185 tires instead of primes 195 tires?

I'd say you can use the smaller tires with no ill effects. This website will compare two tires and give the differences, Tyre Size Calculator. Visually it looks like this, What you have is a narrower and shorter tire. With a smaller circumference, it will cause the speedometer to read a higher speed than you are actually making. Combined with Toyota's already inaccurate speedometer, you'll see indicated speeds about 4 MPH high.

 

Keep in mind it'll skew your odometer and MPG readings too, since they are distance-based. You also lose a little ground clearance. None of it is a huge deal, should be fine.

And just to point it out, snow tires harden with age, and after a few years they really aren't any better than all-seasons.

 

Are your snow tires from ~2006 ? Meaning roughly 13 years old ?

If not, when were they purchased & what's their remaining tread depth ?


Rob43

 

Haven't had my hands on a gen1 prius but the gen 2-3-4 were all "engineered" for a 25" diameter tire, which is the 195/65-15" tire, the 185/65-15" tire is 24.5" in diameter.
If you run the 185/65-15" tires you either remember that when the speedometer says you're going 50mph, your really going 48mph, or you get a garmin gps and use it's speed readout.

The gen2 came with 185/65-15 tires so owners either never knew the speedometer was incorrect or knew and compensated...mentally...or got a garmin.

Remember, the 185/65-15...24.5" tires are going to reduce your miles per gallon, in my gen2 prius I was pleasently surprised when I put on 195/65-15...25" tires and my speedometer read correctly and my mpg increased.

Anyway, for winters, if I had good 24.5" snow tires, I'd use them.
And...if I had excellent 24.5" summer tires, I'd use them also.

 

Not sure what that means, but in-your-shoes I'd get the proper 195/65R15 size snow tires, sell the old ones.

 

To add to this, the Prime's clearance is already low (for my taste), which is 4.8", and I'm always worried about opening the car door into a curb or snow bank, or turning into a sudden incline side street. Keep in mind, I'm coming from a Jeep 4x4, and then a Prius c (5.5" clearance, same as Model 3). Prime is 4.8"...

With 185s you'll lose... is it 1/4 inch?

Someone check my calculations,

195/65/R15 section height is: 0.65 x 195 mm x (convert to inches) = 4.99"

185/65/R15 section height is: 0.65 x 195 mm x (convert to inches) = 4.73"

Difference is 0.26"

 

Yeah, the diff in width is 10 mm, and the width to depth ratio is .65 so:

10*.65=6.5 (mm)

About 1/4"

 

I’ve run 185’s for about 5 years on a car requiring 195’s and have had absolutely no issue whatsoever.

I have them because it saved $200 on a full set.

Generally going down a tire size does absolutely nothing dangerous and is much safer than going up a size.

So don’t overthink it, burn off your remaining rubber and replace it when it’s time

 

Put them on the rear and your speedo will be fine if that concerns you.

Many cars read 5mph fast @ 65mph, my dads TDI did, it’s not anything important to worry about.

 

I think most speedos read fast, by design. It's a safety measure.

 

corrected

I was thinking the car was slower than what the speedo read

 

All of our Gen IIs running the specified 185-65-15s read 2 MPH higher than reality in the 60 MPH range, 1 MPH higher at 30 MPH.
I replaced the Goodyear (POS) Integrity tires on my '04 when it was 3 months old with Goodyear TripleTreds - 195's because at the time they didn't come in 185. Car ran fine, probably one of the few "all season" tires that did well in real snow. Most "all season" tires are good in all seasons that don't have snow.