Suspension Lifts & Lift Kits, What does is all mean and do??

When people ask about suspension lifts on public internet forums or at offroad shows and meets, you get a lot of people saying you don’t need one and that it’s perefectly ok at standard height. This is in part true. A Defender is very capable in standard height and you only need to put a suspension lift on a Defender if you want to fit tyres 33″ or higher and/or to help improve approach/departure and break over angles.

Other people just do it because they can or they like the look.
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Adding a Suspension lift can improve your vehicle and its offroad capabilities, but it’s worth noting that there are some drawbacks to lifting your suspension. Your centre of gravity is now higher, most multi storey car parks are now out of bounds and if you are a short you are going to have more of a problem getting in or out.

You can easily achieve a suspension lift by either fitting longer or heavy duty springs or altering the spring mounts. It’s that simple! For springs there are many available on the market including springs from Terrafirma, Britpart and Procomp. Which you decide to purchse is upto your budget and needs. Some springs give a much harder ride, so this also needs to be taken into account.

A very easy way to raise your vehicle is to alter the mounts by fitting a spring spacer/packer to base mount…

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This will raise your hight buy will not increase travel of the suspension as the length of the spring or shock has not changed.

Once you have increased the height of your vehicle other suspension components will be effected.

Shock Absorbers
If you increase you spring height by 2″ your shocks will have further to travel. This will have the effect of reducing the amount of travel/articultaion in your suspension. You can solve this by buying longer shocks or altering shock mounts. A popular make of longer shock is the Procomp ES9000, available in +2″, +4″ and +5″ options, and Terrafirma which come in 2″and 5″ and a more extreme 9″ and 11″. Other include Rough County, De Carbon, Koni, OME and many more.

Adjusting the shock mounts is a common option. By altering the shock mounts to fit lower shock chassis mounts with a -2″ mount, will lower the mounting point of your standard shock, giving you the extra two inch you require. Here’s a pic of a front -2″ shock turret…

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The downside of this is that you have now reduced upward travel by 2″ on your shock. Having a shock ‘top-out’ under compression is a bad thing as it will damage the shock quicker. So people fit bigger extended bump stops to stop this from happening. This is all well and good, but now your axle can’t come up as high as it used to and this limits articulation. Some shocks like DeCarbon seem to have greater upward travel by design and do not ‘top-out’ on a Defender with -2″ shock mounts and so don’t need extended bump stops, but it is trial and error.

Once you start to fit long shocks and have lots of articulation the shock will actually move in an arc with the axle. This can induce fatigue on the mounts/bushes and over time the shock. This is why you see revised mounts from the like of Gwyn Lewis and WhitePeak (QT Services) etc …

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It’s also why Devon 4×4 introduced their rotating swivel shock mount…

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Articulation
Articulation is the amount the axle will move up and down. It can be affected by length of shock travel, radius arms/bushing, anti roll bars if fitted, spring extension/compression and upward axle travel. As said above if you fit a lift of 2″ and don’t change your shocks you have just reduced your articulation by 2″. Now if say you fitted a 2″ lift and +4″ shocks you would now have an extra 2″ of articulation.

When off-roading most people like extra articulation as it aids traction over uneven ground and can aid stability. On a Defender, once you have increased the articulation by 2-3″ over standard through shock travel other items will start to limit the articulation. Also note that you’ll also have to fit longer brake hoses as standard ones will not stretch to the new travel and will be ripped off their mountings. On the front of a Defender it is the radius arms and their bushes that limit articulation the most.

Articulation and radius arms

When an axle drops the angle of the radius arms increases downwards and causes the lower part of the chassis bush to compress…

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It will only compress so far and once at this point it will stop the axle from dropping any lower. It also damage the bush quite quickly if under constand compression, ie from a 2″ lift. These will need replacing and could cause a MOT failure. To overcome this people fit kinked radius arms to decrease the angle…

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or jointed radius arms from the likes of QT, Equipe and X-Eng for even more movement…

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An alternative for the front suspension to achieve even more front end articulation is to change the layout completely and opt for something like a 3-Link set-up from the likes of QT, Safari Guard etc..

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To allow more articulation you also have to consider lateral movement and again jointed radius arms or 3/4 Link systems provide greater movement here. On the rear you need to look at lateral movement of the A-Frame joint too…

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Articulation and Spring extension/compression

If you have enough articulation your spring will come out of it’s mounts, this is know as dislocation, and when the axle lifts back up it will not reseat properly on its own. This can be overcome in a number of ways…

  • Secure the top and bottom of the spring to stop it from popping out. The downside of this is that if your spring is not long enough under extension it will stop your axle articulating enough.
  • Fit long/softer springs. The problem with softer springs is that they are not great on road and on side slopes when off-road. So people like Max Traction use this route, but with progressive rate springs. These give better handling on and off-road and they have the length to still put downward pressure on the axle to aid traction…Posted Image
  • Dislocating Springs allow the spring to pop out and by using a re-locating device like a cone etc guide the spring back into it mount. This is a very common option and comes as part of kits from Terrafirma etc.Posted Image
    There are various versions of this with some fitting to the top mount and others fitting to the axle.Posted Image
  • The latest to hit the scene is the helper spring design from X-Eng, X-Flex springs. This is an additional spring that sits inside a spring mount cup on the bottom spring mount. As the axle articulates past the length of the main spring the helper spring takes over the extra length and still provides downward pressure for traction. That way you can fit springs for good on-road/side slope stability yet still have traction at large amounts of axle articulation.Posted Image

Spring compression can also affect articulation. If a spring is too heavy duty it will not compress in length that much and can affect axle upward travel. You also have to be careful with too soft a spring as it can start to bend out under compression and can catch on other components or the wheel/tyre. On the same lines you need to make sure that on upward travel that your wheels/tyres are not fouling on any components.

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Articulation and anti roll bars In doing their job anti roll bars reduce axle articulation. If you want more, you either have to remove it or fit detachable axle or chassis mounts. This way you can detach it for off-road use, but still have good handling on-road.

Articulation and prop-shafts You may have noticed that the your diffs are not in the centre of the axle.  If so you’ll know that is the axle articulates more it’s going to alter the angle and length of the propshafts. At slow off-road speeds vibration is not so much of an issue but the UJ’s binding is a problem. This is why people have fitted wider yoke props or custom props with with bigger UJ’s that have a wider operating angle…

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When you lift your suspension you alter the angle and the length of your prop-shafts. Lift it too much and you will cause excessive vibrations in the propshafts at road speeds. Also a large lift will cause the UJ’s to bind. This can be solved with use of large wider yoke props for the binding and Double Cardan jointed props for the angle induced vibrations. It is often suggested to use the Discovery II front prop as this has a double cardan joint as standard…

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Note that it has a different flange, doesn’t have bigger UJ’s/wider yoke and doesn’t have grease nipples so longevity can be an issue. Custom made props can overcome this though…

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Suspension lift and castor correction

Castor angle can affect the steering of the vehicle, especially self centering. If you lift your suspension it affects Castor angle. On Defenders a lift of greater than 2″ can seem to affect castor angle. To overcome this you can fit castor corrected swivels, radius arm bushes or corrected radius arms. I personally don’t see the point of lifting past 2″ and would advise that you see how your steering is first before spending any money here.

http://www.terrafirma4x4.com/index.php

Lift Kits on ebay

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