Does More Tyre Width = Less Power?

[jake33]

had my 33 for roughly 2 weeks now. when i started off with it i was running stock rim and tyre specifiaction. now have upgraded 19's with perrrelli p zero's, which ive been told arent a bad tyre. anyway there 9.5's on the rear. now my delimea is obviously the title of the topic. am i feeling less power due to there being bigger tyre and rim diameter? or is it me just getting use to the car.? i mean this is not a big decrease or anything. it just seemed that my car went a bit harder with stock tyres and rims (still same performance mods). sorry i know the questions is kinda up in the air, just wondering if its my head or a fact /possibility. i mean i definetly know the tyres are quiet harder to spin than stock. but is there a power loss?

thanks

Jake

[GTshortie]

Go weigh your Stock 16" rims and compared to your new 19" rims, your new rims are heavy/wider rubber hence better traction and grip and more friction on the ground so your car will run slower then it use(thats taking into account you don't have 300rwkw that has no traction with the 16" and you have traction with the nice wide 19" rubber)

From Experience, my car same power nothing else changed other then Rims

Previous 17" Sparco 255 wide dunlop tyres ran Consistent 14.2 and best 14.0 qtr mile

Stockies 16" 205 wide Toyo t1r's tyres ran consistent 13.6 and best of 13.5 qtr mile.

So as you can see there is quite a difference in my qtr mile time just by going back to my lighter stock rims.

[MANWHORE]

yeah, seriously, it's the weight of the wheels.

the gtst wheels with tyres weight approximately 18-20kg give or take depending on what tyre.

I wouldn't be suprised if your 19 " wheels weighed 30-40kg.

Keep in mind that wheel weight is worse than static weight. It is rotational mass.

so that extra 40-80 kg overall could be the equivalent of having about 120-240 kg extra weight in your car

[khunjeng]

what rims u got? weight?

thats why we pay for forged rims..

china rims...heavy as.

[jake33]

what rims u got? weight?

XIX exotic wheels (u.s company)

model: X-O5, 19x8.5 19x9.5

couldnt find the weight of the wheels.

what MANWHORE says makes a lot of sense.

Edited February 21, 2007 by jake33

[GTR-Dad]

An increase in rolling diameter gives you a taller overall gearing. This, in combination with heavier rims of larger diameter will result in you feeling less torque. (Seat of the pants dyno is working!)

Interesting thing on rotating mass...

Imagine two wheels that weigh exactly the same, but one is a 19" and the other is a 16" (very light 19" wheel, right?) fitted with tires that result in the same rolling diameter. The mass moment of inertia (I=mr²) of the 19" wheel will be 40% greater than the 16".

If the wheels are light enough, a 40% increase in 'effective mass' may be offset by benefits of stiffer sidewall or hawt looks , but directionaly you're making your car feel heavier.

I've read that the performance sweet spot for wheel diameter is around 17 or 18 inches. I suppose this would depend on your car, but this is one case of 'bigger is not always better.'

Cheers,

Dan

[psi]

Rule of thumb..

For every 1 kg u shave off your rim/tyre combo, it is equivilant to shaving 2 - 3 kg off your body!

add to that the rolling diameter of the new rims.. u do the maths..