Hi All,
about 20k miles ago I tried to significantly improve brake performance by replacing front brake lines, calipers, pads and rotors. My indie mechanic did the work. The idea was to overcome sticking calipers etc.

The job had its moments but went OK. In the time since we have observed the inboard pads wear at a very high rate and the outside pads wear hardly at all. About 10k ago we actually did an emergency inboard pad replacement. We did wondering what was going on and trying to eliminate pad material as a cause. This last oil change the inboard pads were down to 0 almost and the outside still had plenty of meat.

So yesterday we changed out the calipers and fitted new Volvo OEM pads. We are surmising that the rebuilt calipers must have been rebuilt by the same person/place and that both calipers had the o-rings to the inboard side somehow mangled such that the fluid was not traveling to the outside--thus reducing pressure on the outside.

We are all about the science here and are treating this latest move as an (expensive)experiment. If things "even out" I will eventually replace pads and rotors (when needed). My indie guy has worked on Volvos for 20 years and never seen this before. It goes without saying neither have I.

The car is a '91 wagon, 290k auto, NON-ABS car, if it is not going downhill it is usually going uphill.

So my question is: Has anyone ever experienced this before? Can anyone develop a theory explaining it?

Thanks in advance,

Rod

Are these sliding-pin or fixed calipers? Unlubricated or seized slide pins would result in wear of the pads on only the side with the piston - but this only applies to sliding-pin calipers. Some people seem to think that dragging the brakes will cause the same wear pattern, but I am skeptical.

It's an interesting phenomenon!

All 240's are opposed piston non-sliding calipers.

...filched from an Art Benstein post:


Dimples on the bottom



--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Hi Bruce,
This was very instructive. I will check the old calipers (and the ones I just fitted!) asap.

The one thing that is odd was that there was no apparent side effect(s) in the operation of the brakes, just the weird wear pattern.

Thanks,

Rod

Those two boneheads never did know anything about 240 repair. I doubt if they could diagnose a flat tire.


--
'80 DL 2 door, '89 DL Wagon

If the inner and outer caliper halves are incorrectly matched*, the internal porting will be screwed up. The result is that the outer-upper cylinder cannot be properly bled. Therefore that cylinder applies little or no braking pressure on the upper half of the outer pads.

I'm not positive that mis-match would cause your pad wear problem, but it's fairly easy to spot, and is a known problem with shoddily rebuilt Girling calipers.

* The Girling factory punch-marks a dimple on the bottom of each half, close to the mating line. If you see a punch mark on the TOP of an outer caliper half, it means the rebuilder didn't reassemble the halves correctly, and that half belongs (inverted) on the other side of the car.

EDIT: Note that just ONE mismatched front caliper will prevent proper bleeding of the upper cylinder on BOTH front calipers as well as the Left Rear caliper, since all 3 make up one half of the dual-diagonal hydraulic circuit on non-ABS 240s.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.