Brake problems
 

Hey guys, my 2015 RX3 with about 6500 miles is having brake problems. First was the surging front brake. After doing a few things that Gerry @ CSC suggested I'm convinced it's a warped disc. I requested a replacement weeks ago buy have not received it. More recently, the rear brake has been acting up. First it locked completely as I was coming to a stop. After dragging the bike to the side of the road I pried the pads apart with a screwdriver and all seemed OK. Since then it has failed to completely release on several occasions and toasted the pads. Gerry suggested replacing the fluid and new pads. I also removed, cleaned, and inspected the caliper. I also put some dry lube around the piston cup. A week and 300 mile later and no recurrence of the problem. Has anyone else experienced this? I commute on the bike so it sees pavement almost exclusively.
Thanks, Mike

The front brake warp is a very common one. Mine did it when super hot, would straighten out when cooled. I read somewhere (forgot where) that Gerry said the front brake pulsation could be caused from uneven paint on the hub where the rotor bolts. I block sanded mine when I replaced my rotor and sure enough, the paint levels were very uneven. I have yet to take the bike out (was temporarily benched), but I'll let everyone know if it fixed the pulsation or not. Notice on attached pic, no paint on the rotor mount surface.

Regarding the rear brake, I'd change the fluid. It sounds like it got too hot and expanded. You may want to adjust the pedal down to eliminate the chance of your boot tapping or resting on it.
Also, on a Hondoid dirt bike I had, I adjusted the slop out of the linkage and when the fuild heated, it locked up tighter than a drum. I can't recall if the RX3 linkage is adjustable or not.

Thanks for the reply 2LZ. The first time the rear locked up I was only a block from the house so it wasn't boiled fluid. The other time occurred a couple miles from home and after only a few normal stops. I think the boiled fluid was the result of pads dragging, not the cause. I have since changed the fluid.
On a slightly different note, I noticed on the CSC website they show an entirely different rear pad than what's on my bike. Same with the rear brake tutorial. It shows a two piston caliper and pads like in the parts section. So I hesitated in ordering pads. Do you think a switch to sintered pads on the rear (I have them on front) would help?
Interesting idea about the paint on the front hub. Gerry never mentioned it to me in our discussions. I'll check that when I get a replacement disc.

Sometimes air trapped in the system will heat up and expand,causing the brake to apply.The system is sealed, so the pressure can't bleed off.Also corrosion will stop the caliper pistons from being able to pull back in the caliper once the pressure is released.Pulsation is warped disc,hub damaged,or in the CSC case,powder coat build up.

Here is another oddity I found while servicing the brakes. I used the squeeze handle, crack the bleeder method for putting new fluid through the front system. Every time I squeezed the lever with the cap off of the master cylinder, fluid would squirt back out of the master. I've never experienced this before. Anybody else have this happen?

Yes, it happens on my Burgman 400. Squeeze slow or use a vacuum bleeder.

Yes, the master cylinder has a tiny bleed hole that points straight up as well as another hole for fluid to enter in front of the master cylinder piston.
Sometimes covered with a small plate sometimes not. As you pull the lever excess fluid is squeezed out the tiny hole, pull too hard and you have a dot 4 geyser. You can see this if you look into the reservoir and work the lever.

I use a large syringe to reverse bleed my brake systems.It works by pushing brake fluid up through the brake caliper bleeder into the master cylinder.Make sure there's no air leaks around the bleeder by giving it a couple wraps of teflon tape.It's cheap.Air wants to travel to the highest point in fluid.This method pushes the air up and out while filling the system.It has worked better than the lever pumping method or using a vacuum bleeder.There's a lot of vids on youtube about it.Just go slow when injecting the fluid.The air needs time to push out of the mater cylinder.The big syringes can be purchased fairly cheaply at farm supply store or contact a vet that deals with large animals.

When you're done,pull the syringe apart,wipe it down really good,and store it in a ziploc bag away from sun light.My syringes last me five or six years before they start to swell and have problems going back together.

Copy that. Withe a little overflow around master cylinder then cap it, a little mess but sounds fullproof. Check that, how high do you fill the master cylinder, is there a mark on the inside?

Yes there is. You should not overfill the master cylinder. There is meant to be some air between the top fluid and the diaphragm that goes on before the cap. http://www.cyclepedia.com/learning/w...e-90_43-bf.jpg

Of course,:doh: the sight glass!

This is similar to the syringe I use.It's the same size 60cc. https://www.sciplus.com/p/60CC-THUMB-GRIP-SYRINGE_49257

I just gravity bled mine until I saw new fluid coming out the bottom. Then a couple "open/close" squeezes and it was bled. That easy.

Some people have all the luck. :lmao:

Thats what a wave rotor is ment to stop... warping...
So theres to much metal in the out side dia of the disc..
when the disc heats up it exspands & as there is more metal
in the out side dia than the inside dia the outside can exspand feather
than the inside this uneven exspanding makes the outside exspand
more so it has to warp...

the true wave rotor has the cut out that have a two fold perpose
1.. reduces the amount of metal in the outside dia...
2.. gives a gap for the outside to exspand into..

disc rotors use to be made of the same stainless steel that pots etc
are made from & never had this prob so much... but the stainless was
not good for ware or friction..


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