The tire size on my car is 185/70 R13 85 T. Exactly what does each of those numbers mean?

Question

The tire size on my car is 185/70 R13 85 T. Exactly what does each of those numbers mean?

Answer 1

The first number 185 is the width of the tire in millimeters. The second number is the height of the tire represented as a fraction of the first number ex: the tire is 70% of 185 tall (129.5 millimeters). The r stands for radial. The 13 is the diameter of the tire in inches. The 85 is a load rating, how much wheight the tire can hold safely. The higher the number the more whieght it can hold. The last letter is the speed rating.

Answer 2

Very detailed explanation of all that stuff and more here;

http://www.tirerack.com/tires/tiretech/t...

Answer 3

Actually, your tire size is probably "P185/70R13 85T"

"P" means the tire uses the Passenger Metric load and inflation tables which determine how much load (weight) a tire can support at a given inflation pressure.  Some tires are European Metric.  These won't have a P in the description and carry different loads than a P-Metric tire.

"185" is the "section width" or the width of the tire measured at its widest point (not the tread, but about halfway down the sidewall) in millimeters.

"70" is the "section height", often called the aspect ration and is a measure of the height of the tire from the bead to the top of the tread expressed as a percentage of the section width - 70% of 185mm.

"R" means the tire is of radial construction

"13" means the tire mounts on a 13-inch diameter wheel.  Yes, they mix metric and English measurements in tire sizing.

"85" is the load index.  This tells us how much weight the tire can support at specific inflation pressures.  For example at 29 psi this tire can carry a load of 1,036 lbs.  At 35 psi it carries its maximum load of 1,135 lbs.  If the tire uses the European Metric sizing system the size will read "185/70R13 86T" instead of P185/70R13 85T".  Dimensionally it will be identical.   Load carrying ability is slightly different.  For example at 29 psi the Euro Metric tires load capacity is 981 lbs.  Load capacity peaks at 1,168 lbs at a slightly higher 36 psi.  Sometimes one has to be careful switching between P-Metric and Euro-Metric tire sizes because of that.

"T" is the tires "speed rating" which indicates the maximum speed the tire is designed to sustain under specific test conditions.  In this case 118mph.

Hope that helps.

Answer 4

185 is the width of the tire in millimeters

70 is the sidewall height (percentage of width  in this case 70%)

13 is the rim size