2nd Gen Non-Engine/Transmission Calibrating Speedo for larger tires?

[RoosterXP]

Stock on my truck was 245/75R16, I put 265/75/r16s on it now and my speedo is off by about 4 mph (i think). is there any way i can just get the speedo recalibrated without having to buy a $500+ programer? all i want is it calibrated.

 

[kenny61]

Rickson Truck Wheels and Accessories

 

[WestTN]

If you know anyone with a Smarty, they can adjust it for you.

 

[Road Dog]

Any dealer shop can do it but what they charge is all over the place. I paid $40 many years ago.

Your actual speed is 7% higher than your speedo (60mph = 64. 5 actual).

 

[fest3er]

As Kenny said, call Rickson. They supply the TruSpeed correction device, as do many other automotive parts vendors. After my original Abbot box failed, I bought a TruSpeed. It exactly corrects the speedo/odo. I usually set mine to read 1. 5% high for new tires. When the tires are worn down, it'll be 1. 5% low.

I set it by driving 100 miles by the highway mile markers. Then, I divide the elapsed distance on the odo by 100, which yields the % the odo is off. I then turn the adjusting screw on the TruSpeed to compensate exactly that much. Then I drive another 100 miles and verify that it's set correctly. Finally, if the tires are new, or nearly so, I'll tweak the TruSpeed so that the odo reads 98. 5% (reads 98. 5 miles travelled for 100 mile markers passed); then as the tires wear, the error will climb to 1. 5% high (odo reads 101. 5 miles travelled for 100 mile markers passed). On average over time, the recorded mileage will be dead on. Every time I pass one of those roadside radar units, my speedo exactly matches the displayed MPH. With 257K miles on the truck, I can honestly say that that reading is very nearly true; it might be 3000 miles off (partly from when the CAB was dead for 1200 miles or so and I had no mileage recorded at all).

One advantage of using the TruSpeed is that your MPG calculations will generally be very accurate. Say you've installed tires that are 8% larger than stock. This means your indicated elapsed mileage will be 8% low. By way of example, instead of knowing you burned 28 gallons of fuel in 540 miles (19. 3 MPG), you'll think you burned 28 gallons of fuel in 497 miles (17. 7 MPG). Another advantage is that it has two separate settings, so you can easily switch between two different sizes of tires (winter and summer, for example).

The main advantage of the TruSpeed over the Abbott is that the TruSpeed corrects the signal between the CAB and the PCM. The Abbott can only correct the signal between the CAB and the rear-wheel sensor, and we know that circuit is flaky enough as it is.

 

[DIESELWRKS]

speedo

my experience with my larger tires I already had a smarty but the smarty is not dead nuts on. my tires are just under 35 inches I set my smarty to 34. 00 and had to use my gps and adjust the smarty untill I was close to being accurate. so according to my gps I have to have my smarty dialed at 34. 00 for my 35" tires. and if you have someone use the smarty for you then its vin locked on your truck and then the smarty owner could not use his smarty. my gps was about 120. 00 bucks and it seems accurate this way havent gotten a ticket yet. I believe the dealership can reflash based on revolutions not inches and a new tire is different from a older tire. the tire maker should have the revs listed.





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