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"Stuart A. Bronstein" <spamtrap@lexregia.com> wrote in message
news:Y7MOf.44920$H71.10895@newssvr13.news.prodigy.com...[color=blue]
> mrcheerful<nbkm57@hotmail.com> wrote in
> news:8QHOf.30836$wl.17519@text.news.blueyonder.co.uk:[color=green][color=darkred]
> >> I just realized that replacing the rotor and pads will not solve my
> >> brake vibration problem if the pistons are sticking!
> >> Do they make a brake piston force guage which works on 4 piston
> >> calipers?[/color]
> > Use your hands.
> > With the pistons pushed out a bit (by carefully pressing
> > the brake pedal) it should be possible with strong hand
> > pressure to push each piston back in to the caliper[/color]
>[color=green]
> > the easiest way for you to satisfy yourself as to the ease of piston
> > movement is to strip the caliper completely, with no piston seals at
> > all the cleaned pistons should be able to fall freely in and out of
> > the caliper.[/color]
>
> Hi Mr Cheerful,
>
> Thanks for the advice. I guess I just assumed there was a tool to measure
> brake piston sticking. If there isn't a tool, I can do what you say and
> test it by hand with the calipers disassembled.[/color]

Personally I wouldn't bother checking the caliper pistons, as IME the
chances of sticky pistons causing judder or shimmy is remote. The most
likely cause is distortion or chilling of the disc. Chilling can cause hard
spots on the swept surface of the disc. The uneven friction can cause judder
of the brakes.
The only cure in either case is to fit new discs, which is what I would do
If I had the same problem.
Mike.