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The generic "onboard vs portable" question is covered in full on the 12V tire inflator vs onboard air system comparison — this page assumes you've already decided an onboard system is the right category and answers the ARB-specific decisions from there: whether ARB's premium price is worth it over a budget onboard unit, single vs twin, and tank vs tankless. This is also our review of ARB's CKMTA12 twin compressor specifically, based on ARB's own published spec sheet — we don't buy or bench-test the unit ourselves.
ARB's flagship twin-cylinder onboard compressor — the specific unit this page's ARB verdict is based on, referenced against ARB's own spec sheet and aggregated owner reviews, not first-hand testing.
Features
- Twin-cylinder design for higher CFM and faster fill time.
- Suits permanent under-hood or bed-area mounting.
- Compatible with ARB air lockers and other air-actuated accessories.
Already Decided Onboard Is Right for You?
If you're still weighing a permanently mounted onboard system against a portable 12V compressor, see the full onboard-vs-portable comparison for that decision — CFM output, duty cycle, portability, installation complexity and cost are all covered there. What follows here is specific to choosing an ARB unit once onboard is the category you've settled on.
The CKMTA12's Published Specs
ARB's own spec sheet for the CKMTA12 rates it at 6.16 CFM at 0 PSI, dropping to 4.68 CFM at 29 PSI, with a 150 PSI max working pressure and a 100% duty cycle (ARB states it as "60/0" — meaning it can run continuously with no forced rest period, under room-temperature conditions). Max current draw is 68.6 amps, the housing carries an IP55 ingress protection rating, and the twin-motor unit weighs 17.4 lbs at 10.8 by 7.5 by 4 inches. ARB markets it as "designed for inflating tires and air locker activation when used in conjunction with optional accessories," and states it is "suitable for many air tools when used in conjunction with a 4L air tank (optional with on-board models)" — so running air tools off the CKMTA12 alone, without the optional tank, is not the configuration ARB itself describes.
Is ARB Worth the Premium Over a Budget Onboard Unit?
ARB's onboard compressors carry a real premium over generic budget onboard units, and that premium buys two things a cheaper unit often skips: a 100% duty cycle rating an owner can plan a full four-tire air-up around without a forced cooldown, and a service and parts-availability track record that matters when a compressor is a permanent, hard-to-swap installation. For an owner running a locker or other air-actuated accessory that depends on the compressor working every time, that duty-cycle margin is what the premium is actually paying for, more than any single CFM number on the box.
Twin-Motor vs a Single-Motor Onboard Compressor
The CKMTA12 reviewed here is ARB's twin-motor unit. ARB's own spec sheets show what the twin-motor step-up actually buys against the single-motor CKMA12: the CKMA12 is rated 3.08 CFM at 0 PSI (2.34 CFM at 29 PSI), a 100 PSI max pressure, a 50% duty cycle rated 30 minutes on/30 off, a 32-amp max draw, and 7.7 lbs — roughly half the CKMTA12's airflow, two-thirds its max pressure, half its duty cycle and less than half its current draw. For airing up 35-inch or larger tires regularly, the CKMTA12's roughly double CFM output and 100% continuous duty cycle is a genuine, measurable upgrade over the CKMA12's lower airflow and 30-minute run limit. For smaller tires or occasional use, the CKMA12 delivers adequate fill time without the twin-motor premium, and is the more common choice on daily-driven trucks that only see occasional trail use.
Tank vs Tankless ARB Setups
A tank-equipped ARB system stores compressed air in a reservoir, delivering an instant burst of air pressure for a quick top-off or a single air-tool cycle without waiting on the compressor motor to spin up. A tankless ARB system compresses air on demand only, which is simpler to install and lighter overall but delivers noticeably slower response for any task needing pressure right away, such as actuating an air locker mid-obstacle. Owners running an ARB air-actuated locker generally add a tank for reliable, on-demand engagement — a plain compressor-only CKMTA12 has to spin up and build pressure before the locker actuates, and ARB itself specifies a 4L tank as the "optional" accessory needed to run air tools at all. Owners using an ARB compressor purely for airing tires report the tank's benefit as smaller, since tire fills are a sustained job rather than an instant-burst one.
Fitment: Where an ARB Compressor Actually Mounts
Under-hood mounting is the most common location for an ARB unit, positioned away from major heat sources like the exhaust manifold and with enough clearance for the compressor's own cooling airflow. Engine bay space varies significantly by platform, and an ARB compressor sized for a full-size truck's bay does not always fit a compact SUV's tighter layout without relocating other components. A bed- or cargo-area-mounted ARB system sidesteps engine-bay space constraints entirely, at the cost of a longer air-line run to the front tires. Checking ARB's specific mounting footprint against actual available space on the target vehicle, rather than assuming a universal fit, avoids a return or an improvised mounting compromise after purchase.
Buying a Used ARB Compressor to Lower the Entry Cost
A used ARB compressor, sourced through off-road-community marketplaces, is a common way owners reduce the upfront cost gap against a new unit, provided the motor and wiring are tested before purchase. A unit with visible wiring corrosion or an untested motor carries real risk of an expensive early failure, which is why owners recommend a functional test before completing a secondhand purchase rather than buying sight-unseen — ARB's parts and service network makes a used unit a more repairable bet than an off-brand equivalent if something does need attention later.
The Verdict
ARB is worth the premium for owners who run a locker or other air-actuated accessory, air up frequently, or run larger tires and want a documented duty cycle they can rely on. An owner who only occasionally airs up, and hasn't yet ruled out a portable unit entirely, should start with the onboard-vs-portable comparison before committing to any onboard brand.
Sources
- ARB USA — Twin Motor Onboard Air Compressor (CKMTA12) Specifications — ARB CKMTA12: 6.16 CFM at 0 PSI, 4.68 CFM at 29 PSI, 150 PSI max, 100% duty cycle, 68.6-amp max draw, IP55, 17.4 lb, 10.8 x 7.5 x 4 in; designed for tire inflation and Air Locker activation; air tools require the optional 4L tank.
- ARB USA — Single Motor Onboard 12V Air Compressor (CKMA12) Specifications — ARB CKMA12 single-motor compressor: 3.08 CFM at 0 PSI, 2.34 CFM at 29 PSI, 100 PSI max, 50% duty cycle (30 min on/30 off), 32-amp max draw, 7.7 lb — the single-motor comparison point against the twin CKMTA12.
- ARB — Air Locker — Air Lockers are engaged by compressed air delivered from the compressor at the flick of a dash switch.
- ARB — Air Compressors & Tyre Accessories — ARB compressors are individually leak-, current- and flow-tested at the factory and carry a multi-year warranty; used as the basis for the used-market reliability discussion.
- VIAIR — Compressor Comparison Chart — Cross-reference point for the portable-vs-onboard comparison this page links out to.