How do I adjust speedometer for larger tires?

[bassman]

When I bought my 99 I had 285/75R16 tires put on. Clocked with a GPS, my speed is about 10% lower than it should be. Can I adjust my speedometer or do I have to have the dealer do it?

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1999 2500, Quad Cab, 4x4, auto, 3. 54 gears, long bed, and all the goodies. White and driftwood.

 

[MikeR]

The dealer can only program the speedo for the factory gear ratios available from Dodge: 3. 21,3. 54,3. 55,3. 81,4. 10.
If you click on the "links" section,you see a ventor called Rickson Wheels,maybe even Abbot. They sell an electronic device called the Abbot Speedo Corrector.

-Mike

 

[Rambling]

Bassman,

An eletronic unit can be added to give you correct speed and odometer readings. Check out http://www.abbott-tach.com/era.htm .

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<font color=#990000>~<font color=#990000> '99 2500 SLT <font color=#990000> ~ QC ~ 4X4 ~ LB ~ Auto ~ 4:10 LSD ~
<font color=#000000>*<font color=#990000> BD E-brake<font color=#000000> *<font color=#990000> BD Autolock<font color=#00000> *<font color=#990000> Gear Vendor OD<font color=#000000> *<font color=#990000> Jordan Research 2020 T-brake <font color=#000000> *<font color=#990000> Bullhide spray-in Line <font color=#000000>*
<font color=#000000>*<font color=#990000> 2k Komfort 5'er - 9,700 lbs <font color=#000000> *
<font size=-2>... Lookin' for the 'RE' to go in front of my 'TIRED' so's I got more time to Play!... <font size=-1>

[This message has been edited by Rattlin (edited 02-25-2001). ]

 

[MTullus]

Your dealer can adjust the differential for larger tires by changing the number of time the tire rotates in a mile. My dealer has tables that tells him that info. He hooks up the dianogistic computer and makes the change. My buddy had this done for the same size tires you are talking about and it took all of 5 min. Good luck