I recently did the brakes and rotors on my 1995 940 front brakes.

Because the pistons were very hard to push in, I became concerned that there might be some issue with the calipers sticking.
The car seems to drive and brake fine.

Seemed logical that to test it, I should just jack up the front and see how the wheels rotate. I did, and both wheels rotate quite easily, just one can hear a very slight sound as the caliper brushes the rotor at a point during each rotation.

Question: Is this normal? Or should the calipers not touch the rotor at all with wheel rotation?

Also, if the piston is to be lubricated... what's the best thing to use? Anti-squeal lubricant? brake fluid? WD-40? (which contains silicone) I'd think that anything with silicone wouldn't be a good idea with DOT 4.

Thanks for any input...

peter, did you do a full flush of the braking system? it wont cure the issue but its areally good idea to do one every couple of years at least..

if not can i recomend a presure flusher (powered from the spare wheel) they make the job easy, safe and clean - and i recon i can 'really' tell tell the difference changing out old grotty fluid..and if you have got and crap floating round the system this is the best way to remove it!

Your calipers sound ok. Normally the pistons are lubed by the brake fluid. Disc brakes have no return springs to pull back the pistons as drum brakes have. When you take your foot off the brakes, the small amount of run-out or wobble in the brake discs serves to push the pistons back into the caliper cylinders and also pushes the moveable slide on the 940 caliper back. The distance they get pushed back is small and there is usually a slight rub as the high spots on the disc rubs the pad lightly. That is what you are hearing.

When replacing brake pads, I've had some pistons slide back with only moderate prying with a screwdriver and a block of wood. In other cases, I've had to use a large C-clamp and lots of pressure. If the piston is hanging up and won't retract in the caliper, the reason is likely corrosion in the cylinder walls. The only cure for this is to replace or rebuild the whole caliper.

Sometimes, when the pistons are pushed back, they dislodge corrosion and dirt and this stuff gets back into the brake system. A good practice is to open the brake bleeder valve on the caliper while pushing the piston back. This allows the dirty brake fluid to exit out the bleeder valve.

The 940 calipers have two bolts on which the moveable part of the caliper slides. These bolts sometimes lose their protective rubber boots and get rusty or loaded with road dust. Then the caliper sticks, letting the pads rub on the disc. This wears out the pads and can warp the disc by overheating it. This seems to be the weak point in the 940 calipers. The 240 had no sliding caliper design.

You don't want any kind of lubricant to get on either the pads or the disc. However, the bolts mentioned above can be cleaned and lubed with a silicone grease such as Sylglide. Renew any torn or missing boots. Some recommend a light coating of silicone grease on the rubber dust boots on the pistons. This isn't to lubricate but to preserve the rubber. This same lubricant can be used on the backs of the pads to reduce brake squeal.

Hope I haven't been too wordy. You sound like you are just getting started on Volvo Maintenance which is a good thing. These cars are among the most satisfying to maintain of the many, many cars I've owned. I've learned more about them on this forum than from my manuals.

Well put Jim! For those used to working on the brakes on 240 cars, the sliders on 700 and 900 series are an adventure.

Thanks for the insights, Much appreciated. I'll save that message to the databank.

The thing about brake work is that there seem to be so many variables.

There is special brake lubricant to use on the pistons/slides. A light touch as the wheel spins is no big deal, probably due to a little warping of the rotor. From what you wrote, all is normal. The wheel should rotate 2 times with a hefty tug on the wheel.
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95 854T, 88 780, 88 245