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I installed a new front float rotor, the ones that you can get from AliExpress. I have Deore XT brakes.

While using the front brake the lever moves back and forth while pulling it. I inspected whether the rotor was bent or the caliper was not properly aligned but everything is okay.

I can't figure out what the problem is or is it expected to work like that for float rotors. Need help. Please

enter image description here

  • Could you explain in more detail what the problem is? All you say is that your brake levers have resistance and move back and forth, but all brake levers have some resistance, and all levers move -- they wouldn't be levers, otherwise! Also, AliExpress sells everything under the sun, so "the ones you can get from AliExpress" really doesn't say anything, but maybe the picture makes it clear enough what you have. There's an "edit" link under your question which you can use to add more information. Thanks! – David Richerby Jul 22 '18 at 11:08
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    Do you mean you feel a pulsing of resistance at the lever. What frequency? The same at the rotor rotation? – Argenti Apparatus Jul 22 '18 at 12:24
  • What i meant is that when i am pulling the lever it moves back and forth. Yes it feels like pulsating same as the rotor rotation – Kuntal kalai Jul 22 '18 at 13:11
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    This is something to be expected from Aliexpress products. I wouldn't use anything from there in a critical spot like brakes. – ojs Jul 22 '18 at 15:18
  • You could try wrapping a cable tie around the fork leg, trim it to length as a pointer and then spin the wheel by hand. I bet your rotor is sub-standard. Brakes are the single most mechanical critical component on your bike. Don't cheap out and buy knockoff discount parts for brakes. You're probably not going to get a refund from the seller. – Criggie Jul 24 '18 at 1:22
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Assuming that you've already checked that the rotor is true (and out-of-true rotors are more responsible for rub than pulsation), I would take a micrometer and measure the thickness of the rotor in multiple places. You are likely to find that it was not machined correctly. Also, check the surface finish of the rotor on both sides. It doesn't matter what it is so much as that it is uniform, all the way around.

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Most likely explanation is that the rotors were machined improperly, so they're not the same thickness all the way around. This causes the calipers to go in and out as the wheel rotates. There's nothing you can do to fix that, except get better rotors.

(There's no such thing as a floating rotor. The calipers may be floating, but not the rotors. See here, under "two types of disk brakes". The article is about automotive brakes, but a bicycle hydraulic disk brake is basically the same mechanism.)

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    A "floating rotor" is one where the steel rotor is loosely mounted on central spider so that it can expand and contract with temperature without warping. The picture shows one of those. – ojs Jul 22 '18 at 15:17
  • Agree it could be non-uniform rotor, seems like the first thing to check. But it is a floating rotor! – Swifty Jul 22 '18 at 16:09
  • @Swifty Please don't propose edits that delete chunks of text from answers. If you believe that text is wrong, downvote and explain why. – David Richerby Jul 31 '18 at 12:47
  • @David OJ’s Explained why in the comments. It’s been a week. I want to upvote the bit that’s correct! – Swifty Jul 31 '18 at 13:15
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Place a steel ruler along the brake disc and check for gaps. There is not much brake disc with lots of slots. Push the bike slowly whilst applying some pressure to identify the area this happens.

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The rotor and the brake pads were probably not bedded in properly. Happened to me too. Clean the rotor surface with isopropyl alcohol and change the pads. If this does not work than check the caliper alignment and if the rotor is in someway bent.

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