the markings on the sidewalls of tyres will help you to choose the right tyres
for your car. Here's a guide to those sidewall markings using a 175/80 R14
88H tyre as an example. (29.6.08)|
175 - Tyre width across the tread measured in mm.
Aspect ratio or profile height of the tyre calculated as the sidewall height
expressed as a percentage of the tyre width. So a tyre with an aspect ratio of
80 is a tyre whose height is equal to 80% of its width. Modern tyres have lower
aspect ratios - for example 60 - than the 80 originally fitted to the MGBGTV8.
R - Radial construction. This marking is almost redundant these days
because very nearly all tyres for cars are radials but when the MGBGTV8 was launched
in 1973 tyres with crossply construction were still available and fitted to some
vehicles. Radial tyres were specified equipment for the MGBGTV8 from its launch.
14 - Wheel rim diameter. This is the diameter in inches of the rim
of the wheel that the tyre has been designed to fit.
88 - Load index
is a numerical code which gives the maximum load that the tyre can carry whilst
it is travelling at up to the maximum speed set by the speed rating of the tyre.
H - Speed rating indicates the maximum permitted speed that the
tyre can endure for a period of ten minutes without being in danger of sustaining
is a summary of a more detailed note which is available as a download.
regarding load index and speed rating. It is essential you do not fit tyres to
your vehicle with a lower speed rating or load index than recommended by the vehicle
manufacturer. Fitting lower speed rated tyres or tyres with a lower load index
may invalidate your insurance. Although the UK speed limit is just 70mph, most
vehicles are more than capable of exceeding this speed. Therefore vehicle insurance
companies will insist that the tyres of the correct speed rating are fitted to
Replacement tyres for the MGBGTV8 model
The original tyre specified
in MGBGTV8 Driver's Handbook AKD 8423 was 175HR x 14 radial ply. The current
replacement tyre to maintain the key original features of the model - the original
appearance of the wheels in the wheel arches and drive train gearing - is a 175/80
Replacement tyres for the MG RV8 model
tyre specified in MG RV8 Owner's Handbook AKM 7144ENG was 205/65 ZR 15.
The current replacement tyre to maintain the key original features of the model
- the original appearance of the wheels in the wheel arches and drive train gearing
- would be a 205/65 R15 94V.
Tyre Size Change Calculator
Enthusiasts preferring what they feel might be uprated handling with other wheel
size and/or tyre width and aspect ratio combinations will need to use the Tyre
Size Change Calculator on the etyres website to check the net effect on drive
train gearing, refer to the useful information in V8NOTE187
and seek advice from a reputable tyre specialist with experience of modern tyres
for classic sportscars like the MGBGTV8 and MG RV8.
Size Change Calculator