1993 940 NA
Single Piston Girling

I've recently beginning to go through my third set of rotors due to pulsing. They've only been on for about 1500 miles, and I can tell that they will get bad again. Here is the history.

July 2003 - 130K replaced rotors/pad Zimmeman/Volvo. Also replaced struts, strut rod bushings (poly), BJ's and tie rods.

Aug 2003 - replaced strut rod bushings with rubber - did not like poly. Also replaced left front hub due to a broken indexing stud.

February 2004 - 136K New Zimmerman rotors/Volvo Pads - New caliper hardware (flat shiny pieces) Cleaned caliper slide pins

October 2004 - 142K New Brembo rotors, PBR pads, New remanufactured Volvo Girling calipers, new front brake hoses. Now at 144K, noticing the early beginning of what will be bad pulsating again in a few thousands miles.

What could I be doing wrong? What should I look for? Could tires be the source? I have Kumho ecstas, and sometimes they feel a little rough, like sidewall cracking) I think I got these tires about the same time I started going through rotors (130K), but I don't see the connection between tires and warping rotors. I'm very careful about the wheel stud torque. I keep it at 65 - 80 ftlbs.

Someone sugggested that strut rod bushings going bad could feel like warped rotors, but I doubt it in this case since they are relatively ew, and the pulsation goes away when I replace pads/rotors.

I'm about ready to sell this car do to it's repeated brake problems, slight radiator leak, AC leak. It just always seems to want maintenance. Next T-belt at 150K, she's going to need new front seals to, which I can do.

Thanks, Tom

Do you drive in bumper to bumper traffic a lot? I commute to downtown L.A. every day and I'm on the brakes more than the gas. Both my 764T and the 965 warp rotors within 1K miles. I've tried everything and have finally given up. The only thing I can deduce is that the brakes just get too hot from riding the brakes in traffic without having any air blowing past them. I've got cross-drilled rotors on the 965 and it seemed to help a little bit, i.e. they didn't warp as bad as they usually do. Wheel nut torque, break-in procedures, and cleaning up the hub are all good suggestions. However, you might just find that your particular driving style and/or commute just is not conducive to keeping the rotors true.

Btw: this is not a Volvo-only problem. I've experienced rotor warpage in plenty of bimmers, benzes, Hondas, etc. that spend a lot of time in slow-moving traffic.
--
Lance '92 965 w/ 200K miles

I have/had a similar problem w/96 960. When I noticed the pulsating brakes was about 4k after new Brembo rotors and pads had been installed. The runout I found on the LF rotor was .013". I removed the rotor and cleaned up the surface of the hub and also the rotor ID. When I checked runout after reinstalling it was down to .001". I think the specs allow .003" but don't quote me. Less is better. The only thing I saw was the rust on the hub where it mates with the rotor ID seemed to cause the rotor to move over time causing the runout problem. Before I change my next set for pulsating brakes I'm doing a runout check. If I find the runout bad I'm going to clean up the rotor ID and hub mating surface diameter first and see what happens. Just my $.02.

Dear hip82,

May this find you well. The proper torque for lugnuts is 63 pound feet (85 nM). My source for this is the Volvo pocket data booklet - Cars 700,850,900 (1991-1996), p. 126.

You seem to be over-tightening the lugnuts (i.e., tightening them to 65-80 pound feet). This can lead to warped rotors, especially if the torque is not evenly applied.

Try torquing the lugnuts in stages. start at 40 pound feet, then go to 50 pound feet, then to 63 pound feet.

Further, do so, as suggested in other posts, by tightening the nuts in opposing "pairs" (after tightening a nut to the first stage of tightness, go to the nut most nearly opposite it, and tighten that one to the first stage of tightness), etc.

Hope this helps.

Yours faithfully,

spook

Do you use a torque wrench on the lug nuts and do you use a lower toque than the shops? I generally don't go over 75 Ft lb. and I make sure the Nuts are torqued gradually going around using a diamond pattern, skipping over the neighboring nuts as I go. But you probably knew this anyway.

it HAS to be heat (unless your hub faces are rough as a bears arse!

