Brett Jenkins

My car seems very susceptible to variations in the road surface, sometimes very strongly. On my drive home from work, there is a section of the interstate that they are working on, so its very uneven pavement. My car gets pulled, sometimes violently, to and fro, depending on the change in the surface. I've noticed this on many roads. The car is recently aligned and tracks straight on an even surface. What suspension/steering parts should I start with looking at, based on these symptoms?

SeanR

Rack bushings comes to my mind 1st.

Chuck Schreiber

How are your tires?? Can't quite see your wheels in your avatar, but they look like the Carerra IIIs?
Offsets are probably ok.

What I can tell you-I just went from Crotch Rotted Fuzions to brand new PS2s and the difference was night and day. The old dry rotted tires used to do the same as yours, tram lined, wandered, etc. Sean and I thought it might be the rack bushings and planned on doing them when we did the mmounts coming up. New tires cured it!

Now, if your tires are ok, it very well could be the rack bushings. Also, on my 79, I had bad tie rod ends and it did the same. New rack and alignment cured it.

Let us know what you find out.

Mrmerlin

check tire pressure, rack bushings, wheel bearing tightness, inner and outer tie rods for tightness, upper and lower ball joints. tire condition/age.. After a 50 mile ride with all of the above things checked out good and possibly replaced tires get the car re aligned

Erling G-P

The offsets on your front wheels may also be a factor if they're non-ideal for 928s.

I'm running 52mm offset myself, and my car is showing some of the same behaviour you describe, on certain road surfaces.

I haven't tried my car with other wheels/tyres yet, so can't comment on how much of a difference the offsets make, but others here have reported that they couldn't believe how much better the car handled when they went from too-small offsets, to the 65mm default.

Regards,
Erling

Brett Jenkins

1 year old kumho ecstas in good shape, pressure correct. The tie rods were replace before the alignment. I plan on checking the wheel bearings when I replace the rotors and brakes soon. I'll have to check the offsets as I don't remember them. Are the wheel bearings serviceable, or is it a replace only deal?

Peter F

Wheel bearings can be adjusted per instructions in WSM.

/Peter

Mrmerlin

when you remove the rotors remove the wheel hubs pay careful attention to the lower inner seat for the inner wheel bearing on the spindle, this is usually a worn area if it is worn then it will let there be play in the wheel bearings, mostly noticable by squealing brakes. Dont try to remove this extra play by overtightening the bearings, just adjust then per the WSM. its something you will have to live with unless you replace the worn spindle.

SharkSkin

Did they jack the car up during the alignment? In addition to the above, any toe-out will cause major tramlining. If the alignment was done before the suspension was 100% settled you will most likely end up with toe-out.

jcorenman

Brett,

The trouble with steering issues is that everything is important. Any play in the front end or a bad alignment will cause a steering "vagueness", even on flat roads. And tires and wheel offsets are big factors in terms of how it behaves over ruts and bumps.

Our S4 suffered vague steering for years until we started doing our own work and found that the alignment was all screwed up (the usual ignorant-shop story) and the rack was very worn (up/down play at the rack ends). After fixing that the steering was crisp with only minimal wandering in Seattle's studded-tire ruts. Then we changed wheels and tires from Yoko AVI's to ET65 Cup-II's and Bridgestone Potenza SO-3's and now it pulls strongly in the ruts. It might be the stiffer tire, or the tread pattern-- I am thinking that the currently-fashionable diagonal grooves (from both sides towards the center) might be to blame. (The AVI's had a tread more like the Mich PS2's).

I was recently talking to Louie about this, he said his Kumo Ecsta MX's were better than the Toyo's on our 90GT (which have bigger diagonal tread grooves). And Chuck (above) said that his new PS2's were "night and day" (and have minimal diagonal tread). Might be a pattern here... but I can't tell if it is tread pattern or tire cost!

But first check rack bushings like Sean said, and the rack and tie-rod ends for any play-- let your fingers do the looking while a helper wiggles the wheels back and forth. The rack is mounted with rubber bushings, if those get old and worn then the whole rack can move around. Those can be renewed or replaced with urethane bushings. There are also bushings inside the rack housing, when those get worn then the rack starts moving up/down in the housing. (When it gets bad enough then the seals start leaking into the boots).

Cheers,

Brett Jenkins

I watched them do the alignment, so it was never lifted. I've never done an inspection of the steering components on this car, so that will likely tell me a lot.

On another note, I started a new job last week, contracting at the IT department of a local company. Parked amongst the cars in the back parking lot, I found a silver S4, 5 speed and in pretty good shape. Now I just need to introduce myself to the owner.

Jim bailey - 928 International

Does sound like rack bushings....they let both wheels point the wrong way at the same time. I wore out the ones in the old very brown 1980 after just a few years of tracking it and it would just about change lanes when it decided to move !

Landseer

Check the fore / aft movement of the driver side steering shaft, as noted, not in/out movement. If you have movement, it will manifest itself to feel like the wheels are going different diretions, but then there may be a way to fit a bushing externally that will reduce/remove the play. Capt. Earl posted about it. I cloned the repair, but made the bushing with too big a hole and it needs to be done again more carefully, but I got major improvement.

My local car repair guy and I were talking about it and he said he's used that fix on other rack/pinion cars.

Last I heard, the rebuild kit did not contain the needed bushings (rack manufacturer controlling supply only to rebuilders in the US market at least). England and Australian markets could get the parts, though.

Tails

+1 for all other suggestions, however, there has been no mention of ride height and corner balancing.

My car used to "tramline" initially until I adjusted the ride height to WSM specifications and has a proper alignment, now tracks great.

At each yearly service I check the ride height, tyre wear pattern, thread depth, wheel bearing movement, steering movement and suspension.

Tails 1990 928S4 Auto

jcorenman

Tails, good point! Part of fixing up our alignment was to restore the car to factory height. The previous shop may have been ignorant but they were conscientious-- after jacking it up and checking the height, they then lowered it back to factory specs.. until it settled ...

After replacing the worn rack, proper ride-height and a good alignment we had minimal tramlining. We then changed wheels/tires from the Yoko's to the Bridge SO3's (17" vs. 16" but same offset), still very crisp on flat roads but now has big-time tramlining in the Seattle studded-tire ruts. That was the only change so I think it has to be tires.

We'll switch back for a test the next time we get to Seattle and report back, just to be sure.

Cheers,