Speedo Calibration Question
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Tuned
Joined: Oct 2003
Posts: 491
Likes: 0
From: Tampa, FL
Speedo Calibration Question
Guys, I haven't been keeping up with new toys for our trucks so I need some updated people to help me out.
I have a '04 6.0 with an 8" lift and 37" tires. I have to deal with an inaccurate speedo and odo, and have done my best to roughly calculate the amount of error in these two gauges. I have a long commute to work that I had clocked before raising the truck, and it came up 32 miles on the odo. Now it reads right about 27 miles, so I see a 16% variance. Is that variance the same regardless of speed, and can I simply add the 16% back into my odometer readings to see what I am really getting out of a tank of fuel?
I also have a Predator on the 100hp program. Driving back and forth all week to work on this mostly highway route, my low fuel light is coming on anywhere between 290 and 320 clocked miles. This varies with how I have been driving the truck. For you other guys running bigger tires, are you seeing about the same thing? Like everyone else, I want to maximize mileage and am wondering if anyone ever came out with anything to recalibrate our speedo. I know the dealer is supposed to be able to correct for up to 35" tires, but I've got the 37"s and would rather get it exact if it is possible.
Thanks....
I have a '04 6.0 with an 8" lift and 37" tires. I have to deal with an inaccurate speedo and odo, and have done my best to roughly calculate the amount of error in these two gauges. I have a long commute to work that I had clocked before raising the truck, and it came up 32 miles on the odo. Now it reads right about 27 miles, so I see a 16% variance. Is that variance the same regardless of speed, and can I simply add the 16% back into my odometer readings to see what I am really getting out of a tank of fuel?
I also have a Predator on the 100hp program. Driving back and forth all week to work on this mostly highway route, my low fuel light is coming on anywhere between 290 and 320 clocked miles. This varies with how I have been driving the truck. For you other guys running bigger tires, are you seeing about the same thing? Like everyone else, I want to maximize mileage and am wondering if anyone ever came out with anything to recalibrate our speedo. I know the dealer is supposed to be able to correct for up to 35" tires, but I've got the 37"s and would rather get it exact if it is possible.
Thanks....
Senior User
Joined: Nov 2005
Posts: 203
Likes: 0
From: Edmonton,AB
I have a truspeed from Superlift. If I remember right it corrects for up to 44" tires.
www.superlift.com/accessories/truspeed.asp
www.superlift.com/accessories/truspeed.asp
Senior User
Joined: Oct 2006
Posts: 122
Likes: 0
Originally Posted by Dsl_Burner
I have a truspeed from Superlift. If I remember right it corrects for up to 44" tires.
www.superlift.com/accessories/truspeed.asp
www.superlift.com/accessories/truspeed.asp
Senior User
Joined: Apr 2005
Posts: 224
Likes: 0
From: New Baltimore, Michigan
I also have Surperlift TruSpeed and set it from a GPS unit while driving, matched speedo to GPS reading.
Greg
__________________________________________________ _______________
2003 Ford F350 6.0 PSD C/C S/B 4x4 Lariat FX4
120,000 Miles
Warn Manual Locking Hubs,ARE MPulse Cap
BFG All-Terrain AT 285/75R16, Superlift TruSpeed
Stock Air Intake,Zoodad Mod., 4" MBRP Turbo Back (No CAT) "JET SOUND"
SCT XCal2 and Tunes from Matt @ Spartan
Greg
__________________________________________________ _______________
2003 Ford F350 6.0 PSD C/C S/B 4x4 Lariat FX4
120,000 Miles
Warn Manual Locking Hubs,ARE MPulse Cap
BFG All-Terrain AT 285/75R16, Superlift TruSpeed
Stock Air Intake,Zoodad Mod., 4" MBRP Turbo Back (No CAT) "JET SOUND"
SCT XCal2 and Tunes from Matt @ Spartan
Senior User
Joined: Nov 2005
Posts: 203
Likes: 0
From: Edmonton,AB
I set mine by the gps as well but I'm sure the truespeed comes with charts telling how to adjust it for tire size and axle ratio. If that doesnt work you can use the mile marker signs on the side of the highway.
Posting Guru
Joined: Jul 2007
Posts: 1,233
Likes: 0
From: Las Vega$
yeah i'm seeing the same number of miles per tank on my odometer as you and mine is lifted,so that's about right.
i know that with 35" tires if you divide the miles on odometer by 0.9 that will tell you the actual number of miles driven. i used mile markers for test this theory and it works.
i know that with 35" tires if you divide the miles on odometer by 0.9 that will tell you the actual number of miles driven. i used mile markers for test this theory and it works.
Senior User
Joined: Oct 2006
Posts: 122
Likes: 0
Thanks guys....
I have 37" tires and 4:56 gearing.
I think it's in the ball park as is.... just want to validate the degree of error of nothing else.
I have 37" tires and 4:56 gearing.
I think it's in the ball park as is.... just want to validate the degree of error of nothing else.
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Senior User
Joined: Feb 2006
Posts: 396
Likes: 2
I think the GPS is the best way to correct the speedometer but the way on the 99-08 superduty trucks the gear ratio will not change the speed signal.
I came up with my own in line correction box, I just cant talk about it. it is like the truspeed but does provide a user interface, which NONE of the others do
Good luck with getting that speedometer dead on again
kenny
I came up with my own in line correction box, I just cant talk about it. it is like the truspeed but does provide a user interface, which NONE of the others do
Good luck with getting that speedometer dead on again
kenny
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