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Rebuilding 4 piston front brakes?
I took some measurements today of my brake pad wear after the track day....all my pads wore fairly evenly between .85mm and 1.05mm in the 1200 miles since I checked them last....with the heaviest wear on the drivers side outside (makes sense since I don't usually have a passenger) BUT the drivers side inside pad has not worn at all in 1200 miles including the track day....it is still at 6.5mm or about 70%???
I did not experience any serious fading of my brakes at the track....just a slight increase of pedal travel at the end of the sessions... Should I rebuild the front calipers just to be safe? How hard is it? So now my "fix this" list went from ZERO to cruise control and brakes...figures |
Take them off, clean them, push out the pistons with air (carefully - with wood stopping them from hurting anything) and replace the seals. There may be corrosion, in which case....
But it should be fine. wiper seals and boots. And some high temp grease (very little) when you put everything back together: (Adding pics) |
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My pads do not wear evenly - outiside ones wear more than inside. Same with Nicole's. I haven't bothered to do anything with mine since the brakes seem to work fine. Nicole complained of pulsing and squeaking, so we took her calipers apart after finding the rotors were fine. I will tell you that the pistons, seals and boots were like brand new. She had full rebuild kits, so we replaced everything. Too early to tell if it will help the pads to wear symmetrically or not.
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Brendan--
NO GREASE on any of the parts that touch the rubber seals, boots, hoses or brake fluid. There are assembly lubes for brake parts that are a lot safer. Some petro greases play hell with rubber brake parts. Think about how well latex gloves work around gasoline. Then go for brake assembly lube or, at minimum, brake fluid. Assembly lube is something wonderful like glycerin, at least that's what it feels like. |
Originally Posted by dr bob
(Post 5343678)
Brendan--
NO GREASE on any of the parts that touch the rubber seals, boots, hoses or brake fluid. There are assembly lubes for brake parts that are a lot safer. Some petro greases play hell with rubber brake parts. Think about how well latex gloves work around gasoline. Then go for brake assembly lube or, at minimum, brake fluid. Assembly lube is something wonderful like glycerin, at least that's what it feels like. |
Its says "Kluber Lubrication"
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My outsides wear faster also. And I demand an explanation.
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Originally Posted by Bill Ball
(Post 5343362)
Nicole compained of pulsing and squeaking, so we took her calipers apart after finding the rotors were fine. I will tell you that the pistons, seals and boots were like brand new. She had full rebuild kits, so we replaced everything.
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usually the out side pads wear faster due to being exposed to more contaminants usually water and car soaps this will make the rotor surface corrode and thus the pads then are polishing the roughed up surface. That siad if you find onhe pad not wearing similar to the other side/position then its a good chance either the pad is binding in the caliper housing or the pistone has an interference fit either from overheating or corrosion or the system has air in it
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Originally Posted by Mrmerlin
(Post 5343861)
usually the out side pads wear faster due to being exposed to more contaminants usually water and car soaps this will make the rotor surface corrode and thus the pads then are polishing the roughed up surface. That said if you find one pad not wearing similar to the other side/position then its a good chance either the pad is binding in the caliper housing or the piston has an interference fit either from overheating or corrosion or the system has air in it
I have been replacing outer brake pads 2:1 over inner for 120K miles and I can't find a reason for it either. |
Originally Posted by Bill Ball
(Post 5343362)
My pads do not wear evenly - outiside ones wear more than inside. Same with Nicole's. I haven't bothered to do anything with mine since the brakes seem to work fine. Nicole complained of pulsing and squeaking, so we took her calipers apart after finding the rotors were fine. I will tell you that the pistons, seals and boots were like brand new. She had full rebuild kits, so we replaced everything. Too early to tell if it will help the pads to wear symmetrically or not.
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It is a common problem (I would almost call it a design flaw) that brake dust accumulates under the metal plates on the sides of the brake pads (clearly shown on Brendan's last pic). These plates are held in with two torx screws. As the pads wear, dust builds up under the plates eventually raising them a couple mm's. Then, when new pads are fitted, they do not go in smoothly. Sometimes mechanics hammer the pads in because they want to get the job done fast and couldn't be bothered with doing it right. On the 968 calipers that I just did recently, there was much more dust buildup on the rear than on the front, presumably because there is a dust shield on the back of the rotor, whereas on the front it's comparatively open. If you have problems with uneven pad wear, I would check how easily the pads slide in/out of the calipers and if the metal plates are perfectly flat with the caliper housing.
Dan '91 928GT S/C :eek: |
The Brembo calipers on my 79 were doing the same thing. IIRC the early Brembo's have a piston size that does not have a rebuild kit (at least 4 years ago when I was doing this).
I flushed a lot of new fluid through the system while working the pistons back and forth. Worked like a charm. |
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