Ride comfort 20 vs 21

[140 degrees]

I switch between the OEM tires on 20 inch and 21 inch wheels for winter and summer. I have seen the 21 inch experience described as more 'connected to the road'. I agree.

I was surprised to find that the 21 inch launch acceleration feels faster from a stop. The 20 inch soaks up road imperfections without feeling 'floaty'. The 20 inch carves through a turn better than I expected. Think skiing powder v packed snow. When they are both new, the noise level isn't very different. I can't speak to noise level later in life.

If you just do some soft road driving, and the streets and highways in your area are smooth, the 21 inch would be my preference. On a full charge, I see roughly 30 mile improvement in range using the OEM 21s. However, I think the 20s look better on the truck.

This is all for OEM options. Usually, the smaller the rims mounted on an EV, the better the efficiency. Here, I have been comparing all season 21s to all terrain 20s. I believe the people who say they are getting better range than the 21 AS on their 20 AS tires. Also, don't forget to consider the rims. The people reporting the best results seem to be running the 20 inch brights, which are now obsolete. (The 20 inch darks have the same surface profile, however.) The Aero covers on the 21s make a small difference in range. I put them on for road trips.

For those looking for great snow performance, I know the OEM 20s are not optimal. They work well enough for me, I live below the snow line, and I wanted to get a set of the 20 inch brights before they disappeared.

Some will point out that the 22 would provide even better handling than the 21. True, but for me it is too easy to collect curb rash when running really low profile tires.

Hope this helps.

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[Porfiry]

The people reporting the best results seem to be running the 20 inch brights, which are now obsolete. (The 20 inch darks have the same surface profile, however.)

What's your source on that, is this efficiency difference quantified somewhere? I'm leaning towards the 20"s (mostly for decent winter tire options). I wouldn't normally pay extra for the dark rims, but if they're more efficient, I'd probably go for them.

Great write up, btw. Very helpful.

 

[140 degrees]

Unfortunately, I haven't seen a test of the efficiency difference between the rims. I have noticed that when people report really good efficiency and include a picture, the 20 inch brights or darks often show up. For example, see the post earlier in this thread from anthonysfl. If you inspect the rims, it seems clear that the darks have a better aero design than the other 20 inch option. How much better, and is it worth the cost? Excellent question.

 

[VSG]

Correct, the 20” General Grabber HTS60 (275/60R20) is equal to or more efficient than 21” OEM. Riviot, LL75, JJE, ajthonysfl, and many others have data to confirm. Other than wearing out very quick and being expensive, not sure what the key attributes of the 21” tire are.

In making this conclusion, have you corrected your efficiency for the change in diameter when you put the smaller 60R20 on your 20" wheels? It seems unlikely to me that you could get a >=15% increase in efficiency.

 

[shap]

In making this conclusion, have you corrected your efficiency for the change in diameter when you put the smaller 60R20 on your 20" wheels? It seems unlikely to me that you could get a >=15% increase in efficiency.

No change in diameter - they both 33". Guys in this thread talkg simultaneously about two totally different things - switching from 21 to 20 but the same diameter tires - like grabber hts60 - this will result in better efficiency and much lower cost of ownership per mile. Ride quality will be the same or better than stock 21".

Others are talking about stock 20" AT tires - they are very different, loud and less efficient by definition of AT tires.

 

[VSG]

Um, there certainly is a difference in diameter between the stock 65R20 and the suggested 60R20. It's a difference of about 3%.

I am aware that some people who bought 21” wheels are replacing them with 20" wheels and the smaller 60R20 tires that are the same diameter as the stock 21" tires, so they don't have to recalibrate, but in context that doesn't seem to be the case for the post I quoted.

Regardless, it was claimed that a 60R20 tire, necessarily on a 20" rim, is at least as (or more) efficient than the stock 55R21 tire on a 21" wheel. That's the claim I'm doubtful of.

Yes there is a lot of confusion about this issue because posters don't say what they mean and probably don't understand the facts. But it is meaningless to claim that a smaller diameter tire is more efficient if you don't take into account either tire diameter or wheel size

My 20" Pirellis are still quiet after 25k miles, BTW.

 

[Agassi]

I was wondering why you might want to switch from 21" to 20 AT's. I like the 21" street tire because it's quiet, good in deep sand. and gives better mileage. So basically I have no need to switch and would like to understand what I m missing.

Same here, it serves the purpose. Light off road is also fine. If there is a need for rock crawl or hard off roading go with it.

 

[Rivian_Hugh_III]

Yes, just put 275/60/20 AS Pirelli AS Plus 3 tire on 20’s. I have that on my R1S and it’s 7% more efficient than my R1T with 21’s.

Whoa, my man, what HAVE you done to those wheels?

 

[Rivian_Hugh_III]

Um, there certainly is a difference in diameter between the stock 65R20 and the suggested 60R20. It's a difference of about 3%.

I am aware that some people who bought 21” wheels are replacing them with 20" wheels and the smaller 60R20 tires that are the same diameter as the stock 21" tires, so they don't have to recalibrate, but in context that doesn't seem to be the case for the post I quoted.

Regardless, it was claimed that a 60R20 tire, necessarily on a 20" rim, is at least as (or more) efficient than the stock 55R21 tire on a 21" wheel. That's the claim I'm doubtful of.

Yes there is a lot of confusion about this issue because posters don't say what they mean and probably don't understand the facts. But it is meaningless to claim that a smaller diameter tire is more efficient if you don't take into account either tire diameter or wheel size

My 20" Pirellis are still quiet after 25k miles, BTW.

