Speedometer compensation for tire size?

[ifunlisted]

How accurate is the GPS? Not saying its wrong but its just as likely to wrong as the vehicle. I know some are very accurate others are not. I know coming from mountain biking I can see GPS thinking I am taking a straight line but at no point was there ever a straight line. That is due to it not that accurate.

Great point. My GPS using Google Maps through Apple Carplay is consistently off by around 3% (shows slower mph than the dash gauge)... but if I disconnect it from Carplay it's only off by about 1%. In other words, there can be a lot of variance in GPS speed readings just based on the app being used and the platform the app is being run on.

I definitely agree with the earlier comment about the lack of an option to input different tire sizes into the vehicle's computer system. With such a significant difference in the factory options alone across the 4Runner/Tacoma lineups you'd think Toyota would have a way to adjust for accuracy. Either they do and we don't know it or their just ok with the variance.

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[mfoga]

Yeah I have often wondered if it was they set speedo based of the median tire size, or largest or smallest tire or did they really have 3 different computer settings that came be changed?

 

[NotApplicable]

Given the trd lift kit installation instructions includes tire-size-based calibration settings for the installer to perform, I’d think there is a non-user-exposed way to update the calibration

 

[mfoga]

Given the trd lift kit installation instructions includes tire-size-based calibration settings for the installer to perform, I’d think there is a non-user-exposed way to update the calibration

There Is 3 modes. Normal is 32-33” mode 1 is 33”-34” and mode 2 is over 34”. So that gets it close I guess.

 

[bancroftdg]

I'm sure there are errors but my wife's car's speedo matches perfectly with the Waze GPS speed. And there are a number of radar speed monitors in town and my 4R is always off by 1 to 2 mph. Also my CC set speed is often not the same as the speedometer speed (I've read thats a common Toyota thing - running error maybe). First world problems

 

[ifunlisted]

There Is 3 modes. Normal is 32-33” mode 1 is 33”-34” and mode 2 is over 34”. So that gets it close I guess.

If an installer is able to adjust this, shouldn't a dealer or Toyota service dept? I've gone to three dealerships and two of their service departments and all of them have said there's no way to calibrate for different tire sizes. Is there documentation online for the TRD lift kit or those 3 modes? I'd like to take it in to Toyota.

 

[mfoga]

Yeah go in the 2.5 lift thread Ed Martin Toyota posted the document. At the end there are specs for setting things based on the new tire size, original tire size and adjustments for cameras around the lift.

Then numbers I posted are based around 265/70r18 on the OR, Pro and Trailhunter.

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