Front wheel cylinders

Front wheel cylinder diameter, for all cars with drum brakes is always 15/16" (23,8mm). Right and left wheel cylinder are mirror images and cannot be mounted one in the place of other.

Three different wheel cylinder bodies were fitted, these being of 60, 66 and 72 mm lengths, measured end to end with the rubber boots removed.

Three different front drum diameters were fitted to the R4: 180mm (Berline up to 1968), 200mm (Berline from 1968 onwards, Fourgon up to 1968) and 228mm (Fourgon 1968 onwards, GTL 1978-1982).

All wheel cylinders and backplates have the same mounting pattern, that is any wheel cylinder will fit to any backplate, but:

60mm wheel cylinders are not suitable for 228mm backplates, since pistons will be too far extended and may come out.

72mm wheel cylinders can not be fitted on cars with 180mm backplates as the brake shoes will not be able to fully retract.

All other combinations are possible and permissible, including fitting different wheel cylinder lengths on the same car.

60mm wheel cylinders use different piston seals than the other two types, so repair kits will be different.