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I have a Whistle B-Race 7.1 e-bike that's about 3 months old.

Recently the front disc brake has started touching the brake pads when not braking, when it does you can hear a "zing" sound.

It does so during hard turns or when i'm riding without hands on the handlebar, but when i try to willingly reproduce the problem, i can't, for some reason. It is not constant, it happens in short intervals.

I tried removing and putting back the front wheel, making sure that everything is aligned, but nothing has changed.

The front tyre is slightly crooked, i think i messed up changing it when i got a puncture, but thats just the rubber, not the rim. Could that be the problem?

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    Have you pulled the pads and inspected them? Could be simply worn, and the noise is a consequence of too much space ?
    – Criggie
    Aug 12 at 9:39
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    @Criggie I don't think that the pads are worn (altough i have to check), the bike has only about 300 KMs. The other thing is that the noise happens when i so NOT brake. It feels like the rim (or the disc?) goes slightly out of alignement when i corner hard.
    – Yeeter
    Aug 12 at 9:42
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    Check the tightness of the thru-axle or the QR.
    – Carel
    Aug 12 at 11:49
  • 3 months old. Guarantee?
    – Tim
    Aug 14 at 13:56
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Rotors can and do bend, subtly. Have you checked it's flat? One of mine sounds flat (or rather doesn't sound) cold, but has a high enough spot when hot to sing.

Have you checked for play in your wheel bearings? That can cause rotors to touch especially when cornering.

Even if the rim is a little out of true, that won't affect the rotor, which is rigidly mounted to the hub (check the rotor bolts as well to be sure).

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    Last time i checked the rotor was perfectly flat, but i will have to double check. Now that you mention it, it might be the wheel bearings, because i feel like something is going out of alignment when i corner
    – Yeeter
    Aug 12 at 9:48
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    Also, some (most?) forks have replaceable thru axle threads/inserts, on my Ritchey the fixing for this had come slightly loose. Felt like a loose headset, but it was actually causing twist, I can imagine this causing random brake noise. Aug 12 at 21:20
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This is something that I have been experiencing as well. With my bike upside down, I had a light on the ground and could peak through the caliper as the disc spun with the wheel. I could see that the rotor was moving closer and then further from the pad. Aha, I thought, the rotor is warped. But then by chance I noticed something else. The whole wheel would bobble slightly, and of course the rotor with it. I took the wheel off and partially disassembled the hub. It seems that the bolt (or whatever it's called) that clamps on the ball bearings was a little loose. Tightening that is a bit of an art form. Too tight and the wheel feels very rough and you'll wear out your bearings quickly. Too loose and the wheel wobbles. You gotta get it just right. Playing around with it a bit and I was able to reduce the wobble quite a bit and it still spins nicely. I think over winter I'll just replace the bearings but for now it seems alright. So check to see if your wheel wobbles slightly and if so it's probably the hub/bearings.

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    I'll definitely try that, feels like it very well be the problem
    – Yeeter
    Aug 13 at 7:27
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One possibility: if the pads are really worn, it could be the case the brake disc is not touching the pads but rather the pad spreading spring.

My experience with hydraulic disc brakes in general is that very minor inaudible pad rub is inevitable, contrary to rim brakes where it can be avoided. To offer any decent amount of braking, disc brakes must have very minor pad gap, because the rotor diameter is an insignificant fraction of the wheel diameter (unlike in rim brakes where the rim at wheel periphery is the brake "disc"), and because the coefficient of friction of disc brake pads is worse than with rim brakes.

If the pad rub is making any noise, then it seems it could be so significant it could rob you of useful power.

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    Unless i did not understand correctly, but i don't think it can be what you mention, the noise happens when i do NOT brake. My worry is that the rim or something goes out of alignment (or bends, idk) when i corner hard, if i'm going fast and something happens i don't want to destroy the bike (and myself) for something that i can fix
    – Yeeter
    Aug 12 at 9:46
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    I had a pad spreading spring touching the brake disc when not braking. Cause was too worn brake pads.
    – juhist
    Aug 12 at 9:53
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    Oh now i understand, i will take a look at it!
    – Yeeter
    Aug 12 at 10:05
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An occasional “zing” sound is completely inconsequential. Just ignore it, brakes do stuff like this. Even if the pads slightly touch the rotor once on every rotation, the energy loss and pad wear is probably negligible.

Of course, do regularly check the axle, bearings, spokes etc. for stability, as well as the bolts for the calipers and rotors – but brake noise usually doesn't have anything to do with that.

Only if there's a permanent squeal or the wheel stops rotating after only a few seconds when you spin it in the air, is it worth investigating the brakes themselves – trueing the rotor and/or pushing back the pistons. There are many tutorials for this on the internet.

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Also check that the caliper bracket bolt ends are not too close to the rotor.

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So, after quite a long time i managed to solve the issue.

After a close inspection i saw that the external brake pads was really, and i mean really close to the brake rotor, so close that when braking the rotor was actually deforming (i don't know if that's normal). I guess that when cornering the brake rotor and pad were actually touching, maybe there is a bit o play in the QR system or something.

After a bit of fiddling i managed to get the two brake pads the same distance from the rotor, moving the calipers a bit to the right.

I tried riding quite hard down a trail and the problem was gone.

NB: Many guides suggest that you loosen the caliper screws, brake hard and while braking re-tighten the screws so that the calipers are centered. This did not work for me, i had to center them manually and keep them in place while tightening the screws.

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    Note - do still check that the calipers are bolted with all bolts correctly torqued to the fork. I had this exact issue because one bolt was not tight causing the caliper to be at an angle when the fork was strained from the stress of turning. Even if the clearance is close - the position of the caliper relative to the disc should not change much in a turn.
    – Neil
    Oct 4 at 20:14

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