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Checking Speedo

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Old Oct 11, 2004 | 08:23 PM
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Red face Checking Speedo

Has anyone used their Predator to check the speedometer accuaracy?? I have used mine and it shows to be reading about 3 mph fast. I am wondering how accurate the readout on the Predator is??? I am still running the stock 235's.
 
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Old Oct 13, 2004 | 08:28 AM
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Any help here guys??
 
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Old Oct 13, 2004 | 08:34 AM
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Maybe the truck speedo is off.
 
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Old Oct 13, 2004 | 08:36 AM
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Daryl Hunter
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My truck's speedo reads 2.5 to 3 MPH faster than actual speed at 70 MPH.

This seems to be pretty common.
 
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Old Oct 13, 2004 | 08:47 AM
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I have checked mine with a GPS unit and my speedo seems to be 2-3 mph slower then actual speed.
 
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Old Oct 13, 2004 | 09:17 AM
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Daryl Hunter
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Originally Posted by jimcald
I have checked mine with a GPS unit and my speedo seems to be 2-3 mph slower then actual speed.
Mine checked with GPS too. Tires are stock 265s

Do you by chance have larger tires, or are yours stock too?

I'm not sure what the spec is for speedo accuracy on these trucks but +/- 3 MPH at 70 is less than 5%

Which is still pretty bad IMHO these days.

Given the high likelihood that someone is going to throw on larger or different profile tires, how hard would it have been to include a user programmable feature that lets you self calibrate your speedo/odo for your conditions. My $20 bicycle computer does this for goodness sake.

If they were worried about users fudging mileage by putting in a calibration designed to report much lower than actual mileage, they could still save the uncorrected mileage and state that warranty and other official things would use that for a basis. Given that the truck's computer driven it would add no appreciable cost to the vehicle in that it would be less than a man days worth of code and test time.
 
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Old Oct 13, 2004 | 09:20 AM
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Well just yesterday I put a set of Bridgestone Dueller A/T 285's on the truck. Prior to that I was running the stock 235's. I have not had a chance to check it with the Predator and the new tires yet. It is amazing how these bigger tires make it look soooooomuch better. I am also hoping that it will help with the highway milage since I have a few long trips planned this winter.
 
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Old Oct 13, 2004 | 09:28 AM
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I checked mine with the Predator and my GPS. My speedo reads about 2 mph fast over 35. I have the stock Pirelli Scorpion tires 265s.
 
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Old Oct 13, 2004 | 10:37 AM
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Does the Predator read the same as your GPS ????????????????????????
 
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Old Oct 13, 2004 | 02:20 PM
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Originally Posted by Motown Fire
Does the Predator read the same as your GPS ????????????????????????
Yes! The PCM feeds the speed info to the Predator.

According to the Workshop Manual, the instrument cluster is hardwired to the four wheel anti-lock brake system (4WABS) module. The instrument cluster micro-processor monitors the vehicle speed sensor (VSS) data from the 4WABS module and commands the speedometer with a corresponding movement of the pointer. The vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4WABS module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems that require a vehicle speed signal input.

I would imagine if they put in a digital display for the speed, it would be more accurate than the analog dial.
 
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Old Oct 13, 2004 | 08:45 PM
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I had my computer recalculated (under warranty) or maybe just because the service manager was beng nice????

New, my Excursion showed 70mph on the dial, but GPS showed 67mph.

They adjusted the computer to think I had larger tires and all is well (I think it was set to think they were larger).
 
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Old Oct 13, 2004 | 09:13 PM
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They won't recalibrate it for 2.5 miles off. If it is 3 or more, they will I believe.
 
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