brake rotors[850][97]   rob -- Monday, 10 December 2001, at 4:08 p.m.

i've gotan 850 wagon (58k) with a pulse in the brakes. the dealer told me it was the rotors being slightly warped, that it was quite common, that it was not cvovered by any warranty, and that you could not "cut" the rotors, becasue that made them too thin, and they would just warp right away again.
Why does this happen, is there any otehr ideas for dealing with it, and anything i can od to insure it doesn't keep happening?
--
rob
 

The number one reason stock rotors warp is due to lug bolts being overtorqued, and unevenly torqued. All the people I know that torque their lug bolts on their 850's (and I know many) have never ever warped a rotor. Even if they've been overdriving their brakes, and REALLY abusing them.

This is the best place to begin if you are warping stock rotors. Do you do this? Your dealership won't. They use "torque sticks" which are HIGHLY inaccurate.

Whether you can have your rotors turned or not is highly dependent on a number of things. First of all, if it is your front rotors, I wouldn't bother, and they are almost definetly going to show problems again, VERY quickly. So I NEVER ever recommend having front rotors turned, just replace them, and PREVENT warping from then on. As for rear rotors, they warp VERY easily on this car, and for the same reason of improper torquing. These however CAN be turned IF there is sufficient rotor thickness left. Obviously, your dealership either doesn't think your rotors have enough left, or are trying to ensure the problem stays away for longer by insisting on new rotors, or are simply trying to make as much off of you as possible.

Go out and invest in a $100 Canadian torque wrench, and I can assure you, the likelihood of your rotors warping will be significantly reduced.

*Another hint, clean the mating service on your hubs everytime you remove the wheels. This area corrodes rapidly, especially if you have alloy wheels. This corrosion creates a non-flat surface which when the wheel is torqued, causes uneven stress on the rotor.
 

The front rotors are good for about 60K (normal use) so you
should replace them. Your pads might be close to needing
replacmement and if someone is replacing rotors might
as well have that done, too.

Volvo says the rotors should never be turned (actually, I think
most modern rotors should not be turned). You can feel
a lip at the edge of the rotor. When the rotor is new it is
flat -- the lip is the amount of wear on the rotor (only touch
the rotor after car has been sitting a while, it will be hot).
There is actually quite a bit of wear.

www.volvoparts.com can be searched to see the cost of rotors
and pads -- this would be the low end of what you might find
at a local dealer.

I have a 95 855 and 98 S70 and have had no rotor problems.
I do torque the wheel bolts myself and if the car has been
serviced I re-torque them (and the settings from local tire
shops and the dealer have varied by quite a bit).

I received my torque wrench for Christmas one year (hint, hint) :)

Also, I have seen posts here where the rear rotors were warped
which caused vibration similar to what you describe (seem to come
from the front).
 

--
Ray Niblett 98 S70 T5M / 95 855 GLT
 

I just got a 98 S70 with 80,000 kilometers but came with all new rotors. Apparently, only the rears are worth machining, but my experience is that it's more cost effective to go new unless you have free access to a machining jig. I just installed the Volvo mud guards ($72.00 cdn which I was told is dealer cost/list is $126.00 cdn) and I did use the torque wrench. If you are near a "DEALS" in Ontario, they have 1/2 inch long handled torque wrenches for $35.00 cdn in case with a few adapters. Fairly accurate so far. 81 ft/lbs on the lugs right?

The Volvo dealer wants about $110 cdn per rotor. Crappy Tire lists them for $45/$55. Anybody have experience with these rotors. Pads at Crappy were essentially the same as dealer @ approx. $85.00 so Volvo pads would be a better bet I would think.

Artic Steve
--
Artic Steve
 

Check out www.volvoparts.com for their prices on OEM rotors.

Yep, 81 lb/ft. Right in the manual on the page that tells
you how to change the spare.
--
Ray Niblett 98 S70 T5M / 95 855 GLT
 

so if i replace the rotors, and re-torque them after the dealer get's through with them, i shouldn't have any more probelms? is there any way to fix the pulse w/o replacing the rotors, if i re-torque them will they "straighten out"??? (haha)

--
rob
 

Well, at best you should have a smaller chance of having problems
if they are torqued correctly (after all, any given batch could
have been improperly heat-treated which would lead to warping).

The pulse could also be something else (ABS?).

I think you can re-flatten rotors by removing and placing under
your mattress. If your wife feels the rotor under the mattress
that means she is a Volvo Princess :)
--
Ray Niblett 98 S70 T5M / 95 855 GLT