We measured the original 225/55-16 Proxes 4 at 7.875” (7 7/8”).
Our new 255/40-17 Extremecontact Force tire measured at ~8.6”. TireRack.com officially records this tire at 8.4” with their consistent measuring tool, which I personally highly value.
These wheels instantly improved the stance of the RX-7. The classic, wide 6-spoke design adds a motorsports inspired aggression, while the bronze color with raw aluminum highlights create another layer of depth to them without being too “busy”.
The 255/40-17 Continental Extremecontact Force has a TireRack.com-measured treadwidth of 8.4”. This is a fantastic fitment for our 17×9.5+51 Titan 7 T-D6 wheels. While it’s just slightly more stretched than my personal rule of thumb:
“For ideal handling: when sizing a wheel for a given tire, I usually target the WHEEL to be the same width as the tire’s TREAD width, or 0.5” wider”.
Having a taller 40-aspect ratio tire helps prevent this from having adverse effects of being too stretched. I would not put an 8.4” wide tire on a 9.5” wheel if it had a 30 or 35-aspect ratio, but 40 is fine and works out quite well. Plus, this is a very common sizing used in the S2000 and RX-7 communities for many years. I would also not put a 245/40-17 on this wheel if it had a treadwidth less than 8.4”.
The 17×9.5+51 offsets fits great under the stock fenders. The tires are not poking out of the fenders and risking fender damage, nor are they sucked in too far and look like stock. There’s a nice stance to the car that’s aggressive without worry of issues when pushing the limits of fitment.
6 comments
Great article. I can’t wait for the track test. I am also looking at some Titan 7 made wheels for my 08 Miata. Evasive Motorsports has a custom line made for them by Titan. 17×10 +47 EVS Tuning 52R, which should need just a 3-5mm spacer to fit the NC properly. They are meant for S2000’s, but luckily that offset is very close to what the NC’s need, too.
Where are the Titan’s made?
Minor correction: the reinforced wheel is on the left, unreinforced on the right.
Valve stems are placed where they are most aesthetic on modern aluminum wheels, not on the heavy spot of the wheel. It’s nice to be consistent about aligning the dot on the tire with the valve stem but it really means nothing.
That’s all well and good but the author didn’t even mention the dot.
I think he was just saying that on pro race cars, they make a mark on the tire at the valve stem to keep an eye on slip.
Correct, it’s easy to make a small line with a paint pen to mark the valve stem position to monitor tire slippage on the wheel.