tires

[OSUALUM78]

I am planning on going from stocker 17x8 245/45/17 to either an 18x9 or 18x9.5 wheel (18x9 is more likely though because I my wheel choices, Steeda Ultra Lite I's to be exact right now, but powercoated black much like FR500's).

What is the recommended size to keep all four tires same size for rotation purposes?

275/35/18 or 245/40/18, or a different size?

I am looking at BFG KDW 2's or BFG KD's by the way for my tire choices

BFG KDW 2's, 275/35/ YR18 which spec at: UTQG 300AAA; Max Load 1521 lbs; Max. Inflation Press. 51 psi; Tread Depth 10/32"; Tire Weight 28 lbs; Rim Width Range 9-11"; Meas. Rim Width 9.5"; Sect. Width 10.9"; Tread Width NA; Overall Diam. 25.6"; Revs Per Mile 814

BFG KDW 2's, 245/40/ YR18 which spec at: UTQG 300AAA; Max Load 1433 lbs; Max Inflation Press. 44 psi; Tread Depth 10/32"; Tire Weight 27 lbs; Rim Width Range 8-9.5"; Meas. Rim Width 8.5"; Sect. Width 9.6"; Tread Width NA; Overall Diam. 25.7"; Revs Per Mile 809

They don't make the BFG KD in 275/35/18

BFG KD 245/40/ YR18 which spec at: UTQG 200AAA; Max Load 1433 lbs; Max Inflation Press. 44 psi; Tread Depth 9/32"; Tire Weight 27 lbs; Rim Width Range 8.9.5"; Meas. Rim Width 8.5"; Sect. Width 9.8"; Tread Width 7.9"; Overall Diam. 25.7"; Revs per mile 809


specific stock tire sizing specs:
sidewall height: 4.34
section width: 9.65
overall diameter: 25.68
circumference: 80.68
revs per mile: 809.97

specific 275/35 tire sizing specs:
sidewall height: 3.79 difference -0.55
section width: 10.83 difference 1.18
overall diameter: 25.58 difference -0.10
circumference: 80.36 difference -0.32
revs per mile: 813.14 difference 3.17

specific 245/40 tire sizing specs:
sidewall height: 3.86 difference -0.48
section width: 9.65 difference 0.0
overall diameter: 25.72 difference 0.4
circumference: 80.79 difference 0.11
revs per mile: 808.71 difference -1.26


I have heard many times on here, and on the other Mach site, and from local tire shops, that the 275/35 is the optimum size, but the 245/40 looks to be closer to stock sizing. Am I missing something? Which is more optimal for my needs of being a DD on the street? My track time will be limited to under 10 runs in the life of my Mach. Are the 245/40 going to give a harsher ride since they are not as wide as the 275's? Are they going to look too small compared to 275/35's?
Thanks

[GOTdaBLUE1]

I would recommend 18 X 9: 255/40/18. In my opinion 275 anything is too wide up front. They tend to create what I have coined as auto-pilot. In other words, they follow every groove in the road. Secondly, one would feel every groove, bump, and pothole on the road with a 35 MM section height. And finally, my gut feeling tells me a 245/40/18 may come up a little narrow on a nine inch rim. Perhaps it is better suited for a 8 - 8.5 " rim. Though both produce excellent wheel diameters (0.43%, 0.11% differences respectively), a 255/40/18 (1.35% difference) may provide you with the best of two worlds. :33:

[GOTdaBLUE1]

...Are the 245/40 going to give a harsher ride since they are not as wide as the 275's? ...[/QUOTE]
Missed this statement the first time. FYI, harsh rides are produced by section height, not section width. Thus, 245/40, not 275/35 would produce the best ride. :smokin: