Hi chaps.
This is just a little heads up for anyone who experiences the same problem, or is thinking of painting their brake calipers.
Basically, my brakes were fine. I noticed some of the pads were different makes, the rear ones needed changing. I bought the whole lot, front & rear.
I fitted the pads to the original discs (they were a bit scored but otherwise fine). When I travelled down the motorway, I discovered a juddering when braking, which then got worse until it was a juddering without braking. Warped discs I thought.
Next day, travelled to work, no judder. Got to a straight where the limit is 60, braked and got judder, developed into serious judder again without braking.
Set off from work that night, no judder at all, all the way home it was fine.
This went on for a couple of weeks until I eventually decided to get some new disks on the front (where the juddering is coming from). Ordered the discs, picked them up, took one of the old ones off, compared with new one, wrong size disc - back to swap and pay the extra £12 for 345mm instead of 323mm diameter
.
Anyway, fitted the new discs. Went home, no judder. Set off to work the next day, juddering again. WTF I thought. Got to work, had a look at the discs, noticed that on O/S they were wearing in nice and even both faces of disc. Checked the N/S and noticed one face was evenly wearing, the other was wearing at the inner circumferance and outer circumferance only, about a half inch gap between the two wear bands.
Took that side apart, checked the flange was clean, checked the pads were pushing out ok, no problems visible. Went for a test run, no problems. Next day, went down motorway and the juddering was so heavy with no braking, I was forced to do 45mph until I could get off the motorway.
Now it's here that I remembered when I fitted the pads on this side, there are four metal guide plates that bolt to the inside of the caliper. The pad slides between these when you push it into it's recess. I couldn't get mine to fit, so I sanded a bit of the excess paint off the pad edges. Still couldn't get them to fit. Then I noticed that the bottom two of these metal guides were twisted up slightly, so that when the pads were worn, they fitted snugly, but new pads wouldn't slide in because the guide plates were raised at the back.
I sprayed loads of brake cleaner in there as I thought it must be chocked with brake dust which has wedged the plate out a little. I managed to tap the pads into position and thought nothing of it.
To shorten the tale a little (!!) - someone has painted these calipers and took the guides out before they painted them, but only the bottom ones. When the paint has dried, it has raised the mating face where the guides bolt in, twisting the back edge out and stopping the new pads being fitted properly. This caused the pads to pivot top and bottom on the misaligned guide plate on one side, causing uneven wear on the disk and hence the disk to warp slightly under heat.
I've had the caliper apart today, split the two halves, undone the splined bolts holding the guides in and chipped/wire brushed the paint away back to metal, refitted the straightened guides and put everything back together - the pads now slide with minimal friction into their recess, after a quick test run, the disc is now wearing evenly.
I just thought I'd bring this to your attention, as I know lots of people like to paint their calipers. My advice is to strip the calipers down totally, remove the guides but leave ALL mating faces completely untouched, try to mask the pistons off and the hex bolts that clamp the two halves of the caliper as clearances will be affected when the paint is dry and you try to reassemble.
Sorry it's so long - I should have taken pics so you know what I'm talking about. I'm gonna do the other side just to make sure it's ok, so I'll photograph the areas affected to make it clearer
Edit:- Hope this diagram makes it a bit easier to see what I'm getting at?