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I've just installed some Sram Level T brakes on my hardtail as the Shimano Deore brakes seemed to be leaking from every seal possible. It has stupid centre-lock rotors so I kept the rotors from the Shimano brakes.
With the new brakes they have a weird pulsing feel when pulling them (much more so on the rear). It is as if the rotor is thick/thin/thick/thin and that feeds back through the lever. So I pull the lever then after the rotor rotates 15-20º the lever pulls in slightly further and another 15-20º it pushes back a little and repeats. It isn't that the rotor is bent as it happens too frequently over the rotation to be bent.
Anyone any ideas why this is? Is it simply as I've written that the rotor is worn and is indeed thick/thin/thick? Weird that it could wear out only in certain sections if so.
Warped or contaminated rotor would be my guess. If you've had leaking calipers, you're likely to have had oily spots on the rotor. Pad material will be deposited on the uncontaminated bits, but not on the oily bits. Also, if you drag the brakes down a long hill and then stop at the bottom with the brakes clamped on, you'll get hotspots on the rotors and pad material deposited there. Checking that the rotors aren't warped and then sanding them down with fine grit paper and cleaning them with alcohol is probably a good starting point.
Are the pads contacting the rotor in the right place, on the braking surface and not on the "spokes" ?
Is the disc one with a wavy edge? As Scotroutes says it may be the pad sitting too far out on the disc and making contact with the wave edge. I had this on avid discs with shimano brakes, so might be similar.
I knew the rotors were contaminated so I cleaned them thoroughly with soapy water, alcohol and then sand paper. I'm pretty certain they're not contaminated any more as they work well and are sharp now, there's none of the typical contaminated brake feeling.
Also thought it could be that Scotroutes but rotor seems to be sitting nicely in line with the pads.
My guess is that they are not fully bed in yet
I've had the same problem on guide brakes on a brand new [complete] bike. Front brake only - pulsing feeling through the lever.
New pads and thoroughly cleaned rotor didn't fix it. I'm going to stick a new rotor on at some point as I suspect the current one must be a bit shonky in some way, but haven't yet got round to it.
I occasionally get annoyed by it, but mostly manage to forget about it - i've had the bike for about 9 months and use it frequently.
My vote is the pads are overlapping the spokes of the disc. I took a disc off over of my bikes last year and it was scary how it was where the arms joined the braking surface!
I get this with the maguras on my big dummy. Pretty sure it's the spokes of the crappy avid rotors. Keep meaning to order some magura replacements.
I hate centre lock rotors.
A loose rotor?
I don't have centre locks, so no idea if this is possible, but had a similar thing when the rotor bolts came loose on my rear hub once.
Rotors will be worn thinner in places. We used a gauge at the shop that measured thickness, pulsing was always due to unevenly worn rotors. Icetech were notorious for this but with affect all rotors . The fact you are using old rotors only reinforces this. Time to replace