Front brakes pulse

[Shores]

Been working on my friends 06 Roadstar that he bought from another friend. It has 38,000 miles. The front brakes are pulsing at low speed. I'll be removing the calipers and cleaning them as well as putting in fresh fluid. The pads appear to have plenty material left on them. What is the likely cause of the pulsing?

[davej]

warped rotor "s"

[Lug Nut]

Rotors.... Warped or at least thin... measure to if they are within spec

[Horsehammerr]

My '01 Stopped Pulsing when I put New Brake Fluid in .

[Tcontrol]

Does it pulse in time with your blinker?..... if that be the case..... you’re low on blinker fluid.... you should go by autozone and pick some up ..... just in case...

[MikeyC]

LOL one in every crowd

[grubsie]

Bike probably has Italian rotors. OOPS! Is that OK to say?

[Shores]

I bled the lines with new fluid and it helped some, but still some pulsing. Can I safely spray brake cleaner on the caliper cylinders with the brake lines still connected?

[jd750ace]

You can have air in the system (don’t forget to burp the splitter) warped rotors, or a binding piston in the caliper. Rotors are pretty easy to check with a framers square for a straight edge without removal. The semi floating rotors are designed to accommodate a little distortion, but the intent of the design is to absorb temporary thermal distortion, no permanent, like dishing.

[Shores]

I checked the rotors and they don't appear to be warped. Can I spray brake cleaner on the caliper cylinders without disassembling them or removing the fluid?

[Duke]

Yes Steve. Spray any crud around the pistons and clean the rotors good, then blow off the residue.
Take the bike out and work the crap out of them, using them hard.
See if that helps.

[grubsie]

do 1 caliper at at time. I pull 1 caliper and place something in between the pads that is slightly narrower than the rotor and pump the brakes until they are tight to the piece. Pull the pads, spry some brake cleaner on the pistons and use a tooth brush to help clean the pistons. Blow them dry and press the pistons all the way back in making sure they glide in easily. Then pads back in, re-install the caliper then go to the other side.

[Tcontrol]

These are your front brakes we are talking about.... probably 70-80% of your stopping power....

do you really think it is wise to take shortcuts spraying the calipers with brake cleaner?

removal of the calipers is relatively quick. A small air compressor can pop the pistons out of the caliper (with extreme caution to prevent launching those pistons at breakneck speeds at the wall/ceiling/yourself ) a quick inspection of the seals, o-rings, and pistons will usually identify the problem rather quickly...

complete rebuild kits for the caliper are very affordable compared to the risk of defective brakes.... a good pad inspection can also give you clues to the underlying problem... and this will force you to flush the old brake fluid out and potentially address a problem before it fails at the most inopportune time...

it would be best to err on the side of caution.... or tempt fate....
As quoted time and time again:

Are You Feeling Lucky?

[Shores]

Yes I have totally rebuilt calipers before so I'm familiar with the process. My experience last time was that in my attempt to free the pistons, I damaged the seals so I had to rebuild the whole thing. The previous owner was a very conservative rider so I suspect the brakes weren't worked very hard. The other day after bleeding the fluid, I took it out for a ride and work the brakes really hard in forward and reverse. That seemed to help some. I'll remove the pads and inspect the cylinders before I take them completely apart. I like the suggestions from grubsie and Duke.

[Shores]

Problem solved! I did what grubsie suggested above. I cleaned the cylinders real good with brake cleaner, working them in and out with my fingers by pushing on one side to push the other side out slightly. Then I sanded the pads and cleaned them with brake cleaner. Put it all back together and no more pulsing. The rear brake doesn't appear to be pulsing but I will do the same with it. Pads are about 50% remaining.

[grubsie]

Good deal. Glad it worked for you.

[DEEPHATE]

You cleaned the pads with brake fluid???

[Shores]

No, typo that I corrected. I used brake cleaner.

[Jclevesque]

Glad you got it sorted out Shores.