Porsche 928 S 1986 Driver Manual page 73

Tyre designations
Due to new speed and load ratings for radial
tyres, new designations have come into force
for winter tyres for your car.
During the transitional period tyres may bear a
dual designation, e.g., 205/55 SR 16 Q M+S.
If so, the valid designation is the new one.
The old designation continues to be used for
VR tyres, e.g., 225/50 VR 16 (VR = code letter
for radial tyres for speeds above 210 km/h).
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