[GrimJaw]

I have 18 stock wheels on run flats. I have the tire insurance up to 5 years. I'm thinking about changing my set up to BBS SX 17s to hopefully avoid rim bending. I got this idea from a previous thread called (BENT RIMS ) where BBS SR 17s were mentioned.

My questions are: 1) what will I sacrifice performance wise going down an inch?

2) my wheel insurance covers aftermarket wheels IF BMW approves them?

[GrimJaw]

For reference

[Sportstick]

Originally Posted by GrimJaw

I have 18 stock wheels on run flats. I have the tire insurance up to 5 years. I'm thinking about changing my set up to BBS SX 17s to hopefully avoid rim bending. I got this idea from a previous thread called (BENT RIMS ) where BBS SR 17s were mentioned.

My questions are: 1) what will I sacrifice performance wise going down an inch?

2) my wheel insurance covers aftermarket wheels IF BMW approves them?

I can address question 1 only. In most cases, downsizing a size will improve performance due to the reduction in wheel weight. A lower rotating mass will directionally improve acceleration, braking distance, and, FWIW, ride quality. Depending on the choice of tire and it's sidewall height, there could be a small change in the perceived steering "crispness" of response if the sidewall height increased much. Of course, the higher quality tires choices, for example Michelin Pilot Sport AS3+ for a UHPAS, provide excellent performance in the sizes you would be considering.

I changed from 18" to 17" BBS SR due to my unfortunate location on Michigan's lunar landscape roads, to gain the ride quality improvement (or in Moonchigan, just make it livable). The performance results were also excellent.

I'll finish with what the suspension engineers at the car company where I worked used to say, "Designers love big wheels. Engineers don't."

[GrimJaw]

Originally Posted by Sportstick

I can address question 1 only. In most cases, downsizing a size will improve performance due to the reduction in wheel weight. A lower rotating mass will directionally improve acceleration, braking distance, and, FWIW, ride quality. Depending on the choice of tire and it's sidewall height, there could be a small change in the perceived steering "crispness" of response if the sidewall height increased much. Of course, the higher quality tires choices, for example Michelin Pilot Sport AS3+ for a UHPAS, provide excellent performance in the sizes you would be considering.

I changed from 18" to 17" BBS SR due to my unfortunate location on Michigan's lunar landscape roads, to gain the ride quality improvement (or in Moonchigan, just make it livable). The performance results were also excellent.

I'll finish with what the suspension engineers at the car company where I worked used to say, "Designers love big wheels. Engineers don't."

Thank you very helpful

[wntrsnowg]

Those are kind if heavy for 17" wheels, surprising that bbs would make such a heavy wheel

[GrimJaw]

Ugh I would go with the BBS SR but I want black wheels :/

[Sportstick]

Originally Posted by GrimJaw

Ugh I would go with the BBS SR but I want black wheels :/

What color is your car or added trim (spoiler, etc.)?

It is true that black wheels won't show brake dust as much!

With this treatment, you get some of each....

https://bbs.com/de/produkte/design_line/sr.php

[GrimJaw]

Originally Posted by Sportstick

What color is your car or added trim (spoiler, etc.)?

It is true that black wheels won't show brake dust as much!

With this treatment, you get some of each....

https://bbs.com/de/produkte/design_line/sr.php

Car is mineral white with carbon fiber spoiler. Grills are gloss black. Side markers are blacked out reflectors. I just feel like a glossy black bounces nicely off mineral white

[Sportstick]

Originally Posted by GrimJaw

Car is mineral white with carbon fiber spoiler. Grills are gloss black. Side markers are blacked out reflectors. I just feel like a glossy black bounces nicely off mineral white

I get it...

[GrimJaw]

I'm thinking 18 inch wouldn't be bad now since I'm realizing if I do 17s I may lose some ride height. I hate deciding on wheels so many complications

[Sportstick]

Originally Posted by GrimJaw

I'm thinking 18 inch wouldn't be bad now since I'm realizing if I do 17s I may lose some ride height. I hate deciding on wheels so many complications

Ride height should not change with the correct spec. Imagine your favorite glazed or chocolate donut...if you eat more of the hole (the wheel part of the analogy getting bigger) the outside (circumference) of the donut doesn't get larger or smaller. If you shrink the hole (making the "wheel" smaller), the circumference of the right size tire still stays the same. This is the effect of chaging the proportion of metal to rubber of wheel to tire, but within the same overall envelope of wheel/tire combination.

Use this calculator to check your wheel and tire size...check overall diameter in particular to be sure.

https://www.1010tires.com/Tools/Tire-Size-Calculator

[Sportstick]

Follow up....when I went from 18" to 17", my 17" size of choice (using BMW specs) was 225/45-17. Try that in the calculator to compare to what you have now.