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Working on rehabbing donated bikes for Christmas Anonymous, I regularly encounter bikes where the rim brake pads have hardened to the point that the brakes are ineffective. We have a stock of salvaged pads that we've generally drawn from as replacements, but that stock is getting pretty thin.

So I took a pad from a bike (a BSO with relatively conventional cantilever brakes, which is the most common config we see) and visited a local bike shop. Here they sold me a couple of pairs of Shimano BR-CT91 pads. These were a pretty close match in terms of appearance -- the actual pad is a hair shorter, and the mounting shaft lacks the ribbing of the old unit, but otherwise pretty close.

But when I went to install the pads they wouldn't go in. The mounting shaft of the new pad was ever so slightly larger in diameter than the old one, so it simply wouldn't fit.

I'm suspecting that the Shimano pads are intended for V-brakes, not cantis.

So, the question is: What different configurations of brake pads are there, and how do you tell them apart? And is there any terminology (other than obscure manufacturer's part numbers) that will distinguish one type from another? (This is particularly important if we want to order some replacement pads online.)

  • So I understand the shaft is too big to go in, but is it in the right place otherwise? – ebrohman Apr 23 '16 at 0:06
  • @ebrohman -- ??? There really is only one place for the shaft to be. Yes, it can be off-center or not (it isn't in this case), but that doesn't greatly affect braking performance. – Daniel R Hicks Apr 23 '16 at 0:14
  • Does your group have a good rapport with a LBS ? We buy lots of consumables from one for a good rate, and refer the most complex repair jobs to them. – Criggie Apr 29 '16 at 0:54
  • @Criggie - The guy who runs our outfit is super cheap and hardly buys anything other than tires and some cables -- everything else is salvaged. And bikes we can't repair are scrapped. I "sneak" some parts on my own money from time to time. (We do have a relationship of sorts with one bike shop in town in that they often give us trade-ins.) – Daniel R Hicks Apr 29 '16 at 1:04
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I've made some observations checking out different bikes here and there and at today's workshop for Christmas Anonymous --

We will assume, for the sake of this discussion that brakes fall into three categories, calipers, cantilevers, and V-brakes. (Yes, there are others, but not common enough to worry about unless you're really into odd bikes.)

Calipers appear to (almost) always use simple pads with threaded studs. I'm vaguely recalling from the past that there are some variations on this scheme, but I haven't observed them of late.

I have observed at least four variations for cantis:

  1. (Updated) A pad with a female thread, designed to accept an Allen-head bolt. This pad appears to be very much similar to the pad for V-brakes.
  2. A pad with an unthreaded stud with striations running parallel to the stud's length.
  3. A pad with an unthreaded stud with "ribs" (shallow grooves) about every 2mm along the stud's length.
  4. A pad with a smooth unthreaded stud.

(Note that I've been shown/sold pads of both the #3 and #4 variety from local shops, and both are labeled simply as "canti" pads. It's not clear how one differentiates.)

From what little I can tell, there is a slight variation in diameter between the three varieties of unthreaded studs. The stud with parallel striations (#2) has the smallest diameter, while the smooth stud (#4) has the largest diameter. The #3 is somewhere in-between. This variation is probably not enough to make a #2 unstable in the mount for a #4, but a #4 stud will not fit in a #2 mount, and a #3 stud is borderline fitting into a #2.

(Updated) V-brakes appear to always use a brake pad with a female thread, designed to receive an Allen bolt. On the bolt are typically washers and bushings that allow the pad to swivel, after a fashion, for adjustment.

(Everyone, of course, is encouraged to reply with your specific observations on this topic.)

  • The cantilever brakes on my bike actually use v-brake pads. So you might want to add that to the list. – Kibbee Apr 27 '16 at 1:05
  • @Kibbee - How would you differentiate those from the cantis that use caliper pads? – Daniel R Hicks Apr 27 '16 at 1:49
  • I'm not sure how you would differentiate them. But a v-brake pad is seem to measure larger from the braking surface to the brake arm attachment point than a standard caliper pad, so I would think that if you were meant to use caliper pads vs v-brake pads that the brake would be designed to accommodate that specific type of pad. I'm not sure on this and they could be completely interchangeable. I would probably use the style of pads recommended by the manufacturer of the brakes. – Kibbee Apr 27 '16 at 12:54
  • @Kibbee - See my update. On closer inspection the "threaded" canti pads I saw were very much similar to V-brake pads. – Daniel R Hicks Apr 29 '16 at 1:06
  • I've got an old Raleigh Michigan with cantis. It had two different type 4 sets, I put type 3 on with a perfect fit. The hole is too big to securely hold an M6 stud (accidentally bought some caliper/V "universal" pads). My impressionis that the grooves on type 3 cantis are to act as a ruler and measure the distance from the arm. There may be some minor benefit to grip. I'm sure I've seen cantis that use v-brake pads, but never handled them. – Chris H Apr 29 '16 at 6:58

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