Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Brake Issues

I went up to the shop yesterday to put the front brakes together with the new rotors and rebuilt calipers. The reason for reworking the brakes was that I had noticed last year that the outer pads on both sides were not making full contact with the rotors. When I got the right side back together and gave the rotor a spin, there was a slight rubbing sound and I found that the caliper is not centered on the rotor, but offset outward by ⅛", explaining the aforementioned wear anomaly. I will remedy this by installing 1/16" hardened steel washers as shims between the caliper ears and the spindle mount. BTW, the old rotors were nearly ⅛" thinner than the new ones. Thoughts on shimming the calipers?



While I was there, I collected the rear shoes to send them out to Porterfield to have them relined with their "street" compound to match the new front pads. When the rear axle was disassembled to install the Quaife ATB diff, we discovered that the grease seals on both sides were leaking and that the rear brakes weren't doing much of anything. The inner surfaces of the drums are smooth and I will clean them up today and do a proper inspection, but I'm wondering if anyone knows what the limit on I.D. is should they need to be turned. I did a quick check and they appear to be uniform with an I.D. of 9". Does this sound right? I will have the relined shoes arced to match the drums.

May be wrong but with a twin piston caliper like that won't the pads automatically self-centre on the rotor ? ... if the caliper is a bit uncentred could the noise be the rotor kissing the caliper?

K

The calipers are fixed, not floating, so they will not self center. And, yes, the noise is because the rotor is scraping on the caliper. The shims will center the caliper on the rotor and eliminate the scraping sound. With all of the other buggered work I'm finding on the car, I'm assuming either the calipers or the spindles have been changed out over the last 60 years, and whoever did it never checked.

Sorry sailor ... read it as you thinking the offset caliper was responsible for the mismatched pad wear ... shims will sort your rubbing problem just fine 👍

K

I believe it will solve both the rubbing and pad wear problems.

This is what was happening, even with the outer piston fully extended...

That's odd wear ... even with the rotor centered in the slot in the caliper, once you get to about 1/4 pad wear then the problem will recur because that's as far as it's moved ... the pad doesn't seem to be hitting the rotor perpendicularly ... the piston should have plenty of movement to push the pad far enough to fully contact the disc (they'll keep pushing right up til the backing metal if you let them) 🙂. Odd because with driving the disc would wear the bit of the pad in contact until it wore away enough to let all the pad sweep the disc

What does the back side of the rotor look like?

K

Perfectly normal. The back pads were making full contact with the rotor.

Is it possible the outer pads were somehow hanging up on the pins and/or the holes were oversize? If they were stuck then the piston would be pushing the pad and it would be hinging on the pins, leading to contact at the lower edge but not at the top.

Is it possible that the outer half of the caliper isn't perpendicular to the inner half when bolted up together? I've had a similar problem with an out of true mounting face of a starter motor in the past.