Calibrate Speedometer for larger tires

Hi Everyone,

I am new to this forum, in fact, I'm new to owning a Toyota truck. This truck has bigger tires on it and the speedometer is screwed up/wrong. How do I fix this? I'm sure this has been asked before, I just can't find it.

Truck is a 2006 Tundra, SR5 double cab.

Thanks in advance,

Harleyman

 

I wouldn’t sweat it. I’ve been running 285/75r16’s for years. The larger tires add about 2-3mph to what your odometer reads. So, if you are reading 55 mph then you are actually doing 58mph.

As far as the od being wrong, again I’d not worry about it.

Option is take it in and have the od calibrated for $100-150? Why spend the money?

 

You can get a speedometer calibrator for most vehicles except I have never seen one for the first gen Tundra. What size tires are you running? How far off is your speedometer?

 

There were two options, one of which I am not sure remains in production. That unit was called truspeed. The trouble is it involves soldering thin wires behind your speedo cluster and apparently the wires are different colors depending on year and model.

The other is called YellR Box or Yellow Box. On most older models the wiring harness needs to splice into the vehicle speed sensor at the back of the transmission. Some models with ABS apparently don't cooperate with this. However, wait a while... I ordered a direct plug in version to find out if it will work. When I get it, if it works, I will post a thread to discuss.

As far as your odometer, if you are running a larger tire the inaccurate reading is in your favor. In my case odometer displays 9% more miles than my truck has actually covered, so I could use correction.

 

I'm running 275/75R17 and add 10% to my speedo reading. It's easy. Speedo reads 35MPH, add 3.5MPH. Speedo reads 55MPH, add 5.5MPH. Never just add a few MPH to your speedo reading.

 

For me, knowing how fast I'm going is the least of concerns. I'm more concerned with if my truck uses speed vs rpm for fuel/ignition or load sensing. Also even though I have no bbn plans to sell my truck, it shows about 12k miles more on the odometer than it should. For those with big tires there is a benefit to leaving it alone, for me with low gears it slightly depreciates value. (Says the guy with cut pinch welds, no inner fenders, a million holes drilled in the bed and illegal headlights)

 

Thank you all for your replies. Question for Baller, when you say you add the 10%, are you doing that in your head, or have you changed the speedometer to reflect that? If you changed the speedometer, how did you do it?

Again, thank you all.

 

In my case (not Baller), we have those neighborhood city speed sensors that post your speed on a screen. Mine over the years is anywhere from 2-5 mph over what my od reads depend on my given speed. At 25mph its plus 2. At 45 its plus 3-4.

 

I deduct 10% in my head. Give me a week and we will all know if an easy plug and play option exists.

 

Yes, its available and its plug and play. Installed mine today and can't be happier.

https://www.tundras.com/threads/yellow-box-speedo-calibrator.31996/

 

I have 37s with the stock speedo. I still hit 80 on it too, I just act like I’m actually only doing 80 so it’s ok

 

this link is great. it takes you to a calculation site. mainly for tire sizes, but it will also show the differences between your old tires and your new tires, Including the differences in speedometer speed. be sure to read the instructions, including indication the maximum allowed difference is tire size (i messed that up at first and it would not return a result if your tire is bigger than what the number is in that field)
http://www.dakota-truck.net/TIRECALC/tirecalc.html