Air Compressor Test
By Jonathan Hanson
From the Spring 2008 issue of Overland Journal
The pressure is on:
Overland Journal puts six 4WD and four motorcycle compressors to the test.
My first portable air compressor was a gift from a well-meaning but non-au- tomotive-oriented friend. The yellow plastic contraption boasted not just a compressor (“250 psi!”), but a built-in gauge, a flashlight and a red hazard blinker, nozzles for inflating beach balls and pool toys, and a couple other at- tachments I’ve forgotten. I swear there was a bottle opener on it somewhere—which would have been its most useful accessory, given the Pleistocene-like interval the thing took to inflate a stock All-Terrain from, say, 16 psi to, say, 17 psi, while vibrating in circles like an enraged Chihuahua.
Alas, it went to Goodwill days after I got it, and so could not be included here for baseline data/comic relief.
A reliable, powerful air supply is the last component of the tire repair process I have explored in the last few issues of Overland Journal. Nearly as importantly, and far more frequently, an air supply allows you to properly reduce pressure in your tires on the trail to enhance traction and flotation while reducing erosion, and then quickly air them back up to safe levels for driving on pavement. If the supply produces enough volume, it can be used to reseat tire beads. With a nozzle you can clean small parts or blow impacted grass out of a radiator.
Essentially, air on the trail can come from one of two sources: a pressurized storage tank— usually liquefied CO2, since it stores a much higher volume than atmospheric air given the same size tank, at a lower (safer) pressure—or a compressor, which can be either electric (usually 12- volt DC) or engine-driven via an auxiliary belt. (A compressor can also be plumbed through a modest air tank to provide a regulated supply of air to run air tools, and some compressors have a small built-in reservoir to operate air-locking differentials.)
I decided to confine this test to 12-volt DC compressors, which I believe are generally the best choice for overland journeys, especially extended expeditions. They are compact, and avail- able across a wide spectrum of power and output to suit different budgets and needs. Most 12- volt compressors can be installed either in a hard-mount configuration—bolted somewhere in the vehicle and wired directly—or purchased as a portable kit that includes clip-on battery leads, a hose, and a case, making it simple to move from vehicle to vehicle.
I excluded the engine-mounted, belt-driven units (such as the Kilby) that employ a modified AC compressor, which, while very powerful, require special brackets, increase complexity and reduce accessibility in the engine compartment, and cannot be quickly moved to different vehicles. (That doesn’t mean they aren’t worth considering, just that they didn’t fit my current parameters.) I also excluded the excellent Oasis 12-volt DC compressors, which are extremely powerful, extremely heavy, and extremely expensive—probably overkill for most overlanding use unless you want one compressor to service a group of vehicles, or are driving something with very large tires such as a Unimog. Finally, I also excluded CO2 tanks. They are excellent in many ways—I used one for several years, and was always impressed with the fast, quiet operation. There’s no electrical draw, and no connections to worry about—just open the valve and go. They’re easy to move from vehicle to vehicle, will run air tools and reseat beads easily, and on a cfm-per-dollar basis they can’t be touched by any compressor on the market. The problem with CO2 is, it runs out—and guess- ing when and where is the rub. Yes, you can weigh the tank and estimate, but it’s imprecise, and you’ve still got a finite supply and are tied to outside sources—common in some areas, non- existent in others. The cfm-per-dollar advantage doesn’t count the cost of refills. A CO2 tank is worth considering if your travels are restricted to North America, but if you plan journeys farther afield, or just want complete independence, a compressor is the way to go.
We received six 4WD compressors to review (see following story for the four motorcycle- specific models). Three of the 4WD units—the ARB, Warn, and Quick Air, arrived as bare units, and three—the Expeditionaire, the ExtremeAire Magnum, and the Viair, were furnished as por- table kits that included battery cables and air hoses. Every compressor employs essentially the same configuration: a 12-volt DC electric motor powering a piston-actuated compressor. The piston is not what you might be picturing; that is, the reciprocating, tuna-can-shaped internal- combustion piston that goes straight up and down. Most small air compressors employ what is known as a WOB-L piston: a flattened disk attached rigidly to a connecting rod with no wrist pin (it’s also called a fixed piston). A WOB-L piston actually wobbles back and forth slightly since it’s one piece with the rod, and the up-and-down movement (stroke) is relatively small. Thus friction is minimized, less heat is generated, and the piston does not require oil lubrication. (The excep- tion here is the Quick Air, which does use standard pistons that are oil-free.) Inlet valves are nor- mally simple flaps of metal or composite material; outlet valves can be a flap or a poppet valve.
