Set-up of basic kit
We often get asked about motorhomes that people have bought and the instructions have been lost.
These notes are for guidance only about how to operate most of the commonly available systems and are based upon never having seen your particular motorhome or conversion and based upon how I set them up, and are intended for guidance only.
Please take extreme care when working on air suspension as it can be dangerous, cause injury or death if incorrectly handled.
The most common system on the market is the basic, simple, minimum connections type Schrader valve type system. This is our favourite because it has the minimum amount of items to go wrong or leak, and is therefore by far the most reliable.
The next step up has a gauge and valves but in reality this adds little in the way of benefit but a lot more to go wrong, and as these systems are “fit and forget” type installs they don’t really like being left. Valves seize, gauges go faulty due to moisture and unions leak. This is probably the second most common type and the set-up instructions are the same.
Airbags These instructions relate to airbag systems fitted to “assist” the original suspension on the vehicle which is normally leaf spring. They are fitted because when converted into motorhomes, or when fully laden as vans or minibuses the suspension drops dramatically and the ride quality and stability suffers significantly. Air bags tend to be rolled sleeve or double convoluted (twin donut) type bags. Most bags on the market have a maximum working pressure of around 100psi and so bags should never be inflated beyond this point unless they are clearly marked as being able to accept more pressure. This relates specifically to Dunlop and to Firestone bags. The bags that we use are rated as being capable of taking 200 psi, and have a burst pressure of 600 psi but in use they are still rated for 110 psi. Many bags do not have internal bump stops, and also many installations replace the bump stop with the bags as this is almost always the perfect position for the bags, so bags should never be deflated below 20 psi when you are driving. This will give little or no support and little or no lift, but will prevent the bag from rupturing (and also act like a sort of bump stop)
Ride Quality This type of kit is fitted to a vehicle to improve ride quality. This is a subjective criteria and as such each person would probably say when it is right for them at a different point. Thus there is no right or wrong, so long as you are between 20 and 100 psi. Each vehicle is built differently and loaded differently and the correct pressure on each vehicle is different.
Testing To test the system you will ideally need to have or to borrow a tyre inflator with a gauge. Most have a side button which will gently lower the pressure although most people don’t even notice it!! Inflate the vehicle to 20 and notice the height of the vehicle – you can even measure, and if interested measure at 10 psi intervals right up to 100 psi. This will give you an indication of the range the bags work at – initial increases will provide little or no increase in height of the vehicle. Then you will notice in the mid range that lift occurs and as you get to the top little in the way of additional lift is observed. If the hand brake is on some creaking may occur as it is lifted and dropped – you may also find the handbrake tighter to release. Leave the vehicle at 100 psi and go for a drive. Ideally on both bumpy back roads and smoother main roads. After you have a feel for the vehicle stop and where safe to do so drop the pressure by 10 psi and repeat. Do this until you get to 20 psi (provided you have clearance from your measurements). I strongly advise taking notes of each pressure and how it “feels” on both roads, and around corners. What is the handling like? What is the ride quality like? What is the load support and stability like? Does it bounce? Does it crash? After this you will have a good indication of what pressure is needed to drive. It may be different on main roads and back roads and you will probably have to make some sort of compromise. Leave a note in the vehicle of what pressures you decided as it can be hard to remember years later, or for a new owner to know. Hope this helps.