4WD MODIFICATIONS - SUSPENSION & BRAKES
Most 4WDs spend their time relatively lightly loaded around town and fully loaded on bush trips. Trying to make a fixed-setting shock absorber handle both damping tasks isn’t easy: hence, the adjustable shock absorber.
At the outset, it needs to be understood that our evaluation of Tough Dog adjustable shock absorbers was not intended to impart race-vehicle dynamics to our LandCruiser 75 Series and HiLux crew-cab OTA Team vehicles. We wanted to check out whether adjustable dampers could manage ride quality and handling better than non-adjustables, under varying load and road conditions.
We’ve been running Bilstein monotubes on ‘Harry’ – the 75 Series – for several years and have been very happy with their durability and effectiveness. However, after seven major bush trips to remote, rugged areas, over badly corrugated roads, they were starting to show some wear and tear: hardly surprising!
Years ago, the old workhorse had a 50mm suspension lift, a 700mm wheelbase extension and a post-registration, engineer-approved GVM upgrade to 3.5 tonnes. (We checked with the engineer concerned, John Wilson, to be sure that the proposed shocker change wouldn’t void our GVM upgrade conditions.)
The hard-worked HiLux had been fitted with a 50mm-lift OME suspension kit that was also losing its damping effectiveness. This vehicle retained its manufacturer’s GVM, so there were no compliance issues with the shocker swap.
Adjustable Tough Dogs
We took both vehicles to Tough Dog’s Sydney-west HQ, where Simon Vella, the company’s product director, took charge of proceedings. Firstly, he checked front and rear axle weights and spring rates. Then he disappeared into his lab and emerged some time later with appropriate Tough Dog products.
For the 75, he chose BMX 70mm external diameter models with 45mm bores and 22mm piston rods. Each damper had an adjustable foot valve that varied bump and rebound damping in nine successive steps.
In addition to this variable-flow foot valve the Tough Dog Adjustables have an internal replenishment or bypass tube (on the right, at right) that allows oil flow between both sides of the piston without restriction by the piston valves. This helps control piston speed.
Internal or external bypass tubes are features of top-shelf and high-performance shock absorbers. If you want to read more on this topic, check out our Tech Torque story.
Because of their size, these dampers won’t fit some vehicles, but, although they fitted comfortably to the 75’s shocker mounts they did foul the handbrake cables that ran across the LandCruiser’s rear axle. No problem there, as there are Tough Dog extended brackets to move the wires clear of the shockers.
Also, a very important part of the installation was an extended bracket for the rear brake circuit’s load-proportioning valve, to match the 75’s prior 50mm suspension lift. The valve allows varying rear wheel brake pressure, depending on the load on the rear suspension. (Late-model vehicles have electronic brake pressure proportioning to do that job.)
In most suspension shops, when a ‘lift’ is done, the rear brake balance is ‘preserved’ by bending the load proportioning valve actuator, but Simon Vella reckons that’s not accurate enough. He’s right, we know, because braking was much better after fitment of the bracket and we had on-road brake-meter evidence later confirm that.
For the HiLux Simon selected 60mm-diameter outer casing models, with 40mm bores.
Right out of the shop we noticed ride and handling improvements in the unladen 75 Series, even with the shocks on their lowest damping settings. Interestingly, there was noticeably less driveline vibration when lifting off from rest and we hadn’t expected that.
Simon Vella explained that the heavier construction of the Tough Dogs, with their large rod diameter and substantial rod-guide section, gave them better ‘stiction’ when the axle tried to react to lift-off torque, keeping the diff nose and prop shaft universals more stable.
The rod guide area of the Tough Dogs is particularly robust as this photo shows.
With our Tray-Tek slide-on camper on the back of ‘Harry’, weight went from 2.8 tonnes to 3.3 tonnes and with full fuel and water tanks, to 3.5 tonnes. At that loading we set the front shocks to the second damping setting and the rears to the fourth stage. Preliminary testing indicated those guesses were pretty right, but we need a longer trip, on varying road and track surfaces, to check out the optimum settings and that will be happening during 2020.
Early impressions are more axle control when unladen and loaded – particularly at the back end – and flatter cornering. Ride quality is about the same as before – very good for a 75 Series, we feel – thanks also to parabolic front springs and Polyair helper bags at the rear.
We’ll add early impressions of the re-shocked HiLux and update the 75 experience in April 2020.
Big bore, non-adjustable Tough Dogs
In March 2020 we added a third vehicle to our Tough Dog shock absorber test. The test vehicle was truck journo, Steve Brooks,’ own 79 Series short-cab ute that had done around 100,000km on its standard suspension. It felt tired, he reckoned, doing its main duties as a farm runaround and towing a two-horse float all over the country.
Steve didn’t want adjustables: just some quality shocks that would control the 70 Series’ coil/leaf suspension on the less than wonderful roads in his area.
Simon Vella chose 41mm internal-bore shocks, with 18mm double chrome-plated rods for the task and fitted them, after doing a suspension check that all was in order.
Steve Brooks picked up his vehicle and sent us through his early impressions:
‘It is no exaggeration to state that since Tough Dog shocks were fitted a few weeks back – replacing original Toyota LandCruiser shocks after almost 100,000 km – the difference in handling and ride is extraordinary.
‘Phenomenal, in fact, which suggests I was entirely ignorant of how ineffective the original dampers had become.
‘Roads around our way are generally very poor – little more than an interlocking splotch of roughly repaired bitumen holes, or, a little further afield, heavily rutted dirt tracks.
‘However, on both surface types the ride and handling of the 2012 LandCruiser tray top is vastly improved, with no kick-back through the steering and, perhaps best of all, an appreciable advance in handling stability.
‘My genuine thanks to Tough Dog for the product and the advice, and my old mate Allan Whiting for suggesting the brand.’
We’ll update Steve’s post when he’s done more klicks and some towing. We’re also very interested to know how they compare with the adjustables fitted to the OTA 75 Series.
GVM upgrade implications
Our 75 Series had a post-rego GVM upgrade, so, to confirm it would still be compliant when fitted with adjustable shock absorbers we consulted the certifying engineer, John Wilson, because the conditions of a GVM upgrade include spring and shock absorber models and part numbers that cannot be changed.
However, John Wilson was more than happy to approve the switch to adjustables in writing.
We asked Simon Vella if Tough Dog had done any GVM upgrade packages, using adjustable shockers.
“No, we haven’t done that,” he told us. “Because certifying the components to our satisfaction would be very difficult.
“To cover every contingency would mean brake- and swerve-testing a vehicle repeatedly, with all possible combinations of front and rear damping adjustments.”