Hi, i have a superchip 1714 (old one) for my truck 2004 Fx4 5.4.

My truck info: 04 FX4, 295x70/17 Terra grappler SIDO, AFone air system.

I set 87 perfomeance, 3.73, set height tire 33.00.

My truck by Garmin GPS show read at 65 mph and my gauge MPH shows 70-71 MPH.

Its approx 5-6 MPH off. I dont like it.

I knnow i cant get it PERFECT but...

How to fix this ? to increase in height tire or decrease to get it close to correct MPH ?

thanks!
YOMAN!

 

Make your tire height shorter. A 295/70/17 comes out to 33.26" tall. You need to account for some squish of the tire though, usually about 5%. That would come out to a height of 31.6". Going from 33.0 down to 31.6 will lower your speedo readout by about 5% and make 70 mph read about 66.5 mph.

If you really want your GPS readout exactly, you'll need to use a squish factor of about 7%. That would put your tire height at 31.0.

 

thanks for tip i ll try that today!

thanks!
YOMAN!

 

I got it! Its almost dead right on mph speed read!

I set tire height to 31.00

Thank again..

 

Glad it worked out for ya.