I read this on the Duntov website, make a lot of sence to me, interested in other opinions

Quote from web site as follows:

"There is no requirement in the patent office that an idea has to have merit, only that the application be unique. In my opinion, for C-2 and C-3 Corvettes that are driven on the street, O-ring pistons are an idea without merit.

I have condensed the following from a 20-page engineering paper written by Zora Arkus-Duntov and copyrighted by the Society of Automotive Engineers in 1982. Direct quotes are indicated:

There are three disc brake design types, each with their own unique advantages and disadvantages. The C2-C3 caliper is a floating piston design. The other two types are floating caliper and floating disc. (The C4 caliper is a floating caliper design, and has O-ring seals.) As you can see, the common factor is that something has to float in all three disc brake types.

Floating piston-type brakes (like the C2-C3 brake system) must address piston knock-back resulting from deflections generated primarily from cornering forces.

The C2-C3 brake system was designed with a feature known as a ‘constant contact shoe’. The brake pad floats on the surface of the rotor (at a friction loss of approximately .8 HP at 100 MPH) in order to reduce response time and increase pedal pressure reserve. This float is a delicate balance between the lip seal and the spring behind the piston.

“...it has been found to be necessary that the piston be free to follow the disc. This is accomplished with the spring urging the piston toward the disc. This spring force must be light enough to avoid a dragging situation. In turn, the seal friction must be less than the spring force. A lip style seal satisfies this requirement and provides complete freedom from the piston knock-back problem.”

The reduced piston to wall clearance inherent with the O-ring design (when installed in a floating piston caliper), eliminates what Duntov said was necessary. Obviously, the O-ring piston is not free to follow the disc (rotor). The designed-in balance between the lip seal and the piston spring is completely ignored with the aftermarket O-ring pistons. When cornering forces cause spindle deflection, the brake system is put in a bind. As Duntov said, lip seal pistons have the clearances necessary to eliminate this bind and piston knock-back. O-ring sealed pistons do not, and are subject to sticking in the bores unless the caliper in which they are installed is a floating caliper design.

Here is a graphic from the SAE report:



The floating shoe feature is a safety, as well as performance advantage. Only 5 thousandths of an inch retraction (of the pad from the surface of the disk) equals an inch of pedal travel and 410 PSI of pedal pressure reserve. The C2-C3 brake system was designed to rely on that 410 PSI pedal reserve, which is not available unless the pad is floating on the surface of the disk.

Bottom Line: If your Corvette is a static display show car, O-ring calipers are a good option. If you drive your Corvette, stick with Duntov’s design. If you drive your car only once a month, just depress the brake pedal every couple of weeks, and your lip seals should be leak free for at least a decade.

 

In the real world how many people have had cases of sticking pistons on calipers that have been converted to O-Ring? I know, hard question to answer. So within this C3 forum how many posts are there that have mentioned this problem occuring?

 

I'm curious about this too.

 

I have had standard lip seal stainless steel VBP calipers on my 78 since 1985 at all four wheels and not one has leaked in 26 years of use and with a car that sits most of the time and all winter. Change the brake fluid every 3 years or so and the SS calipers with standard seals have been great-no issues! I have never understood all this controversey about O ring calipers since I have NEVER thought that they were necessary for a properly functioning and maintained C3 brake system!

 

i dont like to argue w the engineers...but...

one of the first things i did when i got my car last summer was rebuild the front brake calipers. used the orings after reading here all the issues people were having with lip seals leaking. no matter how much i bled the brakes, or which bleeding tool i used, i couldnt get a firm pedal. was ticked till i decided to bleed the rears, figuring maybe, somehow a bubble or 2 got back there. thats when i noticed the rear lip seal calipers werent leaking fluid, but i could actually hear air gettin sucked in past them when the pedal was released. ok, found some lip seal kits locally, and figure id put them on since i really wanted to drive the car. rebuilt the rears w the lip seals, had everything squeaky clean - and yep, they sucked air past still. ordered another set of orings for the rear and all is well. just my little story. mebbe i got old stock dried out lip seals in my kit, maybe everything wasnt as clean as i thought. but the orings have been great. i doubt ill ever encounter spindle deflection during cornering - and i do know that with both the new and old lip seals the internal spring wouldnt hold the pad tight against the rotor. that said the rotor rivets were already drilled out, and the wheel was off, so the rotor wasnt held tight. but i was amazed to see the pad pull away from the rotor when the brake pressure was released.

i dunno, this has been argued quite a bit, believe me i read all the threads goin back years when i was gettin ready to rebuild my calipers.

my personal thought...if time and money arent a concern, and you have perfectly true rotors and spindles and push your car hard, maybe you should consider buying lip seal calipers new, or even upgrading to one of the high perf brake kits out there. if your a casual driver who will be rebuilding your own calipers, be ready to order some orings when the new lip seals u install leak

humbly submitted

hehe

 

Learje,

I noticed in your post above that you said the rear rotor rivets were drilled out which means that the OEM rotors were replaced. If the new rear rotor is not perfectly aligned with the correct rotor runout, the rear caliper can leak from the rotor causing caliper piston pulsation that was not present when the rotor and caliper were trued at the factory. In that case, O ring calipers would be necessary since the brake system is NOT properly setup. Like I stated above, my rotors are all OEM with the SS lip seal calipers and I have not had problem in 26 years. I also use braided stainless steel brake lines, front and rear, with my setup with Performance Friction brake pads and my brakes are phenomenal with excellent brake pedal feel-strong, hard pedal with very consistent brake feel and modulation under normal and severe braking.

 

i drilled out the rivets to work on my parking brake. i seem to remember i did put a couple lug nuts on to hold the rotors in place while i bled the brakes, but, i never put my runout gauge on the rotor with it installed.

i figure the o-rings are simply a cheat for those of us looking to save a buck. i can see where there would be a performance gain with the lip seals/springs. how much, i have no idea.

just from looking at the whole rear wheel/brake assy, lots of factors would come into play to make sure the rotor was aligned under load. i wonder what the factory specs were for rotor alignment, and weather they checked it with everything assembled?