4 pot caliper orientation

[Pink_Floyd]

My 4 pot calipers have 2 small pistons and 2 larger ones, which ones go at the top.
If the disk rotates in a clock wise direction, the calipers are at 3 o'clock I think that the small pistons should be at the top, the idea being that the bottom of the pads connect first due to the larger piston and the rotation of the disks pull the top part in. Can anyone confirm this.

[garagewidow]

larger pistons at the top,as the pad bites into the disc there is tendancy to wear the friction material away quickest at the leading edge then pressure tails off along the pad contact area,the large piston somewhat restores the pressure balance across the complete pad surface.

[PhillipM]

Small pistons at the top like you thought. As the pad grabs the disc they try to twist forcing the leading edge of the pad to clamp harder and the trailing edge to clamp softer, so the bigger piston at the back counters the force imbalance, hence it should go on the trailing edge of the pad, which is the bottom.

Edited by PhillipM on Saturday 14th August 20:02

[Pink_Floyd]

Thanks Phillipm for confirming this.

Edited by Pink_Floyd on Tuesday 17th August 22:11

[garagewidow]

ah yes,i got the orientation wrong,sorry.the theory is the same.