R1100s (1999) front brake callipers

[hooperman]

I have renewed and seals and pistons before when the front discs started to drag. That was successful. It has happened again so I have taken out what appeared to be the sticking pistons - one by one via pumping the lever - there must be a better way of taking so long and using gallons of fluid? I cleaned the minor corrosion from the pistons with fine wet and dry and replaced them but with existing seals. Still drags. Are new seals essential? If so can I buy them separately - kits are £56 per calliper! Or am I just being bloody tight? These are 4 pot callipers Evo Brembo 4 piston callipers or is there a model reference?

[nab 301]

I cleaned the minor corrosion from the pistons with fine wet and dry and replaced them but with existing seals. Still drags. Are new seals essential? ?

Removing the pistons is a pain because the "plastic " inserts prevent the use of piston pliers. Did you clean out the seal grooves in the caliper, corrosion in there can make the seals tight.
Are the pistons not "Teflon" coated ? Removing corrosion also removes the coating, probably not a good idea.

[fatnfast]

You can by a tool for removing the pistons from the caliper. Around £15 I think I paid from ebay.
I've never had to strip my bmw calipers but have done plenty of others. Im sure you have done this, but check the seals are in the correct way. Some, but not all, calipers use seals with a slight taper on them.
I would also be tempted to give the master cylinder and hoses a health check to make sure they are not contributing/causing the problem.
With regard to reusing the seals, only you can make that call really. Unless I was 100% satisfied with their condition I would replace them.

Edit: Just seen above reply, quite correct about some pistons and even bores being coated. Can the little plastic bit just be prised out?

[Corvus]

I cleaned the minor corrosion from the pistons with fine wet and dry and replaced them but with existing seals. Still drags. Are new seals essential? ?

Removing the pistons is a pain because the "plastic " inserts prevent the use of piston pliers. Did you clean out the seal grooves in the caliper, corrosion in there can make the seals tight.
Are the pistons not "Teflon" coated ? Removing corrosion also removes the coating, probably not a good idea.

If one had corrosion on a ptfe coated piston, how would one remove the corrosion without damaging the coating? Maybe corrosion spells the end for the piston either way?

The idea of ptfe coating I assume is to achieve an almost frictionless interface? Are the caliper bores prone to ovality?

Cheers.

[timbox2]

I have renewed and seals and pistons before when the front discs started to drag. That was successful. It has happened again so I have taken out what appeared to be the sticking pistons - one by one via pumping the lever - there must be a better way of taking so long and using gallons of fluid? I cleaned the minor corrosion from the pistons with fine wet and dry and replaced them but with existing seals. Still drags. Are new seals essential? If so can I buy them separately - kits are £56 per calliper! Or am I just being bloody tight? These are 4 pot callipers Evo Brembo 4 piston callipers or is there a model reference?

The pistons are in fact Ceramic which is meant to resist corrosion better, but im puzzled why you are calling them EVO calipers, a 1999 bike should have the early Brembo Calipers, have the forks etc been swapped?

[Corvus]

I have renewed and seals and pistons before when the front discs started to drag. That was successful. It has happened again so I have taken out what appeared to be the sticking pistons - one by one via pumping the lever - there must be a better way of taking so long and using gallons of fluid? I cleaned the minor corrosion from the pistons with fine wet and dry and replaced them but with existing seals. Still drags. Are new seals essential? If so can I buy them separately - kits are £56 per calliper! Or am I just being bloody tight? These are 4 pot callipers Evo Brembo 4 piston callipers or is there a model reference?

The pistons are in fact Ceramic which is meant to resist corrosion better, but im puzzled why you are calling them EVO calipers, a 1999 bike should have the early Brembo Calipers, have the forks etc been swapped?

Ceramic coated? Or solid?

Cheers.

[timbox2]

I have renewed and seals and pistons before when the front discs started to drag. That was successful. It has happened again so I have taken out what appeared to be the sticking pistons - one by one via pumping the lever - there must be a better way of taking so long and using gallons of fluid? I cleaned the minor corrosion from the pistons with fine wet and dry and replaced them but with existing seals. Still drags. Are new seals essential? If so can I buy them separately - kits are £56 per calliper! Or am I just being bloody tight? These are 4 pot callipers Evo Brembo 4 piston callipers or is there a model reference?

The pistons are in fact Ceramic which is meant to resist corrosion better, but im puzzled why you are calling them EVO calipers, a 1999 bike should have the early Brembo Calipers, have the forks etc been swapped?

Ceramic coated? Or solid?

Cheers.

Pretty sure they are solid ceramic, I once broke one and it didnt look like any type of metal.

[Corvus]

The pistons are in fact Ceramic which is meant to resist corrosion better, but im puzzled why you are calling them EVO calipers, a 1999 bike should have the early Brembo Calipers, have the forks etc been swapped?

Ceramic coated? Or solid?

Cheers.

Pretty sure they are solid ceramic, I once broke one and it didnt look like any type of metal.

Ouch. Bet that hurt...££££

Wonder if the piston being ceramic affects heat transfer to fluid?

[oyster]

I did a full service a few years back on my Brembos. The piston drag on those was caused by the tiniest amount of pale corrosion/deposit in the seal groove. I used a cocktail stick to clean the groove followed by a plastic bristled paint brush to ensure they were spotless. Then lubed them with new brake fluid for reassembly. Two of the worst scored pistons were replaced along with new seals from a single replacement kit. I also used red rubber grease on all the dust seals. So far, they have not become 'sticky' again. I have also always refreshed all the brake fluid on the annual service, back and front. Salt is the enemy, as is irregular usage of the bike.

[nab 301]

quote="timbox2"
Pretty sure they are solid ceramic, I once broke one and it didnt look like any type of metal

.

In the interest of , well, being interested I butchered a caliper piston I had . And then googled ceramic brake pistons , but i'm none the wiser...
The piston feels cold and metallic and looks like aluminium when the coating is scraped. The insert on the pad contact surface resembles very hard bakelite

Wonder if the piston being ceramic affects heat transfer to fluid?

I guess the insert reduces heat transfer and prevents squeal caused by vibration between pad and piston.?

[timbox2]

Ahh, maybe it is just the insert then thats ceramic? Thats the bit I remember breaking, but it was Motorworks who told me they were Ceramic Pistons.

[Corvus]

Any sign of magnetism?

[nab 301]

Any sign of magnetism?

None in the caliper pistons ...