Change tire size to correct speedo?

From the factory my speedo reads 4mph fast, and the dealership hasn't been any help. I'm getting new rims and tires anyways, so does anyone know of a site that has an "old tire size to new tire size and the speedo change because of it" calculator?

Thanks for the help.

JD

 

http://www.net-comber.com/tirecalc.html

 

In a lot of cases (atleast my truck), the speedometer that you see (the dial) is wrong but the information in the computer is accurate. I have a Scanguage II and it displays MPH taken directly from the computer. The dial that you see in the dash is calibrated wrong. So, you just have to keep that in mind..... or get a Scanguage II (you can calibrate it to the proper tire size and it'll show proper MPH).

Use www.google.com and search "Tire size calculator" (or similar).
LIke this one - although I don't know how accurate the info is on here.
http://www.tacomaworld.com/forum/tirecalc.php

 

My brother has a scan tool, so I'll check that tonight, also I'll check the forums to see if there's anything about calibrating the needle.

Thanks everyone.

JD

 

The simple answer is yes... To my eyes, the speedometer on my 2010 DC Tacoma looked to be about 3 mph too fast (compared to my GPS)... When I replaced the 265/70-16 Rugged Fails with 265/75-16 Dynapros (1" taller tire), the speedometer read RIGHT ON!

 

Perfect! I wanted to go with a 265/75-16 to begin with, and my factory tire is a 245/75-16, so the added height difference should get me the 4mph.

Thanks David.

JD

 

since i got my 285's my spedo is spot on (or so gps says)

 

In my experiences, the speedos are always faster with stock tyres. Why?
I think its a big scam. Our Jeep liberty speedo was off almost 6% (verified with GPS). The tacoma is 3%. Jeep wouldnt do anything stating it was how they all were. We even test drove the exact same model for comparison.
When you think about it your being ripped off for mileage that isnt there, and exiting warranty coverage before you should. We threw the biggest tyres on that Liberty and it corrected it to about 1% fast. Have to check what my tire upgrade did to my Tacoma...

 

If you search, you'll find what David said is exactly true. And since you wanted to go to that size anyway, problem solved.

 

I never thought about it that why, but it does make sense, and in my experience I've only seen it in newer vehicles. My '05 Jeep GC was 2mph off @70, but my '02 Olds Aurora with 252k miles is spot-on and so is my '86 Camaro w/275k. Granted the shown miles on odometer vs. actual driven miles aren't drastically different, but the potential for more and sooner services is there.

 

Yes Sir it is, didn't think it would work out so smoothly though.

 

Ok so by upgarding my tyres from 265 65 17s to 275 70 17s I effectively changed the spedometer from being 3% fast to 1-2% slow! 5% change! sweet!

 

Agreed.

 

http://www.tacomaworld.com/forum/tirecalc.php

 

Burn some rubber and get that thing down to dead on.

 

It's been said on here many times that even tho the speedometer is off, the odometer is spot on so your maint. schedule will still be accurate

 

Never! I get longer warranty coverage this way! haha

 

Just got the new rims and tires put on. Bought the black rock crawler rims from wheelersoffroad.com and ordered a set of Kumho KL78's from the local tire shop. The speedo is dead on.