Rotor runout can and should be measured with a dial indicator; if your hub is out of true then replacing rotors wouldn't fix the vibration issue. Of course, if that possible cause of vibration is eliminated, other suspension parts should be checked. I'm curious to know what's the culprit in your case, I'll have to go through the diagnostics with my recently acquired 940...
--
'98 965

I thought I mentioned that the vibration is through the steering wheel, but I guess I was wrong.

So when I'm braking at high speeds the steering wheel vibrates. The vibration is more of a up and down vibration, and not the side to side vibration like warped rotors.

The vibration seems to be with the front of the car.

I did replace the front brakes and the caliper pistons pushed back fine.

Should I rule out the back of the car as the source? I didn't even consider it.

I've been too busy to check anything out yet.

Thanks-

Paul

Once I had a vibration when braking in my 90 240, thought it was warped rotors. A little surprisingly, it turned out to be bad ball joints. Only happened at high speeds as you mentioned.

I also like the stuck caliper piston idea as brought up by Ted and Art.

check each caliper piston looking for a stuck/jammed one, normally on the rear but not always

i'm having the same problem with my 89 244. I was thinking its either the driveshaft center support bearing or the rear torque rod bushings. i dont feel it in the steering wheel. i feel it through the whole car.

Others will provide better, more useful suggestions.

Maybe failed large (rear) control arm bushings?

The bushing material in the large control arm bushings would have had to deteriorate to have little or no connection between the outer control arm bushing shell and the inner (I forget what it is named) shell through which the control arm bushing retaining bolt, to secure the large (rear) control arm bushing housing and the control arm are secured.

In another instance, if these rear control arm bushes have been replaced, yet not properly torqued, the nut at the bushing rear inside the box may be lost. Or, the bushings were installed, yet torqued while the car body was raised. You want to tighten to snug, take to an alignment mechanic or from a service trench, apply proper torque. Some will "double nut" this here.

You install solid bushings and then tighten with the vehicle on a level surface, like a garage or shop floor, or alignment mechanic's alignment rack.

How many miles?

Do you know whether what suspension bits have been replaced on your 240 before?

Else, ball joints have play? Or the strut mount bearings and / or strut mount bushing matter has failed as easily seen by crack or tears, usually concentrically.

Also, maladjusted / worn front hub bearings. Grease pack okay? Grease pack clean and plentiful with ample grease yet propr air pocket so grease can gyrate?

You experience shaking through the entire 240 or at the front, through the steering wheel?

Any issue with steering? The steering rack U-bolts, to secure the rack to the engine support member, have come loose a bit?

https://www.brickboard.com/FAQ/700-900/Brakes.htm
--
Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.