Pulsing Back Brake

Ok so I ran into a guy with a 2012 RSMV and he is very happy with the bike except.......

He as a back brake problem that the dealer cannot seem to fix. He took it in because the rear brakes were pulsing when coming to a stop. They changed the rotor and it seemed OK for about 1500 Km and the problem came back.. So he went back and they changed the rotor AND the caliper. Again the problem went away for about 1500 Km and came back.. He just wants to have it work properly. Otherwise the bike is great and all works as it should..

So asking the folks on here if anyone as any solution to this problem... or something to check? Could dry pins cause this?

PS I told him about the site and highly recommended it

Well I would think it has to be a pedal feedback issue. I dont know how it could be anything other than parts that have been changed. Rotor, pads, caliper and if they changed the caliper then it been bleed out. only other thing would be either wheel run out, or the rotor is not running true. Weather it is because the wheel is not running true, or the rotor is not running true due to mounting.

Warped rotor................

Pulsing brake.

As this problem seems to be recurring after some distance from the previous fix I wonder if, it is possible that,

Has the rider subjected the rear brake rotor to washing, or some rapid cooling after a ride and getting the rear rotor fairly hot, and then quickly cooling it?

I believe that some treatment like that, might cause the rotor to become somewhat warped .

This would cause the pulsing as feedback through the foot pedal.

Has the rotor been checked for run out or warp-age whilst on the bike.

Are there any other further clues?

Such as,

How hot does the rotor get when riding normally?

Can the rear wheel be easily spun by hand when jacked up clear of the ground?

If not then there is probably too much residual pressure in the calipers to release the pistons after braking this causing an excessive heat build up in the rotor.

These questions are only intended to be food for thought.

Cheers, Winston66,

Northampton , Western Australia

My guess would be the rotor is warped again. Id bet that there is something wrong with the master cylinder not releasing the caliper fully, causing excessive brake drag, rotor gets hot and warps.

I agree with the above. Maybe they can mount the rear wheel on a spin balancer, and check the rotor for runout. He may have a bad wheel from the factory, with the rotor mount not straight with the wheel. After some braking, the rotor gets hot and warps. I think it doesn't have anything to do with the caliper or rest of the brake system, I believe it is all in a warped rotor.

Is this bike still under warranty? Even if not, maybe Yamaha will look at it as a warranty issue if the rear wheel is defective.

Highly unlikely, but if the wheel bearings were pressed in wrong or the axle is not true 90 degrees to swing arm, either could cause that problem.

Goose

Check the master cylinder adjustment and hoses. The system may not be fully releasing causing the rotor to overheat.

Mike

Thanks guys it gives me a few more things to look at or to suggest to the dealer. The dealer is actually trying and not giving him a hard time. It is still under warranty for a year.. I'll try and keep you posted on the solution (when we get it)

Wayne,

They should be able to put a runout gauge on the rotor to check for warpage or whether the wheel has issues? Then he might think about changing pads to sintered copper HH pads rather than the oem organic, which are much smoother?

Rick

Thanks guys it gives me a few more things to look at or to suggest to the dealer. The dealer is actually trying and not giving him a hard time. It is still under warranty for a year.. I'll try and keep you posted on the solution (when we get it)

Wayne, I've heard of brake hoses (on cars) collapsing inside and not allowing the fluid to return to the master cylinder. Therefore keeping the brake applied and heating the rotor. Should be able to feel some drag when spinning the rear wheel if this is the case.