I recently purchased a few things for my bike, of which were both front and rear rotors along with brake pads, all brand new. There's a bit of a "pulse" when I use my front brakes, and it actually caused me to wipe out the other day for the first time ever. I'm not sure exactly what might be causing them to do that. I did put Disc Brake Quiet on the reverse side (obviously) of the brakes prior to installing them/remounting the calipers because I had an issue in the past with squeaky brakes -- it's annoying and I figured I'd go ahead and do that while they were off. But yeah. The pulse -- I'll pull the brake lever in and maintain a steady pull on it, but the brakes will go from hard to soft and it will slow down as the bike does. The rotors I took off were stock OEM ones as far as I know and I never had an issue with those, considering putting them back on and seeing if it still happens. Would like to hear some thoughts before I do that though.

Thanks much in advance!

-D

 

Hi , have you tried a run-out meter on the rotors?

 

If you have a run-out meter, Id do as CaBaRet suggests, if not..

First I'd give the discs a thorough clean with brake cleaner.

If the problem persists, I'd change the discs back, that way you can narrow things down a bit.

 

It seems like a pretty aggressive "pulse" but I'll give the brake cleaner a try over the weekend. What exactly does a run-out meter test? The depth of the grooves or..?

 

It measures warp in the disc, like this

 

Forgot to ask...

Are the replacement discs good quality, or are they cheap Chinese knockoffs?

 

Are the mounting points on the rim good, flat, and clean?


You can see excessive run out by observing the size of the gap between the pads/caliper and rotor. It should be pretty obvious since it's as bad as you say it is.

 

https://www.ebay.com/itm/122803055318

Those are the ones I bought. I honestly didn't even clean the mounting points before installing them. Would there even be noticeable (without a meter) run-out after only a few days of riding? I've been using the rear brake a LOT more since the front ones are sketchy. I put the old pads back on and it isn't as bad though still noticeable. Also haven't tried cleaning the rotors yet with brake cleaner but I'll be doing that sometime today.

 

Hi , do you know, were they bought as Fully Floating or Semi Floating, that is are the bobbins turning

 

I honestly don't know the difference..