C2 front and rear caliper torque settings

[William G.]

I opened a Pandora's Box when deciding to replace the rubber brake hoses on my 67 roadster. I was not planning o rebuilding the calipers until until I found the brake fluid having a rather maroon look to it. Also, I had to drain the silicone fluid I had in the system, which was working fine, as it was the old formulation. Now, I am pretty much rebuilding the whole brake system. New Master Cylinder and new seals and boots in the calipers, in preparation to putting DOT3 back into the system. I hate using the DOT 3, as I live in Florida and DOT 3 absorbs condensation pretty quickly here.

I have the calipers apart and ready to put back together. I have not found any torque specifications for the bolts that hold the caliper halves together ( front or rear if they are different ), or the mounting bolts to the frame brackets. Could use some help here!

Thanks

[Mark L.]

Re: C2 front and rear caliper torque settings

Bill,
If all else fails check out youtube videos. I believe I saw one that showed the rebuild of a caliper and it was done by one of the brake vendors. Sorry I can't remember what company.

[Leif A.]

Re: C2 front and rear caliper torque settings

Caliper mounting bolts to brackets - 70 lb ft
Caliper housing bolts (front) - 130 lb ft
Caliper housing bolts (rear) - 60 lb ft

[Owen L.]

Re: C2 front and rear caliper torque settings

Why are you switching away from DOT 5? Your seals are more than likely EPDM material so should be fine with any new DOT 5 you put in.

[William G.]

Re: C2 front and rear caliper torque settings

Why are you switching away from DOT 5? Your seals are more than likely EPDM material so should be fine with any new DOT 5 you put in.

The reason is that the Company where I am buying the restoration/ reproduction master cylinder ( Zip-Corvette ), three times has advised me not to use present day DOT 5. Both in the Catalog, and from their rebuild Technician, as well as postings on this forum, present day silicone fluids have been reformulated, per Federal regulations, and will attack the seals and dust boots, as well as the seals inside the master cylinder. It will also void the warranty on the Master Cylinder.
Trust me, I don't like the idea of going back to DOT 3, or 4, Glycol based fluid. For the six years prior to when I started using DOT 5, I had nothing but constant brake caliper leakage. I have only found one company on line, "Champion Oil," in Missouri, that advertises their DOT 5 silicone specifically for classic cars. I have had zero luck contacting this company both online and via phone to ask any specific questions. Bottom line is, I feel like I am between a rock and a hard spot in making the decision of fluids. I have to trust the technicians of the companies who sell and service the restoration parts. They deal with these part failure issues all the time.

[James W.]

Re: C2 front and rear caliper torque settings

My '65 has SS calipers (re-sleeved in 1983) both front and rear and have always use DOT 3 with out a leak.

James

[William G.]

Re: C2 front and rear caliper torque settings

I bought this car in 1975 and the calipers were leaking severely! In fact, not realizing it, I almost crashed the car the first time I drove and got on the brakes hard! Over the next five years, I rebuilt the calipers three times and they continued to leak after a short time. Finally had them sleeved with SS, by Vette Brakes and took their suggestion to use DOT 5 Silicone. Atthat tie, I bought two quarts, from Eckler Corvette, of which I have about a half pint left. That fluid was installed in 1980 and I have had no leaks since. It really frustrates me that I can not find a chemically safe DOT 5 to use again. However, I am 75 years old and it is doubtful I wil be keeping the car many more years. Even though I am frustrated that I can not use the present DOT 5 Silicone, If I change out the DOT 3/4 eery couple of years, I should not have any trouble with water being absorbed and rust.

Bill

[Richard M.]

Re: C2 front and rear caliper torque settings

Bill, Just a FYI I found this link about Champion DOT 5 silicone fluid with some contact information.

See paragraph 6. Not sure if it applies.

Rich

[William G.]

Re: C2 front and rear caliper torque settings

Hi Dick,

I found this also and tried both sending questions on their submission form and also calling the number. I got no reply to any attempt to make contact. Certainly, if I had and they said they are using the former, or old formulation for the fluid, I might have ordered some and experimented with some old seals and boots to see if it created any distortion affects on the seals.
As I have said in my posts, I have used a silicone fluid in my car for 40 years with no ill effects on the seals. I live in Florida and moisture is a major concern here. I bought the car in 1975, so it was only 7 1/2 - 8 years old and all four calipers were rusted and leaking. After three attempts to repair them using DOT 3, I had the calipers sleeved with SS and took the recommendation of Vette Brakes and refilled the system with DOT 5 silicone. Frustrates me that the manufacturers were apparently forced to reformulate the fluid we can buy today!

