1st design calipers - O rings?

[Dan M.]

Need some advice.
The last item I have to deal with after many years of restoring my 66 are the brakes. After reading countless threads on this topic I'm still not quite sure what I should be doing here.
I have a set of 1st design calipers which still have the piston guides. I had them rebuilt with lip seals a couple years ago but have not yet installed them.
Given the discussions I've read online I believe I should consider converting to o rings. The car will sit more than it will be driven and I understand orings are better suited to this.
Would the piston guides need to be removed to accommodate o ring pistons? Or are there o ring pistons that accommodate the piston guides.
I also have a set of 3rd design calipers that I could rebuild using o rings although I've tried to make the car as original as possible in every other way. So I'd rather use the 1st design if I could.
Finally, I'll be using Dot 5 brake fluid. No way am I going to risk Dot 3 leaks and the paint damage that may result. I've spent too much time making this car nice. I've read all that I can read about Dot 5 and the issue regarding o ring expansion. I have edpm orings that I'll use in the hope this will help, but still unsure about it.
Any advice is much appreciated, tks
Dan

[Gary B.]

Dan,

If you really want to use DOT-5, then I think you really need to use EPDM rubber. Which means you need pistons that use O-rings, since I don’t know if anyone makes lip seals in EPDM. Whereas O-rings in EPDM are easy to source.

Gary

[Owen L.]

Dan,
If you really want to use DOT-5, then I think you really need to use EPDM rubber. Which means you need pistons that use O-rings, since I don’t know if anyone makes lip seals in EPDM. Whereas O-rings in EPDM are easy to source.
Gary

Not sure if the 1st design uses the same seal kits but for 2nd design, Raybestos Evolution 3 lip seals are EPDM and very easy to source from Amazon, Rock Auto, and Summit.
WK 452/WK 453

[Dan M.]

I do have o rings which I acquired from the Oring store which are supposed to be epdm rubber. I don't have o ring pistons though for these 1st design calipers. Not sure if they are available.
Ill definitely check out Raybestos for epdm lip seals.
tks guys
Dan

[Gary B.]

I do have o rings which I acquired from the Oring store which are supposed to be epdm rubber…

If you purchased the right O-rings from https://oringstore.com/ that are listed as EPDM, then they will be EPDM. I’m confused by your “supposed to be” qualifier.

Gary

[Dan M.]

Poor choice of words on my part, I meant no harm or confusion

[Joe L.]

I do have o rings which I acquired from the Oring store which are supposed to be epdm rubber. I don't have o ring pistons though for these 1st design calipers. Not sure if they are available.
Ill definitely check out Raybestos for epdm lip seals.
tks guys
Dan

Dan-----


I know of no 1st design pistons that are available for use with o-rings.

As far as original lip seal type seals, my preference is for PEROXIDE CURED epdm rubber whether used with DOT 3/4 OR DOT 5.

[Dan M.]

Ok tks for the feedback Joe.
I've read it's certainly possible to remove the guides and convert to 2nd design o ring pistons.
I'm wondering if it's wise to attempt that myself. Seems it would be easy enough to cut them down so the
pistons would clear the guides
I'm a bit wary of messing to much with the braking system however.

[Joe L.]

Ok tks for the feedback Joe.
I've read it's certainly possible to remove the guides and convert to 2nd design o ring pistons.
I'm wondering if it's wise to attempt that myself. Seems it would be easy enough to cut them down so the
pistons would clear the guides
I'm a bit wary of messing to much with the braking system however.

Dan------


Have these calipers been sleeved? If not and you wish to use 2nd design o-ring pistons, I would have them sleeved and the rebuilder will remove the guides. Even if you choose to stick with 1st design with lip seals, I would have the calipers sleeved. This can be done while maintaining the guides. I'm certain of this because I have a set of 1st design calipers which have been sleeved while maintaining the piston guides [not for sale].

[Dan M.]

Yes they have been sleeved. They are in very nice condition as well

[Timothy B.]

Dan, If it was me I would use the lip seal first design calipers and DOT5 and don't look back. I used DOT 5 on my 63 corvette 30 years ago and have never had any problems.

Every now and then go out and exercise the brake pedal.

[Dan M.]

I agree, I think it's worth trying. I have a set of both 1st design and 2nd design calipers, both sleeved and both in excellent shape. I've ordered the Raybestos element 3 seals for the 1st design and I've also got the peroxide cured edpm orings to rebuild the 2nd design calipers with o ring pistons.
so I've got ths option. But we'll go with the lip seals first.
thank you
Dan

[Patrick B.]

Dan— Probably all lip seals are made of EPDM rubber and should be fine with DOT 5 fluid. They are made by regular brake parts manufacturers using industry standard materials. The problem with DOT 5 compatibility started with o-ring piston kits which are made by a machine shop not a regular brake parts manufacturer. We have not been able to find what rubber was used in the o-rings supplied with o-ring piston kits, but it is not EPDM. The only drawback of using your stock 1st design calipers with DOT 5 fluid is that lip seals can leak if the brake petal is not pressed for long time.

[Dan M.]

Patrick
I think I'll install the 1st design lip seal calipers with dot 5 and monitor it closely.
I'll rebuild the other calipers i have with the epdm o rings as a backup.
Thanks for the reply
Dan