Speedometer correction

Because with the stock size tires from the factory has always over reported speed/mileage (never was accurate from the factory until you put a inch taller tire on).. This isn't only a Toyota thing, all manufactures do this, I'm assuming they do it to get past the bullshit EPA gas mileage regulations

 

The speedo and odometer have separate calibrations in the gauge cluster. Over-reporting is done intentionally for the speedo but not for the odometer.

 

Correct. Note both measurements are subject to mfg tolerances, but the median value for the speedo is shifted by about 3 mph.

Common with most vehicles: https://www.caranddriver.com/news/w...iving-accurate-mpg-readings-and-how-to-fix-it
Most of the error in the in-vehicle MPG display comes from the fuel system. Since there's no flow meter in the system, fuel consumption is estimated indirectly based on injector pulse timing. The fuel injected in each combustion cycle, on the order of microliters, will have huge variation when multiplied thousands of times each minute.

 

Dude... You're killing' me at 1:19am with that sig.

 

In summary...

Just to be clear-- we assume the speedometer and odometer are operating via the same mechanism. They're both dependent on RPM of the wheels.

It's been established that our trucks come from the factory with the speedometers reading 2-3mph faster than "reality" at hiway speeds (ie. when your speedometer says 67mph, you're actually going 65mph). Who knows why they do this. It's not relevant to the conversation. When you're driving at 5mph, the speedometer will be spot on (imperceptible error). The "error" gets larger the faster you go.

That said, its likely (and evident, as per forum posts) that even though the speedometer is under-reporting from
the factory, the odometer is accurate.

So. If you put a bigger than OEM tire on (~1" larger in diameter) there are fewer RPM. This has the effect of "correcting" our speedometers. Your speedometer is now displaying "reality". But your odometer is now under-reporting by a small percentage (ex. ~3000 miles per 100,000 miles).

Speculation here, but I'm guessing that the onboard mpg calculations are based off the odometer and not the speedometer (it just makes sense). So, mpg calculations will be ~correct with OEM tire size, even though the speedometer is off by 2-3mph at hiway speeds. If you install larger tires, your displayed mpg will not be accurate. It will likely show worse mpg that what you're actually getting.

 

Unfortunately she's married

 

Subbed

 

I have noticed my speedo is about 2 to 3 off of my digital speedo .

 

Same here.

 

Happy for him then!

 

My GPS shows 64 when the cruise is set at 65. Hopefully my new 265/70/17 bfgs will make it spot on.

 

I’m using 285 70 17... my speedo is slower by 4 mph. It’s crucial to know this and correct it especially when you get pulled over and you’re arguing with the police officer that in fact you were going the speed limit when in actuality you were not. 75 mph on speedo is actually 79.... any fix?

 

See post #27.

 

Thank you! 229.00 though?! Wow is there a cheaper way to fix this? I don’t have original rims to put them back. Truck was like this when I bought it.

 

It was worth it for me, I could not stand the speedometer and odometer being off. I'm not aware of any other device that'll fix it.

 

How did it work out?

 

I purchased and didn’t look back, with it

agree

 

ill call Hypertech in the am to see if its the same for the 2020

 

Don't waste your time. The Hypertech in-line module currently doesn't support the 2019 or the 2020, and they have no idea when or if they'll ever update it for the Tacoma. I've asked them several times since November of last year, and always get the same answer.

 

What about 235 85 16?