ksurfier
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R2 efficiency at 70 mph, normalized to 70°F and sea level
The available lines of evidence converge on approximately:
The 21-inch estimate assumes it is exactly 5% more efficient than the 20-inch A/T setup.
1. Wisconsin interstate measurement — strongest direct evidence
( First short road trip in R2 - Initial range and efficiency )
The owner reported approximately 2.5–2.6 mi/kWh during the interstate portion while traveling around 78 mph. The vehicle had 20-inch A/T tires, and the overall trip efficiency later increased to 2.8 mi/kWh only because the second half included slower two-lane roads and 30–45 mph towns. Therefore, the 2.8 figure is not the appropriate highway benchmark.
Relevant conditions were:
Normalizing the competing effects:
2. The 500-foot climb modestly depressed the trip result
The route ended approximately 500 feet higher than it began and included rolling terrain.
For a vehicle of the R2’s approximate mass, a 500-foot net climb likely represents around 1 kWh of additional battery energy, or roughly a 2% effect across a 131-mile trip. The exact effect on the interstate-only segment is unknown because the elevation profile was not provided.
This supports a small upward adjustment—but not a dramatic one—to the observed result.
3. Sea-level normalization slightly reduces efficiency
The Wisconsin route was approximately 700–1,200 feet above sea level. At sea level, the air is somewhat denser, increasing aerodynamic drag.
Because only part of total highway consumption is aerodynamic, the likely sea-level penalty is approximately:
Together, elevation and temperature normalization likely reduce the measured efficiency by around 1.5–2.5%, partially offsetting the benefit of eliminating the net climb.
4. New 20-inch A/T tires may have slightly understated mature efficiency
The owner clarified that the 20-inch A/T tires had only 45 miles on them.
Commenters with tire experience noted that new tires can require several hundred to approximately 1,000 miles before their rolling resistance stabilizes.
This is a plausible but weakly quantified correction. A reasonable allowance might be:
5. All-Purpose mode makes the result representative of normal driving
The R2 was driven in All-Purpose mode, rather than a special efficiency mode.
One commenter suggested a Conserve-type mode might have improved the result. However, without direct testing, the improvement cannot be quantified. At steady highway speed, the difference may be limited unless the mode changes ride height, axle operation or thermal strategy.
Thus, 2.6 mi/kWh should be understood as a normal-use estimate, not an absolute best-case result.
6. The 66 mph datapoint provides an upper-side check
A separate owner-provided datapoint was:
Even so, adjusting from 66 to 70 mph would reasonably bring the value down into approximately the 2.8–3.0 mi/kWh area, rather than 2.5. This provides evidence that the Wisconsin result may be somewhat conservative, but the missing details prevent treating it as equally strong evidence.
7. The 68 mph measurement supports the 21-inch estimate
Another reported value was approximately:
8. The user test-drive result supports approximately 2.7 mi/kWh but is highly confounded
( R2 Highway Efficiency Test: 80 MPH vs 70 MPH Changed Everything)
The Van Nuys test drive produced approximately:
It is nevertheless consistent with the proposition that an R2 on 21-inch wheels can operate around:
9. CdA comparison independently supports an intermediate value
The supplied aerodynamic drag areas are:
The R2 therefore has:
This places the R2 logically:
10. Basic aerodynamic calculation is consistent with the estimate
Using:
At 2.60 mi/kWh, total battery consumption is:
1÷2.60=0.385 kWh/mile1 \div 2.60 = 0.385\text{ kWh/mile}1÷2.60=0.385 kWh/mile
At 2.73 mi/kWh, total battery consumption is:
1÷2.73=0.366 kWh/mile1 \div 2.73 = 0.366\text{ kWh/mile}1÷2.73=0.366 kWh/mile
That means aerodynamic drag represents roughly half of total battery consumption, with the remainder attributable to:
11. The 5% wheel/tire assumption produces a defensible 21-inch value
Applying the specified 5% improvement:
2.60×1.05=2.73 mi/kWh2.60 \times 1.05 = 2.73\text{ mi/kWh}2.60×1.05=2.73 mi/kWh
Equivalent energy consumption:
The 5% improvement reduces consumption by approximately 19 Wh/mi. That is a credible tire-and-wheel difference at highway speed.
12. The mixed-trip 2.8 mi/kWh result is a useful consistency check
The entire 131-mile trip averaged 2.8 mi/kWh after combining:
It does not, however, establish 2.8 mi/kWh as steady 70 mph efficiency.
13. The displayed efficiency may introduce measurement uncertainty
A commenter noted that the Rivian energy display in an R1 did not always agree with independently calculated energy consumption.
