Solid Axle Smackdown

Updated: Jan 9, 2019


You’ve been lied to. Flex and handling are not mutually exclusive when it comes to solid front ends.

It’s a line we’ve all been force fed for years. “Oh, you got a solid front axle under your rig? Good luck getting it to flex properly, and it’ll never handle.”


As with all blanket statements like the above, there may be a kernel of truth at the core of it but once you understand how suspension systems work and how they can be tweaked (or even redesigned from the ground up), it quickly becomes a steaming pile of bollocks.

Yes, you can get a huge amount of flex from your front end. No, it doesn’t have to come at the cost of your vehicle handling worse than a Great Dane on roller -skates. It’s true. It’s just that we’ve all been told over and over that suspension is always a compromise. And while I totally agree with that statement, you can reduce the sacrifices right down with a little bit of clever design and, more importantly, being realistic with what you’re trying to achieve.


THE FALLACY OF FLEX

First off, let’s look at what you really need in terms of flex. No doubt you went to Tuff Truck Challenge a couple of weekends back and saw the all the purpose-built crawlers ramping way over their wheelbases on the travel ramp and you thought to yourself, “man, it’d be cool if my HJ75 could do that.”.


While I’m not disagreeing with you, for a touring vehicle, you simply don’t need to be able to put a wheel up on a 44gal drum while the other three are still planted. Why? Because chances are those other wheels – particularly the one at the front that’s at full droop – will have bugger all weight on them and will find it incredibly hard to gain traction. You’re miles ahead ditching the 18+in travel shocks and buying a locker. Yeah, you’ll lift a wheel, but you’ll make it over the obstacle.


Then there’s the whole nonsensical argument that lift provides more flex. Once again, it’s a gigantic pile of what’s left behind after a Clydesdale eats a dodgy curry. Fitting taller springs and shocks may net you a little more travel, but your suspension arms, bushes and geometry will always have the deciding say on how much articulation you’ll get; and let’s not get started on changes to caster, kingpin bearing preload, maxing out the Panhard angles, reduced braking, changes to roll axis and centre of gravity that big lifts bring (shudder).


Don’t get me wrong here. Flex is important for a number of different reasons and is dependent on what purpose a vehicle is being built for. A rockcrawler will want a lot more down travel while a desert racer will want down and up travel split more or less evenly – your touring bus doesn’t need nearly as much wheel travel as either of them. These days with modern traction control systems, you don’t even need lockers as much as in the past. Basically, for most builds – forget flex. It’s yesterday’s hero.


SCREW YOU, FLEX IS AWESOME!

Well, hell. Ya got me there. You already have the solid axle, you may as well chase the articulation they’re known for right? However, at-speed handling and low- range crawling exhibit a bunch of very different forces on your front end, and as we’ve already established, it’s all about making the right amount of compromise to suit you, so how do you dial it in to your taste?


Ready for the hard truth?


Sorry, but unless you’re willing to spend tens of thousands on replacing stock link set-ups, laying down the equivalent of Bolivia’s GDP on multi-bypass shocks and tuning coilovers and spending a few hundred hours dialling things in with a professional suspension expert, then your vehicle is never likely to perform like a Trophy Truck through the Madigan Line.


With that said, there are a few key rules you can follow to make your solid-front-end beast handle a whole lot nicer at the speed limit, even with taller suspension and bigger rubber without hurting low- range crawling. Read on.


KEEP IT AS LOW AS POSSIBLE

When it come to going fast, lower equals better. Simple as that. There’s a host of very good reasons you don’t see F1 cars on 2in lifts and 33in rubber. But for similar reasons you won’t see an F1 car on the Gibb River Road either – it’s all about compromise (have I mentioned that yet?). The basic tenets of good handling are to have the wheels as close to the corners of the vehicle as possible, have them as wide as is practical and to have the centre of gravity (CoG) as low as possible. Sounds easy hey, but when you’re dealing with wagons with nearly a metre of overhang or; loaded utes with their weight bias leaning towards the rear of the vehicle and larger than stock tyres, it all become quite difficult.


