brake pads too thick?

[Agemax]

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.

any ideas guys?

[tkent02]

0.25mm on each side should do it, no?

[Agemax]

0.25mm on each side should do it, no?

yes in theory it would but i am having difficulty taking anything off!!!

[Flyboy]

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.

[TooManyToys]

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?

[Agemax]

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?

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]

Are you certain its not a master cylinder problem?

[Agemax]

Are you certain its not a master cylinder problem?

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

[TooManyToys]

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

Are you certain its not a master cylinder problem?

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.

[Agemax]

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

[TooManyToys]

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.

[Agemax]

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!)

[Nessism]

I think Stan's suggestion is worthwhile. I'd look for a local shop that relines brakes and see how much they would charge.

[hampshirehog]

What about taking 0.5mm off the pots? Or are the pads flat on the caliper when they are full retracted?

[Agemax]

I think Stan's suggestion is worthwhile. I'd look for a local shop that relines brakes and see how much they would charge.

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