I've just tried replacing the pistons and piston seals in an old set of Formula Oro callipers as the pistons were seized. Getting the pistons out wasn't a problem (track pump attached to bleed valve) although required a lot of pressure. However, fitting the new pistons and seals has proved problematic. I can't find any instructions on the web so maybe someone on here can tell me where I'm going wrong.
Covered seals in light coating of supplied grease.
Pushed seals into seat, making sure not twisted.
Pushed pistons into place one at a time by using old brake pads and levering with a screwdriver - took a bit of effort but the eventually clicked in place.
Went to bleed brakes but when applying pressure with the syringes brake fluid leaked out of pistons.
When I took the calipers apart again i found that both the new piston seals were badly damaged.
I'm obviously doing something wrong, I just can't see what. Any suggestions would be greatly appreciated.