So far, the only thing I see in a 305-40-18 is a drag radial, in either a tread wear rating of zero, or 100. I wouldn't mind a 305-40-18 rear, but I don't want a drag radial. I checked several sites, and unless I missed something, I can't find what I want. Plan B is to go to a 305-35-19, which I can get in a tread wear rating of 300 from a few tire makers..... which also involves buying new 19" rear rims.
305-40-18's in a 200-300 tread wear rating ?
- Thread starter Pentalab
- Start date
fourdegrees11
forum member
Yeah that size doesnt look like it's used, which is weird. 295/40r18 has a few good options
mrfatride
Junior Member
that is a pretty tall tire. any particular reason you are looking for close to a 28" tall tire?
A 305-40-18 is 27.6" tall. Oem 235-50-18's are 27.25" 285-40-18 is 26.97"
275-40-18 is 26.66" 305-35-19 is 27.40". 305-35-18 is 26.4"
So a 305-40-18 is only .35" taller than oem. Based on past experience, and my current 1 to 1.25" rear drop, 3.31 rear gear, then factoring in the lower gear ratios on my auto in 2nd + 3rd gear vs the 5 speed manual.... I really don't want to go less than 27".... and not much taller than 27.5".
Another option might be a 295-40-18 = 27.28" tall. I'll keep looking.
Ok, a 305-40-18 is a 300 tread wear rating doesn't exist. I'm going to proceed with plan B, new rear 19 x 10 rims and a Nitto NT-555 G2 in a 305-35-19. Then shift the existing rear 285-40-18's (on their 18x10 rims) to the front.
The tire is the most important part of any race car. Running taller than stock tires is.... unusual, often detrimental. We usually advise racers to run enough tire height to not alter ride height / ground clearance on its own dramatically (within 1-2" of stock height, usually shorter) while keeping "enough" sidewall, and maximizing width above all else. The reality of the performance tire world is that there aren't a lot of options in the right tires above 27" in total height.
The stock S197 tires in the 27.0-27.25" height range limit you to very few "good" options outside of the drag racing world. Using tire height to "fix" gearing problems is a "low reward" end game. Changing final drive ratio is painfully easy and inexpensive in the S197 8.8" rear end, especially compared to some other markets. That image above shows a 255/40/19 OEM 2011 GT tire next to a 285/30/18... which is 24.8" tall.
MASSIVE difference in height, and the 285/30/18 is popular on a lot of other cars, but looks ridokulous on the S197, even after being lower 3" in ride height on proper coilovers.
For BMWs like this E92 M3 above you have as few as 3 gearing options, and they are all $1200+ for the ring and pinion alone. For the EVO X next to it the choices are even worse. But for the Ford 8.8" 28-31 spline axles that come in the S197 chassis you can get proper Ford Racing gearing options in dozens of ratios for under $200 in parts. Its about 2.5 hours of work by a properly qualified shop, so its relatively CHEAP compared to many other cars.
Taller tires add more mass - which has to be sped up and slowed down, turned and damped, and the sidewall acts as a spring, too. But I'm not one for ultra-low profile sidewalls, either. There has to be balance in sidewall height, total tire height, wheel diameter (just enough to clear the brake rotor/caliper), and tire availability.
That last bit above is the key element that drives many builds: what sizes are available that fit the class/car/weight/power. We often look at a chassis, figure out what class we want to build for, then find the ideal tire for the car/chassis... and build the entire car around this tire. We have done that many, many times. Why?
Because the tire is the most important part of any race car.
The stock S197 tires in the 27.0-27.25" height range limit you to very few "good" options outside of the drag racing world. Using tire height to "fix" gearing problems is a "low reward" end game. Changing final drive ratio is painfully easy and inexpensive in the S197 8.8" rear end, especially compared to some other markets. That image above shows a 255/40/19 OEM 2011 GT tire next to a 285/30/18... which is 24.8" tall.
MASSIVE difference in height, and the 285/30/18 is popular on a lot of other cars, but looks ridokulous on the S197, even after being lower 3" in ride height on proper coilovers.
For BMWs like this E92 M3 above you have as few as 3 gearing options, and they are all $1200+ for the ring and pinion alone. For the EVO X next to it the choices are even worse. But for the Ford 8.8" 28-31 spline axles that come in the S197 chassis you can get proper Ford Racing gearing options in dozens of ratios for under $200 in parts. Its about 2.5 hours of work by a properly qualified shop, so its relatively CHEAP compared to many other cars.
Taller tires add more mass - which has to be sped up and slowed down, turned and damped, and the sidewall acts as a spring, too. But I'm not one for ultra-low profile sidewalls, either. There has to be balance in sidewall height, total tire height, wheel diameter (just enough to clear the brake rotor/caliper), and tire availability.
That last bit above is the key element that drives many builds: what sizes are available that fit the class/car/weight/power. We often look at a chassis, figure out what class we want to build for, then find the ideal tire for the car/chassis... and build the entire car around this tire. We have done that many, many times. Why?
Because the tire is the most important part of any race car.
fourdegrees11
forum member
Yeah that 285/30 looks like a clown car. There are a decent amount of options in 26" tall tires, which seems to be what a lot of auto-x guys run on these cars. To me it's not worth it to drop that far down from 27" if you drive it on the street, it would have to be a dedicated track setup for me
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