Hi, so i sent my 17s away for refurbishment and have 16inches on now. I dont know if its just me that didnt drive my car hard in a while perhaps, but the gearing with 16s feels so much longer, on high revs it takes longer to reach 7k rpm. In otherwords, acceleration slowed down. Does smaller wheels do this?

 

What tire size do you have on the 16" and what were they on the 17"? I suspect that any difference is going to be 2% or less--not something you would really notice.

The tire O.D. would have to be larger on the 16" to see the effect you describe. A smaller tire O.D. would give you a lower effective gearing, making accleration more brisk, and reach redline faster.

 

It is not the wheel size that matters -- It is the diameter of the tire - that can effect gearing.

Compare your two set ups here:

http://www.discounttiredirect.com/di...foTireMath.jsp

 

Well i had a 17 inch lightweight wheel on (215/40/17) now i have the standard 16inch on (s-lites) with the pirelli run-flats it comes with (thick profile). Maybe its because the 17s were lighter?

 

It is not the weight it is the diameter -- Do the math or use a tire diameter calculator. What tire size where you using on the 16inch wheels?

 

Yes i know, but i thought perhaps the slightly added weight made a difference?
The profile is 195/55/16

 

The weight is not going to effect acceleration measurably, unless it is extreme. Suspension handling is the biggest reason to go with light weight wheels as you reduce your un-sprung weight.

diameter comparison: 17"wheel setup 23.77 vs. 16"wheel setup 24.44
circumference: comparison 17wheel setup 74.68" vs. 16"wheel setup 76.8

The 17inch set up is smaller which in effect gives you lower gearing - theoretical better acceleration lower top speed.
The larger 16inch wheel raise gearing - hence your longer pulls

 

That is just under 3% difference. Would that be noticeable? I'm guessing there is a reverse placebo in effect.

 

What brand and tire model do you have in 215/40-17?
I want to get the exact "Overall Diameter" of the specific tire.
I know that your 195/55/16 Pirelli eufori@ is 24.44 Overall Diameter, is taller than my current GP 18 inch wheels with Goodyear F1 GS-D3s in 225/35-18 at 24.20 Overall diameter. If you were to replace with 205/45-16 Hankook RS-2s ($75 at Tire Rack) your overall diameter would be 23.20 or the Kumho XS ($94 at Tire Rack) at 215/45-16 would be at 23.6 overall diameter.
Check this out: "Car Wheel Sizes"

I believe this is correct.
My GP came with 18 inch wheels after the oem Dunlop RF 205/40-18 and 24.42 O.D. tires wore I got Goodyear F1 GS-D3s in 225/35-18 which were smaller in O.D. at 24.20. And then I got 17 inch wheels cause I wanted a smaller OD but thought I needed 17s to fit over JCW brakes and found some used track tires for cheap but they were 225/45-17 these big suckers did not even fit cause the O.D. was 25.1, they were bigger due to the "fatty" 45 series sidewall. For me either 225/40-17, 215/40-17 or even certain 215/45-17 would be better.