I had a persistent problem like this on my "91 940, and it didn't go away
even after I replaced all the brake parts. What did seem to make it go away
was being absolutely sure the wheels themselves were tightened to the
specified torque. On my car, at least, the specified torque is surprisingly
low, and unless you call that to the attention of whomever is installing
your wheels (which I switch twice a year to install mounted snows/summers),
they tend to tighten randomly (apparently). Since I've been insisting on
the correct torque in foot-pounds as stated in the owner's manual, I've not
had the shuddering problem.
"AB" <firstname.lastname@example.org> wrote in message news:email@example.com...
> Be careful if tempted to use drilled discs - they have a nasty habit of
> cracking around the holes.
> If you do want cross drilled discs use ones where the hole is cast in as
> opposed to driled as they have much higher resistance to cracks.
> Alternatively try using grooved discs - much the same effect as drilled
> but with none of the cracking problems.
> As regards the issue reported, look at the discs to see if there are spots
> of dark material on the disc... this is known as pad transfer and can
> cause the same problem you were describing.
> There is a very good discussion of brakes and pads at
> "Randy G." <frcn@DESPAMMOcncnet.com> wrote in message
>> "Paul Colini" <firstname.lastname@example.org> wrote:
>>>I have a '91 240 with 100 000 miles on it and feels like I'm riding on
>>>square tires when I brake. I had the front rotors changed but the problem
>>>persisits. Wheels were balanced-no difference. The front end is tight
>>>it's not so much a vibration at the steering wheel (although there is
>>>but you can feel it in the seat of your pants. It does it only when the
>>>brakes have warmed up so I suspected a warped rotor but the new ones do
>>>too. I tried braking with the emergency brakes and the problem is gone.
>>>What else could cause the shaking other than what I've mentioned?
>>>Also whenever it is cold it lets out a groan whenever I go over a bump.
>>>Doesn't feel like something is loose but either a shock or other
>>>component is worn out and metal is scrubbing metal. Not as bad once the
>>>has been driven for a while. Difficult to isolate if coming from front or
>>>back. Any help is greatly appreciated.
>> If it is only when the brake are warmed up then I too would suspect a
>> bad rotor. Any good suspension shop should be able to rule out most
>> other causes such as bad steering rack, bad tie rod ends, worn
>> suspension bushings, etc.
>> Although unlikely, it could be dripping brake fluid on the drums, but
>> that is a stretch of the imagination.
>> New rotors do warp, and this is more likely with cheap after-market
>> rotors and those which have been improperly installed or over- torqued
>> You might want to try cross-drilled rotors which dissipate heat more
>> efficiently and reduce the chances of warping.
>> __ __
>> Randy & \ \/ /alerie's
>> '90 245 Estate - '93 965 Estate
>> "Shelby" & "Kate"