Different rolling diameters between the R2's wheel options

[MisterMack]

How are the rolling diameter differences between the R2's wheel options integrated into its speedometer and odometer readings?

I ask, because there have been a number of online discussions about the advantages of taking delivery with the 20" all-terrain wheels because eventual replacement of 20" tires will offer more options and likely be cheaper than replacing the currently very limited options for 21" tires.

Bottom line; would it be workable to replace the standard 21" tires - 255/55R21 - with more available aftermarket 255/50R21 tires? The R2 would somehow need to know it was running on tires with a smaller sidewall, and approximately 3% less circumference.

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[keamoro]

I've had different diameters before on my cars, including the Model Y Performance. The speed difference at slight differences in circumference was never an issue for me. The speedometer probably wasn't exact, but it probably wasn't very far off either.

Going with smaller circumference might not be great though... I usually went up, though there's one time I had slightly smaller due to the winter tire selection at the time.

 

[Mos Eisley]

Both the 21's and 20's are 32" diameter

 

[VSG]

All the R2 tire/wheel combinations have the same diameter, so it's a moot point unless you use aftermarket tires of a different size. In that case, I assume the R2 will have the same sort of setting used in the R1. If that setting doesn't exist for the R2 yet then it will surely come in a future update.

 

[MisterMack]

Both the 21's and 20's are 32" diameter

As you've said. I looked it up, and the 20" 255/60R20 has almost the exact same outer circumference as the 21" 255/55R21. The difference is insignificant.

 

[Mos Eisley]

So the outside diameter of the 21" and 20" plus tire is the same, and no changes are needed for the speedometer and odometer; is that correct?
What about the 19" wheels that are due on the base model next year?

The car allows you to set new tire configurations in the software. Details on Page 360 of the Manual.

 

[VSG]

What, there's a manual? And you read all 400 pages? Unreal.

 

[UnsungZero_OldTimeAdMan]

Understanding tire markings/size: https://www.tirerack.com/upgrade-garage/what-do-tire-sidewall-markings-mean

Tire size comparator, and other tire-related resources: https://tiresize.com/comparison/

The favor towards 20” has nothing to do with instrumentation. Everything to do with having more alternative options than just the one factory offering.

R1 do come in configs with different overall diameters. Calibration of instrument readings is done through software—defining what each full revolution represents—and choosing among the available software profiles that best match tires you have chosen to use.

Factory R2 options all have same overall diameter. One full revolution equals same distance travelled. No need to change software or calibration; unless you chose to run a different overall diameter. The wheel size is just the size of the hole in the tire. Overall diameter of the tire is a different parameter and the one that matters most in instrument readings/calculations.

 

[emk]

LOL. Did take me a while to learn that Wheel Size on cars isn't Tire size. Bigger wheels (the non rubber part) just makes for thinner rubber. I used to contemplate this same question.

 

[Snakedoc]

A 275/50R21 is the same diameter as the factory 255/55R21. Basically just an 1" wider. Should still fit the factory wheels.
Tire Size Comparison

 

[Snakedoc]

Not sure if there would be any clearance issues from tire to strut.

 

[UnsungZero_OldTimeAdMan]

Not sure if there would be any clearance issues from tire to strut.

Main downside of wider tire would be efficiency. Larger contact patch = higher rolling resistance. Dark-Fx is running 275 wide tires (on a 18x8.5 with +38 offset). He would have info on rubbing. And considering there are multiple threads of raging controversy over efficiency, I suspect most will not want to reduce their efficiency any further. And a heavier tire will also alter steering feel, from something that is car-like and sporty, to something closer to a common SUV. Tires alone can make a big difference in how the same car feels.

When I was much younger, I had a VW GTi with H&R coilover suspension and 2 different sets of BBS wheels and multiple sets of tires. When I returned it to back to stock, and drove it, I felt like a complete idiot for having spent all that $.

 

[rfkxyz]

The car allows you to set new tire configurations in the software. Details on Page 360 of the Manual.

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 -

 

[Mos Eisley]

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 -

It’s a range of standard size choices. No, you cannot put in exact numbers for each spec. Not sure there’s a vehicle out there that can?

 

[rfkxyz]

It’s a range of standard size choices. No, you cannot put in exact numbers for each spec. Not sure there’s a vehicle out there that can?

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.

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