I have 20 inch rims and would like to put 17s on for the winter. How do I calculate what size tires I need?

265/75 R 17 or 255/80 R 17 (265/70 R 18 or 255/75 R 18 ) will match the height of the tires.

But best to just go back the the original wheel/tire combo; unless you changed the rear gear ratio.

i didn't get exactly what you mean in your question.but here's what i understand

every tire have a number printed on it that shows this tire for what rim size like you tires (275/60/20) the (20) in the last means that this tire fit 20" rims size and so on. you can find tires made specifically for winter.

Kelley,

I depends very specially on the year, make and model of vehicle. Go to tirerack.com. Enter your vehicle information and then select "wheels". You can then see the suggested tire size for 17 inch rims on your vehicle.

ok, look: in case you placed 20s on a Neon, you're a toolbox. fairly the older Neons, that have been products of crap. On a simpler word, you may could desire to put in a enhance equipment to place 20s on that Neon.

You could start by telling us the year, make and model of vehicle.

go to tirerack.com. they have info on plus and minus sizing for these applications.