But by packing a little smarter and keeping the heavier stuff as low as possible you’ll effectively lower the CoG which will result in lower negative lateral forces on the suspension which basically means better handling.


Long story short: keep the weights as low as practical, keep the lifts to a minimum (need more space in the arches? Cut the guards, don’t lift the car) and if you’re still not happy start looking at stretching wheelbases and widening wheel tracks.



THE MANUFACTURER’S SHAME – RADIUS ARMS

Radius arms are really good for a cheap-to-make, easy-to-set-up, does-the-job suspension system. It’s why they’re under pretty much every stock solid axle front end in existence. The only problem with them is that they pretty much blow. They don’t offer a lot of flex, they don’t handle particularly well and once you start modifying them they become even more of a headache. Sure, you could opt for Superflex arms or similar – which cleverly turn the geometry numbers into something that looks a lot more like a 3-link+ Panhard set-up, but unless you’re willing to spend the tens of thousands of dollars to completely redesign the front end for the ability to do a buck-twenty over whoops instead of only 80km/h, you’re kinda stuck with them.


With that said, there are a multitude of aftermarket things that can help. First off, get a good swaybar at either end. Again, we’ve all been fed the horseshit “oh noes! Swaybars limit mah flex!” And yes, they do. They also increase corner speeds, allow your tyres to maintain a higher amount of traction and throwing one in the rear will also force your radius arm front end to actually flex more. I could go on, but just trust me: swaybars are good, mmmkay?


Feel like upping the ante? Look into upgrading your springs and dampeners to tuneable shocks and/or coilovers. Once the front end bouncy bits are dialled in to match your static weights and required spring rates (not to mention your driving style), it’ll be like day and night over the stock fare. We’re getting into the pricey end of the field here, but have you ever seen a sad person with coilovers and bypasses? Me neither.


GET YOUR PROTRACTOR OUT

Suspension geometry. It’s about as exciting as being forced to listen to a Brexiter, a Trump-hater and a vegan hipster talk politics. And to be honest with you, so much of it is subjective. Some people will have you believe that this amount of caster is the only way to fly, while others will bang on about how if you don’t get your roll axis spot-on you’ll crash into a busload of nuns on their way to cure cancer. Essentially, it’s a minefield of opinion; and more often than not, everyone’s opinion actually holds merit. What works for one driver and vehicle may be awful for the next. It’s all about that word again: compromise. Building your vehicle to suit you. So with that in mind, I’ll give you MY personal preferences for a radius arm front ends (which have severely limited tuneability from their design).


First off, I’d dial in a little more caster. Patrols and Land Cruiser come with 2–2.5° caster from standard. The higher the positive caster, the more the wheel wants to stay in a straight line at speed. For me, I like around 3–4°. It makes the steering a little heavier but gives me more feedback through the wheel, so is worth it in my mind. For the record, rockcrawler vehicles often have 5–6° of positive caster. Why’s that? All together, class: compromise.

Next I’d look at getting a workshop to re-engineer my Panhard and steering mounts to suit whatever lift I’d chosen. This can lead to a bit of a Pandora’s box of flow-on effects so it pays to be careful but in terms of handling, the general consensus is the flatter the Panhard is at ride height, the better. Most are on an angle right out of the box which straight away is a sacrifice. The kicker is that the steering draglink and the Panhard have to be on the same plane to eliminate bump steer so like I said, be careful here, but I’ve set up a couple of vehicles now that have got the ideal (for me) compromise (for me) between all worlds.


Along with a brake and swaybar upgrade, these would sharpen up my solid front axle nicely at speed and not have any major sacrifices in low -range either. Horses for courses though. I’d love to here what works for you. On that note…


GO AHEAD AND TELL ME I’M AN IDIOT

Keep in mind this article is intended for touring vehicles, so getting into the intricacies of 4-links, Racejackers and ORIs seemed a bit redundant. But hey, feel free to jump onto our Facebook page and let us know how much this article infuriated you. We love feedback in all forms.



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