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Tyre Deflation & Re-inflation Made Easy

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    Anyone that has had to traverse an area of soft sand with his vehicle, and possibly trailer, knows that an essential part of that process is aggressive deflation of all tyres. And that means re-inflation as soon as possible after the process is complete, since driving with wheels deflated to 1,1 bar will quickly lead to sidewall damage and tread separation. Anyone who does this regularly knows that it stops being fun after the first time, sometimes even sooner. Squatting beside each wheel for long minutes on protesting knees while the air bleeds out ever more slowly is something that only young people should indulge in.

    To relieve me of this unwelcome duty I created a microcomputer device that could:

    ·         Communicated with my mobile phone via Bluetooth.

    ·         Switch the heavy 12V DC current required by the compressor

    ·         Operated a solenoid-activated deflator valve

    ·         Measure and report air pressure within the inflator hose

    ·         Do some arithmetic

    Control Unit

    I then wrote an app for my mobile phone that could:

    ·         Display the air pressure measured by the remote device

    ·         Command the remote device to switch the compressor

    ·         Command the remote device to activate the deflator valve

    ·         Send a user-defined target pressure to the remote device

    ·         Command the remote device to seek this target pressure

    ·         Operate the flashlight.

    The compressor and deflator valve can both be activated from the mobile phone or a target pressure can be dialled in and the remote control commanded to seek this pressure. Since the pressure measured in the hose does not reflect that in the tyre once air starts to flow in either direction, the remote device estimates the time required to reach the target pressure and initiates a cycle with the remaining time displayed on the mobile phone. The size of the tyre (large, medium, or small) is specified to assist with this. If the target pressure is not reached at the end of that cycle subsequent cycles are initiated automatically until the tyre pressure is within 50 mbar of target.

    The whole system needed to be housed in a container, for which purpose a high-lid ammo box proved eminently suitable, after the lid was hinged into place and those pesky snap-clips were done away with. Should the remote control not be operational for any reason it can be bypassed by connecting the IN and OUT Anderson plugs directly to each other. Similarly the quick-disconnect coupler can isolate the remote device from the air hose.

    That annoying always-too-short spiral plastic hose is discarded and replaced with a generous length of silicone rubber compressor hose.  A good quality deflator and pressure gauge to use as back-up is also a good investment.

    There are undoubtedly many cheaper methods of achieving the same end – I’ve used most of them myself – but this is my most elegant solution thus far. Aside from the remote control all of the components are available from  camping and 4×4 shops and the app is available for download from my website

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    Simon Tasman
    Simon Tasman on

    <p style=”text-align: right;”>This is exactly what I have been looking for for years now. I’ll send you my contact details through your website contact form.</p>
    Another huge annoyance with those horrible spiral plastic pipes is that once you get the connector sleeve screwed onto the valve, which can be a pain all by itself, the the pipe pulls so hard at an angle that it delaminates the brass barrel from the vulcanised rubber cone. The valve then leaks through this gap and you have to dismount the tyre to replace it!

    Why don’t they supply these compressors with right-angled clip-on connectors?

    Also they put the pressure gauge at the wheel instead of near the switch so you are forced to continually walk to and fro between the two.

    Your solution will help me immensely. I don’t care what it costs.

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    Fyko on

    Hi Simon,

    Yes, that screw-on sleeve is another example of a product designer that never uses the product he foists on us.

    They’re not that easy to find as seperate components, so I just cut one off the end of a cheap footpump’s hose, but this is my answer to the problem. It screws into the original hose-to-valve coupler so you can always revert if it fails on you:

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    LexStewart on

    A bit confused here. Brilliant kit – by the way.
    The Complete Kit
    Carry box
    Control Unit
    10M Hose
    Then the next paragraph says you need a suitable compressor etc.
    A bit confusing?

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    Fyko on

    Hi Lex,

    Sorry for the confusion.

    The configuration of the system is quite variable – compressors come in many sizes and prices, carry boxes vary from R150 (Builder’s) to R250 (Outdoor Warehouse), and then you may have a cheap pressure gauge/deflator at less than R100, or a good one at over R1000.