Bill

[Patrick B.]

[Joe L.]

Re: C2 front and rear caliper torque settings

I've said this before and I'll say it again: if DOT 5 silicone fluid were incompatible with any commonly used brake system elastomeric components it would not be a DOT-approved fluid as such a fluid would be a safety hazard. More than likely, not only would it not be DOT-approved, it would be illegal for sale. The entire thrust of DOT approval is SAFETY.

[William G.]

Re: C2 front and rear caliper torque settings

Joe, I absolutely hear what you are saying in your reply and I am firmly in agreement. I have had two manufacturers of fluids tell me the formulation has not changed, so the only other thing is the formulation of the rubber in the seals and boots! Here is what I have noticed so far.
When I took the 40 year old seals and boots off the caliper that I have cleaned up, the seals were in perfect condition and soft and flexible. The new seals I got from Zip Corvette were stiffer and not as flexible. They went onto the pistons fine, but they sure did not feel like the ones I took off! When I open the other calipers to clean them out, I may not even replace the seals. They are not leaking now and if careful, should be able to be put back into the bores.
What really gets me is that Zip, in both their catalog and from Justin Abbott a disclaimer that if DOT 5 is used in the new master Cylinder, it voids the warranty on it. With those statements, it does make me wonder what the seals are made of. What is one to do when one wants to keep their car as close to factory as possible and has to replace a part with a correct reproduction? I suppose you do what the supplier requires!

Bill

[Matthew T.]

Re: C2 front and rear caliper torque settings

I was going to say the reason anyone should shy away from brake fluid flush is fear of busting a rusted bleeder. Otherwise testing dot3 every year with a $15 tester is easy peasy. And gravity flush is a great excuse to have a few beers.

[Patrick B.]

Re: C2 front and rear caliper torque settings

Joe —- You have too much faith that the Federal Motor Vehicle Safety Standards are effective regarding safety issues for aftermarket parts. The standards were meant to regulate the safety of new vehicles, and vehicle manufacturers are pretty careful not to produce vehicles that do not comply with the standards. Only a few standards apply to replacement equipment. Standards regarding lamps, bulbs and brake fluid are among the few that apply to equipment sold as aftermarket parts as well as part of a vehicle because they were considered as things replaced in the normal life of the vehicle. The brake fluid standard FMVSS No. 116 is based on a 1967 SAE standard with very few substantive changes. It specifies various brake fluid properties and tests to certify those properties. When DOT 5 was added, it was required to meet the existing requirements except that was was allowed a somewhat higher viscosity. The rubber compatibility tests still used only the types of rubber common to 1967 brakes.

The Federal brake standards however are vehicle performance standards that specify maximum stopping distances, stability, parking brake performance etc., but do not put any design restrictions on manufacturers. They can use any materials they want that will pass the vehicle tests. There are no material standards for brake parts. However, the brake fluid in a new vehicle must pass FMVSS 116 even if the rubber in the brake system is not one of those tested by the standard. So vehicle manufactures make sure their rubber is compatible with DOT 3 or DOT 4 fluid, whatever they use, but they do not use DOT 5 in anti-lock brake systems so they do not have to be concerned about it.

As a practical matter, whatever rubber is used by OE brakes is probably compatible with DOT 5 fluid also. Where the logic of the Federal standards breaks down is that there is no standard regarding aftermarket rubber parts in brakes because there is no explicit standard for rubber brake parts in new vehicles. There is no requirement that the aftermarket rubber parts are compatible with DOT 3 or 4 let alone DOT 5.

So the situation is that there is a Federal standard for DOT 5 and other brake fluids that has not changed. It is probably obsolete because it tests for compatibility with elastomers used in 1967. There is no standard regulating elastomer materials in brakes, OE or aftermarket. There is certainly a potential for incompatibility but it is not because of any change in the Federal requirements for DOT 5 fluid.

[William G.]

Re: C2 front and rear caliper torque settings

SPOT ON! As I said in one of my original posts early on, I switched to the DOT5 fluid circa 1979/80. At that time, I rebuilt the calipers and the Master cylinder using Old Stock GM seals and boots. Never had a problem with the fluid reacting with the ribber of that period.
If I could find out who is makes the reproduction 67 Master Cylinder I just bought through Zip Corvette, I would order a rebuild kit for it and then test those seals against the ones in my old Master Cylinder with new can of DOT 5. If the new seals deform and the old ones don't, then we would know for certain the problem is not with the fluid, but with the rubber formulation being used today in the aftermarket reproduction parts available for our pride and joys!

Bill