Disc brake question
- Thread starter Sonny
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69L48Z27
Well-Known Member
Drag is okay, lockup or not rolling is bad. Make sure you have clearance for the MC to fully return. If not it may cover the return holes in the MC and you’ll build pressure that results in lockup.
Sonny
It’s all fun til the rabbit gets the gun.
I assume you are talking about clearance at the pedal and rod?
69L48Z27
Well-Known Member
Yep, manual brakes aren’t usually the problem but rather the booster rod to MC.
The action of the seal lip when pedal pressure is released, results in pulling the piston away from the brake pad slightly. This relieves the pressure applied to the rotor by the brake pad and allows it to turn free. The travel is so minute, you won't see it, but as the rotor spins freely, you know it did. Problems arise when the piston sticks in the caliper bore, and cannot move back. The constant pressure will destroy the pad and rotor.
66Satellite47
Well-Known Member
A slight drag is normal, you should be able to turn the rotor by hand with little effort.
SDCoronet
Well-Known Member
Looks real nice. Dr Diff brake kit?
Sonny
It’s all fun til the rabbit gets the gun.
No, MBM brakes from Classic Rods.
miller
Well-Known Member
Real pretty! Need to pull mine, and get a good coat of paint on 'em.
Just for grins. Those calipers are what I call 'sliders'...opposed to the pin type, what mine are. Both are fairly common.
On the sliders, all simple to see, the outer part of the caliper 'moves' very slightly, sliding against machined sections in the inner (fixed) half. Lol, or is it reversed.
Anyway, the two mating machined areas, on both parts are fairly close. In time, can rub down a little, and rust, or collect dirt, either that can make that sliding movement hang up. Nature of the beast!
Don't know if it can still be found, but Lubriplate made a brake lubricant, along the lines of engine assembly lube, but much thicker.
On those slider type calipers, all four machined surfaces needed to be cleaned, and then lubed, a simple thin wipe, to slicken the surfaces, and a little protection from rust.
Movement is only enough to relieve pad pressure, slight drag.
Just for grins. Those calipers are what I call 'sliders'...opposed to the pin type, what mine are. Both are fairly common.
On the sliders, all simple to see, the outer part of the caliper 'moves' very slightly, sliding against machined sections in the inner (fixed) half. Lol, or is it reversed.
Anyway, the two mating machined areas, on both parts are fairly close. In time, can rub down a little, and rust, or collect dirt, either that can make that sliding movement hang up. Nature of the beast!
Don't know if it can still be found, but Lubriplate made a brake lubricant, along the lines of engine assembly lube, but much thicker.
On those slider type calipers, all four machined surfaces needed to be cleaned, and then lubed, a simple thin wipe, to slicken the surfaces, and a little protection from rust.
Movement is only enough to relieve pad pressure, slight drag.
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Gentlemen,
Sometimes, slider calipers especially later production units, came with phenolic pistons in lieu of nickel or chrome plated pistons. The thought was the phenolic pistons will not corrode like the metallic pistons.
Consider using DOT #5 silicon based brake fluid instead of the more common DOT 3 or 4 fluid. The DOT 5 fluid is NON HYDROSCOPIC (will not sttract and absorb moisture), which will cause corrosion and ultimately stuck pistons.
DO NOT USE DOT 5 FLUID IN AN ANTI LOCK BRAKE SYSTEM.... I use DOT 5 fluid in my GTX for 6+ years without any problems.
Bob Renton
Sometimes, slider calipers especially later production units, came with phenolic pistons in lieu of nickel or chrome plated pistons. The thought was the phenolic pistons will not corrode like the metallic pistons.
Consider using DOT #5 silicon based brake fluid instead of the more common DOT 3 or 4 fluid. The DOT 5 fluid is NON HYDROSCOPIC (will not sttract and absorb moisture), which will cause corrosion and ultimately stuck pistons.
DO NOT USE DOT 5 FLUID IN AN ANTI LOCK BRAKE SYSTEM.... I use DOT 5 fluid in my GTX for 6+ years without any problems.
Bob Renton
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