Tire Calibration Question

[GreenLightning]

Hi all, I searched and didn’t quite find the answer I was looking for.
So I just swapped over to some gently used 20” wheels with Michelin LTX 275/60/20/s

The truck previously was running the 21s that it came with (275/55/21)

The service center switched my truck to the 20” wheels in settings, but it looks like the 21s are much much closer in size to the 20s with these tires.
Would you run the 21 settings in the settings menu to keep speedometer etc most closely calibrated?

my speedometer was 3-4mph off compared to google maps on the way home which I wasn’t crazy about. I think 2 off is normal

thanks in advance!

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[UnsungZero_OldTimeAdMan]

Depends on which 20" SC switched you to. Bookmark this tire size comparison calculator: https://tiresize.com/comparison/

275/60R20 is only 0.3% larger than your original 275/55R21—virtually the same circumference and you didn't really need any reprogramming at all.

If SC switched you to the 20" All-Terrain config, just so the wheels in UI would match the wheels you got, then they screwed up. Factory All-Terrain config is 275/65R20, 3.5% larger than your original 21".

If SC chose the 20" AT wheel but set you up with the correct size aftermarket tire (which is what you have), then you're set.

If your software is 2025.06 you can change/remedy yourself:

 

[GreenLightning]

Nice thank you. Yeah service center put the 20s with ATs. I switched it back to 21 and it’s improved.
But it sounds like I can go a step further and enter the correct tire size on 20s instead of choose a factory default?

 

[UnsungZero_OldTimeAdMan]

Nice thank you. Yeah service center put the 20s with ATs. I switched it back to 21 and it’s improved.
But it sounds like I can go a step further and enter the correct tire size on 20s instead of choose a factory default?

Yes. As seen in the OTA review. Overall diameter and circumference is key, because circumference is distance traveled per full revolution. Distance traveled per hour is your average speed for that hour. Distance traveled per kWh consumed is your efficiency. Software warns you range estimates will not be accurate when you use non-factory tires because the tire you chose hasn't been tested and quantified by them.

 

[GreenLightning]

Thanks a lot for this! Super helpful

 

[GreenLightning]

Well I did this but I’m still concerned it chose the right circumference. When you choose the wheel and ‘all season’, it never asks for tire size. So how do I know it got it right?

assuming all season would be the best choice for the Michelin LTX MS2

 

[madhat]

Well I did this but I’m still concerned it chose the right circumference. When you choose the wheel and ‘all season’, it never asks for tire size. So how do I know it got it right?

assuming all season would be the best choice for the Michelin LTX MS2

You could use the Gen 2 20" wheels that are offered with all seasons in 275/60/20

 

[GreenLightning]

Good call thank you!

 

[LL75]

You could use the Gen 2 20" wheels that are offered with all seasons in 275/60/20

I think the best equivalent would be the 21". When you switch to gen 2 20" all season, it is the good year AT tires. That tires technically not a true all season tires. It is an AT/AS. So, the predicted miles is off about 5%

 

[GreenLightning]

I selected gen 1 20s and the generic ‘all season tire’ selection

but that doesn’t show what tire size it’s actually basing it off of?
Any idea if that is remotely close to my Michelin LTX MS2 275/60/20?

 

[madhat]

I selected gen 1 20s and the generic ‘all season tire’ selection

but that doesn’t show what tire size it’s actually basing it off of?
Any idea if that is remotely close to my Michelin LTX MS2 275/60/20?

I switched from the standard you're selection for the 22s to the generic performance tire...I didn't really notice a difference in predictions. Doesn't mean there's not a change, but i wonder if it's not more for the flexibility for more unique tire combos, since you can have six sets and all

 

[UnsungZero_OldTimeAdMan]

If you choose gen2 factory “all season” with Goodyear AT, that is also a guess/approximation. In addition to having the wrong wheels displayed, estimations are no more accurate since you are rolling on tires that IS the unknown variable. I don’t get how you think the custom option is incorrect, without any amount of testing.

Pick the right wheels. Go back to the matching all season size and drive for a week at least. Use one of the trip computers to track mileage. Keep track of SOC consumed. Use any means you can think of, at your disposal, compare/contrast data to get an idea just how far off the instrument might be.

Remember, even in stock configuration, all instrument readings/calculations ARE approximations. Not pin point accurate. Even the EPA certified figures aren’t that accurate. What matters is how good the approximations are: closed enough or not even in the ballpark.

Ignoring logic and process of gaining data/understanding—and you just want simplest path to peace of mind—just remove the unknown entirely; ditch the Michelins for a factory tire.

ps—You should know what your average mi/kWh was before you changed tires from stock 21” combo. A forum or Google search should reveal average figure for other stock configuration, and figures from those running the same Michelins. All these datapoints should define where the ballpark is and provide context for where your own observations may fall. But bear in mind data collected during winter/cold months will always be low.

 

[LL75]

I selected gen 1 20s and the generic ‘all season tire’ selection

but that doesn’t show what tire size it’s actually basing it off of?
Any idea if that is remotely close to my Michelin LTX MS2 275/60/20?

That would be the 21" All season Pirelli 275/55/21.

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