April 25, 1998 April 26, 1998 |
| CAUTION |
| road conditions |
| you need to bring... |
| temp. spare |
| tire quick math |
| tire topics |
| how many chains? |
| M-Class glossary |
| How 4ETS works |
| M-Class topics |
| more M-Class topics |
quick math vs actual tire size |
First the quick math to figure the diameter of a tireSidewall height of a General Tire "255 / 65 R 16" is 65% of 255 mm equalling 165.75 mm. 255 mm (10.04") is the value for the tire width. Two sidewalls of 165.75 mm result in 331.5 mm and translate* to 13.05 " of rubber. Add a 16 inch rim and you get a wheel with a 29.05" diameter. So far so good - and calculators offered at most tire web sites will agree with the result.
The General Tire 255/65 R 16 has a published diameter of 28.21 inches. That is almost one inch off. Why?/ Truth is that rarely ever two tires of the "same size" from different manufacturers will indeed have the same size. Just check the 17" section and you see what I mean. The only way to find out the exact size of a tire you intend to buy: Get the published value for "Static Load Radius" from the manufacturers and compare. I hope to be able to publish all numbers here soon. Send e-mail in case you can't get the numbers from your dealer - I have them in my database.
* 25.4 mm = 1.0 inch |