Questions about rear brake calipers R&R

Post by **Grantkat** » 15 Feb 2026, 14:34

Hey guys! 1999 S70 GLT.

The weather finally broke and I was able to pull the rear wheel and look. I have to replace the rear calipers. Simple enough, or so i thought.

looking at options, there seems to be a couple of configurations for replacement.
I see the following in terms of options:

double piston 10mm mounting holes
double piston 11mm mounting holes

why the 2 versions of mounting holes?
does it make a difference and if yes how do i know which one i should get?

any help/advice is greatly appreciated

Post by **abscate** » 15 Feb 2026, 14:38

I think the holes are both m6 but the hex head bolts are different size?

Conjecture

Post by **Grantkat** » 15 Feb 2026, 15:16

my bolt heads are 13MM.

Post by **abscate** » 16 Feb 2026, 04:38

I think I did come across this once. I mount them up using whatever bolts I had. The clamp force at proper torque won’t be impacted by an extra mm of bolt hole size

Post by **jreed** » 16 Feb 2026, 05:26

I saw the same choice between 10 and 11mm diameter mounting holes and I wasn't sure what size to get for my 97 855, and didn't want to wait to remove the old caliper, measure it and then order. I opted for the 11mm and it turned out that was the size on the old caliper.

Post by **Grantkat** » 20 Feb 2026, 17:08

ok guys... I got new calipers and pads and had a chance to swap them out. The pins were corroded and the pistons while not stuck were very very hard to move. The combination of crudy pins and pistons was the culprit. I took abscates advice and had new parts on hand before disassembly. That was good advice as nothing on the wheels were reuseable.

I will add this. I bought a set of flare nut wrenches to remove the brake lines from the calipers. Absolutely the right tool for the job. They came loose with no rounding. I feel like as much pressure as I had to exert to break them loose, I would have rounded them with a std box wrench.

Post by **abscate** » 20 Feb 2026, 19:01

30 seconds of propane heat on those flare nuts amd off they come

Post by **jreed** » 21 Feb 2026, 06:16

I did the week-in-advance P'Blaster treatment, followed by brief propane heat treatment right before, and had an easy time with the flare nuts using a flare nut wrench.

Post by **Grantkat** » 21 Feb 2026, 07:31

Nice! I did hit them a few times with penetrant over the course of a couple days. I will remember the heat in the future. They were not horribly stuck, but I was taking no chances.

next up is a spring seat replacement....