Use the guide below to easily and quickly find your tyre size from the side of your existing tyres.
Look for a 3 digit number, such as 225
Which is followed by a 2 digit number, such as 55
And then a Rim Size, shown next to the letter R
And finally the Speed Rating, identified by a letter (i.e V)
All tyres sold in the EU must be advertised and sold with the below format label, detailing Fuel Efficiency, Wet-Grip and Rolling noise (measured in Decibels).
Further information is available on the UK .Gov website (opens in a new window)
You should check your handbook for the necessary speed rating before purchasing tyres. Using an inappropriately speed rated tyre could invalidate your insurance.
N - 87mph
P - 93mph
Q - 99mph
R - 106mph
S - 112mph
T - 118mph
U - 124mph
H - 130mph
V - 149mph
Z - 150mph+
W - 168mph
Y - 186mph
Factory tyre codes
B – Tyres for Audi (S3, S4, TT, TT Roadster), Bentley – installed in pairs on the same axle, can be installed on other makes
C1 - Pilot Sport tyres for Chrysler Viper GTS Coupe - cannot be installed on different makes
G1 - A tyre with a larger external diameter; can be mixed with other tyres only when installed in pairs on the same axle (Mercedes: S, CLK, C, SLK, SL Classes - Rear axle, Alfa Romeo: 166, Fiat Stilo, Renault Laguna, Vel Satis), can be installed on other makes
K1 - Approved for Ferrari - cannot be installed on other makes
M0 - Approved for Mercedes - cannot be installed on other makes
N0…N3 - Approved for Porsche, cannot be installed on other makes
R1 - A special CXKA tread – a single tyre approved for Audi
* - Approved for BMW
J - Original equipment in Jaguar
N0, N1, N2, N3 - Approved for Porsche
AO - Approved for Audi
RO1 - Approved for Audi models R and S
MO - Original equipment in special versions of Mercedes Benz (e.g.:AMG) and Maybach
* - Original equipment in BMW
M3 - Original equipment in M class BMW
E - Optimised rolling friction as required by original equipment
(...) - Approved for factory installation
A - American version of Scorpion STR
M0 - Approved for Mercedes
N1...N3 - Approved for Porsche
(*) - Approved for BMW
When it comes to BMWs (and some limited other manufacturers) the question is always the same - Can I use non-run-flat tyres with my O.E. wheels? Drivers seem to be uncertain, but the long and short of it: yes you can.
When it comes to the actual tyre sizes, they are 99 per cent identical and will sit correctly on your original wheels. The difference with the wheels, compared to those that would have come with non-run-flat tyres, is an extra hump behind the seating for the bead. The hump keeps the run-flat tyre in place while driving in 'run-flat' mode - i.e. without air pressure.
Therefore, this extra hump in your O.E. wheel is irrelevant when it comes to fitting non-run-flat tyres. The tyre simply sits on the outer, normal bead seal, performing exactly how a normal run flat would behave.
If the tyre is labelled numerically the same, for example, 225/40R18 RF and 225/40R18 non-run-flat - there will be no issue opting for a non-run flat tyre.
Obviously, in the event of a blowout, puncture, air leak or any other loss of air, you will not be able to drive on the normal tyre. The capabilities of run-flat tyres allow the driver to proceed at a maximum speed of XXX to the nearest garage to purchase a new tyre. Without this capability, you must pull over and make efforts to change the tyre to a spare, use a plug kit or an air compressor and tyre-weld product to seal any small punctures temporarily or call your roadside assistance.
Other time saving options include modern, specialy developed tyres with strong, puncture resistant seals inside such as the Pirelli Total Mobility Seal Inside concept found on Pirelli's website