Let's talk Tire Ratings. What exactly do they mean?

Ever wonder what those markings on the side of your tires are? The ones that say for example, P235/45R17. Those little numbers and letters molded into the tires carry quite an amount of information. There are other markings in the tires and we'll take a quick look at them as well.

Let us use the example above, P235/45R17:

1. The first letter 'P' stands for Passenger cars. There are other variations such as LT (for Light Truck) and may be used for SUVs and similarly sized vehicles. 
2. The '235' refers to the width of the tire in millimeters. This is the contact patch between the rim and the road. As a side not, if you are into the whole car tuning scene, you will see people trying to get the widest possible tires on their rims. 
3. The '45' stands for the ratio of the height to the width of the tire. In simpler terms, it just means the height of the tire is 45% its width. Once again in the tuning scene, you'll come across people with a tire ratio of 30 or even 25... they are referred to as rubber-band tires or low profile tires!
4. The 'R' stands for Radial. This refers to how to tire has been constructed. There are other variations such as 'B' for Bias Belt and 'D' for Diagonal (or Bias Ply) but these are not in use anymore.
5. The '17' refers to the size of the rim (diameter in inches) the tire is meant for. In this case it means the tire is for a vehicle that has 17 inch rims. Tires and rims usually go from 13" to over 30"!

You may also see other markings like 85H and M+S. These refer to the load index, speed rating and the conditions you can use the tire in.

1. Load Index: This refers to the maximum weight that can be applied to the tire. The number is a code and refers to a weight. For e.g. '85' corresponds to a maximum load of 515kg or 1140lbs. There are several others such as 65, 70, 90 etc. that all refer to corresponding weights.
2. Speed Rating: This refers to the maximum speed the tire can be used for. Once again the letter is a code. In our case, the 'H' rating corresponds to 130mph or 210km/h. There are several other codes depending on the maximum speed like 'V', 'Z', 'Y' etc.
3. M+S refers to Mud and Snow. These tires are usually meant for all weather conditions and can be used as such. Depending on where you live they may or may not be the standard tires used by most dealerships.

There are several other markings on the tires that pertain to the temperature, treadwear and traction grades, country of production etc. but we feel the topics discussed above should give you the right amount of information for your next tire purchase or replacement!