I get this question a lot so I thought it might help to have it posted in a thread that can be searched etc.

The best way to set a piston angle without using the gauge is to draw an imaginary “Center Line” down the center of the pad cavity. This is illustrated by the “Red” line in this picture.

Set the angle facing the side that has the bleeder. This is illustrated by the yellow arrow in this picture. This denotes the “Top” of the caliper.

By setting the bottom notch of the piston on the center line it will automatically give you the 20º angle as illustrated by the “Green” line in this picture.

Click to view attachment

Eric, you took the time to post this so rather than it getting lost in the board, Hows about it gets moved to classics?

Thanks Jeff, that's probably a better picture to give people a more complete understanding.

It shows the center line and how it relates to the notch and the special tool used to position the pistons. I've used a green line here to illustrate once again.

The pads need to open into the face of the oncoming rotor.

Click to view attachment

I recently changed pads and rotors and simply pushed the pistons home with a c-clamp before inserting the new pads in the front, and used the adjusters to pull them home in the rear.

Did I miss some important step ??? And is this the front or rear you are referring to?

thx

Good question Phil.

The answer is "probably not". Hopefully, your pistons had been set at the correct angle when they were rebuilt. Always good to check when you're changing pads. A lot of the mass-rebuilders often miss this step or have it backward.

This brings up another good point. "Do not try to change this piston angle while the piston is fully seated in the bore." To do this properly requires special tools and chances are "great" that you don't have them. I simply cannot count the number of pistons I've removed with "Vise-Grip" marks on them. If you're rebuiling your calipers and you goofed... best to blow the pistons back out and start over. It takes a few minutes to get it right vs. a lifetime of chewed up pistons.

Regarding the rears... 914 rears all have flat pistons so, this is not an issue here. It brings up another interesting fact though; ever wonder why 914's have a fat pin and a skinny pin on the rears? The rear pads were actually tappered back in the day to accomplish this. 914 rear caliper are about the only caliper out there that doesn't incorporate this feature.

If we can rope Jeff back in here, I believe he has a picture of an old tappered pad set.

what is teh reason for this piston orientation?

To confuse you ...... (actually, I think it was a function of pad wear. but I don't know anything anyway).

And Eric ... in your image, the green line is 340 degrees ...

That's because you like to view things from the far right (caliper). We need an equally opposing far left viewpoint to make the world "right"... err... correct:

Click to view attachment

I would 2nd that but unfortunately, you've got a better chance of seeing God. A total of 3 posts have been added to that forum in the past 21 month's!

I saw God at WCR. Had a red mohawk... or was it purple?

We generally let threads play out before they head over there but, with the new way of doing it, I'd don't even recall the process. I think there's just a link to the thread there so it may be possible.

If we can rope Jeff back in here, I believe he has a picture of an old tappered pad set.

the bump on the piston top is desinged to force one side of the pad on the rotor first, this gives smoother transition from no pad contact to full pad contact.

one easy other way to get the angle right is to simply use the metal pad spacer that should be under each front pad, the angle is cut into tha metal spacer, line up that angle with the cut bump in the piston top and your in ok this spacer serves to prevent the piston from rotating out of postion. it is the perfect tool for checking the angle.

Only 914 kits come with the angle piece. All others do not. The main purpose of the thread is to show people how to set the angle "without" that piece.