175/65-15 to a 185/65-15.

I wouldn't advise it! It's will throw everything off! Speed, odometer, CVT operation, and dealer will have evidence to denied any warannty claims, pointing to incorrect tires installed! If you have issues with the emissions , hybrid system and etc , the burden be on you to prove them wrong! Vs if not ! The repairs would be performed with no issues!

 

Assuming they fit, our speedometer is going to be 2% low. So will your odometer, your MPG will seem 2% higher.

Why would you want to put the wrong tires on? What are you trying to solve?

 

First, put a garmin gps in the car and check the speed of your current tires, I'm guessing your speedometer is already low, err, it says your going 50mph and the gps says your going 48mph.
In which case the 185/65-15 tires should be on the car, the 175/65 tires are 24" in circumference, the 185/15 tires are 24.5" in diameter, that half inch is going to be 2-3 miles per gallon better mileage, especially if you air them to 40ish lbs of air.
You will not lose any factory warranty if you use the 185's, you will use less gas.

 

In my opinion, Toyota under inflates the tires to get better comfort, you will get more tread on the road if you up the tire pressure about 5 pounds.

http://www.maxxis.co.uk/media/35803/Tyre-Inflation_497x475.jpg

 

The (normally correct) theory that changing tire size will change MPG depends on fixed gear ratios. On the Prius with it's eCVT, tire diameter will have little effect on your RPM at a given speed. (Bigger tires are usually heavier tires and hurt MPG)

Michelin Energy Saver A/S is a fine tire. Michelin Energy Saver A/S

 

I do that trick! Believe me is a wast of time, money and mpg. I lost almost 4 mpg in the switch. Over inflate my tires and maintain lowers speeds to approach to the desire mpg range. I can hit 60mpg in a plane with the wind at my favor. As the tires loose some treadwere the mpg got better, so I guess as I lower the extra half (1/2) inch the car behave as I we spec. I am planing to buy new correct tires even do mine Kelly tires are in great shape (nice tires) but they are heavy tires for a small engine and a CCV transmission, is a lot of rubber for a small car, half (1/2) by 4 is 2 inches plus all the material extra, plus the size! Just a little physics to it torque is equal to the radius times the force done (l=r*F). My recommendations follow the design engineer recommendation, they do the numbers already.

 

Definitely wouldn't recommend that. Big no no for MPG

 

I am a little confused with some of these posts.

How does a 185 vs 175 tire width make any difference in the circumference of the tire?

I know for a fact that if the tire profile was larger or smaller, 65 vs 60 or 70, that would make a difference.
What am I missing?

The op is keeping the same profile (65), he just wants a wider tire.

 

Tires are sized with 3 numbers 185 would be the tread width.
65 would be height of the tire as a the percentage of width. For the same percentage, wider tires are taller tires. As a result, you often see lower percentages in wider tires to keep the circumference from growing too much.

The 15 is a measure of the inside diameter and does not change the circumference.

 

Yes thank you for the reply however where did you learn this info about the percentage? I have never heard of this before.

That's why I would think there many options and combinations, if you want the same width but want more sidewall (= larger circumference) then you have the option, if you want more width you want to keep the same circumference (same ride height) then that's also an option.

Obviously if you get a larger width or sidewall that adds more weight= less real world mpg.

 

I've been looking at the Michelin Energy Saver A/S . Seem like a fan favorite! OEM size is usually best

 

Did you get any cash for your old all seasons... and (hi-jacking) where does one go besides Craigslist to get some cash for tire trade-ins/sales anyway?
I'm thinking of getting Michellin Energy Savers but would wait until summer 2018 to switch since I have one solid year left on GY Assurance FuelMax.

 

this picture will make more sense here.

185/60 r15 is factory recommend wheel size, so this means everything will work properly.
You can check all other factory recommend wheel and tire sizes according to this picture.

Posted via the PriusChat mobile app.

 

I did this, mainly because the tire size was much easier to source at a lower price as well.

I have about 40,000 k on my 185's and I've seen no difference in fuel economy and no difference in my speedometer, it's bang on.

Over the nearly 180k kms I've got on my C I've averaged 5L/100km with vast majority highway driving.