20in wheel worse range even with all season tires?

[emroch]

Yeah bc they put off road tires on the 20" rim. Put the same tire that's on the 22" rim on the 20" rim and it is more efficient than the 22". Smaller rim is always "better" with the same tire and design.

How do you define "same tire" for a different size? Do you keep the same sidewall height and change the overall diameter? Or do you keep the diameter and add more sidewall?
A smaller overall diameter is always better (all else equal) because you're pulling the weight in toward the axel (and have less volume of rubber on the tread surface, though that might be negligible).
A bigger sidewall causes more squish and rolling resistance though, so while the smaller rim pulls the weight of the metal inwards, the tire itself counteracts that.

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[Jeremy3292]

How do you define "same tire" for a different size? Do you keep the same sidewall height and change the overall diameter? Or do you keep the diameter and add more sidewall?
A smaller overall diameter is always better (all else equal) because you're pulling the weight in toward the axel (and have less volume of rubber on the tread surface, though that might be negligible).
A bigger sidewall causes more squish and rolling resistance though, so while the smaller rim pulls the weight of the metal inwards, the tire itself counteracts that.

We've been over this a 1000x in this thread. No need to rehash, just need everyone to read the thread lol. Rotational inertia is key.

Im assuming #2 is referring to rotational inertia, bc saying rim size has “zero impact” would contradict rotational inertia. If two rims have the exact same weight, tires, and design the smaller diameter rim will go further every time due to rotational inertia. So I wouldn’t say it has “zero impact” bc it does.

 

[Who-Dat]

The truth is the 22 inch wheels on my R1T are more efficient than the smaller wheels offered by Rivian. The biggest wheel is the most efficient.

Why? It has a lower rolling resistance tire and a rim that is very aerodynamic.

Smaller size only matters if it improves rolling resistance, and to a lesser extent aerodynamics.

Bigger is sometimes better. Rivian isn't lying to you.

BIG Thanks..... This Clears it up

 

[Who-Dat]

Yeah bc they put off road tires on the 20" rim. Put the same tire that's on the 22" rim on the 20" rim and it is more efficient than the 22". Smaller rim is always "better" with the same tire and design.

So, it's the Rim size that matter, interesting. I was thinking that the 20" and 21" had the same Rim size. Thanks

 

[Lionel_Hutz]

Wild that posters are still in here asserting as fact that the 20" will be more efficient than the 21" if you put the same tires on. The Rivian engineers say that the 20" rim is slightly less efficient even if tires are taken out of the equation. Please watch the Jason Cammista interview.

 

[Jeremy3292]

Wild that posters are still in here asserting as fact that the 20" will be more efficient than the 21" if you put the same tires on. The Rivian engineers say that the 20" rim is slightly less efficient even if tires are taken out of the equation. Please watch the Jason Cammista interview.

That's not what we said here; please read the thread. We said all things being equal due to rotational inertia the 20" wins every time over 21". If the 21" rim is much aero designed than the 20" rim, well then yes the 21" rim will win. But if they have the same aero design, weight, and tire, the smaller rim wins every time, again due to rotational inertia.

Also can you provide the time stamp? I watched the whole video last week when it came out and don't recall them saying that. I'd like to listen if you have it please.

 

[iamnid]

So, it's the Rim size that matter, interesting. I was thinking that the 20" and 21" had the same Rim size. Thanks

Wait what? You thought 20" and 21" had the same RIM size? The numbers 20" and 21" are literally the inches of the RIM size. 21" ≠ 20"

They have the same WHEEL size/diameter (rim + tire) - 32 inches.

 

[FlyingPilot2012]

That's not what we said here; please read the thread. We said all things being equal due to rotational inertia the 20" wins every time over 21". If the 21" rim is much aero designed than the 20" rim, well then yes the 21" rim will win. But if they have the same aero design, weight, and tire, the smaller rim wins every time, again due to rotational inertia.

Also can you provide the time stamp? I watched the whole video last week when it came out and don't recall them saying that. I'd like to listen if you have it please.

It's a brief segment, starts at 46:25 mark.

