2024 Tacoma Odometer / Speedometer Accuracy

US government regulations through the DOT require speedometer accuracy of +/- 5 mph at 50 mph.

https://www.govinfo.gov/content/pkg/CFR-2005-title49-vol5/pdf/CFR-2005-title49-vol5-sec393-79.pdf

 

I'm glad I discovered this early. (I only have 3400 miles on mine). I replaced my 245/70/17s with 285/70/17s and that corrected it. I'm in a lease and only have 30k miles to use before I have to start paying additional money per mile. If I discovered this at the end of my lease I would have been extremely upset. I'm sure it isn't intentional but it's something that is suspicious as there is no way they didn't know this was an issue.

 

I went back to the dealer to discuss this issue on 2024 Tacoma SR5. They said they had certain allowances that they were within and that they had no way to re-calibrate the speedometer. I was talking to a Toyota mechanic in a lab coat the main guy for the dealer. I think Toyota and other dealers are using this issue to meet mileage standards and to save themselves money.

I also asked about the OEM 245 tires and they said the tires were the right size. I was hoping for them to say they should be 265 and they would take care of it but they would not.

Have driven a 2021 RAV4 with same speedometer issue.

Also have a 2017 4Runner with 265 tires and the speedometer is perfect or close to it.

 

On my tacoma pro the speedometer was off almost 4 mpg slower. I changed the tires from factory 265x70x18 to 285x70x18 (34”) now its almost perfect in speedometer readings.

 

Noticed this issue with a '19 Frontier SV. Speedo indicated faster than actual speed. 23 Taco SR did the same thing. Both cases was 2-3 mph.

It seems they calibrate the speedo for whatever the largest tire option is across the option range. If you buy a lower trim with a smaller tire, your speedo reads faster than the vehicle is going.

Quick "here how tire sizes work", for those who don't know. The first number is the width of the tire in mm. How that gets measured can vary by manufacturer, but usually it's the contact patch (outer edges of the tread pattern). A 265 is 265mm across. The second number is the aspect ratio. That's a percentage of the width. 265/70 means the height of the tire from the lip of the rim to the top of the tread is 70% of 265 - or 185.5mm. The last ("R") number most everybody knows. It's the diameter of the wheel in inches.

The SR comes with a 245/70R17. The OffRoad comes with a 265/70R17. The outside diameter of the Off Road tire is about an inch more than the SR. It doesn't make as many revolutions at a given speed, so the speedometer reading is less than a smaller tire. That same principle is why putting bigger tires on your truck changes the indicated speed (makes it read slower than you're actually going).

You have 3 options to correct your speedo. 1st is buying a device that recalibrates (or "translates"). Guys who put 33's and whatnot are familiar. 2nd is buying a tire with a higher aspect ratio (245/75R17), and 3rd is a wider tire with the same aspect ratio (i.e.: what comes on the Off Road).

Yeah, there are two 18" options for the Tacoma too. The TRD Pro is 265/70R18. It's about an inch bigger in diameter than the Off Road. The Limited is 265/65R18 - the same diameter as the Off Road.

You can use and input data to your heart's content.

Here's the comparison between the SR and Off Road sizes. My OR indicates maybe one MPH faster than GPS. It's pretty much spot on.

 

I think pretty much every car I've had with stock rolling diameter tires on it has the speedometer reading 60mph where GPS devices call it 58 or so, and 35 those radar road signs call it 34. Hell, the digital speedometer in my wife's Subaru conflicts with the analog one right next to it, reading 62 on the former and 64 on the latter.

Despite popular misconception, your speedometer is not a precision instrument. It's just a reasonable estimate. Same thing with your GPS gizmo or your phone. Frankly, unless you're using a calibrated instrument to measure your actual road speed — maybe partnering with your local constabulary? — you're unlikely to get it actually right.

I mean, play around with it if it makes you happy, but understand that putting a lot of effort into this is cutting into quality Miller time.