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One of my friends changed his calipers over to Zero Tolerance o-ring pistons a couple of years ago.The calipers were sleeved in stainless and had a correct I.D.After installing them the car began to have a resistance when starting off.When you turn the wheels when off the ground there is a very high amount of drag,much more than a normal disc brake.Calls to the inventor direct yielded no solution.The car has been recently restored with a new master cylinder,lines,etc. and still has the problem.Has any one out had similar problem. Thanks,Lou Lapham #24682
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Re: Zero Tolerance O-ring pistons-Drag problem
Lou----
That's very interesting. Actually, the "Zero Tolerance" piston design should evidence LESS drag inasmuch as these pistons use no piston spring. Consequently, in the "brakes off" condition, there should be NO pressure on the pads whatsoever.In Appreciation of John Hinckley -
Re: Zero Tolerance O-ring pistons-Drag problem
Lou----
That's very interesting. Actually, the "Zero Tolerance" piston design should evidence LESS drag inasmuch as these pistons use no piston spring. Consequently, in the "brakes off" condition, there should be NO pressure on the pads whatsoever.In Appreciation of John HinckleyComment
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Re: Zero Tolerance O-ring pistons-Drag problem
Lou, A few questions... 1) did the drag problem gradually develop over time or was it present immediately afer installation of calipers? 2) is the drag present at all four wheels or only some? 3)have you verified that the drag is between pad and rotor and not wheel bearing itself? I converted my sleeved calipers to Zero-Tolerance a couple years ago and noted that it was not uncommon to find some of the stainless sleeves were slightly off-center from the original bore. Because the sleeves don't go all the way to the "bottom" of the bore, thereoften was a slight ledge partway around the circumference of the sleeve. Even though the O-ring itself never moves acros this ledge, the piston itself can be prevented from retracting all the way into the bore. My solution was to carefully hand-grind the ledge. I would be interested to learn if this drag is present on all or just some wheels.Comment
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Re: Zero Tolerance O-ring pistons-Drag problem
Lou, A few questions... 1) did the drag problem gradually develop over time or was it present immediately afer installation of calipers? 2) is the drag present at all four wheels or only some? 3)have you verified that the drag is between pad and rotor and not wheel bearing itself? I converted my sleeved calipers to Zero-Tolerance a couple years ago and noted that it was not uncommon to find some of the stainless sleeves were slightly off-center from the original bore. Because the sleeves don't go all the way to the "bottom" of the bore, thereoften was a slight ledge partway around the circumference of the sleeve. Even though the O-ring itself never moves acros this ledge, the piston itself can be prevented from retracting all the way into the bore. My solution was to carefully hand-grind the ledge. I would be interested to learn if this drag is present on all or just some wheels.Comment
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Re: Zero Tolerance O-ring pistons-Drag problem
Lou,
An additional thought...check flexible brake hoses for kinks, or if these hoses have not ben replaced recently, check for internal deterioration (you should be able to blow through hose (when it is off the car!!). Restrictions in these hoses can allow application of brakes due to line pressure, but prevent the passive return of fluid to the master. Check this out too. Good luck.Comment
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Re: Zero Tolerance O-ring pistons-Drag problem
Lou,
An additional thought...check flexible brake hoses for kinks, or if these hoses have not ben replaced recently, check for internal deterioration (you should be able to blow through hose (when it is off the car!!). Restrictions in these hoses can allow application of brakes due to line pressure, but prevent the passive return of fluid to the master. Check this out too. Good luck.Comment
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