MuGGzyx

I have a 93 SC400 with 17" rims on it. Right now I have 245/45ZR17 tires on the rims and they look great and fit the wheel wells etc. I am forced to hunt around for used tires though and need to know what sizes would fit. I don't know how wide the rims are exactly unfortunately.

Just need to know for instance if 250/40/17 or 230/55/17 etc etc. I assume there must be some kind of guide online but google is not helping today for some reason.

Sltwtrking

You need to read up on how to read the metric tire size.

The first 3 numbers are the width (in mm) and the second pair of numbers (called the aspect ratio) is a percentage of the tires width. The last pair of numbers is the wheel size (which you know). You can use a tire size calculator to break down each tire size you are looking at.

In short though, below are the most common sizes people run on the SC (non staggered of course)

255/45-17
245/45-17
235/50-17

These sizes may or may not work on your application though. The fitment will depend on suspension and wheel dimensions (width/offset) etc.

I hope this helps.

mitsuguy

iTrader: (2)

I'll add 255/40-17 and 235/45-17 to the list, and 225/55-17 will work as well, but will be somewhat narrow...

one thing to keep in mind - make sure your rear tires are evenly matched in size - even though its an open differential, it will have to do more work if the tire sizes are uneven left to right...

Sonic_RC

iTrader: (15)

225/55-17 is far too tall I think you meant 225/50-17.

Aside from width the OD (overall diameter) plays the biggest factor. You need to calculate the height of the tire so that it doesnt mess with your speedo.

To OP, just so you know the first set of numbers represent the with in milimeters and will always end in "5". So 245 would be 9.65" wide and would fit a 8.5" wide rim perfectly without stretch or buldge. Since rims are measured from inside bead to inside bead an 8.5" rim is actually 9.5" wide

The second set of numbers is the percent of height based on width (eg: 275/35 = 35% of 275)

and or course the R17 is 17" radius.

Here is how you calculate overall diameter.

width x 0.profile x 2 / 25.4 + rim diameter = OD

for example if you size is 245/45R17

245 x 0.45 x 2 / 25.4 + 17 = 25.69 OD

if it was 225/50-17 it would look like this

225 x 0.50 x 2 / 25.4 + 17 = 25.86 OD (+0.7% taller)

Rule of thumb is that you stay within 3% of your OD and you should be just fine.

mitsuguy

iTrader: (2)

Yah, definitely a typo on my part...

I definitely don't need the numbers, you can search my old posts for numerous occasions I've put those formulas on here

Sonic_RC

iTrader: (15)

No worries, the formulas were actually for the OP because he CLEARLY needs them LOL