Opinions on which tire size

OEM for the car (BMW 650) was a 275/35-19. Specs for the original Bridgestone run flats were a circumference of 26.7 and 780 revs per mile. Car came to me with 275/35-20 Michelin all seasons with listed spec circumference of 27.6 and 755 revs per mile. These tires were replaced a couple of times, so it has had this size on for most of its life. Rims are 10 inch wide.

As I look for replacements, I'll pick Hankook Ventus since they have three close sizes:

275/35-20 circ 27.6 and 732 (rim 9-11 inch wide)

275/30-20 circ 26.5 and 760 (rim 9-10)

285/30-20 circ 26.8 and 754 (rim 9.5-10.5)

I can't understand the rim width difference either.

Should I stay with the circumference that has been working and lose more revs per mile compared with the OEM, or should I reduce the aspect ratio and get the revs back closer to original. 275 at max rim width or slightly wider 285?

I've never heard of revs per mile used as a statistic for tires. I would stick with 275mm wide tires because they are a closer fit to 10 inch wide wheels; that will give you the best handling in the rear. The taller height gives you a better ride and taller gearing. You have to choose between that or better handling and shorter gearing with a shorter sidewall.

Tire Rack publishes the revs per mile. I was surprised at the discrepancies. I thought that it would be tied pretty close to the circumference.

diameter not circumference.

the circumference of a 27.6 diameter tire would be app.86.7" with that you can figure the app. revs per mile.