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boothboy 12-10-2012 06:19 PM

Low pedal
 
Here's one for you brake guys.

Will worn rotors cause a low pedal? I'm not talking about warped or scored rotors, I'm talking about the rotor thickness dimension being reduced. I'm not talking about a soft pedal, I'm talking about a low pedal.
What do you think?
BB :confused:

cobalt327 12-11-2012 03:36 AM

Quote:

Originally Posted by boothboy (Post 1621376)
Here's one for you brake guys.

Will worn rotors cause a low pedal? I'm not talking about warped or scored rotors, I'm talking about the rotor thickness dimension being reduced. I'm not talking about a soft pedal, I'm talking about a low pedal.
What do you think?
BB :confused:

In some cases, yes. The square cross section rubber seal between the piston and caliper acts as a return for the piston/pads by deforming when the piston is extended then returning to its normal state when the piston is no longer held extended by fluid pressure. This gives a running clearance, but if the rotor thickness were less, the pads could still retract as though the rotors were normal thickness. This is one reason that new pads often have shims w/them.

Because the caliper fluid volume is relatively large, any extra clearance between the piston/pad and the rotor translates into an increase in pedal travel.

S10xGN 12-11-2012 09:47 AM

Just to give an example of what Cobalt said about travel, my Excel brake calculator shows a 15/16" bore master cylinder at full stroke (pedal to the floor) will move each of my GM Metric front calipers 0.087". That's less than 3/32 of an inch!

Russ

Trucknut 12-11-2012 11:51 AM

I ran into a "low pedal" problem on a 1969 Cadillac. It had drum brakes all the way around. Turned out that the drums had been turned too many times.


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