BlueS2000Boy

i am getting ready to switch out my tires and i live in fl. so there is a lot of rain. i want to put the bridgestone potenza S03's i had them on a previous car and i loved them. i have the S02's on the car before that. so when i got my S i new what to expect from the tire. my question is if i switch over too the S03's i want to put the 255-45's on the rear and the 225-50 on the front. i think this will give me the added contact patch which will help give the added grip due to the fact the S03's just don't grip as well as the S02's. i know its because S02's have more contact. but i have been told by people that i should on put 245-50's on the rear and 205-55 on the front. i have read many posts about how people put the larger sizes on with no problems. but if i do go with the larger sizes what if any effects nagative and positive can i expect. thank you all for the help..

Unicron

245/45/16 and 205/55/16 is the rought I would take with the S03's.

It's good to increase the tread width...but I don't like increasing the overall diameter of the tire. You can increase the diameter if you like...but I would get some coil overs so I can adjust for the tilt the larger diameter tires will put on your car.

Jim@tirerack

Unicorn is correct for the tire sizes. They keep you in the same diameter as original and basically the same stagger in tire width as the OE tires.

Jim

Triple-H

The S-02 grips better than the S-03 because of the UTQG Rating. The Tire Rack web site can explain this rating system if you are interested in knowing. The S-02 is rated at 140 A A, the S-03 is rated at 220 A A. In general terms the lower the number the softer/stickier the rubber.

The added width/contact patch of the S-03 will probably not make up the difference because the S-02 is a much softer rubber as evidenced by the numbers. The disadvantage of the bigger width is also the increase in diameter. As the diameter increases from the stock size the car will feel less capable of putting down the power.

I would go with 205/55-16 and 245/45-16.

Luis

...and I thought the number was a measure of longevity. Usually a softer tyre will have a shorter life, but the tonic is on usually. The S02 Pole Position have a treadwear of 160 and by all accounts they grip less than the S03PP.

Say again? Increasing the diameter, increases the gearing, without no impact whatsoever in power. If anything it improves the capacity to "put power down". Think about it. Is it easier or harder to "put power down" in 1st or 6th?

The problem with increased diameter tyres is that they will increase the moment arm (from the axle to the road), reducing the linear force available to push the car forward.

Triple-H

[QUOTE]Originally posted by Luis
[B]...and I thought the number was a measure of longevity. Usually a softer tyre will have a shorter life, but the tonic is on usually.

schwett

while you are correct that gearing only affect torque, and not power (because speed is increasing as torque is decreasing), the car will be slower in a straight line with larger diameter tires. however you want to define it, triple-h's statement is basically correct from a butt-dyno point of view. the car will feel less powerful.

the parasitic effect of larger tires and wheels is also not insignificant, which will actually decrease the "power" available to move the car, as you pointed out.

Triple-H

schwett, thanks for the support. In my next lifetime I promise to be an engineer, it will help my credibility in these situations if I have the proper terminology down.

I'm not sure how many people have played with them, but the G-Tech Pro is actually not that bad of a little track tool. I know it is not perfect, but it has the ability to quantify things much better than the but-dyno, which as we all know, is subject to a lot of interpretation.

http://www.gtechpro.com/

Luis

parasite? Well, I suppose you could argue the tyre was eating at the axle's table...

BlueS2000Boy

thank you all for your help.