Speedometer calibration after tire and wheel size change?

[Gff313]

I am seeing people changing their tire sizes on these new 2024 Tacomas and am wondering how they are calibrating their speedometer’s after the change. Or are they just not doing it?

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[SR5-GUYS]

Hey so I put some 33s on stock wheels and based on gps comparing to my speedometer there has been no difference in speed

 

[COcurmudgeon]

I am seeing people changing their tire sizes on these new 2024 Tacomas and am wondering how they are calibrating their speedometer’s after the change. Or are they just not doing it?es

I would imagine the speedometer itself is GPS based and doesn't require recalibration with oversized tires, but any confirmation of this is appreciated

 

[cuechairo]

I would imagine the speedometer itself is GPS based and doesn't require recalibration with oversized tires, but any confirmation of this is appreciated

I doubt the speedometer is 100% GPS based, but maybe it can compare the speed based on wheel speed vs. the GPS speed periodically, and re-calibrate itself for a new wheel size?

 

[COcurmudgeon]

I doubt the speedometer is 100% GPS based, but maybe it can compare the speed based on wheel speed vs. the GPS speed periodically, and re-calibrate itself for a new wheel size?

You are probably right, if it were 100% GPS based there are probably parts of the planet Tacoma can go that GPS cannot! I like your theory and would not trust the speedometer after installing oversized tires unless it checks out with a third party GPS speed comparison. Fortunately, by the time it becomes relevant for my impoverished needs there will have been many others who have encountered and dealt with this issue already!

 

[Br8945]

Hey so I put some 33s on stock wheels and based on gps comparing to my speedometer there has been no difference in speed

Any rubbing with that setup?

 

[SR5-GUYS]

Any rubbing with that setup?

Nothing at all, I messaged you.

 

[TheBandit]

To revive an old thread, on the SR with stock 245 70 r17, I was reading about 8% higher than every comparative measure (radar speed checks, speed matching friends) and I never thought to compare odometer readings

I just put on 33s as well (255 80r17) and my speedometer is reading exact. In contrast, my odometer/trip distance has been reading almost exactly 5% less distance traveled than actual.

This leads me to the conclusion that

1) the SR trim at least has a mechanical speedometer and odometer as the speedometer changed proportionately and I believe the odometer reads high with the stock tires

2) Toyota expects everyone to throw on 33s

3) gas mileage is 5% better than I thought when I first put on the new tires

 

[24TacomaGirl]

Can confirm I run 33’s and checking Speedo against GPS it is spot on. Pretty sure the truck was over-estimating speed ahead of time and now is accurate!

 

[Congo]

Can confirm I run 33’s and checking Speedo against GPS it is spot on. Pretty sure the truck was over-estimating speed ahead of time and now is accurate!

I am running 34's (285/70/18) and Mine is off by 4%ish. Cant really tell until 80mph. At 80mph my GPS measures 77.

 

[AltarBoy]

Running 315/70/17 I'm off by 2-3mph according to the speed camera at work

 

[Ron]

My tires are 1" larger than stock.
Radar displays and GPS both show 3% lower than the speedo - opposite what it should with larger tires.

I didnt have the stock tires on long enough to notice any discrepancy. The initial calibration must have been even worse.

I dont like that my warranty is 3% less.

 

[rybern]

Interesting. Subbing for future responses.

 

[Romer]

Pretty sure the speedometer is set by monitoring the wheel speed sensors measuring the rotation of the wheel where it is then sent to the computer that calculates the speed. I don't know of a hack to the computer to change the speed.

I went to 33" tires and my speedometer matches all the "Your Speed is" signs.

 

[MT-Taco]

285’s Speedo is dead on!

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