    The thing that I make quite happily is the control unit and the mobile app. That’s where the R2000 comes in. The app is a free download, but the electronic stuff is pretty expensive because of the heavy DC currents that must be carried and switched, as well as some specialised components like pressure transducers etc

    Putting the whole set together is not something I enjoy too much, but it can be a bit of a challenge for the average handyman, so I actually suggested to one of the big 4×4 shops that they should build these thing in their own fitment workshops and offer it as a package deal in their showroom, since they already sell most of the components. Needless to say I never received any response.

    In the meantime I’ve developed the thing a little further as you see above. I now have 5 tyre sizes to help get to target pressure more efficiently and I’ve made space in the bottom of the box for tyre levers and repair kit etc.

    I’ve had demand for the control unit from as far afield as Dubai where it’s clearly not practical to send a Chinese compressor to, so I just have to trust that they can get the whole kit working out there, but I’m a bit concerned about local chaps not having what it takes to put the set together in such a way that it works dependably, and then the spouses start muttering about how the kid’s schoolfees have been wasted!

    I do spend the extra few bucks on four 50A plugs so the control unit can be taken out of circuit should it or the phone not work for any reason. And I can isolate the air hose in case the electronic deflator jams open on some grit from inside the tyre, all of which pushes the cost higher and higher.

    All in all this is only a solution for guys with fairly deep pockets. There’s lots of cheaper ways to get the tyres pumped and unpumped.

    Best regards



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    Simon Tasman
    Simon Tasman on

    My build of the compressor set cost me about R5,500. Which includes R2,500 for the compressor, if I remember correctly.

    Years ago we would do this on the real cheap – I’d put a family member at every wheel armed with a twig or a hairpin and set them to deflating while I circulated with my pressure gauge bought in Checkers for R40, and monitored progress. That was the easy part.

    On the way out it was not so easy though. The nearest town in Moz was in town 14Km away where there was a single filling station that (sometimes) had air.  In holiday times there’d be up to 20 vehicles waiting to pump their tyres for the trip home. Often the service station owner would get tired of paying for the electricity to supply free air, and switch the compressor off, declaring it broken. Then it was 34Km to the next town to try again.

    To avoid the 2 hour-plus wait at the service station I’d sometimes take out the toy compressor I’d bought at Midas for R500 and try to inflate the tyres myself, generally where the soft sand ended and the hard road started, to save the sidewalls the torture of the 14Km to town.  The trouble with these toy compressors is that they have a design life of about one hour’s operation, after which they literally fall apart. I went through several of these pieces of junk before I saw the light.

    Nowadays the kids are all either in Canada or Oz so it’s just me doing the air work on the wheels and, after doing it more than a hundred times, I look for the shortest and easiest path, without much regard for the cost. These days I’m sitting in the car slaking a persistent thirst while technology does the grunt work for me. I’ve earned it.

    I also used a high-lid ammo box to house the stuff. Hinging the lid is essential if you want to stow the hose in the lid where it’s easily accessible and doesn’t kink, and then there’s plenty of room for the rest of your stuff in the bottom. The control unit comes with mounting brackets that favour corner-mounting in the ammo box, which is ideal. I also have both a snap-on connector and the original screw-on ferrule for attaching to the valve.

    The only problem I ever had with my unit was the deflate valve getting jammed open by some debris from inside the tyre. It was easy enough to fix – it just takes a jeweller’s screwdriver – but you can’t do that at the roadside, so it’s a good idea to be able to take the unit entirely out of circuit quickly, and revert to manual switching, should this happen in the field.

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    Fyko on

    R5000 – R6000 Sounds about right, if you get a strong compressor. That works out to a bit more than 2 cheap tyres, or a bit less than two good ones.

    Car or bakkie tyres don’t suffer immediate harm when you drive on them a little distance at 110kPa, but it often destroys trailer tyres very quickly, because those are often older than the 5-year design life of all tyres.

    After 5 years the rubber compound becomes very hard and inflexible, and running the tyre very soft starts it delaminating from the casing due to excessive flexing.  Some hundreds of kilometres later the tread layer breaks off in chunks on the road.

    Read the little oval stamp on the sidewall to see the 2 digit week number and 2 digit year to find the manufacture date of the tyre.

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    Dan Perkins
    Dan Perkins on

    I lost both the tyres on my Xplorer in separate incidents a couple of years back, but both the result of running them at 1.1 Bar when they were 8 years old or even older.

