www.4×4tec.co.za

I go off-road a lot and I’m always deflating my tyres, then afterwards the tyres need to be inflated again. Up to now I’ve always used portable compressors, but it becomes a pain to unpack it, connect it to the battery, pump the tyre and then the reverse of that to put it way again.

A few weeks ago I had enough and I started off by bolting my tyre compressor to the front side of my load bay, which is covered by a hard lid. I laid some permanent wires from the battery to the compressor, but I only had a midi fuse holder and the biggest fuse I had was 25Amp. The fuse and it’s holder lasted a few seconds before it blew up and I realised the compressor that rated at a 45Amp current draw, really does draw a serious amount of amps!

I had a pressure switch and quite a few tyre fittings, so I thought I might as well add a tank and get a proper fuse and relay installed at the same time.

The 20 litre tank I got from a scrap yard for R300 and it comes off an old Isuzu truck. It has metric threads, but came with a few fittings already and I only had to have a fitting made up for the pressure gauge which cost me R125. Then I used fittings I already had and a manifold I got from a customer.

Sourcing the relay, fuses and fuse holder was a bit of a hassle, because I was looking for an 80Amp relay and 60Amp maxi fuse and fuse holder. PE companies were just useless so I ended up ordering from www.sparxx.co.za and their service was just brilliant. 18 Minutes from order received to order ready for collection, tracking number received an hour and a half later at 16:45, and package in PE by lunch time the next day!

With the compressor already bolted in place, I bolted the tank to the floor next to the compressor with 2 simple M6 threaded rods covered in air hose and bent around the tank.

I did all the wiring and realised the pressure switch was normally open and normally closed as I suspected, so I added a second normally closed 30Amp relay to switch the normally open 80Amp relay. This turned out not to be too bad after all, because the adjustable pressure switch is just too sensitive and I will be replacing it with a normally closed ARB pressure switch and then the 30Amp relay will fall away. The ARB pressure switch is made for this application, but yet it’s way cheaper than anything else I could find.

For added safety, the compressor has its own pressure release valve which I set up to release pressure at around 11bar, while the pressure switch is set to 8bar, but the ARB pressure switch will shut off at 5.5bar.

I added a Y-piece to the pipe coming out of the compressor with a pipe running back under the compressor to the tank. From there I have 2 compressor coiled pipes, one from the T-max compressor and one from my old compressor which I keep in the bakkie as a back-up. I removed the silly fittings at the end of the compressor hose and added a tyre inflation fitting I’ve had for years, and then a piece of hose to clips onto the tyre valve. With this set-up you attach the hose to the tyre valve and stand back while holding the trigger to inflate the tyre. You don’t have to stay down on your haunches to inflate the tyre like a garage inflator. Then when you release the trigger it instantly shows you the pressure in the tyre and then you just pull the trigger again to carry on. To me this is very convenient and it works really well for me.

I also added a tyre valve fitting to the manifold which enables me to either pre-fill the tank, I can hook up my back-up compressor or I can hook up someone else compressor to get an even higher flow rate.

While inflating, the tank stays around 5bar with the compressor running, but you can let it charge up to full pressure to seat a tyre with ease. It not that much faster than the compressor alone, because the tank is still being filled at the same flow rate, but you have that large volume burst of air available.

Some of the costs involved. This is not very accurate since I had some of the items, but I am listing everything I used.

1. T-max 160lpm compressor – I had this, but the go for around R1000 for the same thing at Midas.

2. 20 litre tank – R300 from a scrap yard.

3. Pressure switch – I had an adjustable one that cost R350, an ARB pressure switch is R130.

4. 80Amp relay, 60Amp maxi fuse, maxi fuse holder – R320 from www.sparxx.co.za

5. 30Amp second relay – R30

6. Manifold block – Got it from a customer.

7. Pressure gauge 0-16bar – Had it

8. Tyre inflator, pipes, plugs and fittings – Had it all

9. Heavy cables and all electrical fittings – Had it all

10. Tyre inflation fitting in manifold – Got it from someone

Now, some pics of the set-up.

The Maxi fuse holder situated by the battery.

Cables covered in black plactic tubing running along the chassis to the load bay.

The compressor mounted to the front of the load bay on it's original rubber feet and the tank bolted to the floor with 2 threaded rods.

The relays, note the 80Amp relay with 2 large terminals to handle all the Amps. I sprayed it all with silicone spray for protection against any moisture.

The Y-piece to feed air to and from the tank.

The pressure release valve on the compressor, set to release air at 11bar. THIS IS VERY IMPORTANT.

The manifold block with the pressure switch and the tyre valve fitting.

The air tank, still in pretty good condition for something that came from a scrap yard. It has a certification plate on it with a rating of 20bar and the pressure release valve is set at 11bar.

The pressure in the tank at the cut-off point.

I put a carabiner on my hard lid to lift the pipe up and it is also a place I can hang the inflator from when not in use.

The hose and tyre inflator set-up.