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brake pads too thick?

Agemax

Agemax

Forum Guru
ok here is the set up.....
B6 master cylinder,
HEL stainless brake line,
Tokico 4 pot kawasaki caliper (ZX9R).

Fitted some new Ferodo sintered metal pads today. the pistons are retracted right back as far as possible to fit the pads. wheel spins freely.
pump the lever, brakes are hard and good.
but........brake locked on.
the pistons are good and free, tested with no pads in they move back and forth easily.
ok, the stock ZX9R disc is 5mm width whereas the aftermarket wavy disc i have is 5.5mm width.
i am guessing the pads are not moving in enough to let the natural action of the seals to pull the pistons back again after the brake has been applied.
i figured if i skimmed about 0.5mm off each pad that would allow it to work correctly. easy !
NO... i have tried everything short of a milling machine to skim off the 0.5mm off the pads, coarse file, coarse emery cloth, electric sander.
none of these will have any effect on the pads. :mad:

any ideas guys?
 
I used to run Nissan 1400 LDV brake pads in my GS1000G, they are the same size but half the price of EBC, problem was, they are way too thick, I used to just take them down to the local brake and clutch place and ask them to skim them, cost a few bucks sometimes, most times they wouldn't charge me.
They are very hard to skim at home, bench grinder will do it, but it is near impossible to keep the surface flat.
 
Sintered Metallic friction is ........ rather hard. Take mostly iron compounds, add some aluminum oxide and graphite, heat white hot and press at 3 tons per sqin. Sanding it is basically like sanding any piece of iron based material.

The caliper would have to be very tight to fit over the pads once the caliper pistons are fully retracted if there was a problem with roolback. While my old co-workers are pretty good, it is possible that someone screwed up on the dimensions, but it would be rare.

Have you tried opening the bleeder while the pads seem not to retract to see if that resolves the issue?
 
TooManyToys said:
Sintered Metallic friction is ........ rather hard. Take mostly iron compounds, add some aluminum oxide and graphite, heat white hot and press at 3 tons per sqin. Sanding it is basically like sanding any piece of iron based material.

The caliper would have to be very tight to fit over the pads once the caliper pistons are fully retracted if there was a problem with roolback. While my old co-workers are pretty good, it is possible that someone screwed up on the dimensions, but it would be rare.

Have you tried opening the bleeder while the pads seem not to retract to see if that resolves the issue?
Click to expand...
the pistons are as far back as they will go and the pads only just slide in.
opening the bleeder valve does allow the wheel to spin again but it would do because you are releasing any built up pressure on the pads/pistons
 
tkent02 said:
Are you certain its not a master cylinder problem?
Click to expand...

yes certain, the brakes were working perfect before. with no pads in the pistons go in and out like they are supposed to.
i am convinced i just need to shave a bit off the pads. the pistons need a certain amount of travel in order to allow the seals to roll back the pistons
 
Agemax said:
the pistons are as far back as they will go and the pads only just slide in.
opening the bleeder valve does allow the wheel to spin again but it would do because you are releasing any built up pressure on the pads/pistons
Click to expand...

tkent02 said:
Are you certain its not a master cylinder problem?
Click to expand...

Yep, could be.

There should not be any pressure between the caliper and master when the lever is released, so the piston should move back to its resting position just line when the bleeder is opened.

You may have a M/C that is not fully returning so the compensating port is open, the compensating port is clogged, or there is an issue within the brake hose to the caliper. You can repeat the situation and see if loosening the banjo bolt at the master relieves the situation just like the bleeder does. If loosening the banjo releases the pressure, then you have a M/C issue, If the pads don't fully release unless the bleeder screw is loosened, then you have a hose issue.
 
i cant see what could be wrong with the hose, it is only about 6 months old and the brake worked perfectly before i renewed the pads.
i will strip down the m/c again tomorrow, just in case any contamination got in there while i was bleeding through new fluid.
also the pistons move in and out freely when the lever is pulled, with no pads fitted
 
Last edited:
Your right, at 6 months it should not be the hose. Is there a brake light switch that might be interfering with the levers full return?

I would check how loosening the master banjo effects the situation before i would tear down the M/C.
 
ok, there is a switch but it dosent appear to interfere with the lever. i will remove it tomorrow completely just to rule it out.

i will also try th m/c banjo as well and see what happens.
(too late tonight to start fiddling!)
 
I think Stan's suggestion is worthwhile. I'd look for a local shop that relines brakes and see how much they would charge.
 
Nessism said:
I think Stan's suggestion is worthwhile. I'd look for a local shop that relines brakes and see how much they would charge.
Click to expand...

yeah i will do if every thing else checks out ok.
i had an idea, somewhere in my garage (spare bedroom) i have an old RF900 disc which is 5mm. i can unbolt the caliper and slip this disc between the pads and see what happens when i operate the brake.
that will prove (or disprove) my theory for sure
 
I've not seen that before.

Is the material proud of the steel piston like in the eBay image? Is it possible that it is compressing during application and then expanding upon release so while the piston retracts the insert material is taking up the rollback amount. That would still not explain why there is pressure in the hydraulic side that is relieved during bleeder opening.
 
yeah the material is about 2mm proud of the piston itself. i dont really think this material would compress otherwise this kind of problem could happen from the factory on new bikes. they are genuine Kawasaki pistons.
i will investigate more tomorrow
 
I may be wrong here, but I think that material inside the piston takes the place of and does the job of the old anti rattle springs and plates.
I agree though, I dont see it causing a problem.
Maybe a stupid question, but is your disc running true, exactly in the middle of your caliper carrier, not slightly off to one side maybe?
 
Flyboy said:
I may be wrong here, but I think that material inside the piston takes the place of and does the job of the old anti rattle springs and plates.
I agree though, I dont see it causing a problem.
Maybe a stupid question, but is your disc running true, exactly in the middle of your caliper carrier, not slightly off to one side maybe?
Click to expand...

the disc is dead in the middle of the caliper and is 100% running true
 
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