When asked whether it was the wheel or tire that causes the 20" option to have less range, the engineer says "it's both but its primarily the tire, tire is the much bigger driver. The Cd [coefficient of drag I assume] for the wheels is slightly worse on the 20s but the tire is the massive difference"

 

[iamnid]

It's a brief segment, starts at 46:25 mark.

When asked whether it was the wheel or tire that causes the 20" option to have less range, the engineer says "it's both but its primarily the tire, tire is the much bigger driver. The Cd [coefficient of drag I assume] for the wheels is slightly worse on the 20s but the tire is the massive difference"

Yes, this was brought up almost 100 posts ago (post #20, in fact) but this thread MUST live on!

 

[FlyingPilot2012]

Yes, this was brought up almost 100 posts ago (post #20, in fact) but this thread MUST live on!

Yep! I know. But the question is still being asked, so the answer will still be given.

 

[Jeremy3292]

It's a brief segment, starts at 46:25 mark.

When asked whether it was the wheel or tire that causes the 20" option to have less range, the engineer says "it's both but its primarily the tire, tire is the much bigger driver. The Cd [coefficient of drag I assume] for the wheels is slightly worse on the 20s but the tire is the massive difference"

Thanks! So yeah this lines up with what we've said exactly "it's primarily the tires" and "the tires is the massive difference." Nowhere does he say the 21" will provide more range than the 20" if you gave the 20" on-road tires like Hankook ION EVOs for example.

Again, we are arguing about such minor range impact here if both rims have on-road tires. If everyone reads the thread they will see the discussion we had was around apples to apples comparisons, meaning same rim aero, same weight, same tires and then smaller always wins due to rotational inertia. But again, MINOR.

 

[mkhuffman]

Thanks! So yeah this lines up with what we've said exactly "it's primarily the tires" and "the tires is the massive difference." Nowhere does he say the 21" will provide more range than the 20" if you gave the 20" on-road tires like Hankook ION EVOs for example.

Again, we are arguing about such minor range impact here if both rims have on-road tires. If everyone reads the thread they will see the discussion we had was around apples to apples comparisons, meaning same rim aero, same weight, same tires and then smaller always wins due to rotational inertia. But again, MINOR.

The 20" tires will never be the same as the 21" tires, even if the brand and model are the same. The sidewall is different, which impacts rolling resistance. The only way you can truly say "the tires are the same" is if you only change the rims, and move the tires from one rim to another.

Rivian knows this. And Rivian has determined that they can get the best efficiency out of the R2 21" (22" in the R1) wheels.

Why? I don't know, but I suspect the shorter sidewall decreases the road patch and consequently reduces rolling resistance.

If Rivian could improve EPA range with a smaller wheel, they would do it. Right?

I agree it seems counter intuitive, until you step back and realize that size is not the variable that matters. Multiple variables matter, and you can get better results with a larger wheel. If you design it properly.

 

[sparked]

The 20" tires will never be the same as the 21" tires, even if the brand and model are the same. The sidewall is different, which impacts rolling resistance. The only way you can truly say "the tires are the same" is if you only change the rims, and move the tires from one rim to another.

Rivian knows this. And Rivian has determined that they can get the best efficiency out of the R2 21" (22" in the R1) wheels.

But the 20" wheels on the Premium with the same overall diameter Pirellis and same tread pattern gets the same range as the 21". They both get 330 miles range on All Season Pirellis.

So why would we say 21" has the best efficiency when 20" Premium wheels can get the same range with same brand/model All Season tires?

 

[mkhuffman]

But the 20" wheels on the Premium with the same overall diameter Pirellis and same tread pattern gets the same range as the 21". They both get 330 miles range. So why would we say 21" has the best efficiency when 20" can get a similar range with similar All Season tires?

Because the 20" isn't better. If smaller is always better, the 20" would be better, right?

"Similar" is the key. You can't say they are the same tires when they are different sizes.

I am not saying bigger is more efficient. I am saying bigger CAN be more efficient. Smaller can be more efficient also. It depends on tire design and rim design, not size.

 

[NY_Rob]

Yes, this was brought up almost 100 posts ago (post #20, in fact) but this thread MUST live on!

I'll take the over at 26 on this thread too

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