12 v Portable Air Pump Update MV-50 & EZ Tire Deflators

One of the most important items to have in your off road bound vehicle is an air pump to reinflate tires. Deflating tires off the pavement is key to both puncture resistance and traction/ flotation.

Another use for the air pump is to refill a flat tire after you plug a hole (if you didn't deflate before off pavement driving). So, have a tire plug kit, as well!

I have had three models of electric tire pumps over the past 35 or so years.
I started with one that plugged into the cigarette lighter... It was not so bad because at the time, my 4x4 was a Subaru with 13" tires, and I would just wait the time it took to refill.

When I started off roading in a Tacoma, with 16" x 31" or 32" tires (265/70 or 75 x 16) the cigarette lighter powered unit was just too slow, adding air at the rate of 2 psi per minute. That meant to go from 15 psi to 35 psi (20 psi added) would take 10 minutes per tire or 40 minutes for all four.

The great aridologist, Mr. Neal Johns (who strongly promoted the TRD Tacoma be my next vehicle in 2000), recommended the General Pneumatic brand pump with a power cable that clips directly onto the battery... was on sale for $49.95 at Harbor Freight. That unit filled my tires at the rate of 6 psi per minute, three times faster (3.3 minutes/tire).

On the negative side, the power cable gets very hot and the fuses would melt (not blow, but the plastic housing would melt). The large hard plastic carrying case was a bit bulky, too.

I acquired an MV-50 SuperFlow pump and it was perhaps a tad slower but the wires did not overheat and it fit into a smaller, canvas carrying case. It gave me years of good service until my last use, last year, just south of Gonzaga Bay, when I was refilling my tires and when moving the fill hose to reach the last tire, accidently pinchedd the tube (while the pump was running)... and that blew out an internal check valve and ended its life!

That was not the pump's fault! But, TURN OFF the pump between tires, just in case!

Well, for Father's Day, my kids got me a new MV-50 along with some of those automatic deflator devices you screw onto the tire stems. I did an in garage test, using a stop watch... Here are my findings:

Using a precision dial pressure gauge, I deflated my tire to 20 psi then timed how long to add 15 psi (back to 35 psi). The answer was 2.5 minutes for a 265/75-16 all terrain tire.
1 min = 6 psi ADDED
2 min = 12 psi
3 min = 18 psi
4 min = 24 psi
5 min = 30 psi

The gauge on the pump was pretty accurate when the pump was not running, but jumps almost 10 psi when on and filling. So, to know when to remove the fill hose, I ran the pump until the gauge was just below the 45 psi line (for 35 psi in the tire). You can toggle the on off switch to see the more accurate pressure.


Under 2 minutes???
In 2 minutes, it will add 12 psi to a truck tire, if the tire is flat, you may need closer to 6 minutes if your tire needs around 35 psi for the highway. Obviously more time if you have a higher pressure tire.

A footnote, the automatic EZ Deflators were pretty easy to set up (they are adjustable). You manually deflate the pressure to the desired reduction (in my case 20 psi for dirt roads... and I can quickly let more air out for sand if needed). With the cap and lock ring turned all the way clockwise, attach it to the tire stem and then turn the cap counter-clockwise until air escapes, then clockwise to it again doesn't. Now, bring up the lock ring to hold the cap in that spot. After I refilled the tire, I placed the deflator on the stem, and it let air out... It took a long time, I didn't clock it, and as the pressure got lower, the rate also diminished... when it was coming out real slow, I removed it and checked the pressure... it was 22 psi. The kit comes with 4 deflators, so I will put them on all four tires and after a beer, will finish the job with a pen or similar tool to depress the valve stem.

 

Just a note, that you can get the MV-50 at Pep Boys for $42 using their 30% off online coupon.

 

Glad to hear the wiring is holding up on these pumps. I bought one about a year ago and the first one arrived DOA. Second one was ok though.

 

Ever thought of asking if anyone has a bad pump with a good hose they can part with? Or selling the pump to someone who also had a pump fail, but still has the hose? You really "trashed" a good pump?

 

There are write-ups online about how people have reamed/threaded that outlet hole to fit standard pipe thread (3/8" I think) and installed a standard male hose connector. In case you still have the pump.