17's >>>>18's

[sparty116]

17\'s >>>>18\'s

Probably a real simple question, but I'm looking at getting a set of OEM 18" w/335/30/18 viper rims from a later gen II and was wondering if they are a direct replacement and will not require a speedo recalibration. I did aquick diameter calculation and the 18's come out to be slightly shorter by like ~6mm. Is this within the realm of error on a speedo and tire inflation etc....

 

[Bill B]

Re: 17\'s >>>>18\'s

I forget the exact MPH difference when I did it, but it is minor.

 

[ruckdr]

Re: 17\'s >>>>18\'s

Minor difference; use the following to calculate the actual tire diameter:

*********************************************
TIRE DIAMETER CALCULATION

Tire Diameter = (Width x Aspect Ratio) / 2540 x 2 + Wheel Diameter(inches)

Where: Width is the first number in size (i.e. 225)
Aspect Ratio is second number (i.e. 55)
2540 is the conversion factor to inches
Wheel Diameter in inches

Example: 225/55 x 16
225 x 55/2540 x 2 + 16 = 25.74 inches
225/45 x 17
225 x 45/2540 x 2 + 17 = 24.97 inches

345/30 x 19
345 x 30/2540 x 2 + 19 = 27.15 inches
335/30 x 18
335 x 30/2540 x 2 +18 = 25.91 inches
***************************************************

You will like the newer wheels. See some pictures in my Photo Gallery (click Photos under my Avatar) go to page 2.

Later,