Tire and speedometer questions

So don’t know if its possible but i was wondering has anyone adjusted the speedometer to reflect their oversized tires? If so does it change what it says your mpg is as well? I went up to 295/60/20’s and was curious because it is fluctuating between 4 to 6 miles per hour off, according to the Waze. Just wondering..

 

Hypertech and Rough Country both make speedometer calibration units but I don't think either company has anything available yet for the 22 and newer.

 

Thank you

 

Getting it calibrated to the correct size tire should correct the speedometer, the odometer, and the fuel economy readouts. As @Tundra234 said, I can't speak 100% for how the 3rd gen gets it's odometer info, and that is what would give your MPGs, but in previous gens it was all derived from the speedometer.

 

Ok I’ll have to research the gen 3 fix. Thanks

 

Good luck! If you find the 3rd gen answers be sure to come back and post if for future 3rd gens with the same question.

 

Will do

 

The day I bought my truck, I switched from the factory 20" TRD Off road wheels with 265/60R20 tires(for sale here) to a set of TRD Pro wheels and 285/75R18 tires.



According to an online calculator, I'm off 5 mph at 70, which I'm fine with. It's also going to show that I get slightly less mpg on the dash, which I am also fine with.





This morning, I drove by one of the police radar signs. My speedometer read 40 mph and the sign said I was going 41.

Either the speedometer was off (on the low side)with the factory tires, or the radar sign was(which I doubt). Either way, I'm close enough that I don't care to update it.

 

At 40 it will be fairly close. The higher speeds not so much.

 

Nothing yet from Hypertech or RC on recalibration front. I had asked Hypertech about a year ago. They said they were "working on it" but they've never released one of their modules for the 3rd Gen yet.

TBH...I wouldn't be shocked if RC & Hypertech modules come from the same source. If you look at the previous gen modules, they look identical except for the plastic shell. Hypertech's is black while RC's plastic shell is red. Just a wild speculation though on my end.

 

If only I’d have pointed that out.

 

Ok I appreciate all the help and thanks again for your responses

 

So checked Hypertech and they don’t make anything for gen3 to calibrate the speed or tires size yet.

 

It’s going to be a harder task for the 3rd gens. The 2nd gens both the odometer and speedometer values are derived from the ABS ecu. It counts the wheel speed sensor pulses to determine wheel speeds and calculates speed and distance traveled.

The real way to fix it, which no one has figured out on Toyota is to reprogram the tire size value inside the ABS ecu. Knowing an exact tire diameter along with speed pulses from the sensors gives you the travel speed and distance covered.

The RC and Hypertech units just plug inline between the ABS ecu and Instrument cluster. They read in the signal from the ABS ecu (factory tire size) and just modify it to “adjust” for a larger tire. Then the adjusted value is sent to the instrument cluster.

My assumption is the 3rd gens are moving a lot of more data between the ECUs and you can’t just plug in a third party box and ask it to pass all the data back and forth. Or the network is tightly locked down from a security standpoint. Will be interesting to see if a solution is offered for the 3rd gens. If operates the same as a 2nd Gen, safe to assume they would have had a solution out by now.

 

Thanks for explaining