While efficiency varies somewhat among different compressor designs, in the end you can’t cheat the laws of physics. A faster, more powerful compressor will usually draw more amperage than a slower, less powerful unit. The trade-off is that the quicker unit will draw power for a shorter time, so the total drain on your electrical system might be more or less the same. Another inescapable result of physics is that the higher the pressure, the hotter the compressor will get. Tires that take 60 psi road pressure will put more stress on a pump than tires that take 40 psi.
Many compressors have a duty cycle—a ratio of work time to cool-down time. For example, a 50-percent duty cycle means that for every specified interval you run the compressor you must let it cool down for an equal interval. Duty cycles are rarely a factor when you are working on a single vehicle, but if you want to air up several you might overextend the rated run time. Most compressors also incorporate a thermal cutoff switch that will temporarily shut down the unit if it overheats.
Don’t pay much attention to advertised maximum psi (pounds per square inch) ratings. It’s unlikely you’ll need more than 100 psi for any overland application. Volume in cfm (cubic feet per minute) is more relevant, but again, cfm at 0 psi doesn’t mean much. Look for a volume rating at 50 or 100 psi to get an idea of the compressor’s true capability.
I put the compressors through several trials, starting with the 4WD units (see page 49 for motorcycle specific compressors; test procedures were similar). First, I timed how long each one took to fill a 255/85/R16 BFG Mud-Terrain from dead flat (valve core removed and replaced) to 35 psi, with the wheel and tire off the vehicle. Next, I timed how long it took to re-inflate four tires the same size, on the vehicle, from 15 psi to 35 psi, replicating a typical air-up procedure. Finally, I attempted to reseat the beads on the same 255/85/R16 tire, after unseating them with Tyrepliers. While I also timed this procedure, the results didn’t weigh in my rankings—there are too many variables in how the tire is seated and how good the initial seal is to result in a consistent comparison. During each test, I monitored the power consumption with a Snap-on EEDM56CK digital multimeter and a 400-amp clamp-on probe, which recorded both average and maximum draw. I also monitored the temperature of the head of the compressor cylinder—usually the hottest spot on the unit—with a Snap-on RTEMP25B remote-reading infrared thermometer. Ambient air temperature during the test varied between 72°F and 78°F, so there was little exterior heat stress involved. I used an inline dial gauge supplied by Viair to obtain instantaneous pressure readings. If possible, it’s always a good idea to run the vehicle’s engine while using a compressor, even if you have a high-capacity auxiliary battery. A battery in a non-running vehicle will usually produce a bit over 12 volts—which can drop quickly when supplying a powerful compressor— while the alternator on a running engine will produce well over 13 volts through the same battery. When you supply higher voltage to the compressor, it runs a bit faster yet draws fewer amps.
ExtremeAire Magnum Portable
(Kit, $675, compressor only, $550)
The moment you open the steel tool box encasing the ExtremeAire Magnum Portable, it’s obvious you’re looking at a product with a lot of thought behind it. The hose connections are protected with spring coils, the leads to the stout, 4-gauge battery cables are sealed and shrink- wrapped, and a fat, washable, oiled UNI-filter protects the intake of the compressor, which is powered by a massive, fan-cooled, 1 1/2-horsepower motor. Magnets at each end of the box hold a tire gauge and LED penlight.
The “ordinary” ExtremeAire compressor is already very well-known among serious expedi- tioneers as a fast and durable air source. The Magnum effectively doubles the power of that model in a package only two inches longer—albeit at something over twice the amp draw: 78 amps aver- age, 80.1 maximum. The power was immediately apparent, as the Magnum edged out the Warn SPI for fastest time in the single tire 0-to-35 psi task, at just 2 minutes, 20 seconds, and the four- tire, 15-to-35 psi test, which the Magnum whizzed through in 6 minutes, 39 seconds—35 seconds ahead of the Warn and nearly three times faster than the slowest compressor here (it did get pretty hot during the latter test: 303°F). Reseating the tire beads took just 24 seconds. When I hooked up the Magnum to a five-gallon air tank with a 100 PSI regulator, it effortlessly ran a 1/2-inch Snap- on impact gun while I removed 24 lug nuts from a Land Cruiser.
