Why is my speedometer off with stock tires?

Just like the thread title reads. My speedometer is off and I am still running the stock tires/wheels that came with the truck. The error seems to increase as my speed does as well. Example: When my Speedo is reading 62 both my GPS and another vehicle I was following both indicated 60 mph. At 78 on my speedometer the actual speed is 75. Is the speedometer programed for the trim level of the Tacoma?

 

That's just how it is. You can find a lot of info on the internet, do some research and quit when you've learned enough for your desires.

https://www.caranddriver.com/features/a15136801/speedometer-scandal/

 

Very common across all Toyota models. Theory is European regs have strong prohibitions against speedo under-reporting, Toyota nominally over-reports on the speedo so it never under-reports with all the mfg variations.

If you upsize from stock to 32" tires, the speedo will be corrected, but odometer will be off slightly.

 

Wow, you'd think the service dept at the dealers would know this. When I asked them about it the other day they said there's no reason it should be off. Of course maybe they do know and just act like it's not an issue.

 

Pretty normal. My bike was the same way. Speedo said 173 actual speed was probably 165ish

 

My 2nd Gen ‘06 was the same way, but my 3rd Gen ‘18 is just fine. It’s a Toyota thing.

 

In my experience, the service writers are often clueless (they pilot a desk all day).

Next thing to fuss over is discrepancy between the digital and analog speedometers.

 

Go up to a 32 inch tire and it'll be corrected.

 

My digital and analog at least match. That would truly drive me nuts.

 

Those are rookie numbers. Sike

 

Step up to 265/70r17 or 265/75r16 tires to make it right.

 

+/- 5 miles no big deal. sensors on device, road condition, wind, weight, etc. would be more concerned if it was 10/20 miles off. cop said I was going over 80 but I said no sir my speedometer said 65 mph lol

 

i had my speedo changed bc at one point my analog speedo was at 10 mph when I was a red light xD

 

My bike said 205. Was only 200.3. Complained on a forum. Maybe "complained" isn't the most accurate term. Ok, I boasted on a forum.

Edit: on several forums

 

Yes the speedo only needs to be within 5 mph at 50mph to pass inspection. With different trim packages (tire outside diameter) pressures and digital rounding I'd say yours is within tolerance. Note, GPS speed is less accurate than you might expect and your buddies truck may also be somewhere on the standard deviation curve. Find a legit measured mile, peg it at 60 and then 59 etc several times. Find which give you the closest to a minute. The cruize in these things is pretty good especially on flat/straight.

 

My SCCA street class OE rev limiter didn't hit until the tach was about 600 RPM past redline.

Didn't care, as I didn't have time to look at the tach anyway.

 

IIRC Car and Driver's testing of a 2005 Taco showed top speed of 108, with 112 indicated. I think the truck was just redline limited in 5th.