I recently made a stupid assumption without checking reliable source.
I made the statement that the Air Disc Brakes on FT's would show wear when the slide pins were LONG. I was wrong, when the slide pins show only 1/4 the pads are near worn out, the longer the pin showing the thicker the pads.
During an inspection of a 99 320 for a Friend I got confused and I should have looked it up first.
Attached is a page from the Meritor manual.
Gary, don't feel bad. The list is long, and undistinguished of those of us who have made stupid assumptions.
Hi Gary,
Is there a measurement, how far the pins stick out, when the pads are new?
Thanks,
Raymond, I really don't know of a measurement, on a coach with 29K miles it LOOKED like the pins extended about 3/4inch. I ASSUME ( I know ) that the pins would project the thickness of the pads when new. I will reread the Meritor manual to see if there is a standard.
I replaced brake pads on one rear wheel about 8K miles ago. Measured the pins today at 22/32, so 3/4 inch when new is probably about right. I do not know if rotor thickness would have an effect on this measurement. I had the brakes applied when taking the measurement. Meritor manual says at 1/4" pull the wheels and inspect and at 1/8" to replace. I imagine that one is checking to make sure that one pad is not worn too much at 1/4". Meritor talks about solid and vented rotors. Mine are vented and one side is thicker than the other side. One new brake pad is also thicker than the other in a set. The thick pad goes on the thin side of the rotor and the thin pad on the thick side. What got my attention was that one pin was flush and the other about 3/8". Didn't think that that was possible with the pin properly centered but it was. One pad was worn almost to the metal backing on one end. The other pad was worn very little, but still a little crooked. Of course the caliper was binding and causing the inboard pad to push against the rotor. Whatever drag was there was not enough to detect or overheat the rotor (it wasn't blue or overly cracked). I replaced pads, pins and bushings. Meritor says to replace pads on both wheels when one side needs replacing but James T. said it would be okay to just replace one side in this case. Most likely rear wheel pads wear out faster than the front as they do more work braking 2 wheels instead of one, and the air chambers are larger too and apply more force.