R-comps for SM (275 vs. 285)
#1
R-comps for SM (275 vs. 285)
I am finally to a point where I am about to buy wider wheels and R-comps for my Street Mod Auto-X car. To get this out of the way I usually just run locally but do have grand visions of going to Lincoln for Nationals. These visions could be done as early as next year. The goal would be not to finish DFL.
That said, I am reconsidering what I had originally planned for wheels/tires. I had been planning on going to 18x10 RPF1 wheels to run some 285/30-18 Hoosier A6s. Recently I've been looking up specs on the new A7s to add to my original wheel/tire spreadsheet and noticed they run smaller than the A6s. The new measurements on the 285/30-18 A7 make me wonder if I should just stick to a 17" wheel/tire combo and save on the rotating mass. Specs as follow (per TireRack):
Hoosier A7
Size: 275/35-17
Section Width: 11.0"
Tread Width: 10.3"
Weight: 22 lbs
Diameter: 24.7"
Hoosier A6 (discontinued)
Size: 285/30-18
Section Width: 11.5"
Tread Width: 10.9"
Weight: 24 lbs
Diameter: 24.9"
Hoosier A7
Size: 285/30-18
Section Width: 11.5"
Tread Width: 10.4"
Weight: 24 lbs
Diameter: 24.9"
If I got 17x10 RPF1s w/ A7s instead of 18x10 RPF1s w/ A7s I could save 3.6 lbs per corner on rotational mass for only 0.1" of tread width. Anyone have any insights to help me decide?
That said, I am reconsidering what I had originally planned for wheels/tires. I had been planning on going to 18x10 RPF1 wheels to run some 285/30-18 Hoosier A6s. Recently I've been looking up specs on the new A7s to add to my original wheel/tire spreadsheet and noticed they run smaller than the A6s. The new measurements on the 285/30-18 A7 make me wonder if I should just stick to a 17" wheel/tire combo and save on the rotating mass. Specs as follow (per TireRack):
Hoosier A7
Size: 275/35-17
Section Width: 11.0"
Tread Width: 10.3"
Weight: 22 lbs
Diameter: 24.7"
Hoosier A6 (discontinued)
Size: 285/30-18
Section Width: 11.5"
Tread Width: 10.9"
Weight: 24 lbs
Diameter: 24.9"
Hoosier A7
Size: 285/30-18
Section Width: 11.5"
Tread Width: 10.4"
Weight: 24 lbs
Diameter: 24.9"
If I got 17x10 RPF1s w/ A7s instead of 18x10 RPF1s w/ A7s I could save 3.6 lbs per corner on rotational mass for only 0.1" of tread width. Anyone have any insights to help me decide?
#4
Evolved Member
Not sure how hard you want it, but if I was building another SM car, I would try to fit the biggest tire I could. Even 285s on a car that makes 400+ HP will be border lining it. That said, there is also that game of max allowed weight depending on how wide tires are, which also plays important part of making decision on this.
#9
Evolved Member
iTrader: (5)
2800lb is definitely doable in SM. The min weight with 275s and a 2.0 would be 2620, which I'd reason isn't possible within the class rules. The only reason I'd go down to a 275 is if I could hit minimum, and that's only if I were running 285s. Otherwise the wider tires (315 in my case) are the better bet.