How do you correct-speedometer with larger tires on??

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I've just put on some BFG's 35's and I know it made my speedometer show I'm going slower than I really am by about 10%. . Does anyone know how to re-calibrate the speedometer to the size tire you're running??? Don't want to get too many tickets.

 

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I re-calibrated mine by mounting a GPS on the dash. Works great and gives more acurate milage too. (unless you're in the woods. )

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Gene Stanton
'97' 3500 Laramie SLT, Ext Cab, LB, 5 SPEED, 4. 10 Limited Slip, 4X4. No muffler. (it's a start)

 

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I posted this link, maybe it'll help ? http://pw1.netcom.com/~sgalaba/tiresize.htm

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98 Quad cab 4X4 2500 12 valve,5 speed,3. 54 rears, 8' bed. Boost and egt gauges but basicly stock. 55,000 Mi as of 8/21/00.
NRA life member. High power/IDPA.

 

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Heber:
What year is your truck?
If it's an earlier model, all you have to do is change the plastic gear at the end of the speedometer cable to one with fewer teeth. A ten minute job at best.
I understand the speedometers in the newer models are electronically driven so this may not help.

 

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as you can see from my signature I have a newer truck!!!Can the dealer change the reading electronically or is there some aftermarket gagit that will do the same??? Thanks for the imput. .

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2001 HO, 6-sp, Quad Cab 4x4, 3. 54 Anti-Spin axel, Camper Special Group, 2"lift, 4" exhaust w/5" Monster Tip, BFG 35's, K&N Airfilter, pod gauges, VA-CPU, PS boost module & elbow, Line X box, with everything but leather!!!!( and maybe a warranty)!

 

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Originally posted by HeberRam:
as you can see from my signature I have a newer truck!!!Can the dealer change the reading electronically or is there some aftermarket gagit that will do the same??? Thanks for the imput.

The dealer is *supposed* to be able to do this. However, DC have not gotten this to work in the past for other-than-standard size tires. The service manager at my dealer recently told me they can now do this. I haven't yet verified it.

There is a box you can use to correct the speedo. It is the Abbott Enterprises 'Electronic Ratio Adapter' or ERA. But there have been problems with the Dodge application of it. Check the other threads concerning tires in the non-engine/drivetrain and products' accessories fora (I have one or two huge posts concerning the ERA and its interactions with our Dodge trucks). Sorry, I dont have the URL's handy! For the moment, you have to decide if you want to deal with the potential problems, or just manually compute the differences.

The easiest place to get an ERA box is from Rickson; the number is on their website (www.ricksontruck.com).

Fest3er

 

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Thanks Fest3er... I'll check it out.

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2001 HO, 6-sp, Quad Cab 4x4, 3. 54 Anti-Spin axel, Camper Special Group, 2"lift, 4" exhaust w/5" Monster Tip, BFG's tires 312x75x16's, K&N Airfilter, pod gauges, VA-CPU, PS boost module & elbow, Line X box, dimond plated tool box & rails with everything but leather!!!!( and maybe a warranty)!

 

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If you find the Abbott to be too expensive, SPA technique has a speedometer that is, according to them, easy to install. This way your milage stays a little behind for an extended warranty! #ad


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1998 CUMMINS Dodge Ram
that has absolutely NO modifications!