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I use 6-bolts hub with 203mm rotor and despite it is well aligned and rub free sometimes when riding (even on flat surface) there is vibrations coming (I guess) from crankset and/or road enough to make rotor resonate a bit. This leads to rubbing against pad in audible manner.

This of course is not welcome, I don't even care so much about wear of the pads/rotor, but the delicate noise coming from rotor.

So I wonder -- is centerlock resonance free? Or maybe not 100% resonate free, but more stable in this regard than 6-bolts?

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  • What was the reason for choosing such a large rotor? Is your caliper on any sort of adaptor to get it out far enough?
    – Criggie
    Oct 24, 2020 at 12:33
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    @Criggie 200/203mm rotors are the norm on aggressive trail and DH bikes.
    – MaplePanda
    Oct 24, 2020 at 18:28
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    @MaplePanda possibly, or it may be a caliper on the end of an adapter, which can add flex. OP doesn't say if it was that big originally.
    – Criggie
    Oct 24, 2020 at 23:29
  • @Criggie, it wasn't that big originally, it was simply another adapter. To work with different sizes you change adapters. But this is interesting angle -- maybe the longer adapter vibrates as well, and if they (rotor and brake) out of sync the rubbing occurs. Oct 25, 2020 at 5:24
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    I'd suggest checking how flat and coplaner the mating surfaces of the adapter and the frame and the caliper are. Disassemble, clean, and use a straight edge and a bright light to check.
    – Criggie
    Oct 25, 2020 at 12:44

3 Answers 3

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Intermittent rub that corresponds to load received by the frame or fork doesn't have anything to do with how stiff the rotor or its connection to the hub is. It's the fork or frame being flexed, not the rotor.

Usually the issue is caused by the air gap between the rotor and pads being too little, such that flex that would otherwise go unnoticed is causing rub. Causes can include rotor truth, poor caliper centering, piston stickiness issues, crooked wheel installation, poor parallelism of pad surfaces in the caliper, and/or poor brake mount surface alignment. Sometimes one sees a situation where none of those problems exist but rub is occurring anyway from the rider simply overloading the bike, but that's not very common.

Center lock versus 6-bolt is not a factor. On QR disc bikes, the stiffness of the hub axle can be a factor, however. In particular, going to a thru-bolt hub is one way that rub under load can be mitigated in those cases where it's happening when all of the other potential causes have been pursued. Thru-bolts add stiffness to QR forks and frames.

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  • Thank you for the explanation, especially QR. But in this case i still think it is a matter of big rotor, because when I simply push the bike (like from the stairs) and I hit the ground it is not split second tremble (sound) but rather 3 second sound (ringing). I really doubt steel fork, without me in the saddle, not moving (after hitting the ground) would flex so easily. All in all I will keep an eye on thru-axles instead of wondering about CR :-). Many thanks. Oct 23, 2020 at 19:09
  • The thing is, if the rotor is able to intermittently rub the pad, regardless of cause, you need to look at both why the movement is taking place and also how much it has to move before rub can occur. Usually the problem is more with the latter, as are the factors you actually have control over. Oct 24, 2020 at 1:22
  • A better hub and a good QR skewer mitigated rub somewhat on my bike.
    – gschenk
    Oct 26, 2020 at 14:44
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Your use of the word 'tremble' is somewhat disconcerting. Do you mean the rotor is loose and vibrating in response to road irregularities? If so, stop whatever you are doing and immediately check the rotor mounting bolts and make sure they are tightened to the proper torque specification.

I have a suspicion that you actually mean that the rotors seem to go out of true while riding and causes slight rub on the brake pads, which can be heard as a soft 'ching-ching-ching' as the wheel rotates.

What probably is happening is that the rotor is in fact warping slightly, or your brake pistons are sticking slightly which causes one pad to contact the rotor.

I've ridden both SRAM Force 6 bolt and Shimano Ultegra Ice-Tec centerlock and they both need periodic re-alignment.

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  • Put a glass on the table and hit it with the knife (gently). The glass will tremble and you will hear the sound of it. i have nothing loose, I simply sometimes hear something similar from the rotor-pads and since I get this effect amplified when I hit with wheel with something I guess 203 mm is a long way from the mounting points (bolts) so the rotor edge can vibrate and cause the rub. Oct 23, 2020 at 19:03
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    @greenoldman A rotor cannot tremble like this. Either something else moves/flexes (fork flex is common) or something is very bad with your bolts fixing the rotor. Oct 23, 2020 at 19:54
  • Sorry I suggested "resonate" etc in a comment and OP edited their question.
    – Criggie
    Oct 24, 2020 at 7:49
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You might find that the Floating Rotor on an alloy spider solves this problem. They are made for both 6 bolt and centrelock. Hope and Shimano both manufacture the better rotors in this design, though not cheap. Hope Floating Rotor

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  • Which problem exactly? In which way does it solve it, stiffer rotor? Oct 25, 2020 at 7:27
  • The rotor is stiffer, the alu acts as a sound damper too (alu frames hardly ring compared to steel).
    – Noise
    Oct 25, 2020 at 7:34
  • But which problem does it solve? In my experience it is the fork the caliper is on that often flexes. Does it solve excessive rotor flex? When does that happen? Oct 25, 2020 at 7:36
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    The author says he gets ringing that isn't attributed to rub. Also, all discs rub sometimes, but you find it less noticable with this type of rotor as the spider already acts as an acoustic damper.
    – Noise
    Oct 25, 2020 at 7:45
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    This design is supposed to warp less when hot and dissipate heat faster, those were the main advantages advertised by the manufacturer
    – Noise
    Oct 25, 2020 at 7:49

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