For your situation, I would suggest looking at the Viair 400P-Automatic Portable Compressor or the ARB High Output Portable Air Compressor (CKMP12). Since you're worried about the R1T's internal pump overheating, these are solid 12V alternatives that handle 20-inch AT tires much better.

The Viair 400P-Automatic Portable Compressor is great because it has a 33% duty cycle and hits 2.3 CFM, which is plenty fast for airing up after a trail run. It's really reliable, though it hooks directly to the battery, so you'll need to reach the R1T's 12V terminals. On the other hand, the ARB High Output Portable Air Compressor (CKMP12) is a bit more of a powerhouse and comes in a super durable carry case that fits perfectly in the gear tunnel. Honestly, it depends on your budget, but both stay much cooler than the built-in unit during group air-ups. Hope this helps!

Seconding the recommendation above! Honestly, those 12V options are solid, but I’ve been looking at this from a value-per-PSI perspective since the Rivian already has a built-in unit. If you're looking for a budget-friendly backup that won't break the bank but still packs a punch, check out the Smittybilt 2781 5.65 CFM Universal Air Compressor.

It’s a bit of a beast for the price. I'm pretty satisfied with how it handles high-volume 20-inch tires; it actually moves 5.65 CFM (cubic feet per minute), which is technically faster than many more expensive units. But, well, it is a bit bulky in the gear tunnel.

Quick tip: Always keep the truck running while using a high-draw 12V pump like this. It pulls a lot of amps, and you want that steady voltage to keep the fill times fast and prevent the compressor motor from straining. It’s a great way to save your internal pump for solo trips while letting the heavy lifter handle the group air-ups! 🚙💨

Seconding the recommendation above! Honestly, those 12V options are solid, but I’ve been looking at this from a value-per-PSI perspective since the Rivian already has a built-in unit. If you're looking for a budget-friendly backup that won't break the bank but still packs a punch, check out the Smittybilt 2781 5.65 CFM Universal Air Compressor.

It’s a bit of a beast for the price. I'm pretty satisfied with how it handles high-volume 20-inch tires; it actually moves 5.65 CFM (cubic feet per minute), which is technically faster than many more expensive units. But, well, it is a bit bulky in the gear tunnel.

Quick tip: Always keep the truck running while using a high-draw 12V pump like this. It pulls a lot of amps, and you want that steady voltage to keep the fill times fast and prevent the compressor motor from straining. It’s a great way to save your internal pump for solo trips while letting the heavy lifter handle the group air-ups! 🚙💨

Respectfully, I'd consider another option if you're prioritizing safety and thermal management for group air-ups. Duty cycle is basically a ratio of run time to cool down; cheap units overheat fast! For the 20-inch ATs, I’d skip the budget stuff and go with the Indeflate Two-Hose System paired with a Morphorn 12V Air Compressor 6CFM. It’s a beast with a 100% duty cycle at 150 PSI, ensuring you won't melt your gear tunnel or the R1T's internal wiring. Seriously, it's amazing for heat dissipation!

> I’m a bit worried about the internal pump overheating during long group air-ups. ^ This. Also, looking at the discussion so far, we have covered everything from high-end twin motors to budget high-volume units. One serious caution for anyone going the DIY route: watch the power draw. Most high-output compressors pull 30 to 50 amps. The 12V accessory outlets in the gear tunnel or bed simply arent designed for that load. I have seen people try to use cigarette-style plug adapters and it usually blows a fuse or, worse, damages the internal wiring. If you are using any of these heavy-duty portables, you must connect directly to the 12V battery terminals under the frunk trim. Thermal management is the other big thing. High heat at the compressor head can melt cheap plastic air lines during back-to-back sessions. Better to use high-temp rubber or braided hoses. Its a balance between speed and keeping the gear from melting down.

100% agree

In my experience, you’re absolutely right to be cautious about the built-in pump. While the R1T’s internal compressor is a great feature, its duty cycle isn't really designed for back-to-back group air-ups, especially on high-volume 20-inch AT tires. I’ve seen them get incredibly hot, and I’m always worried about long-term wear and potential failure when you're far from a service center.

For your situation, here's how I’d break down the best options:

1. ARB CKMTP12 Twin Motor Portable Air Compressor: This is the gold standard for high-volume needs. I use the portable version that comes in its own carry case, and it fits easily in the gear tunnel or even the frunk. It has a 100% duty cycle, so it won't overheat while you're helping three or four other trucks. It’s seriously fast—I’m talking under 2 minutes to go from 20 to 50 PSI on a 34-inch tire.

2. Viair 400P-Automatic Portable Compressor: This is a fantastic middle-ground. It’s very reliable and uses battery clamps to pull power directly from the 12V system. It doesn’t have the raw speed of the ARB twin, but it's very robust. FWIW, it’s a bit quieter too, which is nice if you're chatting while airing up.

3. Milwaukee M18 FUEL 2848-20 Cordless Tire Inflator: If you want zero wires, this is the one. It’s surprisingly capable, but honestly, for a long group line-up, you’re gonna be swapping batteries and worrying about charge levels.

Personally, I’m very satisfied with the ARB CKMTP12 Twin Motor Portable Air Compressor. It's a professional-grade tool that gives me peace of mind when I'm leading a crew. I'd definitely suggest a dedicated 12V unit over battery-powered if speed and heat management are your top priorities. Hope this helps!

> I’m a bit worried about the internal pump overheating during long group air-ups. Tbh, I have been dealing with this exact same concern for months. I love the R1T but the thought of that internal pump failing mid-trip is always in the back of my mind during trail runs. I have spent way too much time looking for a backup that fits perfectly in the gear tunnel without being a total hassle to use. It is honestly frustrating that there isnt a more obvious standard choice for us yet. Still stuck in the research phase myself and hoping for a clear winner to emerge.