speedo off
Thread Starter
|
More Turbo
Joined: Sep 2002
Posts: 535
Likes: 10
From: Evans, West Virginia
speedo off
well i just put on 315/75/16's on my truck and need to know if the ford garage can change my speedo to make it right like change the codes? or what are the codes if i can do it myself ?
Logistics Pro
Joined: Feb 2000
Posts: 3,955
Likes: 50
From: Mesa
Yes it can be done. You need to find the revolutions per mile of the new tire. Ford can go as low as 601. The dealer can change this number in the computer. Another option is the Superlift Tru-Speed device.
Thread Starter
|
More Turbo
Joined: Sep 2002
Posts: 535
Likes: 10
From: Evans, West Virginia
Originally Posted by V10man
Yes it can be done. You need to find the revolutions per mile of the new tire. Ford can go as low as 601. The dealer can change this number in the computer. Another option is the Superlift Tru-Speed device.
Last edited by wvabeer; Jul 16, 2004 at 11:39 PM.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Look up your tires at the manufacturer's website or check here; http://www.bridgestone-usa.com/parent/home.asp to find the RPM.
More Turbo
Joined: Feb 2004
Posts: 688
Likes: 3
From: Fairbanks, AK
Use a string to measure the actual circumference of the tire (inflated to recommended air pressure). Divide the distance of a mile by the circumference of the tire to find revolutions per mile. This should give you the most accurate number to calibrate your speedo.
BTW, 1 mile = 5280 feet = 63360 inches = 160934.4 centimeters
For example: a 315/75/16 tire SHOULD (not does) have a 108.71 inch circumference. 63360 / 108.71 = 582.84 revolutions per mile. These numbers here are theoretical values and may not represent your actual tire, but should be pretty close. If what V10man says is correct (Ford can go as low as 601) your speedo will still be incorrect. The error will probably only be about 3% if the 601 value is entered. This means at 55 MPH, your speedo may only read 53.3 MPH. Your current error is closer to 9%, at 55 MPH your speedo now shows 50.3 MPH.
BTW, 1 mile = 5280 feet = 63360 inches = 160934.4 centimeters
For example: a 315/75/16 tire SHOULD (not does) have a 108.71 inch circumference. 63360 / 108.71 = 582.84 revolutions per mile. These numbers here are theoretical values and may not represent your actual tire, but should be pretty close. If what V10man says is correct (Ford can go as low as 601) your speedo will still be incorrect. The error will probably only be about 3% if the 601 value is entered. This means at 55 MPH, your speedo may only read 53.3 MPH. Your current error is closer to 9%, at 55 MPH your speedo now shows 50.3 MPH.