If your electrical system can keep up, the 100-percent-duty-cycle Magnum will run for as long as you need it to. However, there is no automatic pressure cutoff; the portable kit comes with an open chuck that simply bleeds off excess pressure. If you attach the Magnum to a closed air line it will eventually stop from back pressure at about 180 PSI (if the line doesn’t burst first), but that’s not something to do regularly. (Extreme Outback does offer an optional cutoff switch in several ranges.) There is also no on/off switch, just a heavy-duty quick-disconnect on the battery cables, which, while foolproof, is not as convenient. But, those small annoyances aside, no compressor here will get you back on the road faster.
• Extremely fast
• High-quality fittings
• 100-percent duty cycle • Fan-cooled motor
• High amp draw
• No on/off switch
• No pressure cut-off
ARB CKMA12 High-volume
($273 with air locker wiring harness, $330 portable inflation kit)
The original ARB compressor was designed solely to provide a supply of air for ARB’s air- locking differentials, using a small storage plenum to ensure an instant shot of compressed air to activate the unit. However, so many people plumbed the compressors to inflate tires as well, that the company offered a kit for the purpose—even though airing up a single vehicle in hot weather often seriously overstressed the unit. ARB’s new high-volume compressor boasts four times the airflow under load, to properly handle multiple tasks.
It’s still a remarkably compact compressor, by a significant margin the smallest in the review unless you pulled a single AtomAire out of the ExpeditionAire. It is easily mounted in virtually any free space. But it proved a powerhouse for its size, turning in the fourth fastest time in both the single-tire (3 minutes, 55 seconds) and four-tire (10 minutes, 40 seconds) tests—although in the latter its head temperature peaked at a blistering 329°F, the highest I measured. It also drew a fair amount of power: 32 amps average with a maximum of 33.4—close to that used by the dual-piston Quick Air 3. ARB rates this compressor at 50-percent duty cycle—30 minutes on, 30 off. That should be enough to air up at least a couple of vehicles unless the thermal cutoff switch kicks in. It successfully seated the beads on the test tire in 28 seconds.
The ARB is available either in a kit that includes a plastic carrying case, battery cables, and a 20-foot air hose, or in a more diff-locker-oriented set that comes with a very thorough wiring harness and switches, but no air lines.
• Powerful for its size
• Available in a portable configuration, or with wiring loom and switches to run an air locker
• Runs very hot
(Kit only, $299)
The Viair astonished me with its quiet and extremely smooth operation. While it was the second-slowest unit in both the single-tire, 0-to-35 psi test (4 minutes, 17 seconds) and the four- tire, 15-to-35 psi test (14 minutes, 15 seconds), it went about its business so politely that I simply didn’t mind. Several of the other compressors are so loud and frenetic you can hardly wait to turn them off; by contrast you and a friend can stand on either side of a running 450P-A and hold a normal conversation. Average amp draw was a very low 14.4, with a maximum of 15.5, so the drain on the vehicle’s electrical system is modest indeed—most modern alternators can more than keep up with an extra 15-amp load.
The 450P-A boasts a 100-percent duty cycle at an impressive 100 psi—in addition to being polite it’s a hard (if deliberate) worker. There’s an automatic shutoff at 150 psi, so the 450P-A would be easy to hardmount and plumb into a small tank to run an ARB air locker (although ARBs prefer around 100 psi, so you’d need an inline regulator). The Viair uses an easily replace- able foam intake filter element; several spares are included with the kit I received, which also includes battery cables, a 25-foot air hose, and an excellent inline tire gauge with a pistol-grip chuck, in a generously sized nylon soft case. The compressor is attached with rubber isolators to a base that allows you to set it in the dirt, and the insulated handle means you can pick it up even when it’s still hot.
I discovered a curious phenomenon while monitoring the Viair’s head temperature: The in- frared thermometer could not register off the polished fins on the unit; it consistently indicated a reflected atmospheric reading much lower than the obvious true temperature. I finally masked the compressor with tape and spray-painted the head black, which solved the problem. The highest reading was a moderate 220°F.
• Very quiet, minimal vibration
• Good filtering
• Base helps keeps dirt out of the intake
• Insulated handle
• 100-percent duty cycle
• Second-slowest inflation times.
