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Old 11-05-2010, 09:46 PM   #1
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Yet another steering vibration question...

I love driving my box, but only at lower speeds, ie below 60mph or so....

My box has been stricken with the dreaded steering vibration issue and yes I have gone through a number of the similar post here.

Have gone through 2 workshops, got the car tested by a specialist that drives like a race-car driver... And everyone tells me my car is nicely balanced and setup - indeed he was taking corners at sharp speeds (but not on highway) which I never thought possible and the car just takes it in its stride.

However, I can't get them to test the car at higher speeds... esp above 90mph on less than perfect highways... (which unfortunately is what I do when I travel interstate).

The steering vibrates quite a bit at that speed and above, if the highway is less than perfect. So much so that I have to back off on the accelerator. It's a shimmy vibration and sometimes on rougher roads, the steering rocks left and right. I've tried letting go of the steering and although the steering rocks left and right, the car seems to track straight.

So far, I've replaced all 4 rims as one of the front rims was badly dented over 2 axis (left right, up and down), the other front rim was slightly out of round. Which leads me to believe the car has taken a serious pothole before.

Alignment done 3 times, and wheel balancing done 3 or 4 times, with once, on-wheel. Unfortunately I can't locate a hunter balancing anyway here locally.

The wishbone, control arm link, drop link, tie roads all seem ok. Those components being tested with a rubber mallet and checking for free play. Are there any other methods to definitively test whether they're failing ?? I was told the wheel bearings were ok.

The front brake rotors are thin and my mechanic suggested that I replace those as under some rare chance, they may cause vibration (no vibration under braking though), which I agreed to since they are thin anyway.

I'm also going to change the suspension to M030, to try to get some extra stability as I find no much confidence taking highway corners at speed. Seems twitchy and steering gives me no confidence it's going to track around the corner.

Brakes and suspension not done yet as I'm waiting for the M030s to arrive.

Anything else I should check ? Alignment shows everything within range, no sign of bent chassis or suspension components out of whack.

I was also told by the "race-car" mechanic that the vibration is due to the "excellent" steering feedback of the boxster. There seems to be much less vibration on smooth roads. But it would seem excessive if I have to back down on the throttle sometimes to below 80mph to feel confident of the car. ANd that's on slightly imperfect roads and not broken roads. The same roads which my VW Scirocco just flys through at well over 120mph (but then that car has an electrically assisted steering which give very little feedback).

I do remember the first week when I first got my car, it seems to take corners very neutrally, now it seems to initially understeer and quickly transitions to oversteer as I add more gas.... All with the accompaning vibration... Makes taking corners at speed pretty hard work to find the right balance.

The car is a 9 year old with very low mileage - less than 20k miles when I first bought it and since then I've already added 3000 miles in less than 2 months. Maybe this garage queen is not used to be being driven hard...

Sorry for the long post... I'm just tearing my hair out...

Any suggestions on what else to test or other more definitive testing methods, I'm pretty sure something is not right but not broken enough to be obvious.

Oh... one last piece of observation - when I first got the car, the suspension felt pretty pliant... rides over broken roads nicely, now it just thumps and rumbles over the same broken road - could the shocks be on their way out ?? Or is the stock boxster suspension pretty stiff ?? When I press down on the fenders, the front suspension seems softer than the rears, is this normal ?? Rebound of suspension feels normal though, just one time up and down.
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Old 11-06-2010, 05:09 AM   #2
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my o9 cay will get a steering wheel shimmy at 65 if its cold out and the car sits for a few days,once the tires are up to temp its gone. ive been over 135 mph and the car is very smooth. yours has all the classic clues of tire issues......out of balance,out of round,old and hard,over inflated...maybe get them road force balanced....how good/old are the tires ? OEM rims? spacers?
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Old 11-06-2010, 09:07 PM   #3
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Tanker brings up a very valid point re tyres.
Are your tyres the originals or did you change them when you replaced the wheels? If they are the same age as the car, ditch them.
The only real way to identify the fault as being in the wheel / tyre combination is to borrow a set of front wheels from another vehicle. If the vibration remains, you need to dig further.
Front wheel out of balance usually affects the steering wheel, rear wheel out of balance usually is felt through the seat / chassis.
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Old 11-06-2010, 10:30 PM   #4
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Hmmm,

the "new" rims are actually original cayman 17" rims. The only thing was the offset for the rear are further out. The front offset for the front is the same. I had all 4 rims tested without tires - spun on a balancing machine without tyres. All straight.

