F150 Speedo Correction
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Joined: Mar 2000
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From: The Left Coast
F150 Speedo Correction
I have a 95 F150, and will soon be adding 285/70X15 Goodrichs in place of the stock 235/75X15 Goodyears. What conversion constant do I need to use to calibrate the electronic speedometer? Also, if I change rear gears will I need to recalibrate for the gear change? Thanks, John
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Joined: Dec 1999
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F150 Speedo Correction
John,
The list I have doesn't go that high, so you need to calculate the circumfrence of the old tire, and of the new tire, and figure out the percentage of increase. The tire constant is a number between 500 and 1100 (around 980 stock) and needs to be decreased by the same percentage. You will not need to make any changes to compensate for a gear swap, because the sensor is on the axle, not the trans, and it will not be affected.
Jon
The list I have doesn't go that high, so you need to calculate the circumfrence of the old tire, and of the new tire, and figure out the percentage of increase. The tire constant is a number between 500 and 1100 (around 980 stock) and needs to be decreased by the same percentage. You will not need to make any changes to compensate for a gear swap, because the sensor is on the axle, not the trans, and it will not be affected.
Jon
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john jamieson
1961 - 1966 F-100 & Larger F-Series Trucks
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Nov 28, 2015 09:39 PM
