Tip 2 - Truck Tyre Fuel Economy
We all know there's not much you get for free these days, but it
would be nice in the case of your truck tyres that they could
contribute to their own expense. I'm talking about being aware of
what you can do to improve your truck's fuel economy performance via
the tyres, and also what we see in the future in new tyre designs.
analyse where your fuel dollar goes in your operation. In an ideal
steady state condition (i.e. on a straight, flat road), your engine
power is required to overcome around 60 percent wind resistance, 12
percent transmission losses, and about 23 percent rollong resistance
loss through the tyres. In a more realistic long distance
application, losses have to accommodate hill climbing and
acceleration functions, which add considerably to the fuel
consumption. We estimate around 35 to 40 percent. Wind resistance in
this type of service amounts to 30 to 35 percent, plus rolling and
transmission losses add up to around 25 percent of the total.
If your truck
was on general delivery operations, then the major fuel consumption
is taken up in dealing with traffic and road conditions, with wind
resistance and tyre roll resistance contributing little to the total
fuel consumption picture. So the overall statement from this
analysis is that tyres play a major role in fuel consumption in long
distance applications, but a relatively minor role in urban or
The next step in
this tyre exercise is to consider where the greatest effect can be
achieved. The simplest way to figure this out is to go with the
greatest number of tyres. The two steer tyres only contribute about
10 to 15 percent to the overall rolling resistance; eight drive
tyres contribute around 30 to 35 percent; and the greatest influence
of all is through the twelve (typical) trailer tyres at around 50 to
60 percent. I'll leave it to you mathematicians to estimate trailer
tyre influence on B - doubles and road trains!
What can you do
to improve this situation? First, make sure your tyres are correctly
inflated and regularly maintained. Anything less than the ideal
pressure, which is matched to the load, will cost you money, not
only in fuel but also in tyre life. As a rule of thumb, for each 5
psi down on the correct pressure you can lose around 5 percent in
rolling resistance properties and also tread life. We are not asking
you to over-inflate, since that brings it's own attendent problems
such as uneven wear and impact resistance.
the tyre type and size you are using. We know that specialist
shallow tread; ribbed trailer tyres can effectively reduce rolling
resistance. This can be applied to recap selection as well.
Similarly with traction drive tyres, the closed shoulder type tyres
rather than the traditional cross rib have improved rolling
properties. Lower profile tyres may not necessarily give you direct
rolling property improvement, but the smaller packaging
configuration may benefit you indirectly. Also, on the trailer,
consideration should be given to the use of the wide base, super
single tyre concept where six replace twelve standard tyres. This
can improve your roll characteristic by up to 15 percent, as well as
reduce weight contribution by about 20 percent.
sound promising, but it should be understood that rolling resistance
figures are on a ratio of around seven to one for fuel consumption.
Therefore if you improve the overall rolling resistance of your rig
by 21 percent, this will amount to approximately 3 percent fuel
savings. This may not sound much until you translate it into, say, a
3 percent saving on your yearly fuel bill. An average interstate
truck covering 280,000 kilometers a year can go through a serious
amount of fuel and money. We estimate a cost saving of around $4000
could be achieved on the above figures --- which would go a fair way
towards your next set of tyres!
All this goes
out the window, of course, if the wrong type of driver is in control
of the truck!
is that a 3 percent improvement is hard to measure unless accurate
monitoring figures are kept to identify the change. I personally
believe this is a major reason why there has not been more impetus
locally to push towards fuel-efficient tyres. Fleets have been more
interested in obtaining treadwear results rather than economy they
cannot measure easily.
manufacturers now have their versions of fuel-efficient tyres
available internationally and reflect their various approaches to
improving the inherent rolling resistance of the radial truck tyre.
It is inevitable that this concept will become popular here as fuel
costs and environmental legislation escalate while competitive
margins decrease. . We can perhaps revisit this subject in the
future, and investigate just how these design changes in a tyre can
improve their rolling qualities.