Warn Air-Power SPI
($595, no kit)
The Warn is a big compressor—16 inches long, 9 wide, and 14 tall in its tubular exoskeleton, which incorporates both a comfortable carrying handle and a sturdy base. Without any acces- sories, it takes up considerably more room than even the ExtremeAire Magnum Portable in its tool box complete with jumper cables and hose. It’s also the heaviest unit here at 34.4 pounds, including the frame but no air hose. Somewhat offsetting the volume and mass are additional features on the SPI, such as a finned, 1/3-gallon reservoir, which reduces the outflow tempera- ture and provides a ready source for air lockers should you decide to hard-mount the SPI, plus an automatic pressure cutoff switch (100 psi), and a lighted on/off switch.
Even upstream of the reservoir the SPI runs cool. Despite turning in the second-fastest single-tire fill (2 minutes, 25 seconds) and four-tire air-up (7 minutes, 14 seconds), the head tem- perature on the 100-percent-duty-cycle compressor never exceeded 220°F, indicating that if you have the room and the electrical system capacity in your vehicle, the SPI should be a long-lived workhorse. I was surprised then, to note the miniscule air filter, about the size of a thimble. It’s washable porous metal, and should be durable enough, but I expect it would clog more quickly in dusty conditions than the big oiled UNI-filter on the ExtremeAire. At least it’s high off the ground on this compressor. The SPI easily reseated the tire beads in 22 seconds. Given the ease with which it had handled everything to that point, I gave it a sterner test and hooked it up directly to a Snap-on 1/2-inch impact driver. I let the compressor fill its reservoir and shut off at 100 psi (actually 96 psi on my remote gauge), then started zipping off lug nuts on the Land Cruiser. The compres- sor kicked in again, but I was able to undo all 24 nuts with pressure to spare. Very impressive.
There is a cost, of course, besides size. The SPI is a power hog, drawing an average of 83 amps and a maximum of 86.2, the highest I recorded. You’d want a big alternator if you planned to use the SPI for long sessions showing off its capabilities.
• Very fast
• Reservoir reduces outlet temperature
• 100-percent duty cycle
• Automatic pressure shutoff at 100 PSI
• Very bulky
• High amp draw
• Inadequate air filter
Sun Performance Quick Air 3
(Kit, $491, compressor only, $437)
The dual-piston Quick Air 3 is a compact compressor that puts out a lot of air. Barely larger than the single-piston Viair, it filled a single tire in 3 minutes, 19 seconds, and aired up four in 8 minutes, 50 seconds, placing it third overall in speed behind the monster ExtremeAire Magnum and Warn SPI. It also popped both beads back on the test tire in a scant 18 seconds, which, while it says more about how well I happened to have the tire seated just then, still indicates what’s possible. Power draw was a reasonable 35.1 amp average, with a 39.1 maximum, and the head temperature while airing up four tires stayed low at 220°F.
The duty rating on the Quick Air seems odd for such an obviously sturdy unit: it’s certified for a 15-percent duty cycle, with a maximum run time of 40 minutes at 40 psi. While 40 minutes is long enough for any reasonable work session on a single or even multiple vehicles, many tires run higher street pressures than that, so airing up several trucks with load range E tires could push the rating. Also, the maximum working pressure of 70 psi is insufficient should you wish to fill an air tank to run an air impact gun, which normally requires over 90 psi, or to operate an air locker. I suspect the duty rating might be a corollary of the conventional metal piston design in the Quick Air, which appears extremely durable but perhaps needs more cooling-off time.
Each piston of the Quick Air has its own small washable foam filter. To access them you must remove the four Allen bolts that secure each head. Use care not to lose the O-ring and associated parts of the outlet valve when you do so.
• Modest size offers multiple mounting options
• Angled air outlet increases mounting clearance
• 15-percent duty cycle could limit multi-vehicle use
Extreme Outback ExpeditionAire
(Kit, $299, single AtomAire compressor, $80)
What’s one way to ensure you have a working compressor for the duration of an extended third-world expedition? Take two compressors. Inside the ExpeditionAire’s homely but bomb- proof .50-caliber ammunition-can case are twin AtomAire compressors plumbed into a sin- gle outlet hose. In the unlikely event one should fail, the other will almost certainly see you through.
