cruiseroutfit said:
Not sure where your getting your numbers, but they are seriously flawed
http://www.arbusa.com/alac/alsp/6-07.pdf
18 amps for the RDCKA @
1cfm vs
23 amps for the CKMA12 ~
2.2cfm (both rates @ ~30psi). And double the duty cycle too (25% vs 50%). I've aired up a 35" from ~18psi to 35psi in under 5 mins, sure you have to wait, but I would go as far as to call it a marginal pump.
And to that, do amps really matter for a compressor? Its not like a fridge or light that your leaving on all night long, there should be little issue airing up 4 35" tires without the need to even consider starting the vehicle.
Just to be clear its not my chosen method for airing up (I run CO2) but its a great backup... and for many it has become their primary source of air. Can't say I've heard a complaint assuming they knew the facts ahead of time.
I'd have to assume your referring solely to the RDCKA here, the CKMA12 was entirely designed to do both, hence the increased pressure, volume and duty... otherwise they would have just stuck with the CKSA12 as the only offering. Compare the ARB specs with units such as the Viair, it beets or meets many (most?) of their models, models designed just to air up tires. In fact I can find a single Viair unit that has the same volume at 30psi as the CKM, most are half.
The figures I used are from the ARB website for the CKSA12 and CKMA12 pumps, as those are the two closest that I found to what we were discussing, but perhaps these two were not representative.
In fact, the pump I have is not even listed anymore, nor is the part number listed. Mine is either a first or second generation pump and is something like 8 years old. It has no model number on it, but lists performance specifications at "current load 20A @ 12V" and "flow: 24L @ 200 kPa."
These figures are close to the RDCKA currently listed. It is a compact pump, and not suited to airing tires of any size. I don't think anyone would truly disagree. The higher volume pump listed by ARB is only about twice the performance, but is not a compact pump, which limits your choices in mounting locations.
Keep in mind when comparing performance of air pumps that they are not always rated as they will be used. ARB is no different here. Although the CKMA12 is rated to provide a bit over 60L of air versus 28L, it does so at only 200kPa, which is under 30psi (29.007). Fair enough, but that's not usually where we start to stress the pump. As the resistance in the tire climbs due to increased pressures, the performance of the pump falls off dramatically while the electrical load increases. For purposes of airing lockers, these performance ratings are more than adequate because the volume of air needed is so tiny, but for airing tires, the ratings need to be compared carefully to what we actually need. An increase in pressure to 35psi (as mentioned in this string) is an increase of 20% (35psi = 241.3KPa) over the rating of any of the ARB pumps. Twenty percent is a significant increase in pressure, and you will find a correspondingly significant decrease in performance when trying for the higher pressure. However, ARB does not rate their pumps in the street pressure range, so we don't know how they will perform there comparatively. All I have to go on at that point is experience with a variety of trail airing tools.
Whether airing 36 inch tires is the issue or not, I doubt. I have used my ARB pump to air all kinds of tires to various pressures. The pump gets very hot, and it takes forever to air even 30 inch tires to road pressures, largely because of the extended time need to move that much air at higher pressures. My 36 inch Swampers were never aired above 20psi, and I have no real way to tell whether the volume of air needed to air the Swamper to 20psi is more or less than the amount needed to air a 255/75/16 to 35psi. Both tires are flexible pressure vessels. It would take direct experimentation with volume measuring equipment to tell which holds more air. Neither volume nor pressure standing alone are the problem, but rather the combination of the two that over burdens the pump. Airing any tire to 20psi is asking for less than the rating of any of the ARB pumps (all of which are rated at 29psi for rating purposes) yet airing tires to that pressure range overheated the pump every time.
Here, the discussion centers on whether a person can get a locker pump such as an ARB and use it to air tires. I suggested getting a tire airing pump and use it to run the lockers, and not use a locker pump to air tires. My reasoning is that the smaller pump can't take the abuse over time and should not be used for the larger task. It is simple to plumb a larger pump to air lockers, and the result is far more pleasant than spending a half hour airing tires. Whether ARB offers tire airing pumps is more or less a matter of personal perspective. My take on their ratings is that even their best pump would be marginal for airing tires.
Also keep in mind that whether we are looking at 13A of draw or 20A, we are talking about a dedicated automotive electrical circuit. Either rating will require heavy wiring, which most of the pump kits I have seen do not come with. If the wiring harness provided with the pump is intended to run lockers, it will be overly taxed if airing tires due to excess of duty cycle and accumulated heat. I have found it to be so. I had to change my ARB pump wiring to 10ga wire to handle the heat of airing tires, and I still melted fuses. I never blew the fuse, so amp draw was never exceeded, but I frequently melted the solder in the fuse rendering the pump useless. That takes a bit of heat, and I suggest that such heat is too much for an automotive circuit. So I stopped using the ARB pump for tires and now use it only as a back-up source for locker engagement because it does not have the duty cycle to handle the task of airing tires.
If all of our use of pumps were to take place in the driveway, it wouldn't matter all that much, but a pump failure in the bush is generally not acceptable, especially if you are trying to repair a flat rather than simply increasing pressures for road travel. (No ARB pump will re-seat a tire bead). I would rather have a fast and reliable means of airing tires, and not rely on a small pump with no more than a 50% duty cycle at best regardless of flow. So, if you don't have the room or the money for a full-on 100% duty cycle pump, I would still suggest a compact pump for the lockers (pick one) and an alternate source for the tires, such as CO2, as being far faster, more reliable, and cheaper in the end than using too small a pump do do all of the airing tasks faced on the trail.
Just my opinion.
