Daily Driver - Tire width and its affect on traction/mileage

I'm swapping the steelies from my wife's 2005 Corolla with some 15x6 wheels off of a Prius. Original tire size is 185/65/15 for the Corolla and 195/65/15 for the Prius.

Although partially due to being a crappy brand of tire, my wife's car is awful in the rain. I was thinking of jumping up to the Prius tire size because it would actually correct the speedometer and I was hoping the additional size would run a lower RPM on the highway and help with mileage. Do you think the additional size would help a little with traction or and will it be to be negligible?

This is relevant to my interests.

I think negligible due to tire size.. but you might get better MPGs due to the tyre and rim design. The Prius is a pretty slippery beast, every thing they could do to lower the Cd they did. This included designing some rims that don't disturb the airflow

The effect from such a minor change is well lost in the noise of the different tires themselves. It's much more tire X vs tire Y than size X vs size Y.

Aero of the Prius wheel is maintained by using whatever ugly wheel cover came on the car. I think the Prius has some decent looking aluminum wheels but they've always got a plastic wheel cover that closes up the openings between spokes and I'm sure it's done for aerodynamics. So you're going to want to include those to get the most MPG benefit out of such a swap.

You are literally not going to notice a difference with that small of a change. You are gaining a whopping ~6.5mm of sidewall height. Thats like the difference between a new tire and a worn tire of the same size.

Yeah I definitely agree I wont notice a difference (known for never noticing modification changes although significant difference in track times) but that doesn't mean there won't be a difference.

If it's only .05% better, it's still better.

These are the wheels in question. Going to be loosing ~6 #s of rotating mass from each corner. We will be using them without the wheel covers.

The weight reduction is nice. I say go for it!

Hard to quantify. I will say my '03 TDI lost a couple of MPG when I switched from the OE tires (195/65-15) to OE 16" wheels (Wolfsburg Edition BBS) and 205/55-16 tires.

You will feel the 6lbs difference for sure behind the wheel. If anything will make a fuel mileage difference in this case it would be that more so than the tire diameter. Not sure if it will be enough for you to notice at the pump or not.

I'm curious about this too. BMW poured enormous money into developing the i3 as a cleen-sheet high efficiency engineering exercise--and then asked Michelin to design wacky 155/70R19 tires for the car.

For some perspective, I went from 175/95/r14 to 225/55r16 and gained a few lbs of wheel/tire and it only dropped my average (highway) by about 1mpg. Granted, I dont see high speeds (65ish max), but it just didn't make a significant difference in mpg. It does feel a little slower from a stop but the gain in stability (from a 4.5" Wide wheel to 8") makes it completely worth it.

The sidewall change wont make a noticeable difference, but the wheels will.

Was not expecting this.

I was going to relate that going from the 215/45/17 on 17x7 setup on the BRZ to the current 18x9.5 255/35/18 Direzza IIs did affect MPGs.

Never heard of a 95 aspect ratio. that is a tall tire.

You'd probably notice a net gain if the Prius wheels still had the correct low rolling resistance tires mounted on them.