fuego

Hey gang.

I am continuing to post in the 997 forum as a follow up to my Big Brake NOOB thread. I had a terrible steering shake at highway speeds. It got worse under braking, so I ID'ed the calipers with the help of Rennlist, and ordered the correct rotor rings and brake pads. Installation removed the steering shake under braking but the shaking is still too much to inspire confidence for DE's, or even highway cruising really. It is uncomfortable. It borderlines unsafe. This must be what it felt like to be Bill Walton on his messed up feet, or Bo Jackson with a busted knee.

I'm getting really tired of it and of throwing money at it with no desired results. Help me figure out the best path towards owning a functioning sports car again. Please.

What I'm experiencing is:

- a highway shake from 55+ varying in intensity; max intensity around 67mph
- highway speed shake is not present constantly; when there is a bend in the freeway especially cambered, the shaking disappears completely and it rides smoothly
- shaking will return slowly after a turn or bend if the tarmac is smooth, else an expansion joint will return it to original state
- similarly there is a bounce from the entire chassis from 30-35 mph; oscillation is much slower it doesn't seem to be a direct link to the steering shake
- At 80mph+ the rear becomes unsettled and the entire chassis begins to bounce
- Car tramlines even after the alignment; hitting a lane reflector while changing lanes really pitches the chassis and it takes a long time to settle
- When the car sits for a few hours in a parking space and I back out,I get a small sensation through the steering wheel that something moved slightly going into full lock

What I've done to diagnose is:

- 6 & 12 o'clock shake (ball joints) front and rear seem okay
- 3 & 6 o'clock shake (tie rod) fronts were bad; inner and outers were replaced a month ago; rear has a slight click with the wheels on, could be spacers or drop link?
- with car on stands, hands on strut body (avoiding the spring), a push gives the body a noticeable click-click on 3/4 of the struts
- wheels rebalanced about a month ago (non-road force)
- visual inspection of tires show some cracks along the inner left front; all others seem to have even wear
- constant tire pressure monitoring and hand checking;
- inspection of front strut mounts looks tight

The car has:

- 245 & 295/19 hubcentric wheels
- JIC Magic coilovers (with the inverted tubes)
- 7mm rear hucentric spacer (not screwed onto hub however)
- aftermarket adj. drop links
- new inner and outer tie rods
- alignment a month ago (after tie rod installation)

Possible Diagnoses:

- wheel or tire out of round
I don't think this is the case as the tires make no tell-tale whumpwhumpwhumpwhump noise when speeding up.
- poor alignment
West End performed my alignment and they're a beloved institution around these parts. Could be they fudged it but not likely. They also installed the tie rods.
- bad ball joints
Fronts not likely since there is no play. Rear definitely needs investigation. How can I dig beyond just the shaking the wheel on a jackstand?
- bad struts
This is where I currently land. JICs have a reputation for needing frequent rebuilds, and I found a thread where someone on JICs had a similar problem and it turned out to be essentially a blown shock. When I apply my body weight against the strut laterally I can hear a small but definite "click-click" I don't however see scalloping developing on my tires.
- brake rotors out of balance
These are new and I tightened them in the proper sequence to spec. Not likely.
- power steering or steering rack issue
Black magic voodoo to me currently but not likely. Also I don't want to think about how much it'll cost to make right.

So here I stand. Some disappointing wrenching sessions, a lot of mulling, and a shaky car that doesn't safe for spirited driving. I'm leaning towards the coils. They were on the car when I bought them, and I have at least 30K on them. They all look clean and I see no evidence of leaks. If I move in that direction, JIC offers a rebuild but given the costs, I'll probably go with a set of PSS9 and let the JICs go to someone who'll track a car frequently. They work better there anyways. What I don't want to do is to buy and install the coils only to have it be the ball joints or something else I overlooked. What do you guys think?

Macster

Tires might not develop wear typical of a bad shock for some time.

One thing you can try is have someone (with a passenger) follow your car and have the passenger film the car from behind or as behind as it can be filmed while you are driving it in such a way to manifest the untoward behavior.

You can film the car if you can train someone on how to bring about the behavior.

The behavior you describe in some way makes me suspect alignment. Did you get a before/after printout of the alignment numbers? What are the settings?

JF22

I had the same vibration , remove 7mm spacer problem solved !

Linnm

rotor surfaces are not parallel and/or smooth
My Porsche tech has a cutting tool that will cut 2 surfaces (inside and outside) parallel at the same time
Worked for me

fuego

You know, I've asked both my dad and my brother separately if they saw any wheel vibration in motion and they said no. It might be worth re-investigating though, as they are not as car crazy as I am.

Yes, I'm thinking that as well. Just not enough lip on the hub. Unfortunately I don't think I'll have enough clearance without the spacers and the 295s, so I might try stepping up with a new 10mm spacer.

fuego

I have new rotor rings on the front and new pads all around so I don't think that's the issue. Maybe for the rears since I didn't replace them.

JF22

it took me weeks to cure it ... new tires , different wheels ,suspension motor and transmission mounts check ,brakes inspected and nothing after removing spacers vibration gone

MagnusB

Tires damaged on the inside? I.e. not a visible change.
Have you swapped left/right to see if it changes anything?

fuego

Did you have spacers on all 4 wheels? What size and were they hubcentric?

Yes, the fronts have been swapped and the problem persists.

MagnusB

Try to swap rears as well.
When I have had similar symptoms it has either been wheel out of round or tire wear.
In this case the wheel re-balance "should" have seen a bad wheel/tire though.

Not sure what you mean by "bounce from the entire chassis from 30-35 mph"?

captainbaker

It sounds like your spacers are the issue and simple to correct.

Ducati_John

If it was a wheel being out of round or a rotor or spacer not parallel between faces, you could probably see that by rigging up a pointer at the edge of the wheel and rotating the wheel past it. The best would be to use a dial indicator so you could actually measure the run out. You could check it for both radial and lateral run out. If you saw something on the wheel, you could remove the wheel, lock down the rotor and check that to try to see if it was in the wheel or the rotor, etc.

fuego

I didn't know how else to gracefully describe it hahaha If you've ever been in a poorly paved parking lot and maybe it's in a super hot area and the whole lot is just wavy. As the car drives around it bounces and continues to do so.

This is my problem around 30 mph at steady velocity, regardless of the surface condition. From my years of driving lowered cars with bad shocks, my guess is exactly that. There's always a goldilocks mph zone to highlight bad shocks.

I added that little blurb in sort of as a brain barf for myself to collect my thoughts. Bad shocks could be the culprit to the steering shake, or it just could be a peripheral player. Good catch though.

fuego

Well, I only have spacers on the rear. And while I do have a shake at 80mph which I can most likely attribute to the spacers, I'm hoping to solve the front shake as well.

German888

For piece of mind I would re torque the 2 10mm steering rack bolts from under the front end. Accessible by taking off the front 4-6 torx screws holding the forward under tray.

The rack itself has locating pins at those bolt locations and I noticed recently on mine when adding bump steer spacers that only one side had a pin installed.