[mwebb]

Originally Posted by Patrick

Actually, the two tires are almost exactly the same diameter.

OP, you may gain a little mpg due to the lower aerodynamic drag of the thinner (155) tire. There also may be a benefit if the new tire has a higher max pressure (i.e. 51 psi vs. 44 psi), resulting in lower rolling resistance.

Make sure the new wheels will clear the brake calipers.

almost ...
but there are no 13" LRR tires and the 185 60 14 will almost certainly have lower rolling resistance than the 13 " tire

at the same tire pressure

wider - is better for LRR but worse for drag
ever see a 155 80 13 on a prius or insight ? i never did .