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Poor manoeuvrability has long been a trade-off that traditional 8x4 tipper operators have had to tolerate when opting for four axles. But Volvo's Tridem configuration could put the cat among the pigeons for those who dream of better manoeuvrability from their eight-leggers. This Scandinavian-spec vehicle is still a four-axle truck, but the layout means this one turns on a sixpence. A triple-axle bogie sits at the rear of the FM13 chassis and uses a standard double-drive for the central pair of  close-coupled axles, followed by a lifting and steering rear axle in a position where the conventional rear-most-driven axle would normally reside.

Rated at 21 tonnes, the rear bogie uses air suspension for all three axles, while the 9-tonne front axle gets parabolic springs. The result is an eight-wheel tipper with a GVW of 32 tonnes. Volvo says that by placing the two driven axles closer to the front, the Tridem 8x4 rigid tipper benefits from a short wheelbase, and is therefore more manoeuvrable than a conventional tipper. Where the FM Tridem needs just 16.8m between walls to make a 180o turn - ably helped by its lifting and steering rear axle - the traditional FM 8x4 twin-steer tipper needs 22.1m (which is almost the width of an Olympic-sized swimming pool) to make the same turn.

It is a configuration favoured by Scandinavian operators, who run such outfits with hook-lift swap bodies up to a maximum GCW of 60 tonnes when pulling a twin-axle trailer to reach their higher  gross weight. Despite packing a 32-tonne GVW, this particular Tridem loses out in the payload stakes because of its heavy hook-lift swap-body set-up - it means that the payload is a disappointing 16.5 tonnes. But eliminating the hook-lift gear in favour of a muckaway or sand and gravel body would recover some of that higher payload - and this is something that Volvo may look at more closely, if interest arises.

On the road

We tried the 480hp FM13 Tridem tipper, complete with 12-speed I-shift transmission and Globetrotter cab. Weighing-in at 32 tonnes, the ride comfort is far superior to conventional tippers, which is, we suspect, a result of the single front axle soaking up the changing road surface. The single front steering axle also removes the dead feel normally associated with 8x4s - the FM Tridem remains positive, with a self-centering function that makes this truck a pleasure to drive. It's the same when manoeuvring in tight spots, the Tridem turns tighter and responds more fluidly than a traditional eight-legger.

Off-road, the FM Tridem plays with soft terrain. And with that hydraulically-steered rear axle - done passively through steering wheel inputs - the truck can be spotted precisely. Those who need extra traction can lift the steering bogie to transfer weight onto the drive axles. And a two-position switch on the dash means diff-locks and cross axle locks can be sequentially engaged. And if that isn't enough, there's an air-dump facility too, giving yet more weight transfer when the going gets tough. It seems that the Tridem configuration has much to offer. But whether or not UK operators are ready for such radical changes, is something that remains to be seen. What do you think? Do Tridems have a future in the UK?