The front tires are brand new Michellin Pilot Sport 3 (not N specs). I do have a mismatch between front and rear tires - the rears are 2yr old Aspec Db. Had not changed them yet as thread >95% and there was no stock for the tire size I needed.

No spacers - had bad experience with them on my 944.

I had checked my tire pressure and the rears were 2 psi off. Got that fixed and the car now feels more fluid and goes around corners pretty balanced in the dry. What a difference the tire pressure makes. But unfortunately vibration is still there. I still have to take it easy in the wet, but that's prob due to the aspect db tires - those things have no grip in the wet.

Looks like I got to find a Hunter Road Force machine locally, heard there one.

Or hopefully when I get the suspension swapped out they'll find a cracked top suspension mount or knocking strut !!!! ha ha...
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Old 11-06-2010, 10:37 PM   #5
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I just re-read Steve's post - and yes the vibration can be felt through the chassis too. But at the same time, I do have vibration distinctly directly from the steering.

2 separate problems ?? Hmmm, I'll need to do another interstate run and figure out whether I'm feeling the same vibrations through the chassis and steering.
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Old 11-07-2010, 07:04 AM   #6
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i have a volvo and the front passenger rotor had to be machined down because - i don't know something - but before that there was a really bad vibration, afterwards it disappeared.

also, you have to get roadforce balancing. i had the tires rebalanced and the shop didn't use the roadforce balance. i made it about 3 miles away before i turned around and made them do it right. night and day difference.

the boxster is so keen to what the road is doing, the tires, brakes, etc. that anything off could make a difference...
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Old 11-07-2010, 04:56 PM   #7
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Quote:
Originally Posted by tonycarreon
i have a volvo and the front passenger rotor had to be machined down because - i don't know something - but before that there was a really bad vibration, afterwards it disappeared.

also, you have to get roadforce balancing. i had the tires rebalanced and the shop didn't use the roadforce balance. i made it about 3 miles away before i turned around and made them do it right. night and day difference.

the boxster is so keen to what the road is doing, the tires, brakes, etc. that anything off could make a difference...

Tony, before u machined down your volvo's brake rotor, did you get vibration when u braked or while travelling at speeds ?

I did have a front caliper that was stuck, had to get the both front calipers rebuilt, so that rotor was noticable uneven, although since the rebuild, the rotor is physically more even now. But no vibrations when braking even before the rebuild, just that the car wouldn't slide down the slight slope down my driveway.

Both front rotors are at about 22 mm so are due for replacements, the pads are almost brand new though... ha ha, prev owner just changed the pads and did not replace the rotors. The rotors are VERY pricey here from the AD here.

The "old" pads are original porsche items, can I re-use them ? Any way to "flatten" them ? There's still at least 90% left.

Although for this time, I'm going to use my new Textar pads with the new zimmerman rotors, since I'm trying to solve this vibration issue !

Last edited by shlim8; 11-07-2010 at 04:58 PM.
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Old 11-07-2010, 07:10 PM   #8
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I have the exact same issues. Noone can find the culprit.
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Old 11-08-2010, 07:02 PM   #9
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I have the exact same issues. Noone can find the culprit.
Yes, I know, I've been following your thread with much interest. I should be doing the rotors and M030 next friday, when I get back home (me and the car currently outstation in the neighbouring country). The M030s have arrived at home, but now I'm still waiting for the strut mounts - thought I'll change those too, since labour is not cheap and they are 9 year old mounts, even if it's low mileage. And the new ones are updated 997 (front) and 987 (rear) pieces.

