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Author Topic: brake piston clearance  (Read 177 times)

Offline RedCar

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brake piston clearance
« on: Jun 23, 2019, 04:21:50 am »
My brake pads finally wore down to the squeakers and I noticed 'some' uneven wear on the pads. All the pads had one side worn down ~1/16" more than the other side. Outer pads were worn a little more than inner pads too.
I wasn't sure how 'normal' this is so I bought some rockauto reman calipers in hopes that they might push a little truer.

However, in hindsight I think the 'reman' calipers are a waste of $. I'm comparing pistons that I popped out of the new and old calipers and am seeing that the piston and guide pin bores on the reman units are simply honed out to a slightly bigger diameter but that the guide pins and piston themselves are the same size as my old ones. I'm sure they would work, but they just feel sloppier and I don't think they'll help with evening out pad wear.

Piston clearance was .005" on the originals and .008 on the reman. I measured by stuffing a feeler gauge between piston and bore. The original bores are slightly pitted but the pistons still slide nicely, so I guess I'll just replace the seals and re-use them.

I couldn't find much info on nominal piston clearance, just one guy who says .003-.005" on 48mm pistons (celica is 57mm)
http://www.vansairforce.com/community/showthread.php?p=801507

Any of you guys still using original brake hoses? My old ones just came off, I think they're original because I found a 'Toyoda' stamp under some grime... they're actually in pretty good shape still... hopefully the new ones are actually an improvement.
83 GT Sport

Offline sirdan

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Re: brake piston clearance
« Reply #1 on: Jun 23, 2019, 01:07:25 pm »
I feel like usually one side seems to wear more than the other, I think it is due to the design of single calipers. The one pad has to start touching the rotor before it can pull the other side in. So basically the piston side pad hits first so it wears slightly more. The best thing to do is to clean and lube the sliding points of the calipers any time you put pads in. If the sliders get gummed up and stick either one pad will wear more than the other or only one of the slides sticks and the pads wear more towards one side of the pad.
1988 4runner