Shopping Cart

Technical Information

Welcome to the technical page. We have created this to assist in understanding the suspension on your car, how to works, how to repair it and modify it.

Pedders are a specialist Suspension & Brake manufacturer, with a focus on solutions to problems, be that broken suspension, carrying more weight, improving handling, stopping, or resolving known weaknesses in certain vehicles.

Vehicle heights:

For many vehicles, Pedders offer either raised or lowered springs. Traditionally, people refer to a lowering (or a raise) of say, 30mm. Whilst useful, this does assume the vehicle is at the correct height to begin with. It is certainly quite common to buy a set of 30mm lowering coil springs, install them and find that the resulting drop was nothing like 30mm. This is, of course, because the vehicle had either settled on its springs over time, or, had already had springs replaced.

To avoid such disappointment, in most cases we will refer to a specific installed height. The dimensions are quoted using the process shown in the diagram below. So, regardless of the vehicle’s current height, the height with the new springs installed will be as quoted.

Of course, it must be taken into account that other factors can affect the final outcome, the primary one being any extra weight. Our heights are based on a standard vehicle in the unladen condition. If your pick-up has half a ton of “stuff” in the back or your car has had an engine swap to a different type, then the outcome could very well be different! If this is you, please do contact us as we may still have a solution for you.

It will be noted that the quoted height will be, for example, “745mm with 16-inch wheels”. This is a reference wheel size. That does NOT mean, you can’t fit the suspension to the vehicle because it has 17-inch wheels.

803040. Pedders Ezifit Rear Suspension Conversion Kit. For Subaru Forester

Springs and shocks. What do they do?

A common misconception is the function of both the springs and shocks. The term shocks, or shock absorbers in invariably interchanged with dampers.

The springs support the weight of the vehicle, i.e., they hold it off the ground.

The shocks (dampers) control or damp the movements of the vehicle. Shocks do not and cannot * change the height of the vehicle.

With out the shocks, a vehicle once it encountered a bump would continue to bounce long after traversing the bump were it not for the shock.

Of course, both shocks and springs affect the behaviour of the vehicle and are interrelated. This is a complex subject, beyond the scope of this page, and covered successfully by many people.

*There is of course an exception, and that is the Nivomat self levelling system fitted to, amongst others, Subaru Foresters, BMW X5’s, Hyundai Sant-fe, & Kia Sorento.

On these vehicles, the shock DOES carry some of the vehicles weight, but ONLY some. So, a weaker spring than would be normally use is fitted, with the shock carrying the remainder. This means that when the vehicle is loaded with more weight, the shock can respond to this extra weight, ensuring the vehicle remains at its unladen height. It achieves this by using the motion of the vehicle to “pump” itself back up the original height. It is entirely self contained within the shock. There are no pipes or wires to the shock. Whilst undoubtedly very clever, and very effective when working, they can and do fail, the obvious symptoms of which are the rear of the vehicle sitting LOWER than it should.

Frequently, the lack of any exterior features leads to these being replaced with conventional shocks, which does nothing to resolve the “sitting low” symptoms.

Pedders recognise this, and for many vehicles fitted with Nivomat self levelling systems, produce “kits” to convert to conventional suspension at a far lower cost than replacing the Nivomat shocks with like for like replacements such as the Subaru Forester kit below.


In many instances, Pedders offer more than one shock absorber for a given vehicle. Why you may ask?

The manufacturer, when designing the vehicle, has to make a choice about exactly what it wants the shock to do. If we take a pick-up truck such as a Toyota Hilux, it can be used anywhere between unladen and fully laden (1000kg load). This is a very wide range, and the shock will be designed to work at its optimum somewhere in the middle of that range. Elsewhere, it must, of necessity be compromised to some extent. Where different models exist, for example, an Audi A6, the base model will have softer shocks fitted than the RS6 performance version of the same car.

Pedders are able to offer shocks designed to achieve different things to suit how the vehicle is being used. For example, on the pick-up described above, we can offer a shock to work at its best when fully laden and so the driver will experience a better, more stable ride than the standard shock can achieve. Likewise, if the vehicle is used unladen all the time, we can offer a shock that will make the vehicle more comfortable than the original.

Likewise, with a car, to improve the handling and performance, we can design the shock specifically to achieve this.

With these options, Pedders can achieve the outcome that you require and with significantly less compromises than the standard shocks. We achieve this through clever shock design techniques.

