Air compressor question

7997redtail · 03-06-2023, 08:50 PM

Ok. I’ve been watching for a Viair compressor hoping for a deal but at the same time I’m to cheap to buy something I don’t plan on using. So on that note, I’ve seen different versions of the Viair pump.

Most do 150psi or claim to fill 33” tires etc etc etc.

My question is why would you pay $??? For the 40-RV version verses the $??? Big 33 inch tire version that’s cheaper and still does 150lb?

Or, even the difference between the 400 RV and 450 RV. version. Both do 150lbs.

You have cubic space at a specific pressure. A 33” tire at 45lb or an LT245 X 70 RV tire at 80lb s. Am I missing something?

Thanks in advance

BTW, Lordco had a compressor some time back that was a Chinese import (suspected POS) one of the employees was checking out. First impressions were good. My point being it provided lots of air for a medium price.

bigb · 03-07-2023, 06:52 AM

For one, the 450 is continuous duty so that is a good feature for say running a small air tool or airing up all 4 tires on an off road vehicle after airing down to 15 PSI or so for 4 wheeling. Also the CFM makes a big difference but the specs make it hard to compare because nobody lists their CFM at the same PSI. CFM at zero PSI always looks good, it's when under pressure the CFM drops and if you don't have that number it's tough to compare. For occasional topping off probably any of the cheaper ones will work but for long run times and multiple tire air ups you'd want to spend the money for a high CFM unit with a long duty cycle.
I have a 450 with a 2 gallon tank on my Superduty and I can air 4 33" tires from 25 to 55 in 20 min total. Sometimes I air up my son's tires or a friend as well, and I have changed a tire with a small impact (Harbor Freight mini Earthquake
https://www.harborfreight.com/12-in-...lbs-63534.html ) so for me the 450 makes sense. In the MH I am looking to get something smaller because it's just for the occasional top off or emergency.

7997redtail · 03-07-2023, 08:41 AM

Great points especially the varied CFM listings and the need for a higher CFM when at higher pressures.

By 450 I gather you mean the Viair.

I have a Jeep Jl and a 29’ class A. I’d like one small enough for the RV but large enough to air up the Jeep tires. Maybe I should find a 5lb propane bottle and permanently attach it to the Jeep and make into an air reservoir.

I also note your comment about continuous duty. I didn’t catch that in my research.

Thanks

bigb · 03-07-2023, 08:49 AM

Quote:

Originally Posted by 7997redtail

Great points especially the varied CFM listings and the need for a higher CFM when at higher pressures.

By 450 I gather you mean the Viair.

I have a Jeep Jl and a 29’ class A. I’d like one small enough for the RV but large enough to air up the Jeep tires. Maybe I should find a 5lb propane bottle and permanently attach it to the Jeep and make into an air reservoir.

I also note your comment about continuous duty. I didn’t catch that in my research.

Thanks

I have a TJ and a 25 foot Winnebago Via, my plan for that is one of the ARB single cylinder compressors mounted under the hood of the Jeep. Not cheap but good quality, lightweight and good CFM. And yes my 450 is Viair.

Morich · 03-07-2023, 09:29 AM

When shopping air keep inmind that the total pressure will have a lot to do with how quickly you get a flat aired. It sometimes seems if we only need to air a itre to 80, getting one going as high as 90 would do.
The thing missed is that air is kind of like water flow. If we have really high water running to low, it moves much faster. Same with air. If we need to fill to 80 PSI and only have a 90 PSI pressure, it takes FOREVER to get it finished.
That's where the tricky specs listings try to fool us.
The CFM may look great when working into open air but not so good if working 90PSI into 80PSI! If you get a 75PSI trying to fill a tire to 80PSI? Don't try it as the tire loses air!

Ray,IN · 03-07-2023, 05:55 PM

Check out this Viar knock-off: https://www.harborfreight.com/12v-15...sor-63184.html

bigb · 03-08-2023, 06:57 AM

I tried to delete my post. I wonder what the duty cycle is on the HF unit? Also the specs show 30 amps as compared to 20 amps on the Viair with the Viair having slightly more CFM (at zero PSI) but then HF does not list their CFM at higher pressures so we can't really compare that. Viair also gives us the duty cycle of 25 min at 30 PSI while the HF is silent on duty cycle. With the HF unit using 10 more amps (If their specs are accurate) I suspect it will heat up pretty quick and have a pretty dismal duty cycle, if they even tell you in the manual. But it would probably be fine for the average "topper upper". I wouldn't want to depend on it in a remote area to air up after off roading. But the Viar 88P is only $10 more and has a carry case so I don't see any real bargain here.

