GPZ500s Rear brake issues...

[dextersaurus]

Hey guys.

Finally finished the bike today, got the new sprockets and chain on, and I also got the rear brake fitted.

The problem i'm having is that i now have pretty much no rear brake...

I've bled it, but there's no air in the system, plenty brake fluid.... new pads...

When i press the brake lever, i can see the piston's moving, as it's pushing one of the pads into the disk, but the other isn't moving. Does that mean the pins are seized in the caliper? If so, how the HELL do i fix it? I had a go when changing the pads, but i've obviously not done it right.

I can still ride the bike just now, as i usually don't use the rear brake. front brake has been freed off and bled, and it's working fine

Cheers

Dunc

[evoboy]

Did you completely strip the caliper down?

Get any grease on the pads or disc?

Grease up the sliding pins?

Pads might just need bedding in....
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[el_oso]

need to make sure the sliding part actually slides.
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Duke 390
Previous: '05 XR125L | '96 XJ600S Diversion |'05 Suzuki GSXR1000 | '05 Honda CBR125-R | '97 YZF 600R Thundercat | '11 Honda CBR250
Car: Jeep Wrangler 4.0L

[dextersaurus]

hmm...

I did the front brake, and the old man did the rear brake.

I know that both the brakes were seized on, so getting them off was a nightmare.

If i take it back off again, how do i get it apart to grease it up without braking anything? i've limited tools at my disposal... Front was easy, as it was sliding, but the rear isn't moving.

Cheers

Dunc

[dragstaar]

if one piston is moving, its likely that the other piston has seized.

Do you know if the piston was pushed back evenly into the caliper when making room for the new pads?

And yes, greasing the slider pins in a good idea too.

[dextersaurus]

Rear caliper is a single pot. I know the piston's fine

I'm leaning towards thinking the pins are seized that means it'll be off the road longer. Gah.

Dunc

[evoboy]

Rear is a sliding caliper aswell.

Just pull it apart completely and make sure nothing is binding up and that the braking surfaces arent contaminated.
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[Ichy]

If you pump the lever very quickly several times does it improve the braking?
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[stinkwheel]

You can easily check the pins by undoing two bolts and lifting the calliper off the disc.

If it's sliding on the pins properly, you'll be able to unbolt the calliper and just pull the two bits apart.

If you can't, the pins are stuck and you need to pull the two bits apart a bit more forcefully. Not usually too difficult even then.

It's usually corrosion on the calliper itself rather than on the pins. if you look, one of the recesses for the pins has a closed end, the other one has an open end with the rubber boot sticking out of it. This is the one that gets cacked up with alloy corrosion. You need to ease the boot out and scrape all that furry white muck out of it with an old screwdriver or similar. Once it's clean, coat it in grease, refit the rubber boot and coat the pins in grease before reassembling (I usually use moly grease but any general purpose grease will do). It should now slide easily on the pins.

You sometimes land up wrecking the rubber boot getting it out. If it was that stuck, it's junk anyway.

In fact, the entire setup is a waste of space, they were WAY better when they had a drum brake but it's what you've got. Do make sure the slider can move though. As you may have noticed, there isn't really anything holding one of the pads in other than it being trapped between the calliper and the disc. If the calliper stops sliding on the pins, they can and do spit that pad out.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.