TECHNICAL Q&A: Body lifts, duty packs and choosing the right suspension kit.
I’ve got a few questions regarding suspension systems. Firstly: What’s the difference between a suspension lift and body lift? Secondly: I’ve heard people say that a suspension kit can’t increase the ground clearance of a 4×4; so, what’s the point of fitting one? Thirdly: Some suspension kits offer various duty packs, from light- and medium-duty, to heavy-duty. Which one should I fit to my Hilux if I do go this route? And, lastly: Which suspension kit is best?
From the top: What’s the difference between a suspension lift and a body lift? Generally speaking, a suspension lift refers to any suspension modification which results in an increase in chassis height. An example of this would be the fitment of aftermarket coil springs that are longer than the OE units, or the fitment of an additional leaf-spring blade, coil spacer, or longer leaf-spring shackle.
Typically, anything higher than a 50mm lift will show signs of reduced drivability, which can include prop-shaft vibrations, CV joint stress, poor steering performance, castor angle issues, and irregular tyre wear. However, that 50mm measurement is a guideline figure only, as some vehicles will experience adverse side effects even at 30mm, while others can go higher than 50mm before problems occur.
A body lift refers to the use of spacers (usually aluminium) which are placed between the chassis and body of the vehicle. In most cases, this can be done only when a ladder-type chassis is used; in other words, when the vehicle’s body and chassis are two separate units bolted together. Most softroader vehicles employ a monocoque-chassis system in which the body and chassis form a combined unit, which means that no spacers can be used to raise the height of such a vehicle.
As mentioned in your query, the only way to truly raise a vehicle’s ground clearance is to fit larger tyres. While a suspension kit may help to raise the chassis height, it can’t raise the vehicle’s lowest point, which is often the rear diff (in solid axle vehicles) or suspension strut.
In summary: a suspension lift raises a vehicle’s chassis, a body lift raises the vehicle’s body off the chassis, and an increase in tyre size raises the vehicle’s lowest point and all-round ground clearance. At the 4WD Truckin’ Company, we generally advocate no more than a 50mm suspension lift. If clients want more height than that, we focus our attention on bodywork modifications and the fitment of larger tyres – such as an Arctic Truck conversion.
As far as body lifts go, we don’t usually recommend them as they are often more trouble than they’re worth. The kit itself may be cheap, but the lift often results in a host of other problems, such as poor engine- or radiator alignment within the vehicle’s engine bay. What’s more, aside from aesthetics, one could argue that a body lift offers no off-road performance benefits, although, in some cases, it can help with the fitment of larger tyres.
In terms of suspension kits and duty-packs: this question is largely dependent on the vehicle type and setup. A heavy-duty suspension kit is designed for vehicles which are heavily laden all of the time. An example would be a Hilux with a canopy, rooftop tent, drawer system, long-range fuel tank, built-in water tank, and front and rear steel bumpers.
If your vehicle is permanently fitted with the above mentioned accessories (and more), you’ll want to consider a heavy-duty suspension kit. However, if you strip these accessories off your vehicle in-between 4×4 trips, you’ll want to avoid fitting a heavy-duty suspension kit as this will drastically impair the vehicle’s day to day drivability.
For this reason, we fit mostly medium-duty suspension kits to our client’s 4x4s, and if they do need to load a little extra on the odd occasion, we advise the fitment of air-helper springs that can be adjusted to the required load.
However, an important point to remember is that no suspension upgrade can increase your vehicle’s legal payload capacity – this figure is predetermined by law and cannot be altered with the fitment of a suspension kit. The kit will, however, improve your vehicle’s ability to carry its prescribed payload, and it will also improve ride comfort and off-road driving performance (with better traction on a corrugated gravel road), as well as more suspension travel.
Regarding your last query about which kit is best, that’s a tricky question, and often dependent on vehicle type. In general, most suspension kits from Australia are built to a very high standard. Because we’re not bound to a single brand name, we tend to fit everything from TJM and OME, to Iron Man and Fox suspension. We try to offer our clients choice and variety, but, in most cases, we favour the brands which offer the best possible backup service. This, in our opinion, is what really separates one product from the next.
Leon Collett (Managing Director)
For more enquiries call 4WD Truckin’ on (011) 791 3822 or (012) 803 1040.
Or send your technical queries to firstname.lastname@example.org
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