sabb brakes wobble

sorry its a sabb 93 yr 2000 2lt turbo 185bph

At a guess, I'd say the disks have been very badly fitted. There's probably something stuck between a disk and the hub, preventing it from sitting flat. It should be easy to spot because you'll have monster runout on that disk. Take it back to whoever did the disks and get them to re-check the runout. If it turns out to be bad, ask them why they didn't spot it in the first place...

Cheers,

Colin.

thanks colin, I'll check it out top man

The sandpaper sound, does it happen more at about 2000 RPM and under acceleration? If so, it is likely a wheel bearing going, my 9-5 started this, did it for about a year and a half before it got worse and started makign the tell-tale noise of a bad bearing.

As for the brakes, if the wobble is in the steering wheel it'll be the front, if it's in the butt of your seat it's the back. Did you have the back checked?

You have a sticking caliper. The mechanic who changed your brakes needs to free it up. He did a poor job. Try spraying the caliper with WD40. It might clear up the problem.

NEVER put WD-40 near any mechanism you feel is important. It's a water displacer and leaves a film of grit-attracting wax when the carrier evaporates. It's exactly what you don't want to use, pretty much anywhere.

That said, I'm not sure how even a penetrating oil is going to have a lasting effect on a sticking caliper, and I'm not sure I understand how a sticking caliper (a static force in one direction) could cause a wobble (an oscillating force in two directions). Sounds more like a warped disk to me.

New discs are not warped Dave. I use WD40 all time with good results. Try it you might learn something.

Why could "new disks" not be warped? In fact, if the OP did not have any symptoms before replacing the disks, but now after doing so suddenly feels brakes wobbling I would say it is *very* likely that the rotors are the culprit.

And no, one should never spray WD40 on brake calipers. Really bad idea.

Which point about WD-40 that I specified do you disagree with? That it's a Water Displacer (notice the letters), or that it leaves a sticky residue? It's not a penetrant. It's a lousy lubricant. The only thing _I_ use it for, is as a cutting fluid when turning aluminum on the lathe, for that it's fine. As far as any sort of putting it on brakes, though, it's entirely the wrong substance.

Further, how do you reason that pulsating source (bidrectional) is caused by a stuck caliper (a static, one directional force)? What possible circumstances could make that be true? I'm trying to picture a stuck caliper causing a pulsation, and the geometry just isn't there. A drag, sure, but that'd be consistant unless the _rotor wasn't planar_.

So, other than suggesting the wrong chemical to fix the wrong problem which doesn't match the symptoms described, your advice is right on. If you do have some actual logic or reasoning behind your, um, theory, I'd be delighted to read it.

I actually once had a severe wobble caused by a stuck caliper. It caused the brake rotor to heat up so much while just driving (no brakes applied) that the rotor warped and the pulsation was wild. So really the rotor was warped causing the pulsing but the "root" cause was a bad caliper.

Are there any special-purpose aerosol brake caliper lubricants around? When a brake caliper is assembled the sliding surfaces are meant to be lubricated using a special grease (I guess it has properties that make it suitable for the materials and the type of environment - brake dust, heat, etc.).

Craig.

Spraying any lubricant in the area of the calipers seems like a really bad idea - probably accounting for the lack of such lubricants. Careful hand application is the only way to go. If a caliper is sticking, chances are it needs more than lube.