OK, my truck came with 265/70/16 from the factory. Tire height (actual measured on the truck) is about 29.75.

When looking at what it is set to from the factory with my Cortex, it is 29!!

My guess is that 29 is the adjusted installed height for 245/70/16 tires (unmounted height of 29.5).

Just curious, for those who have a superchips or other reader, what is your factory default value?

 

stock speedo's are always 1-2 mph fast, to keep your speed under what the speeo says, for what exact reason IDK, with my 33's, i set the speedo dead on with gps and had to set the SC3865 at 31.75, to get the right speed, even used a second gps thinking something was wrong, with the same results...

 

Mine came stock with the 16s also, when I bought it used it had 17s on it, with the stock 17 size tire, (not sure if the offset is correct, as the front end is warbly)

The speedo doesn't match the GPS, its way short. GPS says 80, speedo says 75 or so. Does this mean I can recalibrate if I get the SC

 

I have my SC3865 set to 28.75 with my 265/70/16 BFGs. That makes my speedo read about .25-.5mph slower than Im actually going. It I went to 29, then the speedo was .25-.5mph fast.

And yes, SC will let you change tire size, gear ratio, and even shift points.

 

rengath, What was your stock setting? What size tires came on your truck? (check door sticker).

I like the shift points better when it is set at 29 vs 29.5, I need to borrrow a GPS to figure out which works best.

 

I had 245/70/16s and the stock size on the SC was set at 28in

 

So it seems Dodge sets them off by .5 to .75 for some reason....!

Factory settings:
28 = 245/70/16
29 = 265/70/16

Anyone with 265/65/17 wanna pipe in here? I know there is almost no difference in actual height between 265/70/16 and 265/65/17, so I am curious

 

My tires are measuring about 29 inches or so .... not the 31 or so that the measurements convert in to.

 

I'll check mine when I get my truck back later this week.