Hi all, is there anything can be done with the standard speedo when running 18 inch wheels? .....ie a different drive ratio or altered internal gearing in the speedo itself. Ive been running it like that for nearly 20 years but think Id like it sorted now if posible!
When I converted to 18inch rims, I was told that the difference was negligible. Unless you are using low profile tyres, then the rolling circumference of the 18 and 19 inch tyres is very similar. Apparently !
Thanks for the reply Hans, my speedo is very inaccurate, maybe its the speedo then rather than the 18inch tyres then?
A good speedo restorer can re-calibrate it for you.
Could also be that the speedo drive is worn?
If you spec the 18 inch tyre correctly, the rolling circumference should be as near as dammit to the original.
The most popular tyre out there for Norton owners is the Avon Roadrider 100/90
Published Diameter is 671mm
The tyre circumference on this is 2108.01mm
Now look at an alternative 18 inch the Avon Roadrider 120/90 18
Published Diameter is 675mm
The tyre circumference is therefore 2120.58mm
The percentage difference between these is 0.59% which is superb.
Thanks for the info, can anyone recommend a good speedo restorer?
He,s actually in Ash near Aldershot. He refurbed my Veglia speedo before Xmas. Very good quality and service.