Help Deciding on Width & Offsets

[EezyBeezy]

Hey all,

About to order new wheels for my wife's daily F80 and decided on a particular 20" wheel, however it is limited to certain width's and offsets. I'm indecisive whether to go with 9"/10", 9"/10.5", or 9.5"/10.5" widths.

Main concern is drivability and comfort since we have kid(s) in the back. Currently, our F80 has 437M wheels w/ PS4S 265/35 and 285/35, 10mm spacers all around, and lowered with Eibach Euro Spec V1 springs in the front only and stock springs in the rear. The ride quality is very enjoyable with passengers and would like to retain that as mush as possible with the 20's.

Wheel options
20x9 et18
20x9.5 et25
20x10 et31
20x10.5 et38

Currently, i'm leaning towards 20x9 et18 and 20x10 et31. For tires, PS4S 265/30 and 295/30 regardless which wheel width combination. We're wanting for more of a meaty tire with straightish sidewall look opposed to a stretched look.

Which combination should I go with?

[M3SQRD]

Going from 19” to 20” diameter wheels is going to have a direct impact on ride quality.

A 295 tire on a 10” wide wheel is not optimal. Increasing tire width beyond its optimal size (285” for a 10” wide wheel) results in reduced grip. Also, a 9.5” wide wheel is the optimal width for a 265 tire. The tire sizes you’ve listed for 9” and 10” wheels will have pinched tires. There are plenty of wheel-tire tests that shows increasing tire width on a fixed wheel width does result in reduced grip. It also changes the breakaway characteristics of the tires, making them less predictable at the limit (high slip angles).

The 9.5et25 and 10et31 are a great match with 265/30 and 285/30 tires. However, you’ll lose the ride quickly you currently enjoy.

[EezyBeezy]

Originally Posted by M3SQRD

Going from 19” to 20” diameter wheels is going to have a direct impact on ride quality.

A 295 tire on a 10” wide wheel is not optimal. Increasing tire width beyond its optimal size (285” for a 10” wide wheel) results in reduced grip. Also, a 9.5” wide wheel is the optimal width for a 265 tire. The tire sizes you’ve listed for 9” and 10” wheels will have pinched tires. There are plenty of wheel-tire tests that shows increasing tire width on a fixed wheel width does result in reduced grip. It also changes the breakaway characteristics of the tires, making them less predictable at the limit (high slip angles).

The 9.5et25 and 10et31 are a great match with 265/30 and 285/30 tires. However, you’ll lose the ride quickly you currently enjoy.

Appreciate the insight, thank you.