Speedo Off??? Which Way

[Doughboy21kd]

Alright what it says is my question?



I have an 06 and i have 33x12. 5x18 tires and wheels on it... . I know my speedo is gonna be off some now am just tryin to figure out which way?



I did the road test the other day on the freeway and going from mile marker to mile marker for me to go exactly 1 mile i have to do 65mph... . Now if i do 50mph then by the time i get to the 2nd mile marker my odometer says i have gone 1. 4 miles... So it seems to me that in order for my odometer to be exact i have to do 65mph.....



Does this mean anything or is there a better(easier) test to do to figure it out?



TIA

 

[Hoefler]

Use a stop watch and clock the time it takes you to travel between mile makers. Try to do this when you can set the cruise and on a fairly flat stretch of highway. Take several times. Take the time it takes you to go between mile markers and divide it into 3600. This will give you your mile per hour. Say it takes you 52 seconds to cover a mile, 3600/52= 69 mph. If your speedo reads 65 and you are actually going 69, your odometer will be off approximately 6% low.

 

[Lightman]

Alright what it says is my question?



I have an 06 and i have 33x12. 5x18 tires and wheels on it... . I know my speedo is gonna be off some now am just tryin to figure out which way?



I did the road test the other day on the freeway and going from mile marker to mile marker for me to go exactly 1 mile i have to do 65mph... . Now if i do 50mph then by the time i get to the 2nd mile marker my odometer says i have gone 1. 4 miles... So it seems to me that in order for my odometer to be exact i have to do 65mph.....



Does this mean anything or is there a better(easier) test to do to figure it out?



TIA

If you are going 1. 4 miles between two mile markers, say mile marker 50 to mile marker 52 you should show 2 miles. not 1. 4 miles you are 30% slow so what you have above is right at 50mph on speedometer you are going 65mph.

 

[Turbo1Ton]

Hoefler is right. You can do it just like that. But, watch out, sometimes they don't get the milemarkers in the right spots. I was headed out west to Phoenix and when I was going through NM I started to do that because I was bored. Turns out at 75mph on the speedometer several times I calculated about 20mph high! Guess the day they put those up was a Friday!



Lightman, not trying to sound condescending but I think he means the 1st sign is the start and the 2nd sign is the stop. For example MM 50 to 51. 51 would be the 2nd sign. I don't think that even Dodge could screw up the calibration that bad. Well... , they might!



Jeff

 

[Doughboy21kd]

I went from mile marker 7 to 8 and by the time i hit the 8 my OD read 1. 4 miles that i had gone and i checked it for a few miles that way and kept coming up the same... . I will try again. .

 

[RMadgar]

Go to the dealer and they will calibrate it for about 35 bucks. I wouldn't even bother for that little of a change personnally. But to your question, the stock tires are on my '06 were 265x70x17 (31. 6 inches) and your Toyos are actually a true 33 inches. This will now make your speedo read about 4. 7 percent SLOW. This means when your speedo says 60 mph, you are really going 62. 8 mph. The dealer says they only have to get the speedo to read within 6 percent of true speed... ... but if you bug them enough like me they can get it right. Hope this helps.