i'd agree that the rear rotors are highly suspect. This is commmon, not a big deal to swap out yourself. I had to do my '95 turbo's rear rotors at 60k solely for this, even though pads were fine. A torque wrench is your best friend when it comes to avoiding warped rotors. Always check them after anyone else has put on a wheel also. I have almost never had a tire shop get it even close to right, and they are always overtight, sometimes by 40 plus pounds. They use those torque sticks mostly to be sure the lugs are tight enough, not to get the right torque. The air guns overtighten, then the torque stick just clicks and it gets OK'd
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Mike Sullivan '07 XC70, '95 855T (100k), '95 855 NA (148k). Past Volvo's: '85 744 (256k), '86 245 (165k), '86 245 (195k), '88 745 (208k), '91 745 (196k), '93 965 (147k) , '98 V70XC (98k).

I recently replaced the rear rotors & pads on my 98 V70. I had lots of vibration that I'd just gotten used to over time. However, when getting new tires I noticed how thin the rear pads were. At 128K mi, they'd never been changed.

Braking is very smoooooth now. No vibration or noise. I definitely waited longer than I should have. I also bled the brake system while I was at it.

Good Luck
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1998 V70 T5 124Kmi; Previous car: 1985 SAAB 900T, 254kmi

I agree with Chris's assessment. Warping of rotors is common if wheel lugs aren't torqued properly. When replacing a wheel, torque the bolts in increments (I do it in 15 lb-ft increments) moving across the bolt pattern (much the same as when you draw a five point star on paper without lifting the pencil). I carry a torque wrench in the car just for this purpose.

If you feel a pulsation in the pedal and by the seat of your pants, it's probably the rear rotors. If the steering wheel shakes when the brakes are applied, it's the fronts. The rotors don't always have to be warped to cause symptoms like I described. It can also be rotors with "hot spots". If you see a blue discoloration on part of the rotors or like a stamped spot, that will cause the pads to "slip and then grip".