The ExpeditionAire kit includes 10-foot, 10-gauge jumper cables with full-size terminal clamps, two inline 15-amp fuses with spares, and a 20-foot coil air hose with quick release. A tire gauge and an LED penlight ride on magnets in the corners of the box. All the air fittings are brass, and the electrical connections are protected by heat-shrink tubing. The Expedition- Aire has no on/off switch—you attach the jumper cables to your battery, then plug them into a pigtail on the unit to start it. This is done for simplicity and reliability, but I have to admit I would have preferred a switch. An open-cell foam gasket on the end of each motor housing filters intake air. Extreme Outback claims you can bury a running AtomAire in sand and it will still function.
Working in tandem, the tiny but sturdy AtomAires delivered enough volume to inflate the test tire from 0 to 35 psi in 5 minutes, 17 seconds. Extreme Outback recommends a 50-percent duty cycle for the AtomAires—15 minutes on; 15 off. Airing up four tires from 15 psi to 35 took a leisurely 18 minutes, 35 seconds, but the unit ran non-stop with no problem (both times were the slowest in the review). Average amp draw was a very modest 14, with a peak of 16.5. Maxi- mum head temperature during the second test was a mild 182° F. The two units never varied by more than 10 degrees from each other.
I had some doubts that the ExpeditionAire would be able to reseat tire beads, but in fact it did so in 2 minutes, 19 seconds. I had to be careful with the tire alignment on the rim to minimize leakage, and I sprayed some extra detergent lube in one spot that was bubbling, but they finally popped on. This means the ExpeditionAire should be capable of any tire repair you might need to accomplish in the bush, as long as you don’t have bandits hot on your trail.
• Extremely compact and lightweight
• Rugged, weatherproof case
• Redundant backup ensures reliability
• Completely self-contained
• No on/off switch
• 50-percent duty cycle and slow speed restrict multi-vehicle use
• Cables and hoses barely fit inside case
In many equipment reviews a clear win- ner emerges within the first few minutes of evaluating the field. In others an obvious choice distinguishes itself, but not until all aspects of every contender have been evalu- ated. This one was different. In fact, I could make a case for several of these compressors as an ideal fit for a specific application.
The ARB high-volume compressor is a smart upgrade by ARB from their original low-volume unit, which was intended solely for activating locking differentials. It’s now vastly more capable as a multi-purpose com- pressor, and a highly recommended upgrade if you currently use an original ARB compres- sor for both lockers and tire inflation. Given how hot it runs while inflating multiple tires, I’d mount it outside the engine compartment to keep it as cool as possible (a good idea with any compressor).
The ExpeditionAire is a brilliant choice if you like the idea of a compressor that liter- ally halves the chances of complete failure in the field. Its ammo-box case and high-quality fittings inspire confidence; there’s little doubt the thing would shrug off six months bang- ing around in the back of a Land Rover be- tween Tangier and Cape Town. It’s capable of handling any job up to and including re- seating beads on a large tire.
However, I think the ExpeditionAire is best employed in a reserve capacity. Used in a situation where it might be called upon to air up four tires several times a day—even once a day—its leisurely inflation times would take significant chunks out of your schedule. Kept accessible for repairs, and used in situations that require tire adjustments every few thou- sand miles, it would be a faithful tool—and, given its Little-Train-that-Could attitude, probably the one that would engender the most affection.
The Warn Air-Power SPI is a very pow- erful compressor with features that give it a near-industrial capacity for work: 100-percent duty cycle, 1/3-gallon reservoir with finned heat dissipation, and automatic pressure cut- off. It ran cool throughout the test, and turned in the second-fastest inflation times. It easily operated a 1/2-inch air impact gun. The res- ervoir and pressure switch mean it could be set up as a hard-mounted unit to run locking differentials (the 100 psi cutoff is perfect for air lockers) as well as doing inflation duty.
But the SPI takes up a near-industrial amount of space, too. Even with the exo- skeleton handle/base removed it is a bulky compressor. You wouldn’t want this thing mounted in the back of your Defender 90, and I don’t know of an engine compartment that would suit it short of a Tatra’s. I think the Warn is a good choice for a big SUV or a full-size pickup, and it would easily service multiple vehicles—you could air up three trucks with 33-inch-tall tires in 20 minutes.
