noddy Posted March 28, 2004 Share Posted March 28, 2004 I have just changed from 195/45 x 15 CR500's to 175/55 x 13 CR500's up front on my R400. does anyone know what values I should enter for the new wheels tyres R400 .......... I love it Link to comment Share on other sites More sharing options...
dave1968 Posted March 29, 2004 Share Posted March 29, 2004 noddy if u go to the avon website they have the rolling circumference on your tyre there i believe Dave Link to comment Share on other sites More sharing options...
Support Team Shaun_E Posted March 29, 2004 Support Team Share Posted March 29, 2004 Best to measure them - mark the tyre with chalk (or get the valve at the bottom) and roll forward one complete revolution - measure the distance travelled. The stack manual will tell you how to enter that on the system - can be downloaded from their website if you haven't got it. Website is here Yellow SL #32 Edited by - Shaun_E on 29 Mar 2004 21:30:05 Link to comment Share on other sites More sharing options...
Chris W Posted March 29, 2004 Share Posted March 29, 2004 Working it out mathematically, where the circumference is equal to.... [(tyre width x percentage tyre wall height x 2)/25.4 inches + (wheel diameter in inches)] x PI gives... The 195/45 x 15's have a circumference of 68.83 inches (174.82 cm) The 175/55 x 13 have a circumference of 64.65 inches (164.21 cm) ie: [(175 x 0.55 x 2)/25.4 +13] x PI Chris 2003 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Chelspeed Posted March 30, 2004 Share Posted March 30, 2004 Then go out find a speed scamera, drive past at exactly 90 on the speedo and those useful boys in blue will send you a little note saying exactly how fast you were actually going. Use the difference to adjust the number in the stack and you have a 100% accurate speedo. Useful or what? Link to comment Share on other sites More sharing options...
Ray Pearce Posted March 30, 2004 Share Posted March 30, 2004 If you want to check your speedo, you could pop round and borrow my GPS, apparently they are accurate to about 0.5mph I can even provide an operator if you give me notice. Ray Link to comment Share on other sites More sharing options...
Pelico Posted March 30, 2004 Share Posted March 30, 2004 Noddy, I will stick my GPS in my pocket for Brands on Monday if you want to test your calibration out there. (It also will tell you your max speed....not that you will be timing on a trackday of course ) Cheers, Peter My Caterham owner's site Link to comment Share on other sites More sharing options...
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