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Skunk Works 2SS · 06-25-2018, 02:02 PM

Hey guys, just wondering if I can get some assistance in changing the tire sizing for my car?

I'm currently running 305/30/20s on an 11 inch wheel for my rear setup which should be a 27.2 inch tire.... I went into HP Tuners Gear/Tire wizard after calculating the size and input 27.2 in tire size and stock gear ratio. I left the speedo calibration and scale trans parameters boxes checked with a 1.0 multiplier, saved the changes and wrote the calibration but my speedo was still 2-3mph off. So I went back in and upped the tire size to 28.2, saved, wrote, same issue. Still 2-3mph off what my GPS speed is saying on both my phone and radar detector.

I'm just wondering if there's something I missing here as to why the tire size change isn't bringing my speedo reading into line with my GPS speed? Do I need to perform a write entire??

Any help on this would be much appreciated and I thank you in advance!

06-25-2018, 02:02 PM	#1
Skunk Works 2SS Drives: Mosaic Black 2016 2SS Join Date: Feb 2018 Location: Orlando Posts: 9	2016 2SS Tire Size Changes Hey guys, just wondering if I can get some assistance in changing the tire sizing for my car? I'm currently running 305/30/20s on an 11 inch wheel for my rear setup which should be a 27.2 inch tire.... I went into HP Tuners Gear/Tire wizard after calculating the size and input 27.2 in tire size and stock gear ratio. I left the speedo calibration and scale trans parameters boxes checked with a 1.0 multiplier, saved the changes and wrote the calibration but my speedo was still 2-3mph off. So I went back in and upped the tire size to 28.2, saved, wrote, same issue. Still 2-3mph off what my GPS speed is saying on both my phone and radar detector. I'm just wondering if there's something I missing here as to why the tire size change isn't bringing my speedo reading into line with my GPS speed? Do I need to perform a write entire?? Any help on this would be much appreciated and I thank you in advance!