scooby_doo_do Posted May 10, 2004 Share Posted May 10, 2004 I normally have 285 30 18's on the back of my car.. Can someone explain what the sizes are ? And can i fit 285 40 18's ?? ect etc/ Quote Link to comment Share on other sites More sharing options...
AJI Posted May 10, 2004 Share Posted May 10, 2004 285 = width of tyre (mm) 35 = profile height (height/width) - ratio 18 = inner tyre diameter (should be same as rims) Quote Link to comment Share on other sites More sharing options...
scooby_doo_do Posted May 10, 2004 Author Share Posted May 10, 2004 So i can go for whatever hieight then ? Quote Link to comment Share on other sites More sharing options...
Rob Posted May 10, 2004 Share Posted May 10, 2004 If you increase the tyre wall height ratio while maintaining the same width, you will increase the diameter and circumference of the tyre. This will affect gearing and speedo reading. Why do you want to do this? Quote Link to comment Share on other sites More sharing options...
scooby_doo_do Posted May 10, 2004 Author Share Posted May 10, 2004 Just that i've been offered some cheap 285 40 18's..... But i've got 285 30 18's on the rear's at the moment... didn't know if they'd fit..... Quote Link to comment Share on other sites More sharing options...
Seb Posted May 10, 2004 Share Posted May 10, 2004 http://www.miata.net/garage/tirecalc.html Best site in the world for this kind of stuff. Stick in the oem wheel/trye combo, and what you want now, and it will show you how far out you'll be on speedo reading etc... Seb Quote Link to comment Share on other sites More sharing options...
AJI Posted May 10, 2004 Share Posted May 10, 2004 I'd stick to same rolling radius because other wise your ride height will change with respect to the front. It would upset the car dynamics in corners. Quote Link to comment Share on other sites More sharing options...
scooby_doo_do Posted May 10, 2004 Author Share Posted May 10, 2004 Cool...Thanks Chaps.. Quote Link to comment Share on other sites More sharing options...
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