Rear brake pulse...

I have a slight rear brake pulse. Only really notice it when I'm slowing to a stop under 15mph. It's not terribly severe, but defintely there.

I have just installed a new EBC rotor and EBC organic pads. They installed fine after using a c-clamp to push the pistons back in. However, when I went to put the bike on the road I could barely roll it out of the garage due to the rear pads grabbing. I decided to ride it anyway and hope the pads would bed in. I did a short 2 mile ride and returned. The caliper and rotor was hot and I could smell brakes. I bled the rear brake and everything is rolling smoothly now.

So what's the verdict? You think I warped the disc when it got hot? Perhaps created a high spot from heat? I think the slow speed pulse was there even before the brakes had a chance to get hot though.

EBC also mentions on the rotor packaging that it can take up to 200-300k before the pads and rotor wear in. And during that time you may not get optimum braking. I haven't quite put that many miles on the new setup. Am I jumping the gun?

 

Give it a little time. It's unlikely that you've warped the disc this soon. EBC is pretty good stuff.:biggrin:

 

That's what I was thinking. The EBC rotor looks sturdy, sturdier than OEM. You would probably need to get it super hot to warp. I'll give it some more time. Thanks

 

Did you clean the pistons before pushing them in? If they were dirty they are probably sticking to the seals and holding the pads against the rotor. Pull the calipers apart and clean everything. If you did clean them (good boy) try a little moly lube on the pad retaining pins to help the pads slide.

 

Naw, I didn't clean the pistons. I know, shame on me. I'm thinking I may just pull it apart for cleaning/inspection if I still have trouble after a couple hundred more miles or so.

 

What he asked^

 

I'm still trying to figure out how that would give me a pulsing feeling though. The bike rolls fine now when I'm not on the brakes.

 

I agree this could be a possibility. One other thing it might be is that if you did not get the caliper pistons pushed all the way back in, when you bled the rear brake the pistons stuck in teh out position. This would also create the extra drag and overheat the rotor (I had this happen on an 82 Trans Am with rear discs). It is possible the the rotor could have warped. I would suggest, as GenLightning did, to disassemble the rear caliper and make sure there is not debris interfereing with the movement of the pistons. Also check the runout of the rotor to make sure it is not warped. If you do not have a dial indicator, this might also be done be removing the rotor and laying on a flat surface and placing a straight edge, like the edge of a ruler, on it and look for gaps between the edge of the ruler and the rotor. Hope it works out for you with little to no expense. Good luck! :thumb:

 

I probably had air in the lines and should have bled them before riding the bike. I'll be peeved if I warped a new rotor. Live and learn eh.

I'll try cleaning the caliper and piston assembly first. Then pick up a dial indicator if I need to go further. Good excuse to grab another shop tool.

 

Is it necessary to disconnect the brake line to clean the caliper pistons correctly?

 

No, just pull the bolts & flop it off; push down on the brake pedal to push the pistons out then clean all the crud out. I always lube the pad retaining pins w/ a little anti seize compound to never hurts to add a little "weinersliden" to caliper pins. It may also be possible that the pad is hot spotted/glazed which will burn off as the pads bed in. No worries I do this kinda crap for a living & every now & again forget to do good prep; kind of a screw me once, shame on you; screw me twice shame on me thing(though when you do all your own work theres only one person getting screwed both times if it goes there)

 

Thanks guys. Yeah I know I got in a rush. I'm usually a very patient and careful tech, but I just got everything back together and was eager to ride the darn thing.

 

I honestly figured the brakes were just tight because both the rotor and the pads were new. I didn't have any trouble sliding the pads over the rotor so I also think I probably had some air in the lines and atmospheric changes could have caused the grabbing. At any rate, I'm a moron, I admit it.

 

I pulled the whole caliper today and cleaned the pistons and cylinders. Sure enough the ends of the pistons were gummed up and one was sticking pretty bad. Flushed and bled the system.

Noticeably better rear braking and it did help with the pulsing. Still have a slight pulse though. Kind of a pisser to think I may have warped the rotor. It's minor enough that I'm gonna ride it out though.

Thanks for the help. I'll make sure to always inspect the pistons from now on.

 

Evereyone seems to price the ebc rotors, but my experiens is not so good.
I buoght a new set of stock front rotors the same summer I buogth the bike, after I noticed one of the stock ones had cracks betwen the holes. Buoght them from a shop over phone, and they posted me the rotors.
After installing them I noticed a slight pulse. It got some better whit time, but not alla gone. No mesurable wraping that I found! Did the modification then so...