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What Do The Numbers Mean!?!?!?

1K views 8 replies 7 participants last post by  twyluh 
#1 ·
Hi there, im just wanting to know what do the numbers mean when your looking at a set of tires. For example: P295/50R15 i know what the last number means, but the other letters and numbers got my head spinning.

THANKS
Jim Jr.
 
#2 ·
Tire numbers.

lanky,

The 295 number refers to the width in milimeters (mm). Cant remember if its the cross-section or the tread, but you get the picture.

The 50 reflects a percentage ratio of the sidewall height to that width. So those tires would be 295 mm wide, the sidewalls would be 50% of that (154.5mm) and the r15 of course is a 15" diameter wheel.

The bigger the first number, the wider the wheel, the bigger the 2nd number, the "higher" the sidewalls in proportion to the width (think not lo-profile) the bigger the 3rd number, the bigger the wheel that the tire fits.

hope this is not too confusing

:buck:
 
#3 ·
Sunroof69 said:
lanky,

The 295 number refers to the width in milimeters (mm). Cant remember if its the cross-section or the tread, but you get the picture.

The 50 reflects a percentage ratio of the sidewall height to that width. So those tires would be 295 mm wide, the sidewalls would be 50% of that (154.5mm) and the r15 of course is a 15" diameter wheel.

The bigger the first number, the wider the wheel, the bigger the 2nd number, the "higher" the sidewalls in proportion to the width (think not lo-profile) the bigger the 3rd number, the bigger the wheel that the tire fits.

hope this is not too confusing

:buck:
i kinda get it...anyone else have a good example of this thing?
 
#4 ·
#6 ·
P means passenger car.

Section width is measured at the widest point of the tire (usually at the sidewall bulge), not tread width.
 
#7 · (Edited)
Tire Sizes 101...

Trying to make it as simple as possible although those above have it correct.

The first number is the width, the bigger the number the wider the width, in milimeters. A 295 will be much wider than a 225.

The second number is the height. The higher the number, the taller the tire will be. Yes, this is a percentage of the width. A 70 series tire will be much taller overall than a 50 series tire. The 30 and 40 series are more the rubberband type.

As you already know, the last number is the diameter of the rim that it fits.

Yes, the "P" stands for passenger car while the "R" means it's of radial construction. You could also have another letter which indicates it's speed rating. "Z" is the highest speed rating you can have and it goes down from there. This letter is of the least significance when it comes to our cats though. It's geared more to the high end exotics that are capable of 140mph +.
 
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