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M-Class site
last updated 12-17-2004
© 1998-2005 Harald Pietschmann
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Understanding tire sizes and ratings
A 1998 press release by MBUSI (manufacturer of the M-Class) states:
"Visually, the ML430 will be distinguished from its V6 powered sibling with body-colored bumpers, rocker panels and side moldings and performance-oriented 17-inch alloy wheels with super-large 275/55R-17 M+S rated tires."
As you see, MBUSI claimed that the 17 inch tires of the ML430 are super-large (compared to the 255/65R16 tire of the ML320)
In fact the "super-large" 17 inch tire is slightly smaller than the 16" !
Here is why: Whether it is a 16", 17" or 18" tire, does not say anything about the diameter of a tire. 16, 17 or 18 indicates only the size of the rim the tire will be mounted on.
Only the 255/65 portion of the 255/65R16 tire indicates roughly the size (diameter).
| 255/65 R 16 |
65 % of |
255 mm |
= 165.75 mm (6.53") |
2 x 6.53" + 16" |
= 29.06" |
| 275/55 R 17 |
55% of |
275 mm |
= 151.25 mm (5.95") |
2 x 5.95" + 17" |
= 28.90" |
However, the "General Tire" 255/65 R 16 found on the ML320 has in fact a diameter of 28.21 inches and not 29.06 inches as calculated above.
That is almost one inch off. Why?
Truth is, that almost every manunufacturer makes a 255/65 R 16 tire at a different diameter. So when replacing a bad tire, make sure it is not only the same size (like 255/65 R 16) but it is also by the same manufacturer.
Just check the 17" section and seethe vaying numbers yourself.
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What are "P" tires ? (coming soon)
What are "LT" tires? (coming soon)
Speed rating of tires (coming soon)
My personal opinion: BFGoodrich tires are unsurpassed off-road champions |
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