https://www.amazon.com/Hypertech-730119-Speedometer-Calibrator/dp/B00GUYCNMS

I didn't buy one though. I don't mind my speed and miles being off ~8%.

 

Is this something the shop/garage usually has if they are throwing on your tires?

 

No, you have to install it behind your gauge cluster. I've put one on the last two tundras ive had and wouldnt change the tire size without one.

 

Depends on how large you plan to go. Changing from 32" to 33" tires on my truck fixed the 3% factory speedometer error.

 

Yeah. You have to consider that different trims can come with different size tires. The RockWarrior trim came with BFG's that were almost 33's and the stock came with 32's. I meant moving up to 34's or more....

 

Awesome thanks for the info. I have one on order now.

 

Late to respond, but have you checked the accuracy of your current setup?

The reason that I ask is that my speedo was off from the factory with the stock tires. When I jumped up to 275/70/18s, my speedo is actually much closer to reality based on GPS and radar tests I have done around town.

 

No, I'll test it today when I leave work. I have stock tires on my 2017 Platinum and I'm getting 305s and I am wanting to ensure when the wife drives I don't get speeding tickets all day.

 

The study I did gave:
Stock tires 275/65R18 (32.1"). Speedo reads ~72.5 at 70mph
275/70R18 or 305/55R20 (both 33.2"). Speedo reads ~70 at 70 mph

305/60R20 (34.4"). Estimated - speedo should read ~67.5 at 70 mph

Not sure if either of these are the 305s you mention. YMMV

 

Sure enough my current tires show me going 70 but GPS said I was going 68. Would larger tires inherently fix this or make it worse?

 

It will make it better...up to a point. Just as Mtnclimber posted. But, once you pass a certain tire size, the speedo will read lower than what you are traveling. With a bigger tire, you travel further for each revolution.

 

Gotcha. I appreciate the help!

 

My 2012 is riding on 315/70/17's(35's). The speedo is about 4mph lower than actual speed.