Big tires, speedometer not doing what I expected.

So I Just bought a Tacoma (my second one) and it came with 265/75-16 tires, i knew the speedometer was going to be off, bigger tires means that my actual speed should be faster than what the speedometer shows, I used the tire size calculator (and common sense) to come to this conclusion. Now, the problem is, my Tacoma is kinda backwards, my actual speed is slower than what my speedometer says, I confirmed this using GPS and by having my fiance drive next to me on the highway and compare speeds (we were on the phone talking to each other during the test). When my speedometer read 70mph she said that my speed was actually 66-67ish. She has a brand new honda crv so I'm sure her speedo is accurate and as i said before, i also checked with gps.

The previous owner new about this too, and he too was confused by it.

Does anyone have a clue of why this is happening? Any help would be appreciated.

Thanks in advance!

 

Perhaps an earlier owner had the diffs re-geared for larger tires, and over-did it.

 

My truck is the same way. I'm around 1-2 mph off compared to a GPS reading. To me, it isn't a big deal as long as I take it easy. I'm glad it's actually faster then my actual speed because I'm less likely to get a ticket.

 

Big tires means lowers speedo mph

 

I don't think so, the guy I bought it from bought it from a dealership, I saw the pictures, it was completely stock, he put the lift and tires on it, he was as confused as I am

Well, I don't mind the speedometer being faster than the actual speed, but that means that the odometer is registering more miles that we're actually traveling, and I'm not happy about that

I agree with you, big tires "should" lower the speedo, but my speedo is faster than my actual speed, which makes no sense

 

Here's a picture of the truck

 

I worked nights last night. I didn't comprehend what you posted the first time.
Yeah that is weird.

 

Yeah man, I've only owned the truck for a couple of days and this is killing me, I have OCD, I need to know own what's happening.

 

Hhmm i have 265/75-16 and it fixed my speedo. It matches my gps. Thats really odd man.

 

Can these trucks be reprogrammed for different tire sizes. If it was reprogrammed for larger tires and then smaller ones were placed on it without reprogramming. This could cause this issue no?

All i see are people posting the Dakota digital piece for tires.

 

I know man, you're lucky!

I'm gonna have to look into that.

 

What year is your truck?

 

It's a 2008 bro, any idea why this could be happening?

 

I done a little researching and a few other people have had that prob with the 2008. Check the mile to mile on it. Like reset the trips on both vehicles, and drive one mile. If they are the same then the mileage is correct, but from what i can tell there is no fix for it.

 

Thanks for looking into it... Did you find a thread about this? If so, can you share it with me please?

 

Wasnt a thred but was through google.

 

Did a test using GPS and found that my speedometer is slower than my actual speed but my odometer is perfectly accurate, how is this possible?