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Wheels will not have an effect on speed unless you change the rolling circumverence of the wheels and tires. This is the same as changing the gear ratio. To increase speed you will need to go to larger tires and wheels. Bear in mind that the car will easily hit the electronic speed limiter as it is. You will have to remove that at a cost of $1500 or more to actually see any increase in speed except that caused by the speedometer error you will get from the change in circumference.

There are two drawbacks to changing the circumference to increase speed. First, the speedometer will be inaccurate. It will read too slow and you will be going faster than you think. Second, any tire and wheel combo large enough to change top speed appreciably will be much heavier than stock. This will have a very adverse effect upon acceleration.

Going to smaller tires and wheels will improve acceleration, but reduce top speed. The speedometer will read to high.

The best option is to buy light weight wheels of approximately the same rolling circumference as stock. The lighter weight will be easier for the engine to turn resulting in some improvement in acceleration. Top speed will not be changed. One of the less expensive light weight wheels is the SSR Integral. BBS also makes some light wheels but they are much more expensive.
 

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speedometer error

so changing the circumference of the wheels renders the speedometer inaccurate....does the factory account for this when adding the C7 package?
 

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Re: speedometer error

maulik said:
so changing the circumference of the wheels renders the speedometer inaccurate....does the factory account for this when adding the C7 package?
The 205/55 16's and the 225/45 17's have almost the same circumference.

The 205/55 16 Michelin Pilot Sport A/S has a circumference of 25.2".

The 205/55 16 Michelin Pilot Sport has a circumference of 24.9"

The 225/45 17 Michelin Pilot Sport has a circumference of 24.8"
 
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