185s rather than 195s for snows...?

Narrower Snow tires are Better.
The 1st number, 185 or 195, is the width of the tire in millimeters.
How to Read A Tire Sidewall | BFGoodrich Tires

Narrow Tires​

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• Narrow tires act similar to a knife cutting through butter when driving in snowy conditions. The thin surface allows the tires to dig right through the snow to get as close to the ground as possible. According to John C. Dixon, author of "Tires, Suspension and Handling," this allows tread on the tires to take hold and provide the best traction.

Wide Tires​

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• Wide tires act similar to snowshoes during winter driving. The wide surface floats on top of the snow rather than cutting through. This means that the tread on the tires often never has a chance to dig into the snow and take hold for optimum traction.

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Read more: Are Narrower Tires Better in Snow? | eHow.com http://www.ehow.com/facts_7467302_narrower-tires-better-snow_.html#ixzz2AXf3q1in​

 

the speedo is already wrong with the stock tires btw. 1.5 mph too fast seems about right.

 

i have yet to drive a car on which the speedo matches GPS speed. i suspect it's for liability reasons.

 

Did you end up using 185s? I'm still debating whether to buy snow tires or not... I'm wondering about the traction control being a liability if I stick with the stock tires. I live in CO where we can get icy roads.

 

The 185s are pretty narrow and usually have a lower load rating. It will work but I don't recommend it. You'll also lose ground clearance because the tires are so much shorter. I'd expect the speedo to read 3mph to high +-. IMO the Prius is too heavy for those little tires.

 

when it comes to snow, I'd like more ground clearance... I don't suppose 205s are an option...

 

They are. They are quite a bit taller than the OE tire but it's better to go taller than shorter. The X-ice Xi3 comes in a 205/65/15.

 

Going to the narrower tire would reduce circumference by around 2%. This would directly effect spedometer, odometer and gearing. Not a lot, but not insignificant. As mentioned it would also reduce ground clearance.

I do not know, maybe not a good idea to impulse shop tire sizes?


Here's a calculator:

Tire Size Calculator - Discount Tire Direct

 

That sounds interesting, increasing the ground clearance.

What are the safety downsides? Less clearance in the wheel well? Would the tire hit the wheel well on a bump?

 

There should be plenty of clearance on a stock height car. I have done it so I can't say for sure.

 

mmm?? you only go down in width .. that got nothing to do with your speedo??

or what m i missing here.

only when you go from 195/65 to 185/60 there wil be a differents in speedo..

 

No. The middle number is an aspect ratio (sidewall profile/height) and dependent on the width of the tire. It is simply a percentage of the width. You can't change the width and keep the same aspect ratio without changing the total diameter.

Tire Tech Information - Tire Size Guide

HowStuffWorks "How Tires Work"

 

so if i want 175 ob my gen 2
dont care if they are 15 16 or 14 rims.
what would i need to have.. 175/80/15?

 

No. You would need a 175/70/15. Unfortunately they don't have any real tire choices in that size. Why would you want a narrower tire? You may end up with worse fuel economy.

 

i was hooping better!!

wy worse?
the gen2 base model also got 15inch and better mpg then the 16inch model

the PIP got also smaller tire size right?

 

Hmmm...looking at the tire size guide it says the 205/65/15 is wider not taller, 205 vs 195 tread width. Where is the outside diameter measurement?