I need new tires again, whats the "best out there?"

185 is the width of the tire. Not the circumference. 195 is slightly wider. How does making the tire slighter wider change the speed?

 

If the aspect ratio is the same, then the height (and therefore diameter) will increase as well.

 

The aspect ration and the wheel diameter is what makes the height change not the width of the tire.

 

I respectfully (and I mean that) disagree. The tire width is a simple number but the aspect ratio is not. The aspect ratio is a percentage of the width. Therefore if you increase the width and keep the aspect ratio the same, you increase the height. Here is a calculator. Plug in different widths with the same aspect ratio and see for yourself:

https://www.discounttire.com/learn/tire-size-calculator

 

Tire diameter = (width x aspect ratio x2) + rim diameter

here's a question....what is the aspect ratio?

it is the sidewall height divided by the width of the tire

50 series tire = sidewall is 50% of the width
60 series tire = sidewall is 60% of the width
65 series tire = sidewall is 65% of the width

This is why the X2 is in the calculation....there is sidewall on top and bottom of the rim when measuring total diameter.

The lower the aspect ratio, for the same width, means the sidewall is shorter, typically improving handling.

 

And for these reasons the correct size (which is what is the Toyota spec in jurisdictions where the 195 is offered) when changing up to the 195 width is:

195/60 R15

I believe the car was designed with 195/60 R15 in mind but for some reason they decided to use the 185/65 R15 in the US. Improve fuel economy to meet some CARB target, maybe?

The trouble with changing tire widths, is that the corresponding change the to height aspect ratio is not an exact science, as the ratios go up by 5 units (i. e. 5% steps). So, sometimes, you have to go with the best compromise.

You can see this by playing around with the Discount Tires tire size calculator linked to in post #44 by Roy Rose, and the corresponding change to the diameter.

 

195/60r15 are a “rare” size that was discontinued.

They and 195/65r15’s both came on the Chevy Cobalt

When I checked the revs per mile metric the 185/65r15’s I bought were only 1% off from the cheap 195/65’s that came OEM with my car.

If you can find revs/mile that is more important than the listed size