65 Dis Brakes

[Bill B.]

The disc brakes on my 65 coupe are leaking periodically and it's not from the stainless steel bores but from the rubber seals the go around the pistons. I have installed seal kits several times and they seem to be good for a year or so and then start to leak again. Is there a kit on the market that is superior to other ones or do I have another problem that I may be overlooking. Any advice would be greatly appreciated. Thank you in advance.

Bill Bonnichsen

[Joe C.]

Re: 65 Dis Brakes

Bill:

First of all, make sure that the bores are clean and free of pits and/or scratches.
You really should replace the pistons to insure that you are providing a good seal. Reason is that the groove in the piston that the seal fits into usually has deposits and corrosion in it. This is very difficult if not impossible to completely remove, and the slightest imperfection will cause leak thru. The pistons are relatively inexpensive-a very good investment.

Joe

[Ed Jennings]

Re: 65 Dis Brakes

A lot of people seem to like the newer style pistons that use o-rings. Not sure what would be required to convert. Obviously pistons and o-rings, but I'm not sure what else, if anything.

[Joe L.]

Re: 65 Dis Brakes

Bill----

As Joe and Ed have advised, I think that your problem likely relates to worn pistons. The piston-to-bore clearance is, necessarily, a very "tight fit". If it were not, no seal would be able to prevent the escape of fluid under the very high pressures that an hydraulic brake system operates at.

Inspect your pistons carefully the next time you have the calipers apart. You will note that the pistons have a gold anodized finish. Carefully examine the circumference of the "sealing ridge" on the piston which is located just forward of the piston seal and is the point of maximum diameter of the pistons. If ANY of the anodize is worn through AT ANY POINT on the circumference of the ridge, the piston is not suitable for re-use.

Stainless steel sleeves should last the lifetime of the car. However, pistons, seals and dust boots do not.

[Bill B.]

Re: 65 Dis Brakes

Thanks for the advice on my disc brakes. I plan on replacing all the seals and piston soon. Where would be the best supplier for the seals and pistons and is one type or brand superior? Thanks again to the board for all your help.

Bil bonnichsen

[Joe L.]

Re: 65 Dis Brakes

Bill------

I prefer Delco, but these are a little "pricey" lately. Here's what you need:

front pistons--8 required----GM #5471370= 23.50/EACH

rear pistons--8 required-----GM #5471371= 23.50/EACH

front seal kits--8 required--GM #5467286= 13.30/EACH

rear seal kits--8 required---GM #5467288= 18.95/EACH

Most of the brake rebuilders will sell you a kit with good quality parts for a lot less than the above prices. Most of the pistons, including I think Delco, are manufactured by a company by the name of Hater. They don't sell to the public, though.

[Gary B.]

A question for Joe: 65 Disc Brakes piston

Joe,

Are the pistons you listed the ones with the guides? I'm asking this questions without having a real knowledge of what the guides are or did; kept the piston from rotating? Will these original pistons work in a 65/66 caliper that's been resleeved and currently uses non-guided pistons?

Gary

[Joe L.]

Re: A question for Joe: 65 Disc Brakes piston

Gary-----

No, these are the unguided pistons used for 2nd design calipers (67-82). Since Bill mentioned that his calipers had been sleeved, I assumed that they were also converted to the 2nd design or exchanged for 2nd design. Most caliper rebuilders machine out the guides found on 1st design calipers and convert them to 2nd design. The 1st design pistons are no longer available from GM and haven't been so-available for years.

The guides were designed to "stabilize" the piston in the caliper bore; they did not, however, prevent rotation of the piston.

1st design pistons cannot be used in 2nd design calipers. Also, 2nd design pistons cannot be used in 1st design calipers UNLESS the guides are machined out.