R2: 20” vs. 21” Tires Detailed Comparison

[stewmander]

What "real world testing" are you referring to? RR is NOT real world testing. It's dirty data without any context to help us analyze it. Is that what you are referring to?

OOS, SOC, Andrew Vaught, Edmunds, Car and Driver, Motor Trend. All ran real world tests and none got the EPA and Rivian stated range. Edmunds came closest but was still 8% under EPA/Rivian stated range.

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[mkhuffman]

OOS, SOC, Andrew Vaught, Edmunds, Car and Driver, Motor Trend. All ran real world tests and none got the EPA and Rivian stated range. Edmunds came closest but was still 8% under EPA/Rivian stated range.

Yes. And none of them claimed the 20s are as efficient as the 21s.

Rivian would be stupid to market the 20s as much less efficient then they actually are. Are they stupid? No. The relative EPA results are accurate. The 21s are more efficient. Significantly so.

 

[stewmander]

Yes. And none of them claimed the 20s are as efficient as the 21s.

Rivian would be stupid to market the 20s as much less efficient then they actually are. Are they stupid? No. The relative EPA results are accurate. The 21s are more efficient. Significantly so.

No one claimed the 20" were as efficient that the 21", not even OOP:

There is currently no evidence of the large 20” efficiency penalty many of us expected.

A 0–2%-ish real-world difference looks considerably more plausible than something like 7–10%, based on the information available so far.

Everything so far has shown that the Rivian and the EPA claimed range for the R2 is overestimated, and it appears so is the efficiency gap between the 21" and 20".

 

[mkhuffman]

No one claimed the 20" were as efficient that the 21", not even OOP:



Everything so far has shown that the Rivian and the EPA claimed range for the R2 is overestimated, and it appears so is the efficiency gap between the 21" and 20".

This is incorrect. If you drive like the EPA cycle, you will get the EPA results. It isn't overestimated at all. You just don't understand how EPA testing is done.

And the OP has actually claimed the 20" is more efficient than the 21". Which is ridiculous, but that is his claim.

 

[stewmander]

This is incorrect. If you drive like the EPA cycle, you will get the EPA results. It isn't overestimated at all. You just don't understand how EPA testing is done.

And the OP has actually claimed the 20" is more efficient than the 21". Which is ridiculous, but that is his claim.

The EPA cycle is not real world, you CAN'T drive like the EPA cycle because wind, weather, road surfaces, elevation, etc. all exist.

Plus I already brought this up, the Edmunds test was the closest to the EPA cycle in terms of city/highway splits, and even they were still 8% UNDER the EPA range.

Bottom line, not one real world test has gotten the EPA estimated range. On top of that, the data is indicating the real world GAP between the 21" and 20" wheel efficiency also appears to be lower that stated.

Feel free to quote OOP where he said the 20" were more efficient than the 21", or provide any real worlds tests that have obtained the EPA stated range.

 

[dub]

The EPA cycle is not real world, you CAN'T drive like the EPA cycle because wind, weather, road surfaces, elevation, etc. all exist.

Plus I already brought this up, the Edmunds test was the closest to the EPA cycle in terms of city/highway splits, and even they were still 8% UNDER the EPA range.

Correct, Edmunds test as both advantages and disadvantages stacked against trying to match EPA numbers. It is driving real cities vs simulated cities, meaning there's no control over start/stop or average speed. For highway, they are cruising real interstate highways at 65-70 vs the EPA highway simulation that averages 48 mph and tops out at 60. The mix of the two values also differs.

The reality is that the EPA tests only really provide value in comparison to other EPA test results, precisely because numbers vary so much depending on environmental conditions and driving styles. The flip side of that is that it would take a tremendous number of controlled real-world tests to actually average out environmental and driving differences to get actual comparable values rather than just a handful of anecdotal data points.

Bottom line, not one real world test has gotten the EPA estimated range. On top of that, the data is indicating the real world GAP between the 21" and 20" wheel efficiency also appears to be lower that stated.

I mean, the "easy" way to compare would be to have two launch edition R2 side by side do a full range test. Then, take them to the shop, swap their wheels and repeat.

 

[stewmander]

Correct, Edmunds test as both advantages and disadvantages stacked against trying to match EPA numbers. It is driving real cities vs simulated cities, meaning there's no control over start/stop or average speed. For highway, they are cruising real interstate highways at 65-70 vs the EPA highway simulation that averages 48 mph and tops out at 60. The mix of the two values also differs.

I read up on the Edmunds test and they define a highway as any road with a posted speed limit of 55, and they instruct their drivers to be within 5 miles of the posted limit. So, their highway test portion would have ranged from 50-70 mph. A small technicality, however, I would much rather have the actual data from Edmunds to figure out the city/highway portions actual speeds.

The reality is that the EPA tests only really provide value in comparison to other EPA test results, precisely because numbers vary so much depending on environmental conditions and driving styles. The flip side of that is that it would take a tremendous number of controlled real-world tests to actually average out environmental and driving differences to get actual comparable values rather than just a handful of anecdotal data points.

ETA: I think this is pretty much OOPs point. EPA tests aren't representative of real world conditions or drivers. The data and tests are not getting the EPA range, and they're not getting the EPA efficiency gap between the 21" and 20" either. We'll see how it goes as sample size increases.