I also intend to do a Hunter Road force balancing, can't find one here, but I managed to locate one back home.

Will keep you posted whether those changes help/solve the problem.

BTW, do you know how they diagnosed the tie rod problem ? Frankly, my suspension components seem solid but I guess the forces when travelling at high speeds should be greater than us shaking the wheel or components for free play.
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Old 11-09-2010, 10:53 AM   #10
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The tie rod was shot and they could easily it was bad.

You must get a Hunter Road Force balance. It is the only way to go.

I will be getting on check this week. My problem is that the speed limit around this shop is only 55 for about 15 miles. The car rides near perfect at 55.
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Old 11-09-2010, 11:43 PM   #11
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I finally found a hunter roadforce balancing machine at the city I'm currently in and it turns out to be just one or two miles from my office !!

However, the balancing guy tells me that because I'm not using N spec tyres, there will always be vibration.... he was most reluctant to do the balancing for me and he claims he has another boxster customer who did it and complained all the way to Michellin (he was on michellins). To cut the story short, they road force balanced 4 times but still vibration... finally on a dare by the Michellin reps, he changed to N specs and viola, no vibrations...

Is there any truth in this ?? Porsche can only use N specs or there will be vibrations ?

Anyone out there with non N specs tires and no vibrations from the steering ?

Anyway just did the road force balancing, seems to reduce the vibration even more at low speeds but really haven't fully tested it out yet.
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Old 11-10-2010, 09:49 AM   #12
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Quote:
Originally Posted by shlim8
I finally found a hunter roadforce balancing machine at the city I'm currently in and it turns out to be just one or two miles from my office !!

However, the balancing guy tells me that because I'm not using N spec tyres, there will always be vibration.... he was most reluctant to do the balancing for me and he claims he has another boxster customer who did it and complained all the way to Michellin (he was on michellins). To cut the story short, they road force balanced 4 times but still vibration... finally on a dare by the Michellin reps, he changed to N specs and viola, no vibrations...

Is there any truth in this ?? Porsche can only use N specs or there will be vibrations ?

Anyone out there with non N specs tires and no vibrations from the steering ?

Anyway just did the road force balancing, seems to reduce the vibration even more at low speeds but really haven't fully tested it out yet.
N spec tires are not required to have a smooth ride. I normally by Michelin PS2's for all my cars but don't pay the extra for the N spec.
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Old 11-20-2010, 04:42 AM   #13
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Finally had the shocks and springs out yesterday to install the M030 kit.

Practically every component on the front end wasn't in good shape. The shaft of the shocks shakes badly, the control arm main bearing moves laterally at the joint and the control arm link ball joint was alittle loose.

And without taking out the shocks and springs, it was not possible to detect any slop in the front suspension.... I've even had a mechanic swear that my car was "perfectly" setup.

Anyway, had the M030 installed and had the failing links and control arm re-installed (have to order for parts first), wasn't expecting much since not everything is in order.

BUT, wow, what a difference there is.... suddenly the car tracks around corners like on rails (whereas before it felt like it wanted to fly into the nearest greenery).

As expected the vibration is also greatly reduced and steering feel greatly improved, but not sure about the high speed vibration yet - will test tomorrow.
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Old 11-20-2010, 05:43 AM   #14
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did I read that you had different tires in the rear than in the front? If so you will find high speed cornering not so much fun because you will be getting different grip levels from the different tires, I did that once and it was horrible, be careful.
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Old 11-22-2010, 06:27 AM   #15
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Harryrcb, yup, I've got low grip tires at the rear at the moment. It does make interesting driving, since the front says good grip and the rear just lets go, esp in the wet.... Going to get that fixed soon... only problem is that my fronts are PS3 and the closest for the rear are PS2N... (no size for PS3) hmm, but at least the difference shouldn't be as bad as now.

Anyway, it looks like the vibration was mainly from the shocks.... hurrah ! Only very slight vibration at high high speeds now... I presume that's from the control arms, which I know has too much lateral movement now.
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