Compressor Selection Help

**Raife1** · 08-29-2020, 04:39 PM

Looking for help regarding which Viair compressor to get as I don't know enough about how they work. I read several threads on the site, but it didn't help as generally the PSIs they referenced where much higher than mine. I have an Grand Design Imagine XLS 21BHE, tire size is ST205/75R14 65PSI cold.

The product selection page on Viair says the 300P-RVS is perfect for towables, but then the actual product page says Class B. The Viair 89P-RVS says it is also for Class B.

So there is $100 difference between the two, but I struggle to understand the big difference or what is means practically.

So why am I asking...we picked up our trailer last weekend and then stored it for the week. We got it today and discovered it had a flat tire (nail). So we filled it up down the street from the storage place so we could get it home. I am picking up a Trailer Aid tomorrow and have a compressor at home to fill it back up. But it struck home the need for an option on the road.

Do I even need something this "big?"

Any info is appreciated.

Thank you.

**FT4NOW** · 08-29-2020, 08:50 PM

Whichever one you get, make sure the pressure range covers your tow vehicle and trailer tires. Also, try to get one that has a 100% duty cycle.

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**Raife1** · 08-29-2020, 09:10 PM

So to get 100% duty cycle I need to two models higher than the ones I mentioned...??

**FT4NOW** · 08-29-2020, 09:15 PM

Originally Posted by Raife1

So to get 100% duty cycle I need to two models higher than the ones I mentioned...??

I dont recall which ones have it, but I think I have the 400P and it doesnt have a 100% duty cycle. It gets pretty hot after continuous use since that's not what its rated for. If I had to do it over I'd spend the extra $ for the one with a 100% duty cycle. If you are airing up your tire from a flat that you may have just repaired, it takes a little while, it's not like a home/shop air compressor that has a tank. If you brought a dedicated air tank with you and hooked it inline with the compressor I'd say the duty cycle isnt as important.

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**BeerBrewer** · 08-29-2020, 09:33 PM

We use the Viar 300p and are happy with it, it runs around $150 on Amazon. It's duty cycle is 33%, you'll have to move up to the Viar 450 to get 100% duty cycle but it's more than twice the price at $350. I agree 100% duty cycle is better, but I didn't think that we needed it since I only use my Viair when on the road. I have a larger compressor at home that we usee to top off the tires before we leave. Below is what Viair says about duty cycle....I hope this helps.

About Compressor Duty Cycle
Compressor duty cycle refers to amount of time a compressor can be operated in a given time period, at 100 PSI and at a standard ambient temperature of 72°F. Duty Cycle is commonly expressed in percentile as: compressor on time (compressor on time + off time) %. As an example, a compressor that is rated for 25% duty cycle means that compressor can be operated at: 100 PSI @ 72°F for 10 minutes on and 30 minutes off. 10 min. on / (10 min. on + 30 Min. off) = 10 min. / 40 Min = 25% duty cycle.

**TheLexx** · 08-30-2020, 03:11 AM

I can vouch that the Viair 450 is very robust. I filled all 6 tires on my dually from 70 to 90-95 PSI, and then all 4 tires on the fifth wheel from 70 to 95 PSI without more than a few minutes break. And it filled the tires fairly quickly as well.

**tfgd21bhe** · 08-30-2020, 06:13 AM

I selected the 400 when I bought my 21bhe. Only used it a couple times so far but has worked well. Unless you plan to fill empty tires regularly I don't see the 100% duty cycle as critical.

For my money I would only spring for the 450 if I was planning to use it for blowing out the water lines every year.

**traveldawg** · 08-30-2020, 10:31 AM

I've got a 400P. I've had it for at least 8 years. Other than a hose going bad I have had no issues. My worst case was having to fill a totally flat 22.5" Class A tire one time. Other than that I have only had to top off tires.

I ran that 400P for at least 20 or 30 minutes filling that 22.5" tire. It does get hot! Even filling and topping off tires on my truck or 5th wheel the compressor head and air outlet will get hot. But so far it has not melted like my previous, less expensive portable, tankless compressors.

I got this hose with the gauge and self holding chuck. It is great. For long fills you can just clamp it on and wait. It beats the heck out of having to hold a chuck down for even a few minutes.

**OurNewEra** · 09-04-2020, 07:37 AM

Originally Posted by BeerBrewer

We use the Viar 300p and are happy with it, it runs around $150 on Amazon. It's duty cycle is 33%, you'll have to move up to the Viar 450 to get 100% duty cycle but it's more than twice the price at $350. I agree 100% duty cycle is better, but I didn't think that we needed it since I only use my Viair when on the road. I have a larger compressor at home that we usee to top off the tires before we leave. Below is what Viair says about duty cycle....I hope this helps.

About Compressor Duty Cycle
Compressor duty cycle refers to amount of time a compressor can be operated in a given time period, at 100 PSI and at a standard ambient temperature of 72°F. Duty Cycle is commonly expressed in percentile as: compressor on time (compressor on time + off time) %. As an example, a compressor that is rated for 25% duty cycle means that compressor can be operated at: 100 PSI @ 72°F for 10 minutes on and 30 minutes off. 10 min. on / (10 min. on + 30 Min. off) = 10 min. / 40 Min = 25% duty cycle.

Thanks for this information! I felt the $350 to $400 for a 100% Duty Cycle was a big pill to swallow for a weekend warrior. If I were full time and it was my only compressor I could justify the 100% duty cycle.

Has anyone tried and had good results with any of the more budget minded inflators? Such as the Pittsburgh (Harbor Freight) 150 psi which I think runs $70.00.

**Fsalmy** · 09-04-2020, 07:54 AM

We have the 450. Works great, but takes several minutes to set up. It is recommended to connect to your vehicle battery and have the engine running while using it. TechnoRV has them on sale right now, but still pricey with $25 off. We also have a Ryobi handheld for quick inflation of bike tires, etc. Already had a couple of 4ah Ryobi batteries and saw the inflator at HD for ~$19, so picked one up. Max PSI is 150. Have used it several times to add a few PSI to the truck or trailer tires. It has a digital gauge that is pretty accurate when double checked against the Viar gauge or a separate calibrated digital gauge I have. It does get pretty hot, though, and I suspect it might get tired trying to bring a large tire from 70 to 100 psi.

https://www.homedepot.com/b/Tools-Ai...5yc1vZc285Zm5d