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About a year ago I swapped the v-brakes with a Tektro Auriga kit. I immediately made a mistake by not properly bedding in rotors and pads, doing "powerful" brakes, sudden stopping of the bike and so on.. (but always on a flat road!). So I immediately felt noticeable vibrations with moderate to strong braking. I'm not talking about annoying noises but rather about vibrations that make the handlebar and the frame vibrate (at the rear), as you can see in this video (enable the audio). Cleaning the rotor many times, properly bedding in, and trying a semi metallic pad, did not solve the problem. Only with a Shimano RT56 rotor I have no vibration, but less powerfull braking. So the question is.. could i have ruined the rotor after a few braking? Or maybe is just a sort of incompatibility between these rotors and my wheels (Mavic Crossride 26 both front and left)? I don't know whether to buy a new Tektro tr-8 rotor or try something else. PS: the Tektro rotor is not bent.

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  • Are those the same wheels that you used with the V-brakes? I'm not sure if rim brake wheels can handle the lateral loads of disc braking properly.
    – calofr
    Nov 20, 2020 at 12:48
  • No, got these Mavic Crossride Dual just a month before swapping from v-brakes to disc brakes.
    – Odradek
    Nov 20, 2020 at 16:15

3 Answers 3

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What QR Skewer do you use?

I had the same problem on my QR disc brake bike. After upgrading to BB7 with a good, brand new rotor and good bedding in, the issue got better but did not go away completely. The scariest part was that the QR would just untighten with brake use, so I had to control regularly.

After that I upgraded the stock QR for a old Shimano internal cam one and the problem was completely gone. The issue was not only a weaker cam mechanism, but also that the stock QR had a plastic part that deformed under braking. The QR I now use is all metal.

Take a look at this article for more details: https://handsonbike.blogspot.com/2013/08/difference-between-good-and-bad-qr.html

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  • I had never thought about the QR, believing I had been given the Mavic QRs.Instead I have just those "bad QR" that you see in the article you linked. Pictures of the QR and fork. I tried the (15 years old) Shimano QR .. unfortunately it does not solve the problem. As you can see in the photos, however, it seems to me that the surface of the nut is quite smooth, even more so the surface of the fork on which they are pressed against. Another source of problem?
    – Odradek
    Nov 20, 2020 at 12:29
  • I don't think so. The wearing seems normal to me. The biggest cause of vibration that could be traced to the QR would be the plastic part.
    – calofr
    Nov 20, 2020 at 12:44
  • Unfortunately, same vibrations with the old metal Shimano QR.
    – Odradek
    Nov 20, 2020 at 15:44
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That kind of vibration can be difficult to eliminate without replacing the rotor.

The window pattern on a given rotor can contribute to it, as can the uneven transfer layer that can develop from not bedding in the rotor properly to start with.

Some improvement can be had by sanding aggressively, then cleaning and re-bedding the rotor. Sanding it off the hub is better because otherwise you'll bias the work on the easy side.

Usually I replace rotors outright to solve this problem because it's more of a guaranteed fix.

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  • Just sanded rotor and pads, at first it seemed better but after a few braking... vibrations again
    – Odradek
    Nov 22, 2020 at 14:29
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    @Odradek There have been many times where I couldn't solve the problem with any solution that didn't involve the rotor winding up in the scrap bin. Nov 22, 2020 at 17:33
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Your question is not quite clear, but there is no braking power difference between rotor brands. Differences are solely in weight, design, durability, heat dissipation on long descents etc.

So if your RT56 rotor is not causing vibration, but it is less powerful, then it means that the other rotor is a different size. Otherwise the braking performance would be the same. Rotors of a different size will require an adapter also to fit to the same frame.

It is quite possible that a bigger rotor causes vibration where a smaller one does not, since the braking force is directly proportional to the diameter of the rotor.

I'd expect 160mm to be sufficient rotor size (you don't mention) for most purposes. Remember that most force comes from the front, so for XC MTB some people use 180mm front, 160mm rear. You could experience with using your RT56 rotors on the rear and the Tektro (?) on the front, or vice versa (depending on size).

Also your fork will definitely have a rated rotor size, which relates to the braking force the fork is designed for. If you are putting too much in, then it might well vibrate. You mention 26" wheels, which suggests an older bike - older forks were often 25.4mm, whereas today 32mm is standard. I'd review the rotor size specs for your fork and the rotor size originally fitted to the bike.

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  • Both Tektro and Shimano rotors on the bike now are 160mm. The kit had 180 and 160 rotors. Thinking that the problem was the old fork, I emailed the manufacturer who confirmed that the fork is suitable for maximum 160mm rotors. So I bought a 160 mm shimano rt 56. But the problem remained with the Tektro 160mm rotor as well (this too not properly bedded in). However, i get those strong vibrations also wit the Tektro on the rear wheel.That's why I exclude that the problem is the fork, if it is not the rotor it can be only the wheels.
    – Odradek
    Nov 19, 2020 at 12:21
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    @Odradek I have experienced the type of problem you mention. The drilling pattern in the disc has some effect as well as the material. You will hopefully find the Shimano becomes more powerful as it beds in and pad material accumulates on it.
    – Noise
    Nov 19, 2020 at 14:17
  • @JoeK Have you experienced the same amount of vibration as you can see in the video? After a year the Shimano didn't improve so much, it seems a little less powerfull.
    – Odradek
    Nov 19, 2020 at 15:03

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