For further information on shocks and how they work, please take a look at the following videos:

153226. Pedders Foam Cell shock. Designed for improved ride comfort. For Toyota Hilux MK7


Springs come in different formats, coils, leaf springs, torsion bars, air bags. They are all springs. As discussed above, these support the weight of the vehicle and control its height.

If you want to lower your vehicle, improve its handling, carry more load or tow a heavy trailer, it can be desirable to change the springs to best suit your intended purpose.

As with our shock range, in many cases, Pedders offer more than one spring option for a given vehicle, in particular for commercial vehicles such as vans and pick-ups.

Again, this allows us to provide a solution best suited to the use you make of your vehicle. In the case of commercial vehicles in particular, it should be considered that a very heavy-duty spring that copes well with heavy loads, will produce a less than desirable quality of ride comfort when unladen. This is not always the case with every heavy-duty spring. However, where this is the case, our description will refer to a minimum load in the vehicle to allow an acceptable level of ride quality.

For those interested in carrying heavy loads or towing, and all that this entails, as well as how Pedders can assist with this, please visit our specific page on this subject.

Air Bags

Whilst a “steel” spring of some sort can often be the solution to carrying loads, there are also situations where it might not be the best solution.

Primarily, this where variations in load are large and often, and where a heavy-duty spring would not be suitable in the unladen state.

Pedders Air Assist air bag systems cater for this situation. When unladen the bags can be deflated, allowing the vehicles suspension to operate in the normal manner, but when heavy loads are carried, the air bags are inflated to assist the existing suspension in carrying the load.

Most of our air bag kits, as supplied, require to be inflated with an airline. The same as is used to inflate your tyres. However, this may not suit everyone. It is possible to install “on board” air so that bag inflation and deflation can be carried out wherever you are. This is an additional kit that can be purchased.

When considering an air bag solution, always remember that its function is to assist the vehicles suspension, not replace it.

494060. Pedders Air Assist kit. For Mitsubishi L200


Most our kits are straight forward to fit. Unless otherwise stated, replacement with Pedders parts is as described in the relevant vehicle workshop manual.

However, in some cases, where fitting differs from the original, or other changes need to be made, the relevant instructions are provided with the kit.

We cannot describe here all the possible issues you may encounter when fitting suspension. If you are unsure, Pedders recommend leaving it to a professional workshop.

We do have a number of installers listed on our dealer’s page and intend to expand this over time.

Each and every kit comes with a handy fitting tips bulletin. This covers various topics, but one that does deserve a mention here is the fitting of components with bushes.

A suspension component with a bush fitted that experience rotational movement, i.e. a shock or a lower wishbone/arm, should NOT have its securing bolt tightened up until the vehicle is at its normal ride height. Tightening this bot whilst the vehicle is off the ground can result in early failure.

These bushes absorb the rotational movement applied by suspension operation by “twisting” the rubber. Rubber can only do so up to a point. After which it tears. If the bolt is tightened with the vehicle off the ground, when the vehicle is lowered onto the ground, even stationary, the bush will already be significantly “twisted”. Once the vehicle goes over a bump, further twisting will take place.

The bush at ride height should not be under tension so that it can move both ways as intended without permanent damage. The likelihood of failure is of course dependant on the range of movement its subjected to, and this will vary from component to component and vehicle to vehicle.

It is also worth noting that the same applies when lowering or raising a vehicle. Any pivot point bushes, even though otherwise untouched, should be loosened off and retightened at ride height.

Not doing so, aside from possible earlier failure, will invoke a degree of harshness, or in some cases such as the Chrysler 300C, prevent a lowered vehicle settling down to its correct ride height.

Wheel Alignment

This subject can make up a whole book!

However, keeping it simple, consider the following.

If you are changing the height of the vehicle, it is absolutely essential that your wheel alignment is checked and corrected. It will be wrong after changing the height of the vehicle. Failure to do so will impact the way the vehicle drives to some extent, but WILL definitely wear out your tyres more quickly.

We also strongly recommend checking alignment after fitting suspension components that could affect the accuracy of the wheel alignment. There are too many variables to explain here what can or can’t affect the alignment.

For further information on wheel alignment, please take a look at the following video:

Choosing the right parts

On our website, on many vehicles, you will find suspension “kits”. We have put these together based on our experience of what is normally required for any given vehicle.

However, in the event, that after looking at our kits, you are not sure if they are suitable, or indeed, know its not suitable for your needs, we may still be able to help you. On some vehicles, with so many options, we cannot list every possibility, so please do get in touch, where our experienced team will be happy to assist in identifying a solution for you.

Please either e-mail on or telephone on 01296 711044