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Steering Wheel Unstable at Higher Speeds


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Porsches are supposed to feel stable at even 80 mph right? However, my steering wheel gets quite jumpy in the 80 mph range though not always at the same velocity. Could it just be the wind or might having the hardtop on play a role aerodynamically? I definitely feel my 98 Boxster has some highway stability issues. Tire pressures are right (33 front/ 36 rear) and NTB has recommended balancing the tires for 10 dollars a tire. So, do you guys think balancing will solve the problem here? Or could alignment play a role? Traveling between cities at 90-100 the car will sometimes seem like it's vibrating... though not always that's why I sometimes thought it was just the wind. But this doesn't even happen so severly in the minivan. And, where do you take your car to get this fixed? Thanks for any help.

James

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Sounds like it could definitely be a balance issue. Balance issues tend to exhibit themselves as speed dependent and have harmonics. On a smooth road do you feel any vibration around 40-45MPH? One other thing - does the shop have a Hunter 9700 wheel balancing system? Sometimes a tire can be perfectly balanced but due to a property called "road force" it may not feel like it's balanced. The Hunter system can detect this and compensate for it.

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It's unlikely to be alignment. Most likely culprit is balance. If this has just started happening you probably lost a wheel weight. If it has been like this since you acquired the car, then the wheels were never balanced properly in the first place. If you can, follow Tom's advice and find somewhere with a Hunter 9700 - click here for a location finder: http://www.gsp9700.com/pub/search/FindGSP9700.cfm (this page was having problems when I tried to go there - hopefully the IT folks at Hunter will have it fixed soon)

This cool machine not only balances the tire, but checks for out of round and other potential issues that can cause vibrations.

Good Luck,

Graeme

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Porsches are supposed to feel stable at even 80 mph right?

A Boxster should be stable at 150mph+. Have your car fully checked by a dealer who knows what he does and operates a Hunter wheel balancer.

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Sounds like it could definitely be a balance issue. Balance issues tend to exhibit themselves as speed dependent and have harmonics. On a smooth road do you feel any vibration around 40-45MPH? One other thing - does the shop have a Hunter 9700 wheel balancing system? Sometimes a tire can be perfectly balanced but due to a property called "road force" it may not feel like it's balanced. The Hunter system can detect this and compensate for it.

Tom,

Thanks for your reply. At 40-45 MPH, I feel some vibration, but nothing that raises red flags. So, I believe at the lower speed the steering feel to be pretty normal. On the freeway, the car just doesn't feel "planted." Thank you for recommending the Hunter 9700 everyone. I'll look for a shop that has it and call around for pricing.

James

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Hi,

I got exactly the same issue as you describe. The culprit was one weight on my rear wheel fell off. It is something like 7 grams and at 80 mph I could definitely feel the difference. My problem was that I just had bought the car and the owner put 4 new tires on it. So I was not sure how the car was supposed to behave at that speed but I was convinced something was wrong.

They rebalanced the tires and found out that one wheel weight had came off and they replaced it. It costed me a day but the car felt perfect, rock solid the way it is supposed to be. I felt obliged to test it at 100 mph just to make sure it was fine. :lol:

Good Luck

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Tom,

Thanks for your reply.  At 40-45 MPH, I feel some vibration, but nothing that raises red flags.  So, I believe at the lower speed the steering feel to be pretty normal.  On the freeway, the car just doesn't feel "planted."  Thank you for recommending the Hunter 9700 everyone.  I'll look for a shop that has it and call around for pricing. 

James

i respectfully disagree with those who think it's a balance issue. you say the car doesn't feel planted, that is for me an alignment issue. wheel tend to spread apart at speed resulting in "toe out" which will definitely make the car wander. i suggest you have an alignment and find out what the toe was at.