It is unknown whether the R2 display behaves similarly. Until controlled tests provide:
14. ABRP is supporting evidence only after calibration
ABRP’s physics-based route model may be useful, but an early default R2 efficiency parameter is not an independent real-world measurement. It should be calibrated against actual energy and trip data.
Therefore:
Strongest evidence
The Wisconsin interstate observation, after considering tailwind, elevation, temperature, net climb and new A/T tires, supports:
The 68 mph, 66 mph, test-drive and CdA evidence generally places an efficient road-tire configuration in the high-2s, supporting:
The available lines of evidence converge on approximately:
| Wheel/tire setup | Best estimate | Reasonable range |
|---|---|---|
| 20-inch A/T | 2.60 mi/kWh | 2.50–2.70 mi/kWh |
| 21-inch road tire | 2.73 mi/kWh | 2.63–2.84 mi/kWh |
The 21-inch estimate assumes it is exactly 5% more efficient than the 20-inch A/T setup.
1. Wisconsin interstate measurement — strongest direct evidence
( First short road trip in R2 - Initial range and efficiency )
The owner reported approximately 2.5–2.6 mi/kWh during the interstate portion while traveling around 78 mph. The vehicle had 20-inch A/T tires, and the overall trip efficiency later increased to 2.8 mi/kWh only because the second half included slower two-lane roads and 30–45 mph towns. Therefore, the 2.8 figure is not the appropriate highway benchmark.
Relevant conditions were:
- Approximately 78°F
- Roughly 78 mph ground speed
- 5–10 mph tail/crosswind on the interstate
- 20-inch A/T tires
- All-Purpose mode
- Approximately 700 to 1,200 feet elevation
- New tires with only about 45 miles of use
Normalizing the competing effects:
- Slowing road speed from 78 to 70 mph improves rolling, drivetrain and aerodynamic efficiency.
- Removing the tailwind increases aerodynamic load.
- Moving from roughly 700–1,200 feet to sea level increases air density and slightly worsens efficiency.
- Moving from 78°F to 70°F also slightly increases air density.
- Removing the approximately 500-foot net climb improves the result.
- Breaking in the nearly new A/T tires could modestly improve the result.
2. The 500-foot climb modestly depressed the trip result
The route ended approximately 500 feet higher than it began and included rolling terrain.
For a vehicle of the R2’s approximate mass, a 500-foot net climb likely represents around 1 kWh of additional battery energy, or roughly a 2% effect across a 131-mile trip. The exact effect on the interstate-only segment is unknown because the elevation profile was not provided.
This supports a small upward adjustment—but not a dramatic one—to the observed result.
3. Sea-level normalization slightly reduces efficiency
The Wisconsin route was approximately 700–1,200 feet above sea level. At sea level, the air is somewhat denser, increasing aerodynamic drag.
Because only part of total highway consumption is aerodynamic, the likely sea-level penalty is approximately:
Likewise, reducing temperature from 78°F to 70°F slightly increases air density. That probably contributes another fraction of a percent to approximately 1% of additional consumption.
Together, elevation and temperature normalization likely reduce the measured efficiency by around 1.5–2.5%, partially offsetting the benefit of eliminating the net climb.
4. New 20-inch A/T tires may have slightly understated mature efficiency
The owner clarified that the 20-inch A/T tires had only 45 miles on them.
Commenters with tire experience noted that new tires can require several hundred to approximately 1,000 miles before their rolling resistance stabilizes.
This is a plausible but weakly quantified correction. A reasonable allowance might be:
That could move a 2.55–2.60 result closer to approximately 2.60–2.65 mi/kWh, but it does not support a leap to 3.0 mi/kWh by itself.
5. All-Purpose mode makes the result representative of normal driving
The R2 was driven in All-Purpose mode, rather than a special efficiency mode.
One commenter suggested a Conserve-type mode might have improved the result. However, without direct testing, the improvement cannot be quantified. At steady highway speed, the difference may be limited unless the mode changes ride height, axle operation or thermal strategy.
Thus, 2.6 mi/kWh should be understood as a normal-use estimate, not an absolute best-case result.
6. The 66 mph datapoint provides an upper-side check
A separate owner-provided datapoint was:
That result is not fully controlled, and the higher temperature reduces air density and may improve aerodynamic efficiency. Depending on wind, terrain and trip length, it could overstate steady-state highway efficiency.
Even so, adjusting from 66 to 70 mph would reasonably bring the value down into approximately the 2.8–3.0 mi/kWh area, rather than 2.5. This provides evidence that the Wisconsin result may be somewhat conservative, but the missing details prevent treating it as equally strong evidence.
