Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing P4 SS tyre choice....

Need to replace the original 205/65 R15 Avon ZV5s.
The straightforward choice is to replace with the successor, Avon ZV7s, same size as above.
The other option would be CR6-ZZ which seem to be a sportier tyre and would suit the SS well. However the closest size wise is 205/70 R15 which gives an extra 1cm sidewall height all around.
Not bothered by effects on speedo but does this sound like a good idea from a ride/performance perspective?
Or should I stick with “OE” ZV7s?
Thanks for considering this rather trivial dilemma :-)

Nick

I'd check the overall rolling circumference difference as it could have more effect on the speedo than you realise

Morgan increased the tire circumference from 60 to 65 on the Roadster Sport in 2010. A further increase to 70 might just be too much. I would measure exactly beforehand whether 70 tires fit in the wheel arches and whether they can still be steered. Also, there are other good tyres in the appropriate size, such as Dunlop Sport Bluresponse.

Nick

I don't know if Avon do a 185/70 x 15 in the CR6-ZZ but that would seem to be a much closer match

205/65 x 15 : Diameter 25.5" : 792 revs per mile

185/70 x 15 : Diameter 25.2" : 801 revs per mile

This is barely 1% difference, and a much closer match than the 205/70 x 15 which is 3% difference (767 revs per mile)

Those Avons are remarkable tyres , but they do come at a price that will make your eyes water, (let us know if you start to suffer from acute financial shock! )

Useful tyre calculator here.