[Justin Fischer]

OK, so I didn't have a great night last night. During my front-end overhaul, I upgraded to Bisteins, and 911S aluminum calipers. The caliper pistons came out without issue using my compressor at 90psi, but they wont go back in .

The calipers are off the car, the pistons are positioned properly at 20 degrees, and straight in the bore. I used new brake fluid as reassembly lube, and have installed new seals. All four go about 1/2 way in and stop. Any ideas..............

I don't want to drop $200 on new stomski pistons just to find out the caliper bores are really what's bad.

-Justin

[Vicegrip]

Try to install the pistons without the seals. If they go in OK reinstall the seals and after making sure they are slobbered up press them in with a C clamp. Feel free to stop by with them this weekend if you are uncomfortable pressing them in.

[jpinkert]

I was talking to my mechanic about the really soft feel of my S calipers...thinking that they needed a rebuild. I want to pass on one thing he pointed out that I wasn't aware of with regards to S calipers.

They use the same size pads as SC and Carrera brakes. But they specify a thicker pad. If you use pads meant for the SC or Carrera, you run the risk of wearing out the bores more quickly. Why? Because the piston is out further with the thinner pads and therefore the soft alum. caliper bore is more likely to be deformed. He said that this is normally the cause for sticking S calipers. And a simple rebuild isn't enough to fix it. In my case, he recommended either putting the stiffer (and heavier) SC calipers on, or bolting on Carrera rotors and calipers for improved brake performance.

I haven't had a chance to carefully check over my calipers...but it would be nice to get rid of the spongy feel of the S calipers. They're not even close to the firmness of my 930 brakes. So far, I've replaced nearly everything that could cause spongy brakes short of the calipers themselves (new MC, new fluid). I have at least 1 inch of travel on my brake pedal before the brakes start to bite. Of course this makes heel-toe downshifts soooper easy.

[cmartin]

Good point Josh. I just finished rebuilding the calipers in the SC tonight. I had to use a c-clamp to get them in the caliper too, pretty snug fit.

[Justin Fischer]

Thanks Guys, unfortunately I have company showing up today, so my garage time will be limited. I'll let you know how it goes.

-Justin