I was able to find a suitably marked speedometer of the same dimensions as my original in a local scrap yard. 176 yards (1/10th of a mile) means the required figure is the resulting turns x 10. It was easy then to calculate my requirement. With a piece of card on the detached cable as a flag and on the new wheels and tyres carefully inflated I rolled the car over the known distance and counted the cable turns. I measured out the longest straight and level distance I could as a known fraction of a mile and marked out the start and finish. The final numbers are the turns per mile. I had such a problem when I changed the wheel size on my Gentry. Or a third possibility is to read your speed from a sat nav. If you have a rev counter and know your gear ratios and rolling radius you can do the same thing at a known speed. Then turn your speedo pointer to the same speed that it was showing, restrain the aluminium disc and twist the pointer to the "Your Speed" position. You can do minor re-calibrations by driving through these "Your Speed" signs and noting your current speedo reading.
If so has anyone got a database of 100cm wide (4 inches) speedos that have a relevent ref no nearer to my ideal?ĭinalpin Berlinette (Alpine Renault A110) One web site I have found suggests that the 1280 should be increased by 20% equating to 1536 - do the experts here agree? My present model has the following on it SN 6144 2685 1280 and I assume the final 4 figures are the revs per mile. I know I can get the instrument recailbrated by the likes of Speedy Cables etc but I thought I would first see if there is a generic speedo which would be suitable. However it would be nice to get something more accurate. My present speedo reads some 20% fast - I have got round this by sticking a piece of paper over the printed figures showing the 'true' speeds.
Posted: Fri 1:03 pm Post subject: Understanding Smith's Speedo Reference Nos
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