demuire Posted June 17, 2005 Report Posted June 17, 2005 I'm trying to work out my speedo calibration at the moment, and I'm not sure if I'm missing something, or if I haven't been to school for too long, or maybe I'm right and my original speedo is very off. Basically, I'm assuming my speedo is calibrated for a 4.11 diff. I'm now running a 4.77. I have a terratrip, so have speed readings from that, and basically I know that in comparison to my current speedo, it reads a bit like: real speed - speedo 60 - 80 70 - 90 85 - 110 100 - 130 110 - 140 Or something like that anyway. Now, ignoring that information, I tried to work it out from a mathematical point of view. So I'm guessing it would be: (speedo reading) = ((real speed) x 4.77) / 4.11 Is that right? I tried to match it up against the graph that my in-gear-calculator-excel-file-thing makes, and it seems right. But this formula brings up: real speed - speedo 60 - 69 70 - 81 85 - 99 100 - 116 110 - 128 These readings are quite different to what I'm getting at the moment, unless my current speedo (assuming I was running a "stock" 4.11 diff) is about 10km/h out? When I was running the stock 4.11 diff I did remember comparing it to the Terratrip and thinking it was pretty much on the money... And if my speedo readings are right, then the speedo would be calibrated for a 3.67 diff... Unless... The T50 gearboxes I've been using have had different speedo gears in them? Maybe that's it. Cause I've changed gearboxes since too... Quote
TRD ke70 Posted June 17, 2005 Report Posted June 17, 2005 you have to allow for the rolling Circumference of the tyre as well. i think!!!! Quote
ancullen Posted June 17, 2005 Report Posted June 17, 2005 That shouldn't affect the calculation if he's using the same wheels & tyres as when using the different diff. But if they're different, then yes, you are right. Quote
demuire Posted June 17, 2005 Author Report Posted June 17, 2005 Nothing else has changed apart from gearbox and diff. Same wheels and tyres. Quote
irokin Posted June 17, 2005 Report Posted June 17, 2005 Both the speedo gears you gave me are the same. 21x9 I think.... Quote
mikeys toy[RL] Posted June 18, 2005 Report Posted June 18, 2005 ok, i know the early k40 was 5x20 the early starlet k50 was 6x19=12mph off the later starlet k60 efi is 7x19=19mph off these only apply to daisy...... :P Quote
Super Jamie Posted June 18, 2005 Report Posted June 18, 2005 use a tire-to-speed calculator. but don't go off tyre size, measure the actual raduis or circumference of the tyre, i've found my "185/60"s are more like a 185/62 or /63, though no doubt that will change as the tyre wears more Quote
demuire Posted June 18, 2005 Author Report Posted June 18, 2005 I'm still using the same tyres as I was before :P Except now they're kinda balder than they were before... Quote
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