THE DEFINITIVE TRUCKING SITE

February 2009

The lack of trailer maintenance often observed during ad hoc onroad inspections suggests many transporters and fleetowners are not aware of the premium they pay in respect of an unwelcome increase in fuel consumption, tyre life and overall maintenance costs as well as compromising safety standards. 

Ways to minimise these avoidable costs begin with trailer selection criteria that contributes to improved transport efficiency and lower lifecycle costs. The unladen mass of road-ready trailers offers excellent opportunities to improve the important payload to gross combination mass ratio. Articulated and combinations of vehicles can, with the correct application of the bridge formula (wheelbase, overall length, mass distribution, etc) and use of lighter materials, increase the payload ratio to 65% or more. When expressing payload increments in ton/km over the useful life of trailers, properly spec’d and regularly maintained improves the bottom line. 

Pantechnicons, volume vans and curtain-siders by definition require a large frontal area. It is important to know how air resistance when travelling at high speeds over long distances, impacts negatively on fuel consumption. Table 1 shows the number of kms required to over-come air resistance at various speeds. 

The impact of air resistance for  lower frontal areas can be reduced by ensuring tarpaulins, covers and side curtains are kept smooth and tight, not loose and flapping in the breeze. Tipping trailers and bodies should be covered to improve fuel consumption and reduce the risk of materials spilling on to the road. 

Whenever fuel consumption is discussed, the question of tyre pressure maintenance will immediately arise. Yes, under-inflated tyres do increase fuel consumption and reduce tyre casing life. Let’s consider a few other factors that contribute negatively to problems associated with tyres: 

• Poor mass distribution overloads some wheels and tyres. It also reduces tyre casing life and compromises safety. 

• Any axle out of line drags and demands more kilowatts to overcome road and air resistances. This is a further contribution to reduced casing life. 

• Brake cam slack adjusters (slacks) that are not correctly adjusted, malfunction or are totally inoperative, cause drag, compromise braking efficiency, reduce tyre life and add to overall maintenance costs. 

• Choice of correct tyres for trailer operations are frequently overlooked inviting more unnecessary running costs. 

Trailer selection deserves the same careful considerations as choosing prime movers best suited for the job. Trailer maintenance should be scheduled to ensure it takes place on time, this is especially so when semi trailers are “married” to a single truck-tractor. 

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