these are going on the back of my 2wd ranger.
205/75R15 overall dia. 27.1", weight- 21.6 llbs., rpm 767 or
215/75R15 overall dia. 27.7", weight- 23.8 llbs., rpm 750 the overall dia. of the stock tire is 27.4" would the slight increase in rpms of the smaller diameter tire be more than offset by the reduced weight and slightly smaller contact patch? thanks

 

Too close to call !

Reduced weight should help.

The rpm thing, not too sure what it references,
What is your rpm at cruising speed, i.e. 60/65 mph ?

Usually rpms spells less mph but if the tires get too big then you need additional rpms to bring the engine/vehicle in a more workable rpm range.

 

I think the rpm simply means given the same distance say a mile, the smaller tire has to rotate 17 more times. I think the engine is turning around 2,200 or so at 60 mph or there abouts.

 

Didn’t think along that line, thanks.

Still think the tire sizes are too close to worry about.

Luck on your choice.