Speedometer reading/calibration
Safety Car
Joined: Jul 2005
Posts: 3,572
Likes: 9
From: Jackson Tn
St. Jude Donor '06-'07-'08-'09
good question. I just looked in my HPTuners and it has a place to change this. It also has a place to put in the rear axle ratio. Mine is set to stock (26") so I'm guessing it is the rear tires. 
Melting Slicks
Joined: Jul 2012
Posts: 2,507
Likes: 9
NO, i think it drive shaft based BUT, 1 roatation of the driveshaft will move different diameter tires different lenghts-that's why the computer has to KNOW what tire diameter you have so it can do the calculation to display.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
The speed sensor reads from a toothed wheel beside the ring gear. The tire diameter is the only thing that has to be compensated/corrected/calculated to make the speedo read correctly.
Thread Starter
Instructor
Joined: Dec 2011
Posts: 221
Likes: 0
From: Auburn Alabama
Which tire diameter? Rears only or both?
Last edited by Damillio; Jan 24, 2013 at 07:09 PM.
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