Size designations such as 235/75R15 and P215/65R15 will appear when looking for new tyres. According to Wheels Tires these labels can be confusing if you don't know how to read them, but once you learn the language of tyres, they become much easier to understand. On the left side of the slash sign, three digits and occasionally letters can be found. The numbers represent the tyre width in millimetres from sidewall to sidewall. The higher this number is, the more road contact the tyre has.