New rotors? Disc brake noob question.

[AllanVarcoe]

Hi!

OK, so I've just built my first disc bike. The brakes tend to "surge" or "pulse" when applied.

Just wondering if this is normal with new rotors? The surface of the rotors has a ground finish that only goes in one direction. Across the rotor, not radially or axially.

http://uploads.tapatalk-cdn.com/20161015/db92418576ade036f234512ba9fd4d7a.jpg

Thanks,
Allan

[hmai18]

Did you do a proper burn-in of the rotors before using the bike?

[AllanVarcoe]

Definitely not. No idea what that is.

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[R3awak3n]

Prettry much ride as fast as you can and brake as hard as you can. Do this a bunch the first time you install new pads. That said I always had similar problems with stock rotors (was also on bb7). Now I am on trp spyres but also on ice tech shimano rotors and I think they are excellent. No noise, no pulsing, really good piece of kit.

[AllanVarcoe]

Prettry much ride as fast as you can and brake as hard as you can. Do this a bunch the first time you install new pads. That said I always had similar problems with stock rotors (was also on bb7). Now I am on trp spyres but also on ice tech shimano rotors and I think they are excellent. No noise, no pulsing, really good piece of kit.
Pretty much have done that. That's when it was pulsing really hard.

What is this pre ride burn in?

[AllanVarcoe]

I was thinking about polishing/sanding the brake surface.

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[Cat3roadracer]

Is the brake pictured above post mounted?

[AllanVarcoe]

Is the brake pictured above post mounted?
Nope. IS.

[Mikej]

It's most likely that brand of brake- it's not your rotors don't sand them.

[HillDancer]

Proper bed-in procedure is on page 12. http://cdn.sram.com/cdn/farfuture/bN7LPXFNZN2ShC8NrhYiKlYLc-bVfqiXCPenrf9IoMk/mtime:1316452980/sites/default/files/techdocs/service_manual_bb7__bb5.pdf

It is possible the rotor has uneven pad transfer, which can create pulsing. It is important to avoid braking to a complete stop before complete & even pad transfer has occurred, and avoid prolonged application of the brake before complete bed-in. Clean the rotor's swept area with denatured alcohol, and follow Avid's bed-in instructions from beginning to end.

Observe the pads within the caliper while in the closed position, clamping the highest/outermost edge of the rotor. If the rotor edge is not raised above the pad, this will cause pulsing and/or noise. Even one corner of the pad(s) peeking above the rotor can create those symptoms. There should be an un-swept strip along the rotor edge of at least .5mm. To remove pad peeking, file the pad upper edge till it contacts below the edge of the rotor. Example below is of a different pad.

https://lh3.googleusercontent.com/DLDl0-fJMgZHzJlCRPKMBDs0745QOS2hLYBMDZTm2OKjW1ivowjETtfV DX_UV2qo_59LvEdfT60EJQ=w1920-h1080-no


Another approach is to face the post-mount ends of the adapter. Another alternative, a 183 rotor with appropriate adapter could be installed, then insert a 1mm washer/shim under the CPS washer stack.

Installation error is the most common cause of noise with a BB7 caliper/brake; re-align the caliper and follow Avid's bed-in procedure.

I used BB7 brakes for years, it is possible to have noise & vibration free performance with this brake. The quietest pad I used was SwissStop Disc17 organic.

[AllanVarcoe]

THANK YOU! I was hoping someone would be able to give better instructions. 😊

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