20in wheel worse range even with all season tires?

[mferring]

And thanks Kanundrum for the link recommendation. Much appreciated.

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[Mos Eisley]

I can't find it at the moment, but in a fairly recent video, guys from Rivian discuss the wheels' aero design vs weight/rigidity etc. I know it was in the Camissa video too - where they said the range hit was the AT rubber. We know that the relative mileage difference between the R2's 20's and 21's is slight and that the rubber for each was selected in combo with the wheel's design. I could see it being possible that the weight and design of the 20's, built to be sturdier off the pavement, could easily offset/negate much if any of the gains by switching to certain 20" tires. The only "appreciable" improvement I'm seeing is the 19" on the standard - but that range might also just be that the standard is probably a slightly lighter vehicle.

 

[Big Kidd]

Rivian has said the Outisde Diameter (OD) is 32 inches for both size rims with tires mounted (20" & 21"). So, the rollout is the same. The 20' wheel & tire combo must be heavier than the 21" wheel & tire combo. That would explain the result of less range when using the 20" wheel.

 

[ksurfier]

This goes against physics. A smaller rim will give better range with all other things being equal.

Absolutely correct! See #6 below:

Moving mass outward will always have a negative effect (albeit to a lesser extent than other variables):

For efficiency, prioritize in this order for relative importance:

1. Low-Crr construction/compound (30%)
2. Less aggressive tread (24%)
3. Lower tire weight, especially tread/belt mass (16%)
4. Reasonable width (12%)
5. Lighter wheel (9%)
6. Smaller rim, usually 20” over 21/22” (5%)
7. Diameter, but 32” vs 33” is not usually decisive (4%)

 

[iamnid]

This question specifically comes up in the carmudgeon podcast. The two Rivian designers say that the range difference between 21s and 20s is almost entirely based on the tires Rivian provides with each. The one engineer says the 21" rims might be ever so slightly more aero efficient but it's negligible. Skip to 46:20 in this video:



There you go. Question answered from the horse's mouth

 

[mferring]

This question specifically comes up in the carmudgeon podcast. The two Rivian designers say that the range difference between 21s and 20s is almost entirely based on the tires Rivian provides with each. The one engineer says the 21" rims might be ever so slightly more aero efficient but it's negligible. I wish I could provide the exact point in the video where it's discussed but here's the video



There you go. Question answered from the horse's mouth

Thanks....will take a listen!

 

[ksurfier]

Nope. For. 20" changing a tire won't increase overall range it'll definitely increase efficiency in the city but if the overall diameter of the tire is shorter/less tall compared to an off road tire you are loosing distanced traveled.

Huh? Range and efficiency are proportional! So efficiency can’t change without also affecting range.

Range = usable battery energy x actual MPK

2.2 MPK with a usable battery of 128 kWh = 282 miles of range

2.48 MPK @ 128 kWh = 317 miles of range

 

[Mos Eisley]

This question specifically comes up in the carmudgeon podcast. The two Rivian designers say that the range difference between 21s and 20s is almost entirely based on the tires Rivian provides with each. The one engineer says the 21" rims might be ever so slightly more aero efficient but it's negligible. Skip to 46:20 in this video:



There you go. Question answered from the horse's mouth

Thanks- that's the segment I was thinking of.

 

[Mos Eisley]

So back to the OP's question, given the properties of the 20" wheel - the service guy is inferring there's not AS rubber out there that will overcome the deficit. Not meaningfully anyway. Which returns a buyer back to the only "significant" reason to buy the 20's is the much wider selection of tires vs the one tire currently for the 21's.

 

[iamnid]

So back to the OP's question, given the properties of the 20" wheel - the service guy is inferring there's not AS rubber out there that will overcome the deficit. Not meaningfully anyway. Which returns a buyer back to the only "significant" reason to buy the 20's is the much wider selection of tires vs the one tire currently for the 21's.

The service guy is likely wrong. See the video I linked.

 

[mferring]

So back to the OP's question, given the properties of the 20" wheel - the service guy is inferring there's not AS rubber out there that will overcome the deficit. Not meaningfully anyway. Which returns a buyer back to the only "significant" reason to buy the 20's is the much wider selection of tires vs the one tire currently for the 21's.

Seems true. Or wait for the Performance which gives you the lighter 20in wheel.

But unfortunately, I would not say that it is even a wide selection for the 20in tire. It is also very limited compared to smaller diameters......but a lot more than the single option for the 21!

 

[ksurfier]

So back to the OP's question, given the properties of the 20" wheel - the service guy is inferring there's not AS rubber out there that will overcome the deficit. Not meaningfully anyway. Which returns a buyer back to the only "significant" reason to buy the 20's is the much wider selection of tires vs the one tire currently for the 21's.

20” is likely more efficient than 21” with the right tire, I only see 1 potential option and it may or may not best 21” for efficiency:

Factory 20” setup (64#): 307 miles EPA with 87 kWh = 3.53 MPK.

Factory 21” setup (62#): 330 miles EPA with 87 kWh = 3.79 MPK, about 7.5% more efficient than the 20” setup. The 7% heavier 21” rim (30 v 28) results in a penalty of ~5%. But the 12% lighter tire (32 v 36) means the net 21” efficiency is ~7% better than 20” OEM option.

20” rim (28#) + Michelin estimate (32#): likely ~332–340 miles EPA-equivalent, best guess ~335 miles / 3.85 MPK, roughly 9% better than factory 20” and ~1–2% better than factory 21”.

My best guess is the 60# 20” combo will at least match the 21” 62# setup, but the cost will be a tire with only 8.5/32” tread depth…

 

[DirkM]

Isn't it true that the wheel (tire + rim) always has the same diameter? With a 21" rim, the tire is 55 high, with a 20" rim the tire is 60 and with 19" rim the tire is 65. Since they all have the same 255 width, the only difference between 20" AT and 21" AS is the tire thread which should make a difference on highways (wind and roll resistance). In city driving, a heavier 20" AT rim may make a difference because it's harder to get moving but overall, using a AS tire on the 20" AT rim should be very close to using the 20" AS rim on the Premium.

 

[Jeremy3292]

Isn't it true that the wheel (tire + rim) always has the same diameter? With a 21" rim, the tire is 55 high, with a 20" rim the tire is 60 and with 19" rim the tire is 65. Since they all have the same 255 width, the only difference between 20" AT and 21" AS is the tire thread which should make a difference on highways (wind and roll resistance). In city driving, a heavier 20" AT rim may make a difference because it's harder to get moving but overall, using a AS tire on the 20" AT rim should be very close to using the 20" AS rim on the Premium.

Every wheel option on R2 is 32” in diameter. So if you have a smaller rim you have 1” more sidewall for every 1” smaller rim.

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