Had an issue with the front LH caliper having uneven pad wear. The inner pad had hardly any wear (the same amount as both pads on RH side), while the outer LH pad was three-quarters worn. There was also some additional wear visible on the outer side of the LH rotor. I assumed this was caused by a sticking caliper, so I overhauled the calipers and fitted new seal kits. There was a large buildup of crap below the piston seals inside the caliper, but there was no wear marks on the pistons. After flushing out all the crap everything appeared normal. The calipers were refitted with new pads (QFM A1RM), and bled through with new super dot 4 fluid. The car has been driven approx. 1,500km since the front brake overhaul, including a hillclimb day and a round of Qld supersprints at Morgan Park totalling 21 race laps and 14 warmup/cooldown laps. Upon checking the front brakes today I am back to square 1. The outer LH pad is about half worn and a significant amount of rotor is worn down on the outside face. They are slotted rotors and the slot is about to disappear! Everything is normal on the front RH side. Questions: 1. Could this be caused by a dud rotor accelerating the wear on the pad? 2. Did the first round of problems damage the rotor and cause the wear issue second time around? 3. Is there anything else that could have caused this wear pattern? I will need to fit a new set of rotors and pads, but don't want to find I still have the wear problem. Prior to the caliper overhaul new pads and rotors were fitted about 11 months earlier, and there was no sign (back then) of uneven wear on the old pads or rotors. Appreciate any input as to what to check before going any further.
Zeds don't have caliper slides ! Front calipers on a 300zx are 4 piston calipers, each of the 4 pistons operate independantly.... 2 on each side. Your getting confused with crappy Falcon/Commodore calipers that have a piston on one side and a slide setup to move the other side.
Yeah what he said. One possible cause is the wheel bearing. Check it for any play. Does the car pull under braking? The final issue might be that the damage has already been done to the rotor (in that it has been hot worked, and is acting as a cutting disk). Highly unlikely, as it would mean only one side of the disk is affected. But, noting that the disk is so worn that the grooves are almost gone, I would suspect that your discs are undersized and they are prone to cracks, over heating (which could be the fault), and generally everything that would ensure your insurance wis not paid if in an accident.
There is no play with wheel bolted on, but I will check the bearing and reset. The car still pulls up dead straight under brakes (am a bit surprised by this). Understand the insurance issues - the car does not need to be on the road until it is fixed. I know I need to replace the disc and pads, but what I am looking for first is to isolate if possible the cause. So far we have only two possibles - 1. wheel bearing or 2. cooked disc from earlier sticking caliper. I would have thought that if the wheel bearing was worn or loose, that any wear on the brakes would affect both outer and inner pads not just the outer pad and outer disc face. Still open to suggestions for what else to check before putting a new disc on.
The only thing that has not been mentioned yet is that the internal fluid route may be blocked for the innner pair of pistons ... it is the only thing that makes sense ... Strip the caliper and inspect the internal fluid galleries - give them a blow with air and see if you can isolate where the blockage is ... Given the disc is asymettrically worn, it is now junk.
All the galleries were cleaned when the calipers were rebuilt, but I guess its possible that some crap has dislodged and caused a blockage. Unlikely that a blockage can stop the inner pistons from working as the feed in is on the inner side and then ports off to a gallery at either end leading to the outer half. Seized pistons is the only way to stop the inner pair working. Will be pulling the caliper out to recheck.
DinoZ, you're probably going to scratch your head over this, but the Zed I've just bought shows signs of similar wear. I don't know the previous driving history of the car, but I suspect street use only, and the passenger side outer pad is worn significantly more than the other three front pads.
Yes, these are the calipers that have been separated and re-kitted, BUT the uneven wear problem was why they were rebuilt (and it was assumed that the caliper was seizing and causing the accelerated wear on the LH side). I'm beginning to think that the problem may purely be rotor related, as there was no problem while the stock discs were on, but at this stage this is still all guesswork. Another difference is the car has done a lot more high speed trackwork this year with PI and Morgan Park, so could be heat related failure. Still searching for answers - all suggestions welcome.
What are your plans on this? Are you upgrading the brakes or just throwing some pads in and see what happens? As a matter of interest - what disc rotors are on the vehicle?
stock rotors. To be honest, we've only just purchased it and the car needs a fair bit of other work to get it reliable and roadworthy, so I haven't worried too much about the brake wear issue yet. I was toying with the idea of just swapping the pads around, and see if the wear continues on the left hand outer, or follows the pad.
Definitely check the wheel bearings!!!! Outside pad wear on the outside caliper of the car (which the LHS is on a clockwise track) is generally wheel bearings! We get alot of this type of problem from guys doing track work at QR (which has 2 massive right hand corners that load the left hand front caliper up) in their street cars that have never given a thought to wheel bearings. Either that, or the internal fluid route as has been said.
It might feel fine, but you need to usea dial indicator to measure the movement. The manual has the details. A very small amount of movement result in a significant issue, as shown.
do the discs line up centrally in the caliper just wondering if the disc has a different offset or thick/thiner face on the hub causing the extra wear on one side due to disc being offset
Update - here are some pics of the wear on the LH rotor and pad. Close up you can see wear is tapered to the outer edge This is the outer pad, bit hard to see but wear on pad is also tapered, with more wear on the outer edge of the pad Inner side of the disc has normal wear I rechecked the caliper and all pistons are free with no blockages in the transfer ports. There is however some play in the bearing, so this appears to be the culprit. Only thing I don't understand is: why is there no accelerated or uneven wear on the inside face of the disc or inner pad?
