Do I Need Suspension Work?

[jyl]

I am starting to wonder if my car could use some suspension refreshing.

For most of my first year of ownership, I could find no fault with the handling or ride in street driving, and I loved the car's handling during a DE at Thunderhill - steered where I wanted it to go, suspension soft enough to absorb the alligators but firm enough to feel very controlled. The instructors who drove my car didn't comment on any weird behaviour (by the car). The old "stand on bumper then jump off" test doesn't reveal any problem with the shocks and there's no clunking sounds. The car doesn't "pull" to either side, although it does have a slight tendency to slowly drift right.

However, lately I notice two things that bug me. They both occur when driving at highway speeds (60-80 mph) around moderate curves where the pavement has a lot of elevation changes. By "elevation changes", I don't mean hills, but rather low and high spots in the pavement. For Bay Area folks, I mean something like Hwy 17 from San Jose to Hwy 1.

First, when the road level changes, the car feels just a little "floaty". E.g. when the road falls away, the car doesn't feel like it is closely following the road level down, rather there is a 1/2 second delay before the car feels "planted" to the road again. I know this is awfully subjective but that's as clear as I can describe it.

Second, when I'm in a curve and the road level changes - rises or falls - the car feels a little "destabilized". The rear feels like it shifts a little, and I have to correct with the steering. It's nothing that threatens one's control of the car, but if I deliberately did not correct the steering, the car would deviate from the line I was on - not dramatically but on a narrow roadway like Hwy 17 you might get uncomfortably close to the barrier or adjacent lane.

Any thoughts? Beyond the thing that came to my mind (shocks),are there other components, bushings, etc, that should be prime suspects? I will get under the car next weekend and take a look, but would appreciate some ideas of what to look for.

I have been thinking about doing some suspension work anyway, but had planned to spend the year doing more DEs and AXs before choosing components for XMas. However, with my summer trips between NoCal and the Oregon Coast coming up - and I'm not planning to take the Interstate! - I am thinking about doing something sooner.

The car is a 89 3.2, 148K miles, lowered to 25" F and 25.5" R (ground to underside of fender lip above the wheel center). New SO-3s all around about 300 miles ago, in stock sizes. Using 29 psi F 35 psi R. I do know the immediate PO (owned it for about 2 years or appx 20K miles before me) had it lowered and corner balanced and the L-to-R weights were very close - he had photos of the scales. He did not replace the shocks and he didn't mention having done anything to the suspension but the lowering and balancing. I have no idea what suspension work was ever done by prior POs.

Thanks, everyone.

[stlrj]

John,

The handling you describe sounds typical of a 911 that has been lowered below euro specs with lots of negative camber and darty behaviour that comes with it. Great setup for track and autoX but you want it streetable too?

Joe

[jyl]

I haven't noticed any great degree of negative camber (or the corresponding wear pattern on the old Dunlops), but I guess it's hard to eyeball this stuff. I will try to check that out carefully. I have what is supposed to be a good P-shop nearby (Griffin Motorwerke in Berkeley) and at some point in this investigation I'll likely ask them to look at it.

I don't think I'd want the car set up in the way you describe. The PO did the set-up, don't think he was a racer but maybe he ended up setting the car up that way.

[911pcars]

Sounds like shocks to me.

Sherwood Lee
http://members.rennlist.org/911pcars

[stlrj]

Negative camber is automatic when you're down to 25" fender height. Best you can hope for is getting the toe close enough to have it track without having to correct your steering all the time.

Joe

[Mike Kast]

What about a bump steer kit? Project #56 in the 101 projects book
"if you decide to lower the front end of your 911, there is a good chance that your steering will develop what is known as a bump steer problem. when traveling over a bump in the road, the steering wheel will jerk in your hands. This happens when the tie rods are no longer at the proper elevation for stiff, sure steering. The solution is to install a bump steer kit. This kit raises the steering rack up to the proper level and minimizes this effect."
I've been wondering about this myself. Wayne says its a $25 part and takes an hour to install, but also recommends front end alignment. Has anyone installed one? It seems like a cheap start to see if this is the problem. Then there's alignment though...

[Wil Ferch]

Shocks.... believe me....shocks.

Sounds *exactly* like what I was trying to describe a while ago in posts about my car...a kinda quick two-step in fast lane change maneuvers, ...a little floaty, but that's not the right word, etc , etc..

