The writing on the sidewall of your tyres indicate the length, width and circumfrence of your tyre. It is important to keep this to manufacturers specification to avoid any unwanted changes to the vehicles characteristics. If you are looking for a quote on your tyres, check the sidewall and you will have numbers that look like this:

                                                                               175/70R14 102T

the first part '175' will be your tyres width and the second '70' will be your tyres length from the rim to top of the tyre. 'R14' will be your tyres rim diameter. Finally '102' refers to your tyres load rating and 'T' will be where your speed rating is.

 Having these numbers to hand will help me choose the right tyre for you over the phone.