Correct method to remove/replace stock front caliper pistons?

What is the correct way to remove the pistons from Tiger front calipers?

What is the best method to reinstall the pistons?

Thank you,

Jim

How to remove the pistons depends on how much neglect they've been subjected to. If they've seen regular use and service, two fingers will do the job nicely.

However, some calipers have been sitting for decades - rotting and rusting. Those are a different story. Some quality penetrating fluid like KROIL helps. (Give it time to work - overnight is not too long.) With calipers in this bad of shape, you'll probably end up needing to buy some new pistons, so you may not need to be as careful with them as if you wanted to re-use them.

I tend to "escalate" my techniques:
1) I'll first try a couple large flat-bladed screw drivers to pry the piston up.
(use the slot at the top of piston carefully - it breaks easily!)
2) Then I'll blow compressed air into the calipers through the brake line fitting, trying to "pop" the pistons out.
3) Sometimes placing a grease fitting into the calipers and pumping in wheel bearing grease will do the job.
4) If none of the above have worked, I split the calipers and then drill and tap a 1/4-28 hole in the flat bottom of the piston, thread in a matching bolt and force the piston out by driving the flat part of the bolt into the bottom bore of the caliper. (Finally, a propane torch can be enlisted to burn off the remains of the tenatious rubber seal.)

good luck!

IIRC Sunbeam Specialties (and perhaps classic sunbeam?) sell stainless pistons for the callipers? If rebuilding i htink these should be a must, as with the clutch and brake M/C's.. the cars tendnot to see that much sue.. so all the hydualic systems should be as high quality as possible and choose items that are a littel more tollerant of limited use (as in dont perish)

I, for one, am quite pleased with the stainless steel caliper pistons I put in several years ago. My OEM steel ones got pitted and started to leak after a while.

At the same time I also thoroughly flushed the system with silicon brake fluid (DOT 5) and refilled with same. A bit expensive, but necessary, procedure to make the change. Silicon fluid is not cheap. But with its very low moisture absorption, it also seems to protect the aluminum brake and clutch components (wheel, slave and master cylinders) from corrosion. Especially if the car sits for meaningful periods of time as mine has over the years. I vaguely recall hearing that silicon fluid brakes down if your brakes ever get hot enough to boil the fluid. But DOT 5 boils at 550 degrees F. So, at least for non-racing applications, I think it is a better choice than the petroleum based fluids. I do not know anything about the Girling Low Moisture DOT 4 fluid. I also think silicon is kinder to the rubber sealing components in the brake system. Just my humble opinion.

Cheers, Gene

the one thing i will caution aout the silicone fluid is it seems to kill the brake pressure switches. I had heard about this.. ignored it.. then killed 2 in 2.5 years.. they start to only work under hard psi.. then just stop.. switch to silicone.. then make a pedal activated switch.

Thanks for the tips. I easily removed the pistons using compressed air. I placed a wood spacer between the pistons so I could come close to getting both pistons out at the same time. With both calipers one piston did release before the other, but in each case the second piston was easily released using a screw driver in the groove of the dust cover.

Followup question: I have some minor pitting in the bottom inside corner of each "cup" into which the piston fits. On one cup I also have some minor pitting in the sidewall of the cup about 1/8" below the groove for the sealing ring.

It's my theory that the pitting is not an issue because the pitting is below the sealing ring and the groove for the sealing ring is perfect. Unlike the case with the master cylinder or rear wheel cylinder, the front caliper sealing ring remains in its groove and seals around the piston as it moves to compress the pads. i.e. the seals are not moving over any pitted areas. I'm concluding that as long as the pistons and seals are new, nothing will leak and piston travel is so slight that they will not wear.

Question--have I got this right?

Jim

As far as I'm concerned, you're exactly right. The seal/piston contact is doing the work. As long as the seal groove in the caliper is clean & OK you just need a nice surface on the piston. Any other areas don't matter a lot.

BTW, ditto on Rick's stainless pistons. They're all I use.

bt

caliper re-builds

We re-build lots of these and get both the smooth & easy to the fossilized wonders. We've had to come up with creative tooling to get some pistons out and always split the calipers for exam reasons. Clean assembly is always a good goal. Honing the bore so there is nothing for the new piston to grab onto is a good move. Deep cleaning the groove for the dust seal to fit in always seems to frustrate the novice; I've re-worked a lot of them where the dust seal was torn up and binding or just riding on the outside of the piston and allowing all the dirt to enter the bore. The end aim is to achieve an even piston movement so that you get equal pressure on the rotor from both sides. As to the comments about synthetic fluids; we've had seal problems with the chemistry of the old stuff not happy with the new. Make sure you flush it all or simply do what the manual suggests and change the fluids every season. Castrol LMA has been our choice for years. keep em' runnin', randy
B382000078 (from new) and B382001529