The fun thing about life is you get to be as skeptical as you want.

It has been reported often and consistently that people with 20" wheels who buy slightly larger street tires get the same efficiency as the 21" stock wheels and tires. Smaller metal wheel = less energy to turn it.

 

[anthonysfl]

Um, there certainly is a difference in diameter between the stock 65R20 and the suggested 60R20. It's a difference of about 3%.

I am aware that some people who bought 21” wheels are replacing them with 20" wheels and the smaller 60R20 tires that are the same diameter as the stock 21" tires, so they don't have to recalibrate, but in context that doesn't seem to be the case for the post I quoted.

Regardless, it was claimed that a 60R20 tire, necessarily on a 20" rim, is at least as (or more) efficient than the stock 55R21 tire on a 21" wheel. That's the claim I'm doubtful of.

Yes there is a lot of confusion about this issue because posters don't say what they mean and probably don't understand the facts. But it is meaningless to claim that a smaller diameter tire is more efficient if you don't take into account either tire diameter or wheel size

My 20" Pirellis are still quiet after 25k miles, BTW.

I am not sure you understand the facts either.



Large pack R1T (which is slightly more aerodynamic than the R1S by the way) on 21’s with inserts in. Lifetime mi/kwh for about 5500 miles was 2.31.
Bought a R1S that came with 22’s. Switched to Rivian 20 brights and put on 275/60/20 Pirelli AS 3 tires. Lifetime mi/kwh with the S around 6k miles was 2.48. Not to mention I have sidesteps and small mud flaps on my S further reducing its aerodynamic efficiency.

 

[anthonysfl]

Whoa, my man, what HAVE you done to those wheels?

I wrapped a portion of the wheel (Rivian 20 AT bright) in 3M stainless steel to match the rest of the car that I wrapped that color for an accent.

 

[jemkewl]

Just rough data:
Over 10k miles on stock 21s and averaged 2.77 per Rivian's trip meter.
Over 1500 miles on AW 20" rims with ms/2 60s (same overall size as 21s) average of 2.51 on rivian trip meter.

I am expecting the 20" ms/2s to be better than 21" stock efficiency as they are close to the overall stock efficiency and haven't been driven in a warmer season yet*.

*I'd get about 3.2 in summer and 2.2 in winter.

 

[ksurfier]

Um, there certainly is a difference in diameter between the stock 65R20 and the suggested 60R20. It's a difference of about 3%.

I am aware that some people who bought 21” wheels are replacing them with 20" wheels and the smaller 60R20 tires that are the same diameter as the stock 21" tires, so they don't have to recalibrate, but in context that doesn't seem to be the case for the post I quoted.

Regardless, it was claimed that a 60R20 tire, necessarily on a 20" rim, is at least as (or more) efficient than the stock 55R21 tire on a 21" wheel. That's the claim I'm doubtful of.

Yes there is a lot of confusion about this issue because posters don't say what they mean and probably don't understand the facts. But it is meaningless to claim that a smaller diameter tire is more efficient if you don't take into account either tire diameter or wheel size

My 20" Pirellis are still quiet after 25k miles, BTW.

Sounds like you are focusing on the minutiae, you are describing an issue of “noise”. All of the efficiency data (MPK) reported here is subject to being “ballpark”.

From what I’ve seen, people smart enough to calculate basic math are in fact reducing their MPK values by ~0.05 MPK to get a corrected value…but I would argue that’s too far into the weeds given the variations due to elevation, Temperature and pressure (air density), road types, driving styles, unequal elevation (hills), vehicle weight, and so on.

Soon I will have test data for a new tire (Geolander CV 4S), look forward to you picking it apart, in the meantime here is MPK ranges for the OEM 20” Pirelli at @56 degrees Fahrenheit and air density of 100%. Note the data above 50 mph is older. Will get the same range of data for the CV 4S…haven’t seen very much test data for the 21” tires…

 

[LL75]

Just rough data:
Over 10k miles on stock 21s and averaged 2.77 per Rivian's trip meter.
Over 1500 miles on AW 20" rims with ms/2 60s (same overall size as 21s) average of 2.51 on rivian trip meter.

I am expecting the 20" ms/2s to be better than 21" stock efficiency as they are close to the overall stock efficiency and haven't been driven in a warmer season yet*.

*I'd get about 3.2 in summer and 2.2 in winter.

2.77 on stock 21" is insane. I swapped my 21" at 16k miles and my lifetime is at 2.29 with about 90% all purpose drive. I'm currently runs the same set up as you but with general grabbers hts 60 and according to limited number from electrify, im getting around 2.5 all purpose with this 80 degree temperature. When I first switched , it was around 2.0 but the weather was a little cold and tires was sticky.

 

[ksurfier]

2.77 on stock 21" is insane. I swapped my 21" at 16k miles and my lifetime is at 2.29 with about 90% all purpose drive. I'm currently runs the same set up as you but with general grabbers hts 60 and according to limited number from electrify, im getting around 2.5 all purpose with this 80 degree temperature. When I first switched , it was around 2.0 but the weather was a little cold and tires was sticky.

I think the BIG problem of the 21” setup is that the rim is reported to weigh something like 48 pounds. Adding the 37 pound tire means it’s a total of 85 pounds vs ~62 pounds for the AW 20” rims plus grabber HTS, wheel weight has about half the impact as tire weight (rotational inertia, ie distance from rotational axis), tire rolling resistance between the tires are likely different…all in all it’s not that surprising that 275/60R20 (20”) is more efficient than 21” setup…is it?

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