Frequently Asked Questions - Air Suspension

This page focuses on full air suspension systems.  For information on load support setups, please see the Load Support FAQs.

• What is air suspension?
• What are the main components in the system?
• Is air suspension reliable?
• What are the common issues with air suspension?
• Can I still drive the vehicle if there's a fault?
• Can I use air suspension on my daily driver?
• Is air suspension suitable for winter use?
• Does air suspension affect ride quality and handling?
• Do I need height sensors?
• Can I tow with air suspension?
• Does air suspension leak overnight?
• Is air suspension legal in the UK?
• Do I need to tell my insurer?
• Will air suspension pass an MOT?
• Can I install air suspension myself?
• How long does installation take?
• How often does air suspension need servicing?

General

What is air suspension?

There are two main types of air suspension: Semi-Air or Load Support setups, or full air suspension.

Semi-air or Load Support systems are designed to work with the existing springs, and provide additional support when towing or carrying heavy loads.  These can be inflated with a tyre pump, or an onboard controller.

Full air suspension replaces traditional metal springs with inflated rubber air springs (air bags).  These are inflated with compressed air, and the combination of the flexible rubber and compressed air create the spring.  The main benefit is that the vehicle height can be adjusted to suit different situations, while still maintaining good ride quality and handling.

What are the main components in the system?

Air suspension systems comprise of a number of components.  Broadly speaking these are:

• An air compressor
• An air tank
• An air management system
• Air springs (aka air bags)
• Air lines and fittings

The compressor fills the tank with compressed air.  The tank stores this compressed air, ready for deployment into the air springs.  The tank connects to the management system.  This is the brains of the system, it connects the compressed air to the air springs when required, and controls how the air is deployed.  Some systems work on pressure, some work in conjunction with height sensors, and some work with both height sensors and pressures.

Is air suspension reliable?

Air suspension isn't a new concept, and has been used reliably on commercial vehicles for many years.  Of course it is more complex than a traditional static suspension setup, so there are more potential points of failure.  But a properly installed air suspension package, when looked after and properly maintained, can be trouble free for many years.  

To maximise the lifespan of your air springs, it's best to keep some air in the bags, particularly if you're parking the car up for more than a few days at a time.  This helps prevent premature deterioration to the rubber.

What are the common issues with air suspension?

By far the most common issue is leaking air.  The majority of the time this is due to ageing fittings which are cheap and simple to replace.

Top mount bearings on air struts tend to be under quite a lot of strain.  However they are inexpensive so these should be treated as serviceable items.

Issues can arise with water in the system, so it is critical to drain the tank of excess water periodically, and ideally run a water trap between the tank and the management system.

Rubbing air springs.  This can be an issue if there isn't enough clearance around the air springs.  It's critical to check for clearances when adjusting the suspension geometry or changing wheels.

Compressor filters and check valves are often overlooked, and should be checked periodically.

Can I still drive the vehicle if there's a fault?

This depends on the type of fault, and if you're unsure it would be best to get in touch with us.  You wouldn't drive a car with a badly broken spring, so it's best to avoid driving with damaged air suspension.

Slow leaks can be OK for years if you know the cause of them, but any leaks should be investigated as a slow leak can quickly turn into a fast one.

If the vehicle is sitting unusually low, leaning to one side or making contact with the tyres, it should not be driven until the cause has been identified.

Practical Use

Can I use air suspension on my daily driver?

Yes you can drive on air suspension daily, and many people do this without any problems.  You should perform a little bit of preventative maintenance to keep the system serviceable though.

Water in the system: As it compresses, the humidity in the air turns to water, which accumulates in the system over time.  Air tanks should have drain valves on the bottom of them to release water, and this should be done periodically (it varies from one car to another, but to start with we recommend draining it once a month until you get a feel for how much water is in there).  There should also be a water trap installed between the tank and the management system.  Some are auto draining, but most need to be manually drained periodically.

Keeping the air bags clean is a good idea, so when you wash the car, give the bags a quick clean with water.

For strut bodies, particularly threaded bodies, a regular coating of anti corrosion spray (such as ACF50) is a good idea to keep them fresh.  It's best to avoid getting this on the air springs though.

Compressors have filters which should be changed periodically.  The frequency depends on usage, but generally once a year is a good idea, they're cheap and easy to replace.

Top mount bearings on struts, these can wear out over time and cause a knocking and/or creaking noise.  If they get noisy, check them and replace as soon as possible.

Is air suspension suitable for winter use?

Yes, with a couple of caveats.  Water in the system is your enemy.  It can freeze valves and air lines, and cause general chaos.  Regular draining is critical when the temperatures start to drop.

On extremely cold days, we tend to recommend leaving the car at ride height, and using manual control instead of preset height adjustment, at least until the system has warmed up.  It's not critical, but frozen valves can occasionally cause unexpected behaviour when trying to reach presets.

Does air suspension affect ride quality and handling?

It varies a little depending on the car, but in most cases with a reputable, modern air suspension package, it's just like fitting a set of good coilovers.  

Comfort is generally rather good, but with aftermarket systems they are more aimed toward performance rather than the smooth floating ride that people often imagine with air suspension.

The debate of "air vs coils" has been around for many years. In reality, a well designed air suspension system can perform extremely well.  It is often used on high performance cars and we have many customers who regularly use their vehicles on track without any issues.

Do I need height sensors?

This depends on the vehicle and usage case.  Height sensors are great in a number of scenarios.  For example on commercial vehicles where the weight changes often.  They are also helpful on vehicles where the suspension moves in a less predictable manner, such as some RWD vehicles where there is a lot of natural camber, which can give unpredictable preset heights based on pressures alone.

Height sensors are somewhat fiddly to fit and set up, and while there are brackets available to help with this, it should ideally be done on a 4-post lift so the sensors can be checked/adjusted at all heights.  The ALP4 system has a fantastic height sensor tool which makes setup a lot easier.

Can I tow with air suspension?

Absolutely, in fact that's pretty much where the origins of air suspension came from.  As long as you don't exceed the vehicle manufacturer's limits, towing with air suspension is no different to towing as normal.  In fact it can be very useful, as you can increase the pressure in the rear bags to compensate for the extra weight.

Does air suspension leak overnight?

A small amount of pressure loss over time is normal.  Particularly as temperatures change.  However a vehicle that drops significantly overnight is likely to have a leak that should be investigated.

Legal/Insurance

Is air suspension legal in the UK?

Yes.

Do I need to tell my insurer?

Yes.

Will air suspension pass an MOT?

Yes, as long as it's in serviceable condition and there is no damage or perishing. 

Installation

Can I install air suspension myself?

If you have tools and some mechanical know-how, then yes you probably can.  It helps massively if you have access to a lift, but if you've ever fitted coilovers and a subwoofer, then you've pretty much done this before.  The main difference is that you need to safely run air lines through to the bags, and check for clearances at all heights and steering angles.  The kits come with comprehensive instructions.

How long does installation take?

When installing a kit as DIY, most people can get it done in a long weekend, but it shouldn't be rushed.

When we install it, we generally require the car for a week, which enables us to take extra time to carry out the final checks and tests.

In some cases such as custom installs and bespoke vehicle projects, it can take significantly longer, but this varies and we tend to give estimates for this individually.

How often does air suspension need servicing?

We generally recommend draining the water from the tank and water trap once a month, and checking everything over once a year.

Vehicles that see regular winter use or are driven in wet conditions may benefit from more frequent inspections.