185/60/15 Potenza RE92

[kimona]

Originally Posted by Pars

yup, but as you said 195 on 7' rim is still within recommended extremes. I'm parading one end of the extreme while you've got the other end cover. True, 195 on the skinny stock rims would look good and have more grip around the turn, but it's not the most efficient setup. I bet you'd be surprised at how well the 175 would perform against a 195 on similar rims&diameter (assuming Toyo tires, since cost cutting could be a factor on stock stuff). And, the 175 would be lighter, return better fuel mileage and cut the wind better at high speeds. Eventually, I do plan on getting 195 for my Yaris, but only after I can afford some bigger rims.

A wider (7") rim than stock is not necessary nor is it a more "efficient setup" to run the sizes I have indicated.

For example, OEM alloys are 16x6, ET51, 195/50/16; and 17x6.5, ET51, 205/45/17.

I do agree that a narrower tire generally delivers better fuel economy, but there is a significant trade-off in handling and safety. If you're going for maximum fuel economy, then replace your 175's with 155's and high offset flat disc alloy wheels (or just install flat aluminum covers on the stock steel rims).

[Pars]

Originally Posted by kimona54

A wider (7") rim than stock is not necessary nor is it a more "efficient setup" to run the sizes I have indicated.

For example, OEM alloys are 16x6, ET51, 195/50/16; and 17x6.5, ET51, 205/45/17.

I do agree that a narrower tire generally delivers better fuel economy, but there is a significant trade-off in handling and safety. If you're going for maximum fuel economy, then replace your 175's with 155's and high offset flat disc alloy wheels (or just install flat aluminum covers on the stock steel rims).

Thanks for the info on the OEM sizes. My next rim is going to be 15x6.5.

I did 300,000KM on the 195/50/15 tires mounted to 7 inch wide rims (Toyo Proxes FZ4 and was on my third set when I sold the car). Excellent setup, since the tires were tightly stretched over the rims, it made for immediate turn-in (the thick sizewalls on the Toyo Proxes FZ4 probably played a factor). The suspension system in my Yaris isn't going to be as radical, so 6.5 inch (rim width) should be good fit.

If tires are stretched tightly over wide rim, it should return more surface contact vs an overized tires on skinny rims which will simply bulge out on the sides.

Imagine identical cars with identical tires on the racetrack (on performance springs). One with 15x5.5 rims vs 15x7 rims (on 195 tires). I bet the differences would be surprising.