Taller tires or lower RR?
 

Since my tires may need to be replaced within the next 1-2 years I'm starting to look around for the next set, just to know what is available. My car came with 195/65R15's (205/65R15's were an option) and this is what I use for most of the year. Winter tires are 185/65R15 and won't be replaced any time soon.
I haven't found low RR models any taller than what I have, and the only widely available tire with a higher profile is 185-195/80R15, but these are mostly for delivery vans. There is no mention as to what their RR is.

Switching to 185/80R15 should lower engine rpm by ~6%, and maybe slightly better comfort on bumpy roads, but will raise the car by ~20mm. I would benefit from the larger wheel only when cruising, not when coasting in neutral (which I do more often).

If van tires turn out to have worse RR than normal tires, then is the switch to taller a bad idea? And how much worse can their RR be to still allow me to switch to 80's?

I'd stick with the stock tire size and get a LRR tire. I don't like the idea of the 20mm raise in height and I also like my speedometer to be accurate. Also, I haven't ever seen any testing that shows taller tires give nearly the gain that LRRs give you.

How about taller LLR tires?
With most vehicles made after the late 90s you should be able to go to the dealer and have them correct the speedo with nothing more than ECU programing change.

Changing the speedo might be as easy as an ecu reprogram, but the last time I saw one done ( on an '01 Tahoe ) tech spent about 2hrs between calls to Gm and various points waiting in the process just to get the special reprogram setup in gms system. Then he still needed to do the actual programming. Aside from the techs time, Gm also charges to do their side of it. The tech was doing this on his own vehicle, but for a customer the cost might be prohibitive. I'm sure there are vehicles out there easier to do this on. There also might be an aftermarket programmer for your vehicle that might allow you to adjust your speedo as you please. I guess I'm sayin check with your dealer first if you're going that route.

I forget which post it was, but it was here, and the two tires with the least RR are the Conti VancoContact with an RR of .0064 and the Nokian Hakka C Van with a .0064 also.

The Honda Insight tires were at .0062!

if your gunna adjust ur speedo and tach go with taller lrr tires ( and drive over 75% hw) , if not just go with lrr tires

I will give a suggestion for 175/80R14 Toyo 350. Same diameter and 20mm narrower. Worked very well on my old Seat. Seat stock size was 185/65R14 so they were taller on my seat.

...*IF* you can easily correct for the increased tire/wheel diameter, then I'd say go for both taller and LRR tires, because the taller tires will help lower your engine RPMs at road speeds, getting you closer to the BSFC "sweet spot" if you're not already there.