Matt _Aero top_ Posted July 27, 2008 Share Posted July 27, 2008 Hi people , right theres a bloke at my work who's into his old cars and he's just restored a nice MGB Roadster and the problem he asked me was if i knew how to work out how much his speedo will be reading out as he's fitted tyres of the wrong size . He's fitted 175/65/14 When they should be 165/85/14 Anyone know how to work this out please . Link to comment Share on other sites More sharing options...
Faye Brother Posted July 27, 2008 Share Posted July 27, 2008 This link should help. http://www.miata.net/garage/tirecalc.html Link to comment Share on other sites More sharing options...
Matt _Aero top_ Posted July 27, 2008 Author Share Posted July 27, 2008 cheers buddie , it says when he's traveling at 60 he's actually doing 55 , Now does this 5 MPH difference apply through the range ? e.g . if he's traveling at 30 will he be doing 25 or does it half because its half the speed so actually doing 27.5 Mph Link to comment Share on other sites More sharing options...
Faye Brother Posted July 27, 2008 Share Posted July 27, 2008 The percentage difference figure is the one to look at as that's the constant. For example, as it's reading approximately 8% too fast an indicated speed of 30mph would equate to around 27/28mph actual road speed (if my maths are correct!) Link to comment Share on other sites More sharing options...
Matt _Aero top_ Posted July 27, 2008 Author Share Posted July 27, 2008 cheers mate much appreciated Link to comment Share on other sites More sharing options...
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