LLY: speedo off

[LEO'S-RIG]

New to sight, I have a 2004 D\D LLY model, Just bought the truck it has a lift kit and 285/75/16". The speedometer was off by 3 mph, Had the speedometer calibrated at a speedometer shop. I watched him punch in the tire size, the speedometer is still 3 mph slower than it should be. tested it aginst my Garmin. any ideas on what else it could be?

 

[x MadMAX DIESEL]

Maybe the Garmin is off? That's what I'm guessing if its there cheap little original handheld like I have at the house

 

[x MadMAX DIESEL]

Or your tires are really worn down lol

 

[LBZ_Duramax]

All tires are not the same size. Your 285's might be shorter than my 285's. Narrower wheels like stock 6.5's will lead to a tire being taller then the sale tire on a 8" or 9" wide wheel.

 

[x MadMAX DIESEL]

True with the ballon effect.. What size did he recalibrate for???

Get a string or something flexible to measure with and measure your tire diameter, then divide it by pie to find your true height, I know my tuner only allows me to change the height in multiples of 1/4 inch, so mine will not be the EXACT speed, maybe he has a more accurate tool?

You have a 285/?/?


EDIT: at what mph is your speedometer off?

 

[JoshH]

It's hard to say what the guy did to calibrate the speedometer. Since the reading didn't change after his "fix", I'm going to have to guess he didn't change whatever it was he was after.