I am unclear if you have fitted entirely new calipers, if not i would try that...

having said all that i used to warp rotors in 15k guaranteed on a pug 405...

i was told its due to my braking technique, i tend to break soft and loooooong..the guarage diagnosed this one night when i pulled in and the disks were glowing visably....

basically wither you have pads rubbing on the disks or its a torque thing...

actually re-reading it ou do apear to have replaced the calipers..ok how are your brake lines/fluid, wondering if a collapsing line is stoping the caliper retracting fully perhaps?

oh - are you bedding the new pads in properly..if you fit new pads and break hard immediately you will glaze the pad and that leads to overheating...and bent discs...

I try to break gently. Probably longer than short, but my V70 that I have driven extensively for the last 6 months does not have this problem.

Recently flushed. New rubber hoses on the front when I replaced the calipers.

Break in. I don't think that I am braking hard during the first few hundred miles. Maybe I should lightly sand the new rotors?

The hub and rotor surface are pretty clean.
What should the max runout in inches be? Could I have a warped hub?

Tom

Did you clean the rotors with brake cleaner? They come coated with oil to keep them from rusting while in storage. This oil must be removed with brake cleaner for proper operation. Also, don’t touch the rotors with greasy hands – or if you do, clean finger prints off.

Breaking-in or ‘seating” pads properly does not involve light braking for the first few hundred miles… in fact, just the opposite.

When you install new pad and/or rotors, you should drive to a secluded road, get the car up to 45-50 mph, and brake HARD (and I mean HARD) down to about 5 mph. (do not stop – you don’t want the pads sitting on one spot on the rotors) Repeat this process 5 times. The idea is to get the pads and rotors HOT – REALLY HOT! When you can smell the brakes getting dangerously hot, you’re doing it right!

As Spook said, torque the wheels to 63 lbs. (it’s stamped right into the cap on the front hubs) 80 lbs is too much. And uneven torque is even worse. Use a torque wrench.

Good luck.

Jeff Pierce
--
'93 945 Turbo ( one kickass family car ! ), '92 Mercedes 190E (my daily driver), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece -- sold to a loving home), '85 Jeep CJ-7 w/ Fisher plow

interesting..i have always been told to avoid what your suggesting to bed in pads as this can cause glazing...and therfore undue heating...leading to warped rotors...

well seems theres two schools of opinions out there...

looking on the web there seem to be all sorts of routines...most seem unified in hard use of the brakesi nthe first 500 miles or so (unless they are competiotion spec) is ill advised...

not to argue with Jeff, but 30mph seem to be the common recomendation rather than the 45-50 and progresive rather than hard..and to allow the rotors to cool between applications..but hey i don't know im just looking at the sites...


edit:---

try this link

http://www.tirerack.com/brakes/tech/pad_rotor_bedin_procedures.html

seems to give various pad manufactures guides and it looks like we were all right...aint life confusing!

hmm...

I am very interested in this thread as both of my 940s have unsatisfactory braking / shimmy.

"The idea is to get the pads and rotors HOT – REALLY HOT! When you can smell the brakes getting dangerously hot, you’re doing it right!"

I thought extremely hard braking could warp rotors from the intense heat...

...or is this just an old myth??


Matt

Tom;

Seems there's lots of discussion here about warped rotors. It appears that Volvo does have a problem with this.

My rotors have 4K miles on them and are starting to pulsate. I don't know the history of the pads (since I just bought car) but I know they rotors were new Brembos.

Here's a link to The Diesel Stop Forum. In it they are discussing the "warped rotors myth" article by the late (I think) Carroll Smith.

http://www.thedieselstop.com/archives/ubbthreads/1999upg2/forums.thedieselstop.com/archives/showflat.php-Cat=&Number=1263164&page=3&view=collapsed&sb=5&o=&fpart=1.htm

Note that this link also provides a link to "warped rotors myth" article. Specifically, I am referring to message from the message poster FMTRVT. The message starts out "OK, this isn't proofed"

If you do a search here you'll also find more discussion.
--
Norm Cook Vancouver BC; 1989 745T 200,000KM