Caliper Dust Seals

[CTDavies]

I am restoring the calipers for my '69 2+2 project. The shells have been zinc plated and I got ten new pistons with refurbishing kits. It turns out the dust seals are not like the original at all, the inner hole diameter is way too small.

I kept one of the original seals when I dismantled the calipers, probably because it was the only one that didn't end up torn to shreds. Here you can see how the two compare



The original seal fits beautifully between the caliper and the piston.



Here you can see how the seal fits in the groove along the top edge of the piston



Here you can see how the new seal fits. Getting it in the groove is much more difficult as it's much tighter. You can also see how it is now warped. There is no way in hell I'm going to get this to fit on the shell properly.



Here you can see the difference in the thickness of both; the new one being much thinner allowing for less travel needed when the brake pads get worn



so my questions are
-does someone make dust deals that are 100% like the original?
-should I just cut away some of the material, enlarging the hole and therefore achieving a better fit?
-shall I put the new seals on the pistons for a few days, hoping they will take on a new shape more like the original ones?

Any advice is, as always, greatly appreciated.

--Chris

[Dave K]

Chris,

You could try putting them in very hot water for a few minutes and then try fitting them.

Dave

[PeterCrespin]

There are two types of 3-piston caliper used on E-types and XJ . Piston sizes differ (later are larger)

Pete

[CTDavies]

Peter, I haven't even tried the three pot (front) calipers yet. I think I'll just get a nice sharp scalpel blade and cut the hole a little larger. Chris

[CTDavies]

Well that wasn't really THAT difficult, just a little finicky. I sliced away about 1/8" (3mm) of material from the edge of the hole with a new #11 blade...



...being careful to keep it round without ending up with jagged edges and corners. The hole is still slightly smaller than on my original seal, but I thought I might need the extra tension.



Here the piston is fully recessed...



...and here partly extended out as if the pads were worn



That wasn't too bad. With nine more to go that should keep me busy for the rest of the day.
Is there anything I need to watch with brake fluids? I think I read somewhere that only silicone free fluids should be used.

--Chris

[Dave K]

Chris,

Everyone who knows nothing about brakes say it's great and it protects the paint work of course plus they have never had any problem with it.
Anyone who is in the motor industry says "Do not use Silicone brake fluid".

So you make your own choices. I had it originally in my car and suffered problems with seals and the master cylinder sticking.
I still use it in my clutch reservoir for the time being.

Dave

[1954Etype]

groan. I've used silicone in all 4 of my E types and have NEVER had a problem. Hasn't this been done to death?

[Dave K]

groan. I've used silicone in all 4 of my E types and have NEVER had a problem. Hasn't this been done to death?

Obviously Chris wasn't party to it being done to death or he wouldn't have asked. I couldn't care less either way as I used in my car with only one M/C and a rear brake piston that was virtually brand new leaking.
What I can't quite get a grip on and no one has ever fully explained why all the motor trade are against using silicone fluid including all major brake component manufacturers but most shade tree mechanics know better!

Same reason I suppose that people say it's OK to fit the front brake housings to rear and not upset the brake balance.

Dave

[Heuer]

Dave

I think it is up there with stainless steel exhaust systems - a product of classic car restoration in the 80's and 90's. Everyone worried about longevity having seen the way cars dissolved in front of their eyes. What they failed to understand was that classics would not be used as everyday transport in the 21st century. Silicone fluid is unessecary in a modern car and a modern classic simply because of the care we lavish on them. The biggest worry with using silicone fluid and using a classic is if you have a problem on a tour. Easy to fill up with Dot4 but difficult to find silicone fluid in your local Leclerc!

[CTDavies]

Still having problems with the dust seals. Turns out the front ones are even worse than the rear!

Here you can see how the trimmed seal billows when the piston has been put in place. The one for the large piston is even thinner than a g**-d** condom!



it's the same around all three pistons - they are all billowing



I'm worried that the discs will rub against the seals removing material and ruining them. How to calipers work? Do the pistons actually touch the discs all the time? What determines how far the pistons extend out?

The brake fluid topic is not that important now anymore after I read about caliper paste on one of the German forums. Thanks for your input anyway.

--Chris

[CTDavies]

I still couldn't resist putting all calipers together, tough

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[vee12eman]

Hi Chris,

The dust seals should not touch the discs because the pads are in place between the cylinder and disc - there should be plenty of clearance. Consider just a smear of rubber grease anywhere the seals do contact a part of the caliper or pad, which will help the seal to "slide" across the surface rather than wear.

If you are still worried, you could make some very small holes in the dust seals to allow air to escape, which will hopefully reduce the "billowing". I think these holes are present in original dust seals of many Dunlop/Girling calipers. Try using a hot needle and practice on some old seal material first to decide how big a hole you may want.

Regards,

Simon