I put 911 brakes with M calipers on not long ago, but the brakes have never been what I know they should be. I have a strange pulling issue which seems intermittent and is much worse when wet.

I've tried new rotors and pads and made sure the system is bled.

I was going over everything this weekend and found the step in the piston on one caliper does not match the orientation of the other. I'm surprised I haven't seen this before. I have the factory manual so I can figure out what they are supposed to look like.

Before I go and take the caliper off and then push out the pistons I figured I'd ask if anyone has an easier way to spin the pistons.

Thanks for your help,

Kelly

I have rotated them using a wrench with some plastic strips between the jaws and the piston. It was a type M caliper from a 911

Well. I had the same problem. So I put some cloth in the space and blew the pistons out after yanking the calipers. Dooohhh!!! Good luck. Mine wasn't full of brake fluid, just the lubricant that comes with the kit, so they were stiff. I had the idea of using a block of hardwood shaped to fit the tiny step. But for me it didn't work.

I am not familiar with 911 calipers but assume they are made by Ate? If So there is a Volvo factory tool that is made to rotate rear caliper pistons. It does not rely on any special notches or anything else besides the hollow part in the inside of the piston. I hope that makes sense. If you could show me a picture of the caliper piston I could tell you if it would work in this application. The tool is made for 240 series Volvo's, (1975-1993).

This is exactly why I come to these forums.

Do you mean this? I know this is intended for rear calipers that have to twist to retract, but I think it could also work to just spin the pistons.

Click to view attachment

Thanks for the tip!

Kelly

Stock 911 caliper pistons are NOT hollow. Tool will not work for stock application. See classic treads on how to get 20 degrees on piston.

Lisle 28600 is the Devil's own tool. I cannot hate those things more than I do.

Look up Lisle 25000, truly worth its weight in gold.

110%

However neither of these tools will do what the original poster wants because there are no notches to engage since our (early Porsche) calipers don't screw back in like a modern car's calipers.

There is a factory tool to rotate the caliper pistons.
It is a pliers with small knurled half round ends that go inside the round edge of the piston (the part that has the step in it). When you squeeze they expand inside the edge of the piston and you can then push or pull to rotate the piston. Can all be done on the car, just pull the pads.

These are probably the same as the Volvo tool or close.

There should be pictures in the factory manual or maybe the 911 manual.

Jim

You will ruin your pistons if you don't simply remove them and put them back in the proper orientation.

You've already spent more time reading this and searching for tools that it would take to pop them out and put them back in properly.

I doubt that's your problem with the pulling though.

MythBusters:

Do not use pliers or a wrench. That's how pistons get f'd up.
The Vulva tool is for a different type caliper (modern screw in pistons)
Later 911 M-Caliper pistons are hollow but, your's probably aren't
You don't need a special tool to set the angle.

E-out

Well Eric that's what I figured, but I thought there was no harm in asking.

yes you are correct, mine are not hollow.

Though I think I probably spent less time on this than it will take to pull one caliper, pop pistons, re-assemble pistons, re-install caliper, and bleed. Don't you think?

kelly

Going to consult factory manual tomorrow. I don't remember that.

Thanks for the tip.

Kelly

No...

The one i was talking About Is Not For Screw In Pistons. It Is Just Used To Rotate The Piston But If 911's Dont Have Hollow Pistons It wont Work For You. Sorry For The "caps",(stupid Phone).