don't have the right kind and I don't know the safe minimal. Using the calipers on the outside is a good idea I haven't tried yet. I can check later, but I only have sliding digital calipers so it may be iffy. Since my back wheel is notorious for coming out of true I tend to check them both often, but I have a front suspension and I don't curb bash so it stays true (don't ask me how). The brake pads are aligned too, I was just checking them the other day. – BPugh Sep 15 '15 at 16:53
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I had a case where my front brake would stick at one point of the rim. I complained at my local bike shop and they scrubbed the rim with a soap/degreaser suggesting it could be surface contamination. It fixed the problem. This is an easy and cheap thing to try.

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I found the solution to my vibration issue. This bike has Continental Touring Plus tires on it which have a interesting multi panel construction that has radial ribs on the outside:

Tire rib detail

However, in an effort to at least clean up the looks of my bike I tucked the left over brake cable back behind the brake arm. Well after a few weeks the pad has worn down far enough that the end of the cable is touching the tire right along the radial ribs. This is the cause of my vibration. I was able to verify it visually and by the sound it made striking it.

It looks like the brake pad is out of alignment for some reason. I noticed that it was rubbing the tire a few weeks back and fixed it, but Looks like it moved back. In this case it will hit the ribs as well, but since I haven't noticed it then, I don't think it was the issue this time.

Cable on tire

I'm not going to mark this as an answer since it doesn't answer my original question.

  • Good spotting - thank you for sharing your results. – Criggie Sep 16 '15 at 21:52
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If you have side-pull caliper, cantilever, or linear-pull brakes and they are not engaging both sides of braking surfaces at the same time, your wheel may be getting pushed one way or the other. At that point, you're at the mercy of the collective spoke tensions and strengths, so vibrations and stop power will vary.

I've only ever let mine get so far out of alignment that I noticed any vibration under braking one time, but centering calipers is part of my cleaning routine now.

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