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!
Tyre size.
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A good speedo restorer can…
A good speedo restorer can re-calibrate it for you.
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If you spec the 18 inch tyre…
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.
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There is only one...
There is only one...
...at least that I would recommend.
http://www.speedorepairs.co.uk
Ashley Pople based in Andover
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I’d also recommend…
I’d also recommend Chronometrics Instrument Services in Nottingham. Run by a very nice guy named Russell.
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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 !