Tyre Glossary D-O


a-c     d-o     p-s     t-z     Glossary Home


Directional Tyres (also see Asymmetric): This type of tyre must be fitted in an indicated orientation. Chevron or arrow shaped patterns are often used to help remove water from under the tyre.

Economy Tyres (also see Budget Tyres): New tyres of fair quality which retail cheaper than mid range tyres. As you would expect performance will also be lower.

Footprint (also see Contact Patch): The area of tyre tread that is in contact with the road surface.

Hysteresis: In reference to Actions and reactions: not all energy applied to a tyre is dispersed. When dealing with an elastic material like rubber energy is always absorbed and this creates heat build-up.

Inner Liner:  The layer of rubber inside a tubeless tyre which stops air seeping out of the tyre during normal use.

Load Index: Indicated on the Tyre Wall a standardised numerical guide that indicates the maximum weight a tyre can carry at the speed specified by its speed rating under conditions specified by the manufacturer.

Low Profile Tyres: These are tyres with shallow sidewalls usually fitted to high performance vehicles.

Maximum Inflation Pressure: Exactly what it says, the maximum pressure a tyre can be inflated to.

Mid Range Tyres: Tyres which retail at a lower price than premium brands; the performance of this range shall logically be lower.

“Mini” Spare (also known as A Space Saving tyre): Smaller than the road tyres, this type of Tyre is designed to save space and reduce weight in the vehicle. A temporary measure to get you home these tyres should be changed as soon as possible,  these tyres also have a lower maximum speed.

“M+S” Tyre:  Tyres which have been designed to perform better in Mud and Snow.

Nominal Section Width: The section width of an inflated tyre mounted on its theoretical rim and indicated in the tyre size designation.

Nominal Rim Diameter:  A size code figure for reference purposes only, as indicated in the tyre and rim size designation.

Original Equipment (OE): This is the original brand of tyre that was fitted by the car manufacturer. Please note that there may be more than one OE brand fitment.

Oversteer (see also Understeer): This is a term used to describe a loss of grip to the rear wheels during cornering causing the car to slide sideways.