I recently rotated the wheels (front to back, back to front) of our 940. Soon afterwards I notice pulsing of the brake pedal and steering wheel shudder when stopping, mostly from highway speed. Previously, there was no pulsing or shudder. Driving at highway speeds produces no shimmy so I don't think the wheels are out of balance. I am wondering if the front rotors became warped in the process of rotating the wheels. The front rotors are original and have 205K miles on them. I did not measure the front rotor thickness but the rotors do show signifiant wear (no surprise considering the mileage). The rear rotors have been replaced and have about half that mileage--they do not appear to be excessively worn. I torqued the wheel bolts uniformly but I'm wondering if the combination of thin rotors and retorqueing may have warped the rotors. If that's not likely, what else could cause the brake pedal to suddenly pulse and the steering wheel to shudder?

Spook is corect as usual. Loosen all wheel nuts and re torque to 63 lbs. A couple of hard stops from 70mph should take care of the unevenly worn pad and/or break pad deposits on the rotors. Rememberwhen breaking hard, let it roll just before comes to a complete stop.

Here's an interesting article on "warped rotors"

http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

Jack it up, and spin both front tires. I've had 3 get major tread bubbles in the last year. Feels just like a badly warped rotor, mainly noticable at very low speeds.

Easier to see if you can have someone else spin it, and you observe.
Good luck with it.
--
Rob Bareiss, New London CT ::: '87 244DL/M47- 230K, 88 744GLE- 220K, 82 245T-181K Also responsible for the care and feeding of: 88 745GLE, 231K, 87 244DL, 239K, 94 855GLT 189K

Dear Biker Bill,

Good p.m. and may this find you well. The torque spec on 740s, 940s, and 960s (all years) is 63 lb/feet (85 Nm), according to Volvo Pocket Data Booklet, Cars, 700,850,900 (1991-1996), p. 126.

As over-torquing can warp rotors, I'd loosen and re-torque the front lug nuts, and see if the pulsing problem goes away.

Meanwhile, kudos for having gotten >200K miles from a set of rotors: that's awesome!!

Post back, hopefully with good results from a re-torquing.

Yours faithfully,

spook