2002 Radical SR3 front caliper seal replacement.
problem with the caliper pistons stuck after new seals were installed.
1st time I lubed the seals and pistons with brake fluid.
2nd attempt I lubed the seals and pistons with caliper grease made for lubing the seals for installing the pistons.
both times I made dam sure the seals did not roll the edges over when installing and both times the pistons are stuck in the calipers bores.
140 LBS of compressed air would not move them at all when that much air should blow the pistons right out of the cylinder bores.
in the photos are the measurements of the new and old seals along with the sizes of the pistons. Hispec when I gave them the specs told me I needed soft seal kit # R114-4 34/41mm. sounds correct to me from the measurements. Calling hi spec again they confirmed this is the seal kit my calipers call for.
When the new seals are installed in the bore the small piston seal measures .64mm bigger with the large piston seal measuring .46mm larger. tells me with the seals being a half mm larger on average that in no way will the pistons move no matter how much lube is used.
any ideas or thoughts would help
Hi David (@rush-rentals), Sorry to hear you are having an issue. It sounds like you are trying all of the things I would try. When you talked with Hispec did you order the parts based on the model number on the calipers or by the diameter of the piston bores? I am pretty sure that these are not the stock calipers for a 2002 SR3 because the HiSpec calipers came later. I would recommend contacting HiSpec and asking them what they recommend. What condition were the cylinder bores in? Could that be contributing to the issue? It does sound like the seals are either the wrong size or material, or they had a reaction to the fluids you were using (which doesn't make much sense) and swelled up. To get the current pistons out of the calipers you might want to attach them to the car again and use the hydraulic system to push them out. I would put a piece of wood between the sides of the calipers so the pistons don't shoot out when they start to let go. If all else fails I would recommend contacting Spring Mountain or one of the Radical dealers and see if they have had this problem before. Many of the Radical suppliers have exclusive contracts so they only sell the parts to Radical. For example, you can't get Hispec to sell you a set of Radical branded calipers. It seems unlikely that the Radical seals are unique, but stranger things have happened.
I hope this helps a little.
@charleyhradicalsportscarregistry-com
the cylinder bores are in perfect condition.
when I called hi spec the women I talked to asked for the measurements of the calipers and specs so I gave her everything I was asked. Hi spec isn't the best for returning any emails. this forces me to call them back when land lines were common calling overseas wasn't a problem calling from a cell phone is with out having overseas calls in your plan. I did contact a radical dealer in the States 1st that knows the car and was the dealer that sold the car to the original owner. after contacting them a few times and not getting the parts I just decided to contact Hi spec directly.
I was having a problem trying to figure out what calipers the car had on the hi spec web site . was on the old hi spec site and the have a new one with the old site not taken down.
fluid used to lube them the 1st time I installed was Motul RBF600 so I'm not thinking it swelled the O-rings/seals. the 2nd install I used caliper grease made for installing the seals/0-ring. being a automotive tech for 45 plus years rebuilding calipers I have done countless times in my life.
I did try and push the pistons out by reinstalling them bleeding the system and pushing them out. they didn't move at all.
how I ended up removing the stuck pistons was to reverse chuck them in the lathe with the jaws holding the pistons from the inside of the cup and pry them out working the flat pry bar back and forth on each side a little at a time.
