Wheel size differences

Just wondering how much difference in rolling circumference peoples wheels on their car are compared to factory standard?

e.g standard size are 195/55-14
mine are 205/45-16 which means an increase of 3.5%

http://www.etyres.co.uk/tyre-size-calculator

i dunno but when i had my sunny gti, it came with 17's and and switching to 15's made a hell of a difference in both handling and acceleration, i have 16's on my r just now as my brakes are too big for 15's  even when i had my honda i had proxes 195 50 r15 and bought wheels whicj were 195 45 15 and noticed a difference in acceleration. i dunno if anyone else has noticed a difference but i did :/

Just working out that I would technically need a 35 profile tyre if I get 17's to keep close to standard but think 35 is too little sidewall for cushion against the littlest of potholes.
Has anyone fitted a 325mm 4pot hispec kit under 16's?

Think 325mm discs could fit under some good brake clearance wheels such as comps but will come down to what offset you willing to go to & maybe even removing some material from callipers.

I do have a 280mm 4 pot kit but prefer the bigger kit, ill have to have a think about it then, cheers.

i tried 17" with 40 hight tyres, was running 16" with eagle 45 hight tyres, and even put some snow tyres on 15" in 195-55-15. better is the 16" and the 15". 16" looks better too, but 17" fits well...but feels uncomfortable

one thing ive noticed on track with the R is that although they accelerate faster with 15's you get a lot more understeer, now why that is I do not know if im honest, but I much prefer 17s on track as they just seem to corner much better, what you lose in acceleration really is not worth mentioning and if anything overall the 17s are quicker over a lap as the top end speed is higher plus you can corner much faster than with 15s

bet that's shocked a few of you lol
if there were huge gains to be had in handling and speed by running small rims do you not think btcc cars and infact all race cars would run with small wheels???

as for running 35 tyres.......my gtr runs 315.35.20's and certainly no probs with potholes

17 inch wheels surly it comes down to the amount of rubber (more) in contact with the surface if you loose acceleration (i know its the rolling radius) but make it up a few ways would be run more power strip weight go for a super light 17

not really johnny as you may have 195 profile 15s and 195 profile 17s yet I find the 17s will have less understeer than the 15s
why that is I just cant work out but the only conclusion I can come to is that its due to the track arm / steering angle with larger wheels

think of say a gtir fitted with 10'' minilites lol, the slightest turn on lock would cause understeer yet with a big wheel (say a tractor) you would physically need to turn the steering more to get round same bend

have a think about it, what your wheels are doing with certain amounts of steering input from the steering wheel with different size wheels.
im not very clever with physics but trust me, bigger wheels understeer less

Don't follow that theory fully :-S
I would assume main benefit of 17's on track cornering is purely due to less flex in the tyre sidewall which helps keep the tread contact higher thus less understeer/front wheel skid.
For bad condition road use I find 16s better compromise

That's interesting Bob, what size tyre are people running on their 17's; 205, 215 or 225?

Maybe your right but i was thinking of  average  17" wheels normally been wider than average 15s and as above the percentage of the tyre etc on the road  is more and rolling radius is different  surly it makes a difference to alot of the way the tyre behaves

i would say 205 or 215 depending on profile. i could be wrong but sure if you go to 45 profile 215 and 225 would not fit standard arches and if lowered gets close to catching on lock and close to bumper but i could be wrong mind

well most 17s are either 195 or 205 profile

but then a lot of 15s are 195 also so kind of rules that theory out

I can see in my head why it could be but I havent got the foggiest how to explain it