7. The 68 mph measurement supports the 21-inch estimate
Another reported value was approximately:
Assuming that result involved the 21-inch setup or similarly efficient road tires, adjusting from 68 to 70 mph would likely reduce it modestly to approximately:
Normalization for temperature, wind and elevation could shift it in either direction. Nevertheless, it is broadly consistent with the current 2.7–2.75 mi/kWh estimate for the 21-inch setup.
8. The user test-drive result supports approximately 2.7 mi/kWh but is highly confounded
( R2 Highway Efficiency Test: 80 MPH vs 70 MPH Changed Everything)
The Van Nuys test drive produced approximately:
- 1.8 mi/kWh near 80 mph with A/C in 91°F conditions
- Approximately 2.7 mi/kWh after slowing toward 70 mph, switching off the A/C and traveling downhill
It is nevertheless consistent with the proposition that an R2 on 21-inch wheels can operate around:
It should be treated as corroborating evidence rather than a controlled test.
9. CdA comparison independently supports an intermediate value
The supplied aerodynamic drag areas are:
| Vehicle | CdA |
|---|---|
| R1S | 0.757 m² |
| R2 | 0.660 m² |
| Model Y | 0.499 m² |
The R2 therefore has:
- Approximately 13% less aerodynamic drag area than the R1S
- Approximately 32% more aerodynamic drag area than the Model Y
This places the R2 logically:
- Meaningfully above an R1S in highway efficiency
- Meaningfully below a Model Y
- Near the high-2 mi/kWh range rather than either R1-like low-2s or Model Y-like mid/high-3s
10. Basic aerodynamic calculation is consistent with the estimate
Using:
- CdA = 0.66 m²
- 70 mph
- Sea-level air density near 70°F
At 2.60 mi/kWh, total battery consumption is:
1÷2.60=0.385 kWh/mile1 \div 2.60 = 0.385\text{ kWh/mile}1÷2.60=0.385 kWh/mile
At 2.73 mi/kWh, total battery consumption is:
1÷2.73=0.366 kWh/mile1 \div 2.73 = 0.366\text{ kWh/mile}1÷2.73=0.366 kWh/mile
That means aerodynamic drag represents roughly half of total battery consumption, with the remainder attributable to:
- Tire rolling resistance
- Drivetrain and inverter losses
- Wheel-bearing and mechanical losses
- Pumps and electronics
- Cabin and battery conditioning
11. The 5% wheel/tire assumption produces a defensible 21-inch value
Applying the specified 5% improvement:
2.60×1.05=2.73 mi/kWh2.60 \times 1.05 = 2.73\text{ mi/kWh}2.60×1.05=2.73 mi/kWh
Equivalent energy consumption:
| Setup | Efficiency | Consumption |
|---|---|---|
| 20-inch A/T | 2.60 mi/kWh | 385 Wh/mi |
| 21-inch | 2.73 mi/kWh | 366 Wh/mi |
The 5% improvement reduces consumption by approximately 19 Wh/mi. That is a credible tire-and-wheel difference at highway speed.
12. The mixed-trip 2.8 mi/kWh result is a useful consistency check
The entire 131-mile trip averaged 2.8 mi/kWh after combining:
- About half interstate near 78 mph
- About half slower two-lane highway
- Multiple 30–45 mph sections
- A net 500-foot climb
It does not, however, establish 2.8 mi/kWh as steady 70 mph efficiency.
13. The displayed efficiency may introduce measurement uncertainty
A commenter noted that the Rivian energy display in an R1 did not always agree with independently calculated energy consumption.
It is unknown whether the R2 display behaves similarly. Until controlled tests provide:
- Starting and ending usable energy
- Actual distance
- GPS speed
- Wind
- elevation profile
- temperature
- tire setup
14. ABRP is supporting evidence only after calibration
ABRP’s physics-based route model may be useful, but an early default R2 efficiency parameter is not an independent real-world measurement. It should be calibrated against actual energy and trip data.
Therefore:
- An ABRP value that agrees with 2.6–2.75 mi/kWh is supportive.
- An uncalibrated ABRP default should not outweigh direct testing.
- Repeated route-planner accuracy can validate total-trip energy predictions without necessarily proving the exact steady-state 70 mph reference consumption.
Strongest evidence
The Wisconsin interstate observation, after considering tailwind, elevation, temperature, net climb and new A/T tires, supports:
Independent corroboration
The 68 mph, 66 mph, test-drive and CdA evidence generally places an efficient road-tire configuration in the high-2s, supporting:
Recommended working values
- R2 with 20-inch A/T tires: 2.60 mi/kWh
- R2 with 21-inch wheels: 2.73 mi/kWh
- Conditions: steady 70 mph, 70°F, sea level, flat road, still air, normal climate load
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