    Tyre makers only support their products for 5 years in which time they almost always wear out if fitted to cars or bakkies, but caravans and trailers can wear tyres very slowly and it’s easy to forget how long you’ve had those takkies on the caravan. I didn’t know about that date stamp either until it was too late – now I check all tyres regularly

    Since I acquired a proper compressor and been able to reinflate timeously, I’ve had a lot less sidewall fatigue from running flat all the way the the service station, so I’ve easily saved that expense back on avoiding tyre replacement, but my knees also aren’t up to all this squatting anymore, so I’ll be contacting you through the form on your website about some remote control.

    Looks like the answer to my prayers. Thanks.

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    Fyko on

    <p style=”text-align: center;”>Update</p>

    After some feedback from the users I’ve provided a wider tyre size option. Also the last setting you use is remembered when you close the app down, and restored when you restart it.

    When you set too large a tyre size the system tends to over-inflate the smaller tyre and then you need a deflate cycle to get the pressure down again, which wastes time. Better to specify something slightly smaller and let it correct with a second inflate cycle if necessary.

    The compressor I recommend is the medium-sized one that pumps 160L/min and draws up to 45 Amps. They cost about R2000 at Outdoor Warehouse, have sufficient duty cycle to inflate 6 large tyres, and they can be connected with 6sq/mm (56A Max) wire, and 50A Anderson plugs. The control unit can switch up to 60A which provides a comfortable safety margin.

    The complete assembly looks like this. The box is big enough to house stuff like tyre levers, a pressure gauge/manual deflator, and your repair kit. Even a back-up foot-pump if you don’t trust technology all that much. Some people like to drill ventilation holes in the high lid of the ammo box because that compressor gets pretty hot after inflating six 15-inch wheels. It’s essential to hinge the lid if you want to use it for storage as well.

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    Simon Tasman
    Simon Tasman on

    Thanks. That slider at the bottom for setting tyre size is a good improvement.

    What I was doing before was stopping the Auto cycle at about its mid-point and checking progress before re-starting. That way I avoided getting overshoots that, as you say, take time to correct. With the slider adjustment that is no longer necessary.

    Have you made any progress with third-party integrators? In my travel group there’s a few old codgers who have moved into retirement villages and don’t have workshop facilities any longer. They don’t want to do the little bit of drilling and cutting that is needed inside the house on the kitchen table, thereby getting the old lady upset, but they have the money to pay someone else to do it for them.

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    Fyko on

    Hi Simon,

    Sadly, not much progress there.

    I emailed the mega 4×4 shop with a suggestion that this was a good way to convert some business. They totally ignored me.

    Subsequently I have directed over a dozen compressor buyers to another dealer, mostly because I don’t trust people who cannot answer a simple email to offer any other level of customer service either. The value of the business they deliberately lost there was over R50,000, but that was their choice to make.

    None of which helps your friends obviously. I no longer do the integration for the general public because I have to invest in the compressor, box, connections etc, and then wait for a refund from the client, which also may never arrive. Since my margins are razor-thin I found I was just losing too much. However if I find someone who can do this reliably I’ll let you know.

    Please send me your email address through the contact form on my website:

    so I can get back to you.

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    Owen Ball
    Owen Ball on

    I am possibly being stupid, but why not connect all the tyres to one point and deflate them according to the single pressure gauge, and in reverse inflate the tyres from this single point.  Pressure would all be equal if my physics is correct.

    So  about 4 pieces of pipe with valve connectors to the tyres, all connected to a manifold block with one pipe leading off to the compressor with a pressure gauge.  Then just sit back and watch the pressure gauge with a frosty at hand.

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    Fyko on

    That’s a good solution if you want them all at the same pressure. You need to be quick about it though because when you uncouple one valve the other tyres will all deflate through the open outlet(s).

    Because of the extra weight per wheel many like to leave the trailer tyres at a higher pressure than the car both when inflated and deflated.

    The 4×4 forum has been pushing a device that couples the air connection to 2 valves simultaneously. Seems quite expensive to me, though some people appear to enjoy it. My device similarly is very much only for the moneyed few, the bulk of the folks put a kid at each wheel with a twig to deflate, and line up at the local filling station when their el-cheapo compressor breaks after the second wheel to be inflated.

    If you only go out once a year on your annual it’s really not necessary to go to any great expense – the chaps I supply are the upper-bracket pro types that go out playing every weekend, and have oldish knees that are prone to complain at repeatedly having to squat beside a wheel or 6.

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