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Porsches are supposed to feel stable at even 80 mph right?  However, my steering wheel gets quite jumpy in the 80 mph range though not always at the same velocity.  Could it just be the wind or might having the hardtop on play a role aerodynamically?  I definitely feel my 98 Boxster has some highway stability issues.  Tire pressures are right (33 front/ 36 rear) and NTB has recommended balancing the tires for 10 dollars a tire.  So, do you guys think balancing will solve the problem here?  Or could alignment play a role?  Traveling between cities at 90-100 the car will sometimes seem like it's vibrating... though not always that's why I sometimes thought it was just the wind.  But this doesn't even happen so severly in the minivan.  And, where do you take your car to get this fixed?  Thanks for any help.

James

James, not sure what you mean by jumpy. If you mean wanders on the road; i.e., seems to want to change direction, I'd say it's alignment and tires. I had similar problems; my car wandered on the road. I personally think it was from my tires. I replaced them with Pilot Sport PS2's, did an alignment, and did a load balance; all done by my dealer. No issues now. In fact the car feels very solid on the road, no wandering, no vibration, and even get's smoother at higher speeds...I tested it at 120 briefly the other day...what a rush. It took me back to the days I lived in Germany and could really drive my 911 like it was meant to be driven.

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Thanks to everyone who tried to help my car's vibration problem.

I took the Boxster to Discount Tire yesterday, which does have a Hunter GSP9700 balancing machine and one of their technicians looked over my car for nearly an hour. Now, I may have omitted a very important detail from this board. The 98 Boxster's tires are from the very beginning- they're original. Despite the mileage of the car only being 5K, the Discount Tire guy strongly recommended new tires. Apparently, their policy is to recommend a new set of tires every 5 years, and my car is pushing past 7 years. Based on the wear of the tires, he didn't think I needed an alignment and also didn't recommend spending the 60+ dollars for balancing because he said my vibration at high speeds problem is from the tires themselves. Furthermore, the technician said that vibrating sometimes and sometimes not at 80 mph is a very bad sign that the tires are near end of life. I guess it's time for me to start reading up here on Renntech to see what set of tires to get. Do you guys think the 5 year tire life estimate is accurate? Thanks for everyone's help.

James

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Thanks to everyone who tried to help my car's vibration problem. 

The 98 Boxster's tires are from the very beginning- they're original.  Despite the mileage of the car only being 5K, the Discount Tire guy strongly recommended new tires.  Apparently, their policy is to recommend a new set of tires every 5 years, and my car is pushing past 7 years.  ...  Furthermore, the technician said that vibrating sometimes and sometimes not at 80 mph is a very bad sign that the tires are near end of life.  I guess it's time for me to start reading up here on Renntech to see what set of tires to get.  Do you guys think the 5 year tire life estimate is accurate?  Thanks for everyone's help. 

James

One thought - email the manufacturer about the expected life of the tire.

If the Boxster was parked outdoors in the texas sun or the tires show fading or cracking in the sidewalls I wouldn't trust them.

While I have done 150 MPH+ a few times, I personally would be real hesitant about taking 5 year old tires over 80MPH if they haven't been garaged and treated with a protectant (like black again).

P.S. If you can afford it, I would splurge - New tires, Hunter 9700 balancing (it really is better!), 4 wheel alignment (man what a feeling). If so inclined you could also go for wider wheels and an aggressive (track ready) alignment. IMO - 225 or 235 in front really let a Boxster shine.

Edited by adsach
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Thanks to everyone who tried to help my car's vibration problem. 

"…The 98 Boxster's tires are from the very beginning- they're original.  Despite the mileage of the car only being 5K,…"

if those are the original tires and the car only has 5k on it then i would be even more convinced that the "not feeling planted" is an alignment issue. the reason being is that the factory alignment can go out of spec very quickly when all the suspension parts bed. if the car is 7 years old and has never had an alignment then i would almost bet money on it.

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Thanks to everyone who have provided suggestions!

