Here at Merlin we stock a large range of AVO universal coilover dampers. These are a quality damper, made in the UK and widely used throughout Motorsport. We have compiled this short guide to help you choose the correct damper for your application.
We keep good stocks of the single adjustable dampers. You’ll find our range here – AVO UNIVERSAL COILOVERS
The single adjustable version has a 1:1 ratio of rebound and bump adjustment via one knob usually found at the base of the damper.
*Please note, double adjustable versions are available and we can order them for you, although they do not appear on our website. As a special order, i.e. we do not keep stock ourselves, there’s normally a couple of weeks delivery time and they are non-returnable.
Making the right choice of coilover damper
1: The first choice you need to make is whether you require a steel or aluminium bodied damper. This is more personal preference than anything else, though if the car is quite heavy and being used on the road, we would probably recommend using a steel bodied damper. Aluminium bodied dampers are roughly 30% lighter than the steel version. Steel dampers are usually powder coated black. Aluminium dampers are usually plain aluminium with anodised black top and bottoms – as below.
2: The second choice to make is dependant on the internal diameter of the springs you wish to use. AVO universal dampers are available for both 1.9” I.D and 2.25” I.D springs. Most race cars use 2.25” springs but always check. If you are building a car from scratch (Kit Car/Hot Rod etc) then the first thing to check is clearance of the springs around other parts (wish bones/drive shafts/ body work/steering joints etc). Some cars, like the classic Mini, have to use 1.9” springs due to body clearance restrictions. Using 1.9” springs does limit your choice of dampers and springs.
3: The next decision is the mounts. As standard, these dampers have a ½” I.D eye at the top and bottom for a bolt or stud to pass through. The dampers are then available with either polyurethane bushes and a steel sleeve or a spherical bearing. For road use, the poly bushes are better, these prevent the harsh vibrations and noise through the damper. Spherical bearings are better suited to race cars where the vibrations are not so much of an issue.
One thing to note: On vehicles that need the damper to be lent over at an angle, spherical bearing mounts should always be used. If using poly bushes, the angle of the damper will cause the bush to wear unevenly and quite quickly split. Poly bush mounts are really only ideal for upright dampers without any mounting angle, unless you want to replace the bushes often. We sell the bushes, sleeves and bearings as separate parts too. You can convert from poly bushes to bearings and vice versa.
4: The last choice to make is the open and closed lengths of the damper. The measurement is taken from the centre of the bottom eye - to the centre of the top eye. AVO list these dampers in a range of open and closed lengths. The closed length is normally determined by the open length. For example, an 11” open length damper will have a closed length of 8”.
One thing to remember, which is a little confusing, the closed lengths we list are without a bump stop fitted. When the bump stop is fitted, the closed length increases by 1” (so it’s now 9” closed). All AVO universal coil over dampers are supplied with a bump stop fitted to the damper rod. If you are not replacing an existing damper, you will need to work out the damper lengths and then purchase the nearest length available. Dampers should be measured off the vehicle.