Going from 20x9 to 18x8.5...Thoughts?

[TURTL3]

So I have a 2017 3.7 with a 20x9 255/35/20 square set up. I recently swapped in 3.55 gears (stock was 3.15) which helped acceleration a lot. However, the 20 inch wheels are very heavy and the 3.7 does not have the torque that the Ecoboost and 5.0 have. I was thinking about getting shorter tires to help maximize the 3.55s. I'm thinking some Enkeis in 235/45/18 18x8.5. It seems like the Enkeis are about 7-10 pounds lighter per wheel (not mounted).

Right now the 20s are on Sumitomo A/S tires. So, I would either get Firehawk Indy tires for the 20s or spend more and get a whole new set of the 18x8.5 Enkeis mounted to Firehawks. What do you all think?

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[BmacIL]

I wouldn't get a significantly shorter tire, but a lighter wheel and tire combo would certainly help a lot. 255/45R18 are basically the same diameter. The tires themselves will be ~the same weight (based on a cursory look between a few different tires of those two sizes), but the wheels will make a big difference. Less mass, and more of the rotating mass is closer to the axis of rotation.

 

[TURTL3]

I wouldn't get a significantly shorter tire, but a lighter wheel and tire combo would certainly help a lot. 255/45R18 are basically the same diameter. The tires themselves will be ~the same weight (based on a cursory look between a few different tires of those two sizes), but the wheels will make a big difference. Less mass, and more of the rotating mass is closer to the axis of rotation.

Ah ok, thank you. I'm new to RWD cars with so much room. The VWs I worked with before could barely fit 19s. I really want to set the car up to be more handling focused and I'm thinking lighter wheels would work. I can't really afford the larger wheels like HRE so the only way I can go lighter is by going smaller. But the Firehawks are really well priced tires so I can kind of match the height of the 20s with the 255/45/18.

 

[Grintch]

Do they make 18x9 or 9.5's that fit?

I think you can improve the ride and handling with lighter, smaller diameter wheels. But if you give up width too, you lose some of the handling. The s550 Mustang is a big girl. I don't like smaller than a 275 tire on one.

 

[NightmareMoon]

Lighter wheels and tires don't help acceleration as much as you would think. The benefits are mainly in the low speed (0-15mph) range. Differences in acceleration above very low parking lot speeds is minimal. You're probably not going to notice. Ride quality might get better from the taller sidewalls, but handling responsiveness might get worse.

You'll get a different final drive ratio from the smaller diameter wheels, which gives you better thrust in each gear, but it also lowers your shift points, so you may end up slower to a given speed if you now have to shift an extra time.

 

[sdiver68]

I think there are more cost effective ways to get the power gain and you may be setting yourself up for other issues.

Not trying to dissuade against new wheels, rather just understand that you will be changing the entire handling dynanic.

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