The Quick Air 3 would make an excel- lent hard-mount or portable compressor for a solo full-sized expedition vehicle. It’s small enough to fit handily in a 110, a four-door JK, or an 80-series Land Cruiser, and airs up four 33-inch tires in a jiffy. The construction seems very solid, and several major compo- nents are owner-serviceable. However, its 70 psi maximum working pressure and 15-per- cent duty cycle were surprising for the price, and could limit its usefulness for a group of vehicles.
I found myself using the Viair 450P-A a lot for inflation duties not related to the re- view, simply because it was so nice to use. It’s light, quiet, and smooth, and the 100-percent duty cycle at 100 psi means it’s willing to keep on working after other compressors need a break, even if at a slower pace. It’s compact enough to install in a hard-mount configura- tion in even a small vehicle. The portable kit is well-equipped and easy to stow in its nylon case, and the supplied inline gauge is a nice touch. I liked the Viair better than several faster and more expensive compressors. It is a worthy recipient of our new Value Award.
In the end the Editor’s Choice had to go to the ExtremeAire Magnum—but not because it was the fastest unit. That performance was expectedly commensurate with its premium price. The Magnum rose to the top because no matter where I looked or which component I inspected, it was clear that Extreme Outback spared nothing to ensure that every last bit of the product is as good as it can be, from the oversize battery cables to the washable, oiled intake filter, from the powdercoated motor housing to the brass fittings and stainless fas- teners. If you don’t need (or cannot afford) the performance offered by the Magnum, you can be assured that the standard ExtremeAire and the ExtremeAire Junior (as well as the ExpeditionAire) share the same quality. And quality is what you can count on to see you through any expedition.
Motorcycle Compressor Test
By Jonathan Hanson and Bruce Douglas
In the interests of keeping your diet free of scorpions, we test four pannier-size compressors to help keep you mobile.
Motorcycle compressors might have an easier job of it than their 4WD cousins, but proper function is not a whit less critical. If the compressor in your Land Cruiser breaks in the middle of a repair in deepest Mauritania, you just pop the awning, grab a Coke and a sandwich from the Engel, and wait for someone to chance by. If it happens on a bike, it’s time to start looking for scorpions to stew . . .
Repairs aside, far too few adventure riders realize that airing down motorcycle tires is just as advantageous as it is for four-wheeled vehi- cles to enhance traction and flotation. Yes, you have to balance reduced pressure against the risk of pinch flats in rocky terrain, but the added performance is well worth it.
We tried four motorcycle-specific compressors on the rear tire (Continental TKC 80, 130/80-17) of a Honda TransAlp. We timed how long it took each to inflate the tire from 0 psi (valve core removed and replaced) to 40 psi, measured the operating temperature, and evaluated each for features, ease of use, accessories, and build quality.
BestRest Products Cycle Pump $100
The U.S.-made Cycle Pump has proven itself on six continents and in service with the British military in Iraq. While we only used it on one continent, it performed well, if somewhat slowly—its time to fill the test tire was 5 minutes, 35 seconds, the longest we recorded. However, it didn’t seem to be working hard, and indeed the unit is rated to 100 psi. The temperature of the compressor head peaked at 129°F.
The Cycle Pump is cased in a stout aluminum box with fold-out legs. The instructions warn not to set the running unit in the dirt, and when the case is opened the reason becomes clear, as there are exposed plastic gears in the mechanism and no intake filter on the pump. The nylon case makes an effective isolator, but we think an improvement would be to replace the legs with some sort of bracket so the compres- sor could be hung from the bike, well clear of the ground. You could easily remove the legs yourself and hang a wire bail from the screws that attach them.
The Cycle Pump does not include a gauge, but the company offers a very nice inline dial gauge for $25. Both the air line on the compressor and on the gauge would be easier to use if they had an angled chuck; the straight chucks provided are awkward to attach, especially on the front tire of a bike with big disc brakes. The Cycle Pump kit weighs 31 ounces, or 39 with the optional gauge. It’s a good value for a U.S.-built product.
Touratech Airpower 115 $172
The German-made Touratech Airpower is housed in a handsome aluminum case which incorporates a positive rocker switch and a small but accurate built-in gauge (exuberantly calibrated to 160 psi). It in- flated the test tire in 4 minutes, 41 seconds, helped by the fact that we didn’t have to keep stopping to check the pressure. The needle stayed rock-steady throughout the process, rather than vibrating into near- invisibility like those on many “free built-in gauge!” gauges. An angled chuck made access to either front or rear tire valve easy. Temperature peaked at a moderate 119°F. Touratech recommends a 15-minute use cycle for the Airpower, which should be enough to air up the tires on a pair of bikes.
