95 850 - Low 'bass' resonance when braking

[mcp]

Just to commiserate, I'm having the same problem with my 1996 850 with 210,000 miles. Pads are down to about 1/4", so I ordered new pads and shims from FCP Groton. Will probably put them on in the next couple of week-ends. I've had the car since 1998 with 25,000 miles. Never had this problem before. When I pulled the pads to inspect them, there were no cut out shims in place.

Some days it does it and some days it is fine.

[jblackburn]

Glazed over rotors/pads can do it from long braking in hot temperatures. Give em a good, hard stop from a high speed and see if it quits.

[xjflexer]

Either have your rotors turned (machined) or buy new rear rotors. Sounds like they are warped. When regreasing the shims, you are kind of renewing the "suspension" between the pads and shims, which are just hiding the pulsation and dampening the noise caused by the warped rotor. Once the grease gets squeazed out some to decrease the amount of dampening, you get your noise and possible vibration back.

TIP...if you buy new rear rotors, used soap and water to clean the anti-corrosion film off of the new rotors. Don't use brake klean. Soap and water does a better job of removing this film.

**EDIT** I almost forgot, if you get new rotors but are going to keep your exisiting pads, sand down the pad surface slightly to make it "true" and remove any glazing. This will help your pads seat into the new/freshly machined rotors better.

[peacock]

Warped rotor(s)?

that was my first guess.


Does the wheel wobble at all? if the wheel wobbles when stopping then the front rotors are a little warped u obviously will not feel it if the back ones are warped but the noise may still be present.

[meine39]

Does the wheel wobble at all? if the wheel wobbles when stopping then the front rotors are a little warped u obviously will not feel it if the back ones are warped but the noise may still be present.

Nope - the car stops straight and true. The car is within a foot or two of being completely stopped before the resonance begins. Nothing is felt through the steering wheel, and the sound seems to originate from the rear.

[meine39]

Bumping this thread. Time to sell this car and this problem is back - definitely associated to outside temps (hot here right now). Note that original post was in August. Tempted to swap out rear rotors and pads for new, as much as I hate putting the labor and money into a car I'm selling.

[RussB]

Try some aftermarket pads...they me just different enough in materials and construction to avert the vibrations

[abscate]

I put on a set of "scored" rear discs that brake really well but have always drummed a bit on the 1999. Are your discs smooth or do they have relief grooves??

[meine39]

Rotors are stock (smooth faced) Volvo parts. Not a fan of drilled/slotted rotors, but that's a different topic