Well, I ordered the tires and they'll be installed this Friday afternoon from Discount Tire. I got the Michelin Pilot Sport N rated tires with the Discount Tire's standard warranty and gsp 9700 balancing with road force for around 870 dollars drive out. Their price was extremely competitive with Costco (no road force balancing). The next expense will be alignment if the problem does not improve. I figure the car's age does logically warrant new tires. Can anyone recommend a chain that does alignment well or any specific shop in Houston? Thanks again.

James

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djantlive,

Well, the Discount Tire I went to doesn't do alignment, but the technician that examined my car was absolutely confident my problem lay in the tires. I asked about alignment and when he examined each tire, he felt that alignment was fine. Though if my car's problem persists, alignment will be the next course of action. Thank you for your shop recommendation.

James

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IMO - Your car should have at least one really good alignment in it's life. Factory alignment is usually not all that good after the springs settle.

Your best bet is to ask Porsche 'track junkies' until you keep hearing the same name mentioned, usually an independant Porsche Shop. Sometimes a speed shop will know what to do, but the Boxster alignment (especially front) takes a bit of patience and some Porsche knowledge to get the camber right.

I would start with the folks who run your local Porsche Club Driver's Ed events http://www.lsrpca.com/DE/DE.html

If you email the DE chairman and flag chief they will probably have a good suggestion - of course they may also try to get you out driving on Texas World Speedway :)

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I really think you should not rule out an alignment. I have had several cars that the tire wear did not show any mis alignment, but when put on the machine was severly off. An alignment severly affects high speed handling. Another thing to check that no one mentioned is your wing, does it raise up at the proper speeds or is your fuse blown causing the wing not to go up therefore lacking downforce. While your at it check your aerodynamics, maybe an airdam is loose or damaged? just a thought good luck. By the way I drive my car at speeds in excess of 120 to 130 mph and it is very stable (even with the top down!) compared to my 2004 MBZe500 it feels glued down!

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I really think you should not rule out an alignment. I have had several cars that the tire wear did not show any mis alignment, but when put on the machine was severly off. An alignment severly affects high speed handling. Another thing to check that no one mentioned is your wing, does it raise up at the proper speeds or is your fuse blown causing the wing not to go up therefore lacking downforce. While your at it check your aerodynamics, maybe an airdam is loose or damaged? just a thought good luck. By the way I drive my car at speeds in excess of 120 to 130 mph and it is very stable (even with the top down!) compared to my 2004 MBZe500 it feels glued down!

my car now has 30k miles on it, its a 99 btw, I think these are the original tires on there too. my active spoiler is working, i can see it in the reflection of other cars, (guilty of looking at oneself), but feel like this driving in excess speeds :drive: :cursing:

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my car now has 30k miles on it, its a 99 btw, I think these are the original tires on there too. my active spoiler is working, i can see it in the reflection of other cars, (guilty of looking at oneself),  but feel like this driving in excess speeds  :drive:    :cursing:

Your car should not feel like :drive: in any kind of scary way at high speed.

Top down/up I could drive with 2 fingers at any speed. I use both hands but that is mostly to look "racy" ;)

Like everyone else, the way to fix this is to go down the list of possibilties:

Check tires - tread, balance, pressure, wear - Always use premium tires and the Hunter 9700 for balancing, you CAN tell the difference

Check Alignment - If you have never had a specialty shop do a premium alignment, your car is not aligned right. Unless you get a LOT of bumps or a crash, a good alignment will often last 2 years or more. I like to max out negative front camber and do front -0.5 (more neg camber) in the rear, factory toe.

Torque all the suspension components and check for wear.

Check for loose/missing/broken aerodynamic components.

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Been there and done that :-). They were the aligment and wheel balance issues.

All you need to do is balancing all the wheels and check the aligment. It should solve the problem.

As others mentioned, @ +120 mph speed the steering wheel should be stabled. :D

Nat

:cheers:

Edited by natzee
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