The Conventional Contenders

the conventional contenders

The short BBC conventional B-double prime mover market is dominated by Kenworth, especially with the T610 arriving, but, what about the conventional contenders in this segment? In the next issue of Diesel Magazine, we look at two of these, the International ProStar and the Western Star 5800SS, to see what they have to offer.

There is little doubt the B-double prime mover is a dominant part of the Australian truck buying scene. The strict constraints of the dimensions on a B-double, both the overall length and the  kingpin to rear of trailer dimension force compromise on truck designers. 

The B-double is normally expected to run high kilometres, so needs plenty of fuel capacity. This puts pressure on getting the front axle mass just right. On a conventional, a set forward axle can often struggle to end up getting to the 6.5 tonne limit, whereas the set back one can get there with if the fuel tanks are placed carefully. At the same time cabover prime movers often struggle to get under 6.5 tonnes, with all of the equipment placed over the front axle.


the conventional contenders


Operators are always looking to maximise productivity, so a 34 pallet B-double is the minimum requirement and a 36 pallet set-up desirable, if often almost impossible to achieve satisfactorily. The space between the front of the trailer and the rear of the cabin can often get pretty short. This is good for fuel economy but problematic for air lines and cables on an articulated vehicle.

Next, there’s the big engine. Australian truckies reckon they need a 15 litre engine at least to pull up to 68 tonnes in a B-double. The common belief is the power must be up into the mid 500s and up past 600 hp to get the job done. 1850 ft lb, thats over 2500 Nm, of torque are also minimums in many people’s minds.


the conventional contenders


The fact is, many B-double run with prime movers below these ideal levels, but there is a clear perception durability is compromised if the power is below the magic 550 mark. Well-performing trucks with horsepower in the 400s, in the past, managed B-doubles over hundreds of thousands of kilometres, but are now considered a liability as trends have changed.

These very specific rules a B-double prime mover must meet also affect the buying decisions for other prime movers. An important part of those buying decisions are about improving utilisation. Therefore, if an operation is looking at a prime mover to pull a single trailer, or even an A-double it also wants the truck to be capable of handling B-double work, if needed.

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