[shotgun]

Originally Posted by pearsonrb

I have a Gryphon CS in a 2010 F150, 4.6 3V 6 speed auto Supercab w 3.73 limted slip rear end. I'm running on Level 2 - Tow.

1. I replaced the stock 275 65 18 tires with 275 70 18's and keyed in the new size on the programmer. When my truck speedometer reads 68 mph, the Gryphon displays 65. All the tire calculators I've use on the internet say that it should be the other way around, that when the CS says 65 I should see 62-63 on the speedo. Which is right?

The CS does not account for squish, so both are probably 'wrong'. Take the unloaded dimension, multiply by .97, use that as a starting point, and adjust until the CS matches your GPS (or until your odometer matches Google maps or another know distance > 10 miles). The speedometer will likely read 2-3 MPH HIGH even when the CS matches the GPS perfectly. This is due to mechanical variations in the speedometer (and may also be Ford's deliberate method to keep you from getting a ticket).

2. I was looking at my invoice, and it describes my programmer as having Economy, Tow and C 87 P tunes. But the unit actually shows Trans Only, Towing and Extreme as the tunes. Why is there a difference? (No Economy tune)

Thanks in advance for any help.

See bold. BTW, there are lots of threads on adjusting the tire size in the CS and CTS.