I mean, the "easy" way to compare would be to have two launch edition R2 side by side do a full range test. Then, take them to the shop, swap their wheels and repeat.

That sounds like a 4 hour 3 part OOS special! Someone call Jose![/QUOTE]

 

[mkhuffman]

...
Bottom line, not one real world test has gotten the EPA estimated range.
...

Not true:
https://www.rivianforums.com/forum/...are-the-260-mile-r2-drives.63219/post-1085278

...
Feel free to quote OOP where he said the 20" were more efficient than the 21", ...

Here you go:
https://www.rivianforums.com/forum/threads/growing-efficiency-gap-r2-w-21-vs-20-tire-sets.62299/

 

[ksurfier]

I read up on the Edmunds test and they define a highway as any road with a posted speed limit of 55, and they instruct their drivers to be within 5 miles of the posted limit. So, their highway test portion would have ranged from 50-70 mph. A small technicality, however, I would much rather have the actual data from Edmunds to figure out the city/highway portions actual speeds.



ETA: I think this is pretty much OOPs point. EPA tests aren't representative of real world conditions or drivers. The data and tests are not getting the EPA range, and they're not getting the EPA efficiency gap between the 21" and 20" either. We'll see how it goes as sample size increases.



That sounds like a 4 hour 3 part OOS special! Someone call Jose!

[/QUOTE]

Pretty much, if Gen 1 could get 95% of EPA efficiency, why doesn't R2? Can R2 get 70%, 75%, ? - It's not clear and that matters a lot for many buyers (for <1%, apparently either don't care or don't want to know)...

 

[dub]

ETA: I think this is pretty much OOPs point. EPA tests aren't representative of real world conditions or drivers. The data and tests are not getting the EPA range, and they're not getting the EPA efficiency gap between the 21" and 20" either. We'll see how it goes as sample size increases.

Yes, I think this is a correct representation of EPA tests. I think it is incorrect to say a vehicle is reporting fraudulent numbers, which I've seen quite a few claim Rivian did with the R2.

As the more extreme example, I would expect the measured highway range to be at least halved going 85 mph vs 50 mph for every vehicle. One can look at the EPA city/highway numbers right away and tell that the testing is never going to capture that reality.

People just don't care as much with ICE. Once you have 500 miles of range on a tank and quick refueling, it's a hit to the pocketbook to go faster and not a change in planning.

That sounds like a 4 hour 3 part OOS special! Someone call Jose!

I think they should probably have a 90 minute recap video first to help people who haven't kept up with OOS coverage.

 

[dub]

Pretty much, if Gen 1 could get 95% of EPA efficiency, why doesn't R2? Can R2 get 70%, 75%, ? - It's not clear and that matters a lot for many buyers (for <1%, apparently either don't care or don't want to know)...

The monkey wrench is that the EPA will apply an arbitrary scaling factor if you don't do additional testing. This is what you see when you hear of a vehicle "beating" their EPA numbers; they opted out of additional testing and potentially took lower values for both MPGe and range.

Where this causes a problem is when you compare say a 70mph range test without first establishing whether the EPA values are accurate at lower ranges. That winds up just stacking unmeasurable scalings (e.g. you don't know the true range at city/slower highway speeds, plus an unknown coefficient of drag impacting efficiency at higher speeds)

 

[stewmander]

Not true:
https://www.rivianforums.com/forum/...are-the-260-mile-r2-drives.63219/post-1085278

3.36 mi/kwh comes out to 295 miles of range. Unless I am missing something I think you've proved my point.

Here you go:
https://www.rivianforums.com/forum/threads/growing-efficiency-gap-r2-w-21-vs-20-tire-sets.62299/

You really should read beyond the headline:

That does not prove the 20s are inherently more efficient.

The remaining question is whether, after controlling for speed, elevation, trip length, weather, and other variables, the 21s actually deliver the ~7% freeway advantage suggested by EPA testing, or whether the real-world difference is materially smaller.

they increasingly suggest that the EPA/coastdown testing may overstate the real-world efficiency benefit of the 21” wheel/tire package

 

[stewmander]

I think they should probably have a 90 minute recap video first to help people who haven't kept up with OOS coverage.

I hope he does it from his kitchen table while reading off a printed spreadsheet.

 

[FL5Guy]

This was one of the things that we thought long and heard about as we wait for our order on the R2. I’m into bigger wheels, to some extent but… In this case, we’ve decided to go with the 20 inch wheels for a few reasons:

It actually looks pretty cool with a meatier Tire.

Replacement tires are about half the cost and there’s a shockingly more available selection. There is only 1 21 inch tire that’s designed to fit that car right now.

By manipulating the size a little bit, I can add a ton more 20 inch tires. It’s still half the cost.

A few miles lost in range are irrelevant to us. And if I eventually replace the 20 inch BFGoodrich, which is actually a very highly rated Tire, with a more EV rated Tire I’ll get that range back.

I’ve already been messing around with some sizing options to keep it relatively the same, but give me more Tire choices down the line.

For what it’s worth.

 

[mkhuffman]

3.36 mi/kwh comes out to 295 miles of range. Unless I am missing something I think you've proved my point.




You really should read beyond the headline:

He hasn't given up and is still using his AI slop to claim the 20s are more efficient.
https://www.rivianforums.com/forum/...ap-r2-w-21-vs-20-tire-sets.62299/post-1085429

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