What's wrong with my rear brake?

[Dougie]

Took my bike up and down the street yesterday and the rear brake would not close to stop the bike. It would eventually slow down but not any where near normal stopping power. I flushed and replaced the fluid today (with my new speedbleeders...awesome product). The old fluid was very dirty. However, it still will not stopping. It feels like pistons on the caliper are not closing correctly.

If I tip it over on the side stand and spin the rear wheel, then put the brake on, it will stop fine. But not when it has riding momentum behind it. I do hear a clicking noise in the caliper when the brake is used.

I Just started bleeding my brakes but I never have taken a caliper a part. Any thoughts on what may be the problem?

[slowxr]

I'm sure you thought of this but did you get any fluid or WE40 etc. on your disk?

[r1superstar]

Or what about some WD-40?

[Dougie]

It is possible I may have gotten some grease on the rotor when I put the wheel back on. I'll clean it off real good and give it another shot. Since it wasn't working before or after the fluid flush, I'm hoping that is the problem. I really don't want to tear it apart.

Can the pistons be pulled and cleaned while the caliper is still on the bike (with the wheel removed of course)? Or am I gonig to have to pull the whole thing off?

[Indy_WR450]

I suspect you have a seized caliper. It has to be taken apart and possibly cleaned up the finish of the bore & caliper to prevent future seizing. ?

[Dougie]

Would a seized caliper be able to move / budge at all? I put a screwdriver (carefully) between the pads to open the pistions more to put the wheel on. When the bike is on a stand, the pistons will close to stop the wheel and open enough to let it spin freely. I am just learing the inner workings of a caliper and am not familiar with the characteristics of a seized one.

[Indy_WR450]

A seized caliper will not allow the piston to move to squeeze the brake pads on the rotor. Sounds like your caliper is OK if it squeezes and releases. You may need new pads to get your braking power back. Either that or you have air in your brake system and need to bleed them completely. ?

[oRGie]

sounds like u still got some air in there.. dont be intimidated by the brake caliper tho, its an easy job to strip and clean it ?

is the brake line ok ? and on my 98wr the exhaust had heated up the plastic master cylinder enough to cause the plastic to warp and the top wasnt sealing ! if you got wd40 or something slippery on the rotor, give the pads a clean too.

[Tony426]

If your pedal is "spongy" and gets harder when you push two or three times quickly(pump it) . then you have air in the sytem and you need to bleed it again. If the pedal is solid and the brake worked well before then you probably got some grease or fluid on the linnings, if that is the case yoou will probably have to replace them , you could try cleaning them with brake cleaner and see if it improves . only other possibility is that you did not get everything back together correctly and the xaliper or linnings are binding up but that is unlikely sinnce yoou say that the brake works with the wheel off the ground.

Good luck

[HighPlainsWR]

Dougie. After several botched attempts through the years, here's the drill that works for me. Remember, the bleeder only simulates the pumping action of the brake pedal which still needs to be done during bleeding (steps c through e).

a.) add fluid to the reservoir.

b.) connect the bleeder tightly * and connect your waste contianer hoses to the bleeder ( * if not tight, it will draw in air).

c.) while bleeding, slowly apply the brake several times (4X).

d.) on the final application push down and hold the pedal.

e.) loosen the bleed screw and allow the pedal to travel to its limit.

f.) tighten the bleed screw when the pedal has reached its limit, then release the pedal.

g. repeat c through f until the pedal is good and tight (no air).

I suspect the pedal push during bleeding and/or the bleeding to the pedal limit was not performed. Up till this point you've described nothing that would indicate a frozen caliper. Good luck buddy.....

[Dougie]

I'll give the rotor and pads a good cleaning (probably replace the pads altogether). The bike has been sitting for three months, but everything worked fine on the last ride in Jan.

I did have to replace the reservoir this morning. It broke at the bolt on part on a crash over a year ago. I've had it zipped tied since then. It worked fine. But I bought a new one a while back and decided to put it on with the fluid flush. No way around getting air in there. I pumped for a full bottle. I pumped and I pumped, but the bubbles just kept coming man. They weren't stopping for nothing. It was like the Viet Cong advancing on Charlie Sheen's regiment in the last battle of Platoon. Oh, sorry. It got away from me.

Seriously though, are there times when you just have to keep pumping and pouring for a long time to get all the bubbles out?

[Dougie]

Looks like we posted at the same time HR. I'll give your intructions a shot.

Thanks for all the help guys. Doug

[RCannon]

Buy mightyvac. You can thank me later.....

Otherwise, how about a master cylinder rebuild kit. Easy to install, and boy, what a difference on my 97. I pais under 20 for the kit.

Auto Zone has the mightyvac for way cheap. Unser 25.00.

To be 100% honest with you, rebuild your mastercylinder.