Guest trickstermusic Posted July 21, 2006 Share Posted July 21, 2006 Hi guys, new to this supra owning. Ive had my j-spec for a couple of weeks now but the speedo seems to be out. Its got an mph dial, but seems to be showing a higher speed than im actually doing. Ive checked it against a tomtom and a garmin sat nav, one says its 7mph out, the other 8mph. So if the clock says im doing 50mph, im actually doing 43mph. (helpfull for not getting nicked) Are the sat nav readouts reliable? Ive also checked it against a friends supra and its 5mph out to that, so whats right?. The wheels/tyres are 17's with 225/45 tyres. Ive checked a calculator thing against original size and it says it makes 0.36mph different to readout.Can someone help me out here, is it still measuring kph or something else. Anyone know how i can solve this or someone who can put it right somehow?. Rolling road? Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted July 21, 2006 Share Posted July 21, 2006 GPS will be as near as your gonna get. My car reads just over 10% fast, so I think it's normal. Quote Link to comment Share on other sites More sharing options...
MrRalphMan Posted July 21, 2006 Share Posted July 21, 2006 Oh and welcome... We need pics/info about your car.. Quote Link to comment Share on other sites More sharing options...
supRo Posted July 21, 2006 Share Posted July 21, 2006 Sounds normal - stock speedo over reads by about 10% - can be adjusted if you use the Thor Speedo convertor Quote Link to comment Share on other sites More sharing options...
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