In this final article in our Beginners’ Guide to Suspension series, Robert Pepper shares some buying advice on suspension for towing. But don’t worry, this isn’t a “hand over your coin for the most expensive kit there is” kind of advice. Keep reading to learn more.
So you have a caravan that needs to be towed, and you’re perhaps not a car nerd whose idea of a fun evening is a three-hour lecture on the differences between monotube and foam cell shocks.
Instead, I’m going to assume you just want a safe, efficient and effective towcar and caravan setup for a relatively heavy – say 2000kg plus van – and spend what it takes to achieve that within reason, which will include the suspension for reasons explained earlier in this series.
First up is the towcar
So, first up is the towcar. For a heavy van that will almost certainly be a 4×4, and that’s one of the most difficult vehicles to design suspension for because it could be any or all of a suburban runabout, offroader, heavy tower or dirt-road workhorse. So it’s a compromise between all these roles, and one of the most compromised components is the suspension.
For example, the suspension you need for low-speed offroading is almost diametrically opposed to the suspension you need for high-speed handling. This is why enthusiast car owners are so keen on changing suspension for their specific needs. Sports car owners might swap to racetrack-oriented suspension, 4×4 owners might prioritise offroad performance, and heavy towers might, and should, focus on heavy-tow performance.
Standard suspension won’t cut it when towing
The simple fact is that when you hook up your 2500kg van to your 2500kg towcar you fundamentally change how that towcar accelerates, brakes and corners. You’ll be much better off with a suspension designed for that job, and the standard suspension won’t be.
What you want from a towcar suspension is, in general, heavier-duty suspension capable of handling increased loads, with a slight increase of ride height, known as a ‘lift’. This is because your 2500kg towcar might be adding 200-250kg of towball mass, which translates to 300-375kg extra on the rear axle. This is a lot, so you need stiffer springs and dampers to match.
In addition, that 2500kg trailer is constantly trying to boss around the towcar. The lift means when the trailer is hooked up, your ride height returns to normal, or close to it, and you don’t get the nose-up, tail-down result which hurts handling. It also helps offroad performance, which is handy because most caravanners will at least nose down an interesting dirt road once in a while.
The towing compromise
The other aspect you might consider is the towing compromise; the car has to perform when it’s not hooked up to that heavy trailer. This is where components like airbag helper systems can be useful, or progressive-rate springs, which offer a balance between loaded (hitched) and unloaded (unhitched) performance.
So, which suspension kit?
The answer is simple – quality. Your best bet here is the name brands that have been around for decades, not some cheapie off eBay. Whether the shocks are foam, twin-tube, monotube or whatever else is far less important than the build quality and the quality of the damping tune. Never buy a no-name suspension on the basis that someone advises “monotube is better” over a well-known brand which offers, say, foam cell or twin-tube.
The springs will just be differently focused versions of the original suspension. Let’s be clear here – generally, the original suspension is good, but it is a compromise, and when you tow, your focus narrows. The exception to this rule is air-sprung vehicles, which can vary their ride height according to load, for example almost all modern Land Rovers.
Whilst most of this series has focused on springs and shocks, there are myriad other suspension components such as swaybar, bushes, control arms and the like. Generally, you don’t need to worry about replacing these items for towing purposes. And you also definitely don’t want a big lift, as in more than an increase of 50mm in ride height which is a whole new world of complexity.
One size doesn’t fit all when it comes to suspension
When choosing suspension, you have to be very specific about your vehicle and not assume one size fits all. For example, some LC100s have independent front ends, while others have beam axles. The latest LC300 has the eKDSS system in the GR Sport, but not in the rest of the range. So in both cases “I have a LC100/300” isn’t specific enough.
If you take advice for your suspension purchase, be sure you’re asked first for your intended usage, both current and future, and the tradeoffs are made clear.
Better yet, seek advice from a reputable company that specialises in custom-built suspension systems.
It is rarely the case that an aftermarket suspension will improve everything, for example, heavier-duty suspension will ride a little more harshly when unloaded. To that end, also be as clear as you can be about your intents, needs and wants. However, if you do make a bad choice, it’s not the end of the world. You can simply pull the suspension out and if it’s a decent quality brand, sell it secondhand and defray the cost of a more suitable setup. But don’t think the same trick will work with your brand-new discarded stock suspension, you’ll be lucky to give it away, unlike say changing tyres the moment you pick up your new car.
Caravan suspension
As for the caravan itself, the suspension is all about towing stability, and the biggest factor there is weight distribution. Generally, you can leave the van’s suspension as-is, and focus on weight distribution to improve towability.
Age is also a concern for suspension as it does wear out. Shocks lose their ability to dampen, rubber bushes harden and so on. Suspension is a consumable like brake pads or tyres, just with a longer life, and that goes for both caravan and towcar suspension.
To GVM upgrade or not?
Then we come to the question of a GVM upgrade – see our weights article for details of what GVM is. Should you get one for towing? Yes is my view, if it’s minimal or little extra cost, but of course there are nuances.
First, if you increase GVM you will most likely invalidate most of your warranty, and you can expect shorter life from your vehicle as it has more weight to carry around. And, it won’t increase your braked tow capacity, e.g. going from 3000kg to 3500kg unless there’s a specific, corresponding tow capacity increase. However, if the weight of the trailer you can tow is limited by GVM to below the car’s max tow capacity, then the GVM upgrade can help you tow a larger trailer.
So all up, having the extra capacity on hand could be useful even if you never need it. But even if you have the upgrade you should keep weights down far as you can and consider the upgrade a bit of extra margin for weights compliance. At some point, it’s better to think of a different vehicle rather than modify smaller-capacity vehicles.
I would strongly recommend heavy towers change their suspension for an improvement in ride and handling from day one. It could mean the difference between avoiding disaster and cruising on to your destination.
