How to adjust speedometer for larger tires?

How can I adjust the speedometer for larger tires? Can I do it myself, tire store or do I have to take it to a dealership?

Thanks,

Killer

 

Mental math is the easiest method...calibrate next to a GPS or something.

 

I don't think you can. Or at least I have never heard of anyone doing it. Get a scanguage and adjust it to you tire size.

 

^^^^^nice^^^^^

need to get me one of those

 

I need both of them!

My tires right now are : 32 x 11.5 R 15 LT Steel Radial Mud King XT

How much bigger are they than stock? How much do you think that the speedometer will be off?

 

barely any

 

What was your stock tire size?

 

I don't know what the stock size was. I have owned the truck for about 24 hours and it did not have any paperwork.

 

Look at the label on the side of the door or jam. It will list the stock tire size for your truck.

 

That and then go to the tire calculator and it will tell you everything you need to know.

http://www.tacomaworld.com/forum/tirecalc.php

 

It'll probably be closer to true speed now than it was before.

 

Factory Tires (according to door sticker) = P225/75/R15

I know the 15 is referring to the rim size but, I need to research the other numbers.

 

225 mm wide and 75% of the width in side wall so 169ish mm side wall height.

 

anyway,

 

thats what my sticker says too, but it came with 265/75/15's.

 

if your truck is like mine, it will be dead-on with 32" tires.

 

Tire caculator says my speedo should be way out...Hooked up my GPS...It's reads 53 kph when my speedos at 50 kph...So I guessing my Taco must be calibrated already to accodate for my larger tires

50 mph 57.81 mph

 

Its actually calibrated to never show you're going faster (from the dealer) than the speedo shows, as per U.N. Regualtion No 39 and US Motor Vehicle Regulation No 25. The US Regulation allows a 5% margin, which the manufacturers take full advantage of due to heavy fines if the speedo shows you're not speeding when you are actually are.

Speedo's are never calibrated for true speed, but for true speed minus a margin (2-3% would be my guess).

So, when you put on larger tires, you're actually getting closer to true speed, until you go over the margin. 32-33's should end up being pretty close to true speed for most of us.

 

http://www.hypertech.com/products-speedometer-calibrator.aspx#in-line