FIRE UP · 03-10-2023, 11:05 PM

It always cracks me up when air compressors, as in 12V or tiny ones are talked about here. None of them work great in my opinion. I've had plenty of them including the Viair ones. Compressors are just like engines. And the old saying for performance in an engine is, "There's no substitute for CUBIC INCHES". That is, while you can get big HP out of a smaller cu. in. engine, you don't get it until it's screaming at 10 bazzillion rpms. Where as, a larger cu. in. engine will develope much more HP and torque at a much lower rpms.

So goes it for compressors. The larger the compressor, the more air it pumps. A little tiny compressor, no matter WHO makes it, has to work seriously hard to get higher pressure built up. Yes, yes, yes, many tiny 12V compressors boast this "150 psi." Some of them may, MAY be able to reach that pressure if, IF they're gonna fill something the size of a tennis ball. But, throw a 33" or 35" at them, and you might as well prepare lunch and dinner while they're trying to get just one of those from trail pressure of around 10 psi (ran that psi for decades in all our Jeeps) to 28-32 psi street pressure.

On the last four or five Jeep's we've built, I installed an engine driven compressor. Some of you may know about Kilby Enterprizes or otherwise known as *On board Air*. Basically Brad Kilby created a business that many of us have been doing long before he started. And that was/is to utilize an air conditioning pump as an air compressor. Talk about some serious air at low rpms. What a small 12V compressor takes to fill a 35" from trail pressure to street pressure is normally around 4-5 minutes, the on board air, at engine idle will do in 45 seconds. Up the idle to 1000 rpms and you cut that time to less than 30 seconds a tire.

Those on board air systems were really easy to setup on our old CJ's and YJ's. The TJ's were only mildly harder due to you had to move the alternator to install the new pump, no biggie. But, the new JK's are all but impossible to to install one.

So, with all that being said, I simply now use a 10 lb. CO2 bottle. It's time is between 45 seconds and 1 minute per 35" tire trail to street psi.

As for what to use on a motorhome, well, there's plenty of 120VAC smaller compressors out there that you can top off RV tires with. But, if you have to fill an RV tire from almost completely empty, pull up a chair, you're gonna be there a while. I had one of those very popular Craftsman (that later branded *Porter Cable* stand up little compressors for a few years 'till it gave up the ghost. My son still has his and is quite happy with it as long as he's not in a hurry.

When mine quit, I'd heard of these new ones being sold by Harbor Freight that were/are supposed to be really quiet. I did a hours worth of Youtube searching and found them. And according to the Y/T videos, yes, they're SERIOUSLY quieter than ANY other compressor in their class. So, I zoomed down to my local H/F and picked the 2-gallon version up. MAN, that thing is outstandingly quiet. And the recovery time from cut-in to cutt-out is phenomenally fast, around 10-15 seconds if I recall.

Compressing air is a tough job. The tiny 12V versions have to work seriously hard to do that and supply at least some higher pressures. They're all gonna labor quite a bit. Pick one you're happy with and, go have fun.
Scott

Wyatt · 03-11-2023, 02:03 PM

Quote:

Originally Posted by bigb

I have a TJ and a 25 foot Winnebago Via, my plan for that is one of the ARB single cylinder compressors mounted under the hood of the Jeep. Not cheap but good quality, lightweight and good CFM. And yes my 450 is Viair.

I have a permanently mounted ARB in the battery bay. Works perfect for topping off tires on the go.

7997redtail · 04-12-2023, 09:13 AM

So i finally bit the bullet and bought what I think makes the most sense. Some thoughts being;

- I'm expecting to be topping up tire pressure not filling tires from empty.
- I'm not interested in putting out $600 for a compressor (the ones I have in my other cars have been used twice in ......50 years of driving) that I may never use.
- I didn't want to go 110 volt because they are physically larger and the poorer performance of the smaller sized compressors.
- I wanted a duty cycle above 20%. Most of the cheaper compressors are 10 - 20%

Lordco sells a Bull Dog brand

https://www.bulldogwinch.com/index.c...=cat/cat93.htm

North Shore Off-road sells the same compressor badged for them as RFX

https://nsor.com/rfx-rfx41000.html

Its on sale right now and that's the one I purchased. When I got home I deflated one of my regular Toyota truck tires and inflated it in about 2 minutes. Duty cycle on the both of them above is 40% which is lots of time.