Tire Size Calculations

Hi, new member here. I'm an old jeep guy and former transfer case warranty engineer so I have seen just about everything on and offroad. I do see that there are sticky threads here for the same topic so I apologize for the duplication. This is for any newbies on here that want to consider upgrading their tires to a more offroad capable vehicle.

To calculate your tire diameter from the rim diameter, tire width and aspect ratio you will need a pencil and paper and a calculator. For this exercise, the calculations are in the (parentheses):

For example, the 2018 TRD Offroad stock wheels and tires are
P265/70R16,

the 265 is in millimeters and converts to inches (265mm/25.4 = 10.43inches).

The aspect ratio is 70, or 70% of the 265, or in this case the 10.43 inches
(10.43*.7= 7.3inches)

There are two aspects plus the rim diameter that need to be added together,
(7.3inches+7.3inches+16inches=30.6inches)

So, P265/70R16 is equal to 30.6 inches overall diameter.


Exculpatory Clause:

Please note that this is just a guideline and should only be used for fun and practice. I make no claims that your tires or potential tires will adhere to this calculation, and the manufacturers are under zero obligation to ensure this is accurate from tire to tire. Factors such as air pressure, rim style, rim width and tread style and wear, along with the distance from your seatpants to the bottom of the mudhole, all affect the overall tire diameter.

Hope you have fun with this. I do not yet have a taco but I am looking at '18 TRD Offroad, although I do have some burritos in my desk. I like the idea of the electronic rear locking diff!! Wish it came with the hole in the hood though. I like that. Anyways have a great day!!

Ed