Quote:
Originally Posted by 1iTim
Hey just a thought guys, with all the upgrading wheel sizes that i've read going on, how are you calibrating the mech speedo on the heralds? I've searched the site but cannot find much on the triumph speedo fixes. Thanks for the engine number info too. (5 weeks to go until i collect my donor!!)
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Try using this tyre size calculator, up to about a 10% increase in rolling diameter will just take out the typical under read that manufacturers build in to make sure their cars don't break the speed limit -
http://www.kouki.co.uk/utilities/vis...ize-calculator
When changing away from standard diffs, matching the speedo and differential helps. I fitted a 3.27:1 GT6 diff, and then sourced a non overdrive GT6 speedo to match (there's a web site somewhere that deciphers the codes on the front of the Triumph speedos). That way I ended up with a very accurate speedo - when it said 100mph on the dyno that's what the dyno said the wheels were doing.
Phil J has taken a slightly different approach, his Spitfire diff and Vitesse or Herald speedo don't match, so he's used a sat nav reading as a known speed and marked the face of the speedo with a marker pen accordingly. Before that, with the speedo reading 55mph he was actually going about 80...
Anyway, good luck getting some means of measuring speed sorted, but it's not rocket science
