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Discussion Starter · #1 ·
I have an 06 Cayman S that is lowered with aftermarket wheels and tires. When I drive over 90 MPH under full throttle, the car will shimmy left to right aggressively. I have owned other sports cars and never experienced such problems. If I gradually increase speed, the car is pretty stable up to 130 but under heavy acceleration after 90 the car will pull left to right aggressively and become very unstable. I am not sure if it is an alignment issue, wheel/tire issue, or even a drive train issue. Any thoughts?? Thanks!!
 

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Well, that certainly isn't characteristic of a well-sorted Porsche. I would first recommend getting the alignment checked, and make sure there isn't something in the suspension that is loose.

Let us know if you find out what it is . . .
 

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Could be an alignment problem, suspension problem, the wheels aren't balanced, etc. Whatever it is, it's not normal and you should get it checked out.
 

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This may sound silly, but in the S2000 (my other sports car) having different tire pressures in the rear (even 1 pound) will make the car act similar to what you are describing. You might check that first and make sure they are the same pressure.

Heck, it's a free solution if it works.
 

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This may sound silly, but in the S2000 (my other sports car) having different tire pressures in the rear (even 1 pound) will make the car act similar to what you are describing. You might check that first and make sure they are the same pressure.
You don't say how your car was changed from oem so there may be a number of variables you've introduced, but I too vote for an alignment issue.

Among cars I've driven on the track, the Cayman is the least sensitive to small tire pressure variations. A 1 psi variation could be felt in the handling of my 993. With the CS I sometimes wonder why I bother to check pressures at all ...
 

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You say the car was lowered with tires and wheels? How did you do that? No suspension mods? If in fact you truly lowered the car by a wheel and tire change you have changed your suspension geometry with both camber and toe. And that's what is causing your poor handling at speed. I bet if you put the factory wheels and tires back on you would find it tracks straight and true at speed. Any time you lower a car, you have to adjust the front and rear alignment settings or they handle poorly.
 

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Could be a number of things.

- Tire pressures
- Wheel lug nuts properly tightened?
- Are wheels the proper hub size?
- Are wheels balanced?
- Alignment
- Shocks/struts old or improperly matched to springs
- Wheel bearings
 

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...If in fact you truly lowered the car by a wheel and tire change you have changed your suspension geometry with both camber and toe...
No offense but..simply not true.
My guess is he lowered AND changed wheels and tires.
I agree with: check tire pressure and alignment - my guess is it's toe.
 

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Discussion Starter · #13 ·
Thanks for all the input. I plan on getting the alignment check this coming weekend and go from there. In addtion, to elaborate on the setup, it has TechArt Springs and Champion Motorsport wheels.
 

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unstable w/ heavy accel. & 90+mph
stable w/ norm. accel. & 90+
Hmmm...
what gear are you in ? 6th, 5th, 4th, 3rd:eek:
rpm's ? 4K, 5K, 6K, 7K:eek:
Does acceleration mean "flooring it" or high rpm ? or simply a high "rate" of acceleration ?

Could weight shift of the chassis during heavy accel. be affecting your lowered springs ? Could the combination of: high-speed aerodynamics, chassis shift, and magnified bumps/undulations in the road result in your suspension tolerences being exceeded, resulting in a side-to-side shimmy ? I would guess your suspension tolerances (travel) are minimal.

Disclaimer: The ramblings of a novice:crazy:;)
 

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You say the car was lowered with tires and wheels? How did you do that? No suspension mods? If in fact you truly lowered the car by a wheel and tire change you have changed your suspension geometry with both camber and toe. And that's what is causing your poor handling at speed. I bet if you put the factory wheels and tires back on you would find it tracks straight and true at speed. Any time you lower a car, you have to adjust the front and rear alignment settings or they handle poorly.

What he said
 
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