Just switched tires on the Z. Enthusiast 17"s are now wrapped in Goodyear F1 GS-D3s 225/45/17 F and 255/40/17 R. The rear tire/wheel diameter is now decreased from 26.25" down to 25.03" giving a smaller rolling diameter and road to wheel height enhancing slip angle for an acceleration advantage and slip angle advantage, respectively. The best part is with the new tire sizes and my S Tune 20mm drop, the tire to fender gap looks stock. Only on close examination does the car look dropped when one examines the door sill to ground clearance. I don't scrap my front end even with the Track Z front spoiler moulding piece. These tires rock! I am an ex-hardcore S03 fan, FWIW.

 

I use that size tire for autocross and it makes a huge difference in accleration.

 

Yup, on a roll the SLIP light comes on a lot more now when I mash it. Nice to be activating that diff and getting the most out of the car. It is really not that rough on the road with the S tune as initially expected. The sidewalls on the F1s do not appear to be made of stone like the SO3s.

 

Can you give a review of the tires as these are what I will be putting on my NISMO rims soon. Also, anyone care to purchase my Touring rims? Perfect condition....

 

I have been using S03s exclusively for the past two years on roadcars only, so my perspective is rather limited. Compared to the Bridgestones, these tires are just a notch better, IMHO. The actual weight of the tire and the more forgiving sidewall stand out the most. At street limit they appear to get less greasy than the S03s when they are heated up. They are a fair bit noisier, but that is the only downside that stands out. Treadwear is 280 vs. S03 220 as well.

 

so now your speedo / mileage is off... ??

 

By the road testing via coutesy Police roadside radar sites, it was already running to fast. I have an old habit of just looking at the tach rather than the speedo and just filling 'er up whenever the light comes on. The trade off is a bargain. FWIW, My front tire/wheel diameter is only 3.4% off of stock; so my speedo should only be offset 2.1 mph faster than stock at 60 mph anyway. I don't think the speed sensor for the speedo is hooked up to the rear wheel.

 

Thats why I went with a 275/35/18 instaed of everyone's 275/40/18. Lower final drive ratio.......

 

so then going 1 mile your really putting 1.15 miles on your car?

 

Cool odemeter perk for increased resale value.

 

other way around, more miles will be on the Odo than the car actually drove.

 

I know hwere u can get a real differnt lower final drive ratio for the 350Z?

 

Oh yeah. Maybe it is not a mod for on a tight lease; however, acceleration benefits with that 5% lower wheel/tire diameter makes the 1.15 miles recorded much more fulfilling than the 1 mile driven with the stock wheel/tire diameter from a hardcore performance enthusiast's viewpoint.

 

ya know...

id like to see some times with smaller diamaters...

because.. it could be a mental though that you are going FASTER and not just feeling it becuase your reaching the higher rpms faster...

know what i mean?

 

All else equal if you are reaching higher RPMs faster you are going faster. That is what gear ratio changes do. They don't increase HP they put you up where the HP is faster and keep you there better through shifts. Changing tire diameter can effectively accomplish the same goal as changing your final drive ratio gears. Shorter diameter tires can increase acceleration but hurt top speed and taller tires can hurt acceleration but help your top speed. The reason people use gears to accomplish this mod is because to gain noticable/useful changes to performance through tire size changes, the car would look ghetto or totally funked up.

 

is there is too much gap between the tire and wheel well or is that the shot angle? I had that prob with my impala it drove me nutz

 

so your telling me.. by making the rear wheels smaller and having the engine at 6000 RPM the car will be going faster?

it will be going SLOWER but the speed will show the same as the gauges said when it was a bigger tire...

the smaller the tire.. the faster / easier it may spin.. but it will travel a shorter distance per rotation then a larger diamater tire...

so if your reaching 60MPH faster with the smaller tire.. well your speed gauge is off and your really going less then that...

i can work out the math if you give me the exact diamiter of the stock tire vrs the new one...

 

oh wait.. i see he posted in the first thread the diamaters...

doing math now...

 

5,280 feet in a mile... 63360 inches in a mile...

A 26.25" diamater tire has a Circumference of 82.47"

A 25.03" diamater tire has a Circumference of 78.63"

(above number rounded to nearest 100th...)

The 26.25" tire needs to rotate 768.28 times to travel the distance of a mile.

The 25.03" tire needs to rotate 805.8 times to travel the distance of a mile.

Tthe 26.25" tire rotates 46096.8 times to cover the distance of 60 Miles.

The 25.03" tire rotates 48348 times to cover the distance of 60 Miles.

For every 1000 miles traveled with the 25.03" diamater tires you will be putting 1048.45 Miles on your car.

 

no i am not saying that at a set rpm your mph will be higher/lower. it will be BUT the idea behind gearing is not a certain MPH at a given RPM point but the RATE OF CHANGE in MPH throughout the RPM range. gearing allows the car to move faster up the power curve. look at a dyno chart. the faster you move through that line, the faster you are at the higher rpms levels and therefore the higher HP levels. it is a rate of change. you will find that mph works the same way. if two cars are both traveling 1 MPH and both cars are exactly equal in terms of acceleration and one car hits the gas just before the other car and is going 5 mph when the other is at 2 mph (keep in mind they are accelerating the exact same speed through the MPH's) the first car will continue to pull away as it is at a higher MPH the whole time (even though both cars can get from 1-20 MPH in equal time) because 10 MPH moves you down the road faster than 5 MPH. if the first car is not pulling away and the cars stay exactly the same distance then the second car is actually accelerating faster. get it?