You have experienced the exact same problem that has been nagging me for the last 2 years.
Had wheels checked, straightened, re-finished, rod force balanced multiple times. New tires, and btw same as yours: Firestone Firehawk Indy 500s. Went back multiple times to the wheel/tire shop to complain. In the end, they told me the tires (new) required a borderline amount of balancing weights, and that I should put in a claim to Firestone... which I never did since I plan on burning them up next weekend at the track  . Never again will I buy those tires.
Another issue to consider is "flat spotting". I've noticed this more on these Indy 500 tires, but I think all low profile tires flat spot to an extent. I noticed that in winter (cold) it does it more. Summer time (warm) less. I really annoys me because I spent so much time and money on my cars to get them to run well, and expect a nice smooth ride at high speed, especially from a Porsche.
The suspension bushings are known to be a potential cause of vibrations, but you would likely notice it more during braking only, especially in the front end bushings. I had that problem go away in my BMW 328. Worn bushings...
__________________
2002 Boxster S - NHP 200 Cell Headers,test pipes,Borla CatBack,Competition Plenum,74 mm TB, EVOMS Tune,Tarett UDP,Eibach Swaybars,BIlstein PSS9s,TuneRS rear toe links,wheel studs,15 mm wheel spacers on all 4,EBC yellow stuff pads,Sebro rotors, EBS oil baffles,160 deg Thermostat,2 quart Accusump,full filtration remote oil filter,rad fan switch,custom gauge/switch plate, Race Capture data logging, 90K miles
|
Threaded Mode
