20

I took my bike for a service recently and was told it needed so many repairs that it was more cost effective for me to replace it.

One of the repair jobs was to replace the wheels due to worn rims. The shop told me they were so dangerous that they refused to replace the brake blocks - which were also dangerous - for fear of causing extra wear.

I am happy to replace the bike but this is a bad time to do so. I'm looking to move house and my eventual location may impact what kind of bike I buy. I'd like to ride on my worn rims until then.

The rims have a groove to indicate wear. The groove is still visible but it has become very shallow:

enter image description here

I've sorted the brakes for now by tightening the cable. But realistically how safe am I riding on these rims and for how long?

Bob Tway
  • 691
  • 3
  • 7
  • 13
  • 4
    If you want to slow down the wear rate of your rim, keep brake blocks clean of hard particles that embed in the rubber. Do a little sanding with medium-fine sandpaper and keep the rim surface clean from oil, grease and brake pad residue. Debris in brake pad is abrasive and wears the rim faster. Other residues in braking surface decrease braking power, making you apply them for longer and harder in order to stop. – Jahaziel Sep 25 '19 at 17:35
  • Did they specifically say that the rim is worn or just that it needs replacing? Maybe it has a crack somewhere? From your photo it’s hard to judge how deep the groove is. Is it completely gone in one area? Also, if you run wide, high pressure tires on narrow rims it’s more dangerous. – Michael Sep 26 '19 at 09:21
  • 1
    Don't confuse the wear indicator groove with a groove cut by bad misaligned brake blocks. – ratchet freak Sep 26 '19 at 12:19
  • It is still with visible groove and you only need to replace the brake block. As above pointed out, cleaning brake (and replace if required) and rim will prolong the lifespan of your rim. – mootmoot Sep 26 '19 at 12:37
  • I think what they meant with “fear of causing extra wear” was that those rims would quickly grind through new pads again. – leftaroundabout Sep 27 '19 at 15:23
  • @ratchetfreak Agreed but the groove in the photograph definitely looks like a wear indicator. – David Richerby Sep 29 '19 at 10:26

3 Answers3

49

Rims are worn out when the groove disappears. If the groove is clearly visible, well-defined and of uniform depth all the way around, the rim is not quite worn out and certainly not dangerous.

New brake blocks will cause less wear as they will be free of hard particles of grit and metal that get embedded in the relatively soft rubber over time.

Given the repair shop's bad advice on the state of the rims and refusal to replace the blocks, I'd disregard all of their other advice about needed repairs. I suspect they just saw a well-used bike and decided they could persuade you to purchase a new one. Find a repair shop with a better reputation and get a second opinion.

Replacing and adjusting brake blocks yourself is relatively easy if you have basic tools. Park Tool has an excellent web page and collection of videos that walk you through the process.

Peter Duniho
  • 820
  • 4
  • 12
Argenti Apparatus
  • 75,665
  • 4
  • 86
  • 188
  • 3
    Thanks. To be fair to the shop, they didn't suggest I get a new bike: I did. The new model is about £120 more than the cost of repairs, but I can get that much discount via a work scheme - but they didn't know that. So this isn't a scam, just bad advice. – Bob Tway Sep 25 '19 at 17:47
  • 1
    Concur - the deepest part of the groove represents the thickness of remaining rim that is still safe. Less than that is too thin, so seeing any groove at all is still on the usable side. – Criggie Sep 26 '19 at 10:02
  • 3
    I don't think it's a good idea to second guess the bike shop here. Perhaps the rim is not too badly worn but it only takes one place where it is to compromise the whole thing. Feel free to disbelieve them and get a second opinion or just replace the pads yourself. – Eric Nolan Sep 26 '19 at 15:01
  • 1
    @MattThrower: trying to get you to do repairs / replacements that aren't truly necessary can also be considered a scam, if they aren't distinguishing between necessary vs. "might as well replace while it's in the shop anyway". – Peter Cordes Sep 27 '19 at 07:48
  • 1
    "Replacing and adjusting brake blocks yourself is relatively easy if you have basic tools." Allow me to state this more clearly: replacing and adjusting brake blocks is trivial and the only tool required is whatever you need to undo the screw fasteners (a screwdriver or allen key). – David Richerby Sep 27 '19 at 11:22
  • 1
    Consider leaving them a review too. – Travis Sep 27 '19 at 19:32
  • Should be fine if the wear indicator is showing. If you want a 2nd opinion, buy a cheap dental caliper which will allow you to measure the rim wall thickness to within 1/10 mm or so. Many advocate replacing at <1mm sidewall thickness. I ride a deep V rim with 0.8 in some spots and it doesn't worry me. But I wouldn't take them on a tour. You could measure the thickness at the groove to see what that would mean. * Is it something odd about the photo or is the rim out of round (flat) in between the spoke there? –  Oct 02 '19 at 15:03
5

You're definitely safe to ride these assuming the wear is uniform the whole way round and you're not just showing us the good bit!

My local shop will recommend things be replaced in front of your significant other if you want an upgrade. Are you sure you didn't inadvertently give a secret code that you want to buy some carbon rims?

Duke McAwesome
  • 51
  • 1
4

I had an experience with worn rims. The wheel suddenly exploded, the tire separated from the rim, and I ended up cycling on the (metal) rim alone. Since I was on a straight, even road, it was not too alarming. As I remember it, I removed the tyre and continued to cycle home on the bare metal rim.

Consequences could had been worse, had it taken me by surprise in a more critical situation. Braking power would have been poor, since the tyre was immediately shaved off.

This happened since I had rims that were very worn, and moments before I pumped the wheel to some considerable pressure.

I would replace the rim if the bike is used for riding downhill or at high speed. If not, I would not be too concerned.

Michael come lately
  • 1,182
  • 1
  • 8
  • 22
Torbjörn Österdahl
  • 41
  • 2
  • 1
    My experience was that a thin strip of the rim peeled off and formed a thin ribbon that wrapped around the brake calipers and completely jammed the wheel. I was very glad this happened when I was moving slowly instead of while I was descending at 60kph an hour earlier. – Eric Nolan Sep 26 '19 at 14:57