AstinaGT Forums - View Single Post - ABOUT: Getting new rims? All the info you need here

Rupewrecht · 10-02-2004, 04:51 PM

The series is only part of the rolling diameter. it combined with the width determines the rolling diameter. series is how tall the sidewall is in percentage compaired to the width.

Tyres are labeled www/hh/rr lls

Where www is the overall width of the tyre in mm

hh is the height of the side wall from the rim to the outermost point and is expressed as a ratio of the width (see twilightproteges post)

rr the total diamater of the rim in inches (some BMW use mm but they are rare and obvious), multipy by 25.4 to convert to mm

ll is the load rating, the higher the number the higher the load rating

s is the speed rating, a letter, the closer to 'Z' the higher the speed rating

So the diamater of the standard BA 1.8 185/65/14 is 65% of 185 = 120.25mm top and bottom of the rim = 240.5mm plus the 14" rim (355.6mm).
Total 596.1mm
BA alloy option 195/55/15 is 55% of 195 = 107.25mm top and bottom of the rim = 214.5mm plus the 15" rim (381mm).
Total 595.5mm

Use this to calculate your original diamater then you can make variations to plan

http://www.miata.net/garage/tirecalc.html

and calculate the offset you need here

http://www.1010tires.com/WheelOffsetCalculator.asp

Or this one which does both:

http://www.rims-n-tires.com/rt_specs.jsp

10-02-2004, 04:51 PM	#1
Rupewrecht Administrator Join Date: Mar 2002 Location: melb.vic.au Car: AZ-1, Astina Hardtop Turbo, BJ Protege, Beetle Posts: 16,525	ABOUT: Getting new rims? All the info you need here The series is only part of the rolling diameter. it combined with the width determines the rolling diameter. series is how tall the sidewall is in percentage compaired to the width. Tyres are labeled www/hh/rr lls Where www is the overall width of the tyre in mm hh is the height of the side wall from the rim to the outermost point and is expressed as a ratio of the width (see twilightproteges post) rr the total diamater of the rim in inches (some BMW use mm but they are rare and obvious), multipy by 25.4 to convert to mm ll is the load rating, the higher the number the higher the load rating s is the speed rating, a letter, the closer to 'Z' the higher the speed rating So the diamater of the standard BA 1.8 185/65/14 is 65% of 185 = 120.25mm top and bottom of the rim = 240.5mm plus the 14" rim (355.6mm). Total 596.1mm BA alloy option 195/55/15 is 55% of 195 = 107.25mm top and bottom of the rim = 214.5mm plus the 15" rim (381mm). Total 595.5mm Use this to calculate your original diamater then you can make variations to plan http://www.miata.net/garage/tirecalc.html and calculate the offset you need here http://www.1010tires.com/WheelOffsetCalculator.asp Or this one which does both: http://www.rims-n-tires.com/rt_specs.jsp __________________ jdmparts.rupewrecht.com Sourcing your not-quite-overnight parts from Japan WRECHT--\|--SLOWTEGE--\|--BEETLE--\|--SUBSTITUTE--\|--AZ-1 Last edited by Rupewrecht; 29-10-2007 at 02:37 PM.