Reprogram speedo after new tires

I just bought new tires that are slightly bigger than stock. Is there a way to reprogram the speedometer so that it won’t read fast and add more miles to my truck than what it actually has?

 

Hypertech and rough country make an in-line calibration device that connects to the instrument cluster in the dash.

 

How big is slightly bigger?

 

Dealership should be able to

 

285 65 r18
Dealership said they couldn’t adjust. Will the programmers be detected by Toyota?

 

There’s no need to adjust for that size. It’s only a tad more than 1/2” overall and only 1/4” or so taller than stock. Your speedometer and odometer are fine.

 

1 mph off on gps. Agree pretty small, but it will add miles to the truck

 

It won't read faster and add miles. It will read slower and show fewer miles than you actually drive.

 

Opposite. A taller tire will make the truck think you’re going slower and thus less miles.

 

BINGO. Slower on the speedo. LESS miles put on the odometer. Less!!

 

^^^ what he said.

 

Hum? I thought that it would be slower too? I used the gps app on my phone with it stock and it was dead on. Afterwards it was like 1-1.5 fast.

 

Your speedometer will read slow after putting on larger tires. Your speedometer determines your speed based off of the number of rotations on the tire. A larger tire has a larger circumference and will cover a mile faster than one with a smaller circumference. That means that your speedometer will read slower than you are actually going, and you will be adding miles faster than your odometer reads out.

 

Thanks for your help. Maybe the Gps app on my phone is wrong?

 

Your GPS is fine. Your odometer does not go off of your actual speed. It goes off of rotations, and it is programmed for the stock tire height. Because you have a larger Tire you will move faster than what your truck thinks you are moving, so you will actually go further than what your odometer will read.
However, If your speedometer read slow before, and is dead on now, that will just mean that your speed is now accurate and your odometer would be as well. Previously if you were actually going slower than what the truck read you would have been stacking mileage on faster. It is not impossible or even uncommon for a stock speedometer to be incorrect.

 

Speaking of reprogramming, I have the Hypertech and have had no problems but was wondering how easy it would be to make a relocation kit for the wheel speed sensors or maybe just mount them on the rear drive shaft if you don't mind not having traction control.

 

If you bought tires that are bigger the speedo will read SLOWER not faster. Honestly, unless you bought 37s or bigger there is really no need to waste the money. I upgraded to 295/70/18 and my speedo is only off by 1mph.

 

It will be off by a percentage that will change based on speed. The faster you go the more it will be off.

 

Correct, I should have specified at 70mph it is off by 1 mph.

 

I wonder if mine is off from the factory? I just went by one of those cop radar sign trailers and it said I was going slower than my speedo indicated? Who knows first world problems

 

THIS!

 

That's what's supposed to happen.

if you set your speed so your speedometer reads 45 you'll actually be going at 46.

if you set your speed so your GPS or radar sign reads 45 your speedometer will say you're going at 44.

Hope this makes sense to you since it's quite simple.

 

Thanks guys. Who knows why it’s not reading the way it’s supposed to? It’s showing faster than the cop radar and the gps. I’m not going to lose sleep over it.it says 55, but it’s going 53 or 54.

 

Here is the difference. It’s pretty small. .9 at 60 mph.

GPS isn’t always accurate either. I know you said it was before changing tires, but it could’ve been off a little then along with your speedometer. Depends on the accuracy of your gps at the time, which could fluctuate between 10 ft or 100 ft.

 

How are some here thinking it adds more miles to the odometer? Speedometer is slower that means less miles on the odometer.

 

American High School Math Teachers.

 

I think only the OP thought that and everyone else was explaining otherwise.

 

Trust me my Speedo reads fast. It’s funny people are trying to convince me I’m wrong. BUT when the radar trailer the cops use to track traffic and my gps say it’s indicating fast It’s FAST. I’m not losing sleep over it. It’s about 1.5 fast. I think it was closer when stock? I didn’t really pay that close attention until I passed the trailer in the past