Opening the case reveals a motor/compressor assembly similar to the Cycle Pump, with about as many plastic components and no intake filter, so it’s clear this unit should also be kept out of the dirt. The nylon case suffices but a hanging bracket would be better. The 10-foot power cord and 21-inch air hose are plenty long; the electrical connec- tor is (naturally) a BMW-style plug with a U.S. adapter. No internal fuse protection is provided. At 31 ounces (without any tire repair materials), the Touratech is a lightweight but thoughtfully configured compressor. touratech-usa.com
Extreme Outback Moto Aire $199
Extreme Outback claimed this kit was a raw prototype, but we cer- tainly couldn’t tell that by its performance. Using a single AtomAire compressor as its air source, the Moto Aire inflated the test tire from 0 to 40 psi in just 3 minutes, 20 seconds. Maximum temperature was 128°F.
The Moto Aire kit includes everything you’d need to connect to any 12-volt power source: battery clips, a hard-wire loom, and a Euro-style power plug with a U.S.-style cigarette lighter adapter. The Moto Aire is the only motorcycle kit we tried that has its own fuse protection. The 11-foot cord and 7-foot air hose are, if anything, too long, and Extreme Outback plans to shorten them a bit. The angled chuck is easy to use.
The AtomAire pump, which has no exposed plastic parts, incorpo- rates an open-cell foam gasket at the end of the motor housing as an intake filter. Setting it in the dirt won’t hurt it a bit; the company claims you can bury a running AtomAire in sand and it will continue to work. We were nevertheless kind to it and set it on its nylon case for the test.
The Moto Aire is clearly the heaviest-duty unit here. Of course it’s also the most expensive, and the heaviest by a factor of two, at 70 ounc- es. However, the Moto Aire kit includes not only the comprehensive selection of power adapters (most of which you could leave home), but also a pencil tire gauge, spare valves and valve cores, a valve tool, even a penlight. extremeoutback.com ￼￼
ADV Designs Micro Tire Pump $50
Enterprising motorcycle riders often buy a cheap auto air pump kit and simply strip off everything but the compressor. That’s the idea behind the ADV Designs Micro Tire Pump. What you see is what you get with this one: a compact electric motor wrapped in a rubber sleeve, powering a tiny compressor (which utilizes a standard wrist-pinned pis- ton). Like the Cycle Pump and Touratech, there is no intake filter or internal circuit protection. But the Micro does include a basic tire plug kit, a pencil pressure gauge, and a pair of needle-nose pliers.
An 11-foot power cord (available with your choice of connector) and 24-inch air hose give plenty of reach to work on a second bike. The Velcro strips that wrap the power cord and air line worked perfectly to hang the Micro from a pannier rack strut on the TransAlp, well out of the dirt. Inflating the tire took 4 minutes, 42 seconds, virtually identical to the Touratech, although it ran hotter, reaching 139°F. Like that on the Cycle Pump, the straight air chuck was a bit awkward. Stripped of the pliers, the weight of the Micro Tire Pump kit with the plug kit is just 30 ounces, making it an attractive choice for the minimalist biker. advdesigns.net
When I first saw the four motorcycle compressors sitting on the bench, all I could think was: Boy, that Moto Aire would be handy in the shop—but it’s way too big to be carried on the bike. I was familiar with the Cycle Pump, after carrying and using one for the last 18 months, I certainly recognized the Touratech name on the other compressor, and I liked the minimalist design of the Micro Pump.
But after a day of testing, that “shop compressor” looked like it was well worth the additional weight and size. The Moto Aire is really the only choice for demanding use: powerful, fast, durable, and quiet. There are no warnings about keeping it out of the dirt, unlike other compressors. The manufacturer only asks that you not submerge it in water. I can live with that.
If riding with a partner, I’d suggest they haul the tire irons and I carry the compressor. With a 15-minute continuous run time, you could quickly air-up several bikes before getting back on the pavement.
Once I stripped down the generous accessories/spare parts to only what I need, the case was just slightly larger and heavier than the other compressors. I would suggest a couple changes, though: take about five feet out of the air hose, and add an in-line switch. - Bruce Douglas