Checking disks for Warpitude and working on cars with ABS

And can I just jam the pistons back or will I upset things?

You can check them with a dial guage. If it claims they're fine then it's the lower wishbone bushes, personally I've found the draper piston retracting kit to be well worth the money but I don't remember needing it for the peugeot.

I've got a piston kit in the shed. Bought it for the MK2 calipers. I've not worked on anything with ABS before so I'm a tad wary.

If you're feeling good, crack the bleed nipples before you push the pistons back to minimise the odds of crap getting into the modulator, getting rid of old fluid never hurts anyway.

Fitted front disks & pads in my dad's Audi at the weekend. I always open the bleed nip as it's a lot easier to push piston back with little more than thumb pressure. Also it doesn't force the old fluid back up the system.

Doki explained :

A dial gauge firmly mounted, pointy end against the disk and spin the disk around. watch for variation in the reading.

Righto. I've not got one. What would I expect to pay for an alright one with a mount? I can see that they are available for £25 or so on Ebay. OTOH it's a fairly safe guess that it's the front discs (I can feel it through the steering) and brake disks are cheap (£25 a pair for the front, £27.50 for the back). I might see if I can borrow one...

If you buy a mini one which are the easiest for brakes (& the easiest to break) you'll get a working one for just over £20.

If you can feel it through the steering I'll bet the bushes are on the way out anyway.

Bah. Any quick and easy ways to tell? Other than looking to see if they've dropped to bits?

Yes. Using a clamp, plasticine, or any other method, fix a 'pointer', which could be a nail, needle, piece of wire WHY, so it just clears the disc on it's outer side diameter. The closer the better. Spin the disc, and look at the gap. If you have good eyes you'll see any significant distortion of the disc. Mike.

Last time I checked discs for run out, I used the "sticky-out-bit"[1] on the end of a pair of vernier calipers, it seemed accurate enough :)

I meant the bushes ;). Although that will save me from running around after a dial gauge.

If there's no noticeable runout on the discs then it's the bushes..There isn't a practical way of checking as they're just softer, obviously if they've split they need doing anyway but there's a big gap between soft & split.

I'd like to be sure the (presumably?) judder is actually caused by this - on many cars it's a symptom of suspension wear.

I just pushed mine back. The caliper unbolts really easily, in fact IIRC you may only have to undo one bolt and slacken off another and it just pivots out of the way. I changed mine about 18 months ago and it was a doddle but make sure you clean it all well. I may not have been scrupulous enough and now the f****rs seem to be warped.

The carriers look like they need to come off on mine. Seems to be no way of getting the discs free without removing the carriers, and they're secured by two BFO torx bolts.

BFO? I like torx bolts - provided i've got the right torqatron bit :-)

Big F*ck Off.