Once shocks were changed...all is well.

Of course, alignment, etc, needs to be correct...

---Wil Ferch

[jluetjen]

I'd elaborate further on the shocks and say low speed dampening. Possibly soften the low speed droop and stiffen the low speed bump. Alternatively, going from "stock" shocks to "sport shocks" will encompass those changes as well as some others.

The shift that you describe in point two could be bump-steer.

Those are my suspicions, but you won't know for sure until you change something and confirm the results. If you can afford the luxury, do the bump steer first (since the solution is the cheapest) and see what difference it makes, and then the shocks.

[dd74]

I'll echo what Jluetjen, Will and Mike say.

I'm having a bit of the same problem, and in addition to changing sway bars, I plan to put sport shocks on the rear. I'll probably leave the front shocks alone - HD Bilsteins are up front - and it's very stiff there.

As for the bump steer problem - yes - a bump steer kit will eliminate the jerking and bouncing of the steering. I had this problem as well when I switched tires - though oddly enough the tires were the same size.

I also installed turbo tie rods, and that made things a lot nicer.

One strange factor was the PO installed wheel-lock lugnuts on all four wheels. Beside being horribly ugly, they threw off the balance on the front end. If you have these, yank them off. Mine had to be drilled out because the tire store lost the key. But after they were removed, the steering wheel "bumped" much less.

The bump-steer kit and turbo tie rods made things that much more solid.

[jyl]

OK, I'll splurge for the $15 bump steer kit (spacers) and see if that helps, then will consider the $300 bump steet kit that includes the turbo tie rods. I'll also do the shocks. Leaning toward Bilstein sports all around from PP (I have Boge struts). Then an alignment - I'll search prior threads for the specs to request.

Now, assuming I don't visually see deteriorated bushings, should I replace any of those as a diagnostic sort of thing? Sounds like the expense is modest if I supply the sweat and cussing myself.

Finally, I have been looking at the Elephant Racing strut, front monoball, and rear cartridge. My impression is that for the kind of street driving issues I described, these wouldn't make much of a difference, so I can stick with my prior plan of getting more track/AX time before spending money on these "racing-type" mods. Is that fair? How much extra noise and harshness will they cause? The car is >95% a street driver on typically crummy California roads, so I need to care about comfort.

[Don Wohlfarth]

Sounds like shocks are the problem, bump steer is a little different feeling but with the car that low it may be that as well.
With 150K on the clock there's a good chance the stock bushings are worn or worn out.
For 95% street driving you should replace with rubber bushings.

[spinner]

Had similar sensations when I first got my car. Changed the original factory Boges with Bilstein sport shocks and what a transformation. Bump steer doesn't cause the floatiness - it causes you to go where you don't wanna

[Steven Alarcon]

If the rear ride height is 25.5" and the shocks are orginal, the
stock limit bumpers could be too long giving you a induced
"Bump-Oversteer".
The Sport Bilstien B46-0975 has a limit bumper that is about
1.5" shorter. If this problem happened only after you had it
lowered, I would guess this is the problem. I recommend the
H/D Bilstein Shocks for the front and the Sport Bilstein Shocks
for the rear. You will a great ride for the street and have more
controll for the drivers Ed. events.
Remember that when you change front Bogie to Bilstein Shocks
the ride height will change and you may have to lower the ride
height of the car.
Before you make any changes take your car back to your tech
and have him check the front toe adjustment. Have it checked
with your weight in the car, it is my guess you have a little
toe out condition.

Hope this helps,
Steve Alarcon

[Hellgate]

Sounds like shocks but checkout the wheels bearings and ball joints too.

[Alex001]

Sounds a lot like what my car did before I replaced the ball joints and tie rods (with turbos).

[jyl]

Great, thanks everyone! This weekend I will get under the car and check out the bushings, etc. Unless they look great I am inclined to replace them just to know it has been done.

I may post some photos in case anyone can give me a remote opinion.

[stlrj]

John,

When was the alignment last checked? All the symptoms you describe could be the result of your front end toe being slightly out of adjustment.

Rather than throwing a lot of money on parts you may not need, why not have your alignment checked?

Joe

[jyl]

I will have the setup checked before writing significant checks . . . always a good idea. I've never had the alignment or any other aspect of the suspension setup checked.

Actually the car has only seen a mechanic once in the year I've owned it, for something quite minor that I should have done myself. Really quite trouble-free.