How do you calibrate speedometer after bigger tire size?

I just bought one on Amazon for $140.00. Its $250 on Hypertechs site. If it doesn't work (based on the few reviews on Amazon), I can always return it and buy one directly from Hypertech. I just went from 285/70/18's to 295/70/18's. My dash, SG3, Waze GPS, and radar GPS all read differently.

 

Once you get it tuned, you could always just buzz by a cop running radar at a good 15-20 over, and when you get stopped just tell him you were being a responsible Tundra owner and wanted to check the calibration on your speedo and needed his professional opinion

 

Lol. I wasnt off until I went from the 285 to the 295.

 

I just use a scan gauge 2 and you can add a speed option and adjust it by percentage off. Works great since I monitor transmission temps and engine temp.

 

Reviving this thread...I just installed the hypertech speedometer calibrator in my 2018. Speed is spot on now. However, the odometer seems to still be off. I didn't drive that far but it doesn't take long running up the interstate to see that the odometer is reading low. Also the cruise control shows the uncorrected speed. So it seems like the Hypertech half works and for $200 I was expecting more. Anyone know how to get the odometer reading correctly with larger tires?

 

I recently picked up a 2018 Turndra SR5 4x4. The spedo is reading 3 to 4 mph over at highway speeds per the gps.

Edit: the mileage thing was my GPS saying 40+ miles. It turns out after mapping it, it is a 60+ mile trip. The GPS must show "as the crow flies" miles.

 

hmmm I would have got that size didn't know that existed

 

Just went from stock 275/55 R20 to 285/60 R20. (By the charts, 1.6" larger diameter.)I haven't put many miles on yet, but I did drive around 70 miles on a local toll road with a 80 MPH posted limit. Comparing speedometer display with GPS on my smartphone (Google Maps) I'm spot on until I get north of 80, then speedo says 81 and GPS says 82; 83 and 84; 85 and 86 - 87. That I can live with; no worries. What I don't want to live with is the transmission downshifting when I don't think it should. Like, at 78 - 79 all seems fine, 2300 RPM, or so. Slow, very slow, acceleration to 80, and it downshifts and RPM is 3100 plus, and that's where it seems to want to stay until I get to 85 and over, then it up-shifts back into the mid 2000s again.

If I'm figuring right, it seems then that my speedo, with stock tires, has always been reading a little higher than actual. However, I've never noticed this gear-seeking behavior until now, and even at slower speeds, it's bugging me, and that's what I want to correct for. Will the Rough Country/Hypertech Calibrator accomplish this? And, if it can, will I be back to my speedo reading a little higher than actual?

 

That's weird. There should be enough difference at 40-45 that you would see the GPS difference then. I went from 255/70/18 to 295/70/18 and this chart is pretty accurate for what I'm seeing. I've never noticed a difference in shifting, but I do have a Pedal Commander. I also haven't been much over 75 either. Maybe a Pedal Commander or the other product, I can't remember the name, instead of a Hypertech. $200 for the Hypertech to fix 3 mph wasn't worth it to me.

https://www.tacomaworld.com/tirecalc?tires=275-55r20-285-60r20

 

I too went up a size from stock and the speedo gps on my phone and truck are still the same.

 

I can't say for positive, as I didn't pay much attention before, but I'm remembering that my speedo was reading 2 -3 MPH higher with stock wheels and tires than actual speed on GPS. In other words, it was reading about the same before, with stock tires, as I would expect the increase to be with my new rubber. The ABS sensors, at least on 2014 - 2021, that feed our speedos measure RPM, not tire circumference. So, my actual speed did increase, but the ABS sensors are sending the same RPM of the wheels. Hence, my speedo is now reflecting pretty close to real speed, and not faster than actual. When it comes to the ECU telling the tranny which gear to be in though, it too doesn't know I put on bigger tires, so it, for some voodoo beyond my pay-grade, is deciding to down-shift when, as the driver, I feel it should not.

I have Drive-9, a Pedal Commander knock-off, and around $250 less expensive. It's always worked fine, as expected. All Pedal Commander, as well as the knock-offs, do is change the voltage sent to the throttle ECU. Higher voltage means open the throttle bodies more, lower voltage means close them more. Changes in voltage to the throttle ECU should not have any effect on speedo functionality, but the state of the throttle, how much open or closed, could, I don't know, affect what gear the tranny ECU chooses.

If I get a Rough Country/Hypertech calibrator, it won't be to see accurate speed on my cluster, it will be to stop my tranny from gear-seeking. A thing it didn't noticeably do prior to larger tires. $170 for a Rough Country is worth it too me to correct Interstate cruising in 5th gear, when my Tundra should be in 6th. 5th gear will burn a lot more gas, and $$$.

Edit: it's 9-Drive, and not Drive-9.

MAIMEIMI Throttle Response Controller, 9 Drive Modes Smart Electronic Pedal Racing Accelerator for Toyota 4Runner Tundra Land Cruiser Prius Camry Corolla Lexus GX 460

https://www.amazon.com/gp/product/B0CB8P19HG

 

I can confirm on my 2018 that with stock tires/wheels my dash reading at ~45 mph was about 2 mph faster than gps. I read somewhere that Toyota does this on purpose to get away from lawsuits related to speeding. Or they just know everyone is gonna throw 34+” tires on it and then it’ll be about right.

 

Thanks, Jake. Makes sense to me. My 2000 BMW, best motorcycle ever, showed 5 - 7 MPH faster than actual speed. (That was before everyone had GPS; Jobs was still years away from releasing the iPhone.) For the first few months I owned it, commuting on the Houston Beltway, I was totally confused how it was that I was doing 75 and everyone, even granny, was still passing me.

So, I've read all the marketing, and even called Hypertech Support last Friday. Claim is that these calibrators do correct for gear-seeking behavior in our Tundras. I'm looking for some tundras.com confirmation as to how well? I can live with my speedo being off a few percent. I just want to be in what gear I think I should be without dropping my selector into S mode.

 

Well, I opted for a TCCS tune instead of getting a calibrator. GPS, speedometer, and cruise control set are all now within 1 mph of each other. Annoying gear-seeking, even at Interstate speeds, is gone. And throttle response is just as quick, but a whole lot smoother, than my now removed 9-Drive (Pedal Commander knockoff). I'm liking this. Thanks @texoma !

 

You’re very welcome, and great meeting you and your wife. I enjoyed your music as well.