Different rolling diameters between the R2's wheel options

[Mos Eisley]

Meaning all you'll see is a pick list with 255/65R19, 255/60R20, and 255/55R21?

Couldn't dial-in 275/55/20? Tiny diameter difference (like a micro-inch?) would be a simple calculation for speedo, but wider tire's wind resistance would be hard to calc for range impact.

dunno how broad the list is. Somebody with OS 2 can answer. But no, no per spec adjustments. You answered for yourself why.

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[rfkxyz]

dunno how broad the list is. Somebody with OS 2 can answer. But no, no per spec adjustments. You answered for yourself why.

FWIW - tire diameters, smallest wheel has the tallest tire (don't understand how in. can change but not mm for OE 19 vs. 20-21, but whatever) -

255/65/19 = 32.1", 814 mm
255/60/20 = 32.0", 814 mm
(275/55/20 = 31.9", 811 mm)
255/55/21 = 32.0", 814 mm

Comparing 20" sizes, very small speedo difference -

Fun stuff.

 

[JasonK]

My impression from the manual is that this might just be a pick list of OEM sizes w/out ability to dial-in something different ("aftermarket") - e.g. 275/55/20 -

I was excited when I I read you could put in aftermarket tire sizes. Then I read the last part that range and efficiency were not effected. That sucks. It seems to me if you know the tire diameter it would not be difficult to adjust the speed range and efficiency. I was thinking of putting on some tires that are 31 inch in diameter. Has any one on here changed to different tire sizes on their Rivian? Were you able to get Rivian to adjust the computer to compensate for the different tire diameter? All the computer needs to know is the different number of revolutions per mile.

 

[UnsungZero_OldTimeAdMan]

Tiny differences don’t warrant a software change. Just as in ICE, virtually identical tire diameter does not warrant a software flash or new speedometer gear. The difference is already within margin of error. No car is pinpoint accurate. Range estimation remains valid because energy consumption is monitored and used to calculate range. With 275/55R20 you will see a drop in efficiency.

Factory speedometers tend to report 2-3% faster than actual speed. Federal regulations cause OEMs to do this and err on the safe side. This is why it’s often recommended to not go over 3% larger than factory (i.e. 275/60R20).

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