 |
Real
world fuel economy measurements take much longer to
make, but far better reflect true fuel economy. |
|
Careful
recordkeeping is essential to accurate long-term fuel
economy measurements. |
|
The snapshot test requires special materials, tools and planning,
along with highly trained personnel, and the results do not accurately
reflect your “real world.”
Tracking long-term effects requires more patience and attention—and
the results are slow to accumulate—but gives you a much better
fuel consumption picture.
At the same time, long-term records will confirm and track trends
you may have observed in snapshot tests, while taking into consideration
the operating factors that make your fleet unique.
Long-term testing requires no special planning, materials, tools
or driver training, just relatively simple but diligent recordkeeping.
Best of all, because long-term fuel economy tracking follows performance
in your normal operations, it truly is a measure of “real world”
effects.
Planning your long-term test
Before you can get to where you want to go, you have to know where
you are. Done properly, a long-term test will tell you both of these
things, and how large a result you can expect from a change.
| Possible
Tire Test Categories |
- Standard
vs. Fuel Saving Tires
- Steer
vs. Drive vs. Trailer Positions
- Original
Treads vs. Retreads
|
|
Bridgestone engineers suggest that you first decide what you want
to track. For example, if you want to look at the effect of tires
on your
overall fuel economy, there are several possibilities:
For each category you want to test, you should select 10 to 20
of your units. The reason for this is that over the time of the
test, you may have to eliminate some of these units for a variety
of reasons. Having a fairly large number at the start assures
that you will have enough valid data at the end of the test period.
Be sure that the tractors are as identical as possible, that they
are pulling the same general types of trailers, and that their
operation, including routes, loads, etc., are as similar as possible.
You’ll divide these units into two equal-sized groups, keeping
one group the same as it has been and changing tires on the other.
How long will it take?
| Test
Time Frame |
- Minimum:
Until wearout of 1st set of steer axle tires.
- Maximum:
Until wearout of 1st set of drive axle tires.
- Alternate:
Until tires reach 60-70% wear.
- Begin
tracking all vehicles within 4 weeks or less from
start of test
|
|
Depending
on your operation, it may take six months or more to collect enough
data. With tires, as we’ve already seen, fuel economy will
vary with tread wear, and data for new tires will be quite different
from those in the middle of their original tread life.
Controlling
variables
Once you’ve selected the units and the things you want to
test, you
can begin your test sequence. Bridgestone suggests that you observe
the following procedures to reduce variation in your results.
Try not to change any of your normal operating procedures during
the test period, because any change may bias your results. In
addition, the less you change your normal procedures, the more
likely your results will be “real world.”
Keeping records
Bridgestone suggests that you use a separate form, like the ones
included here, for each vehicle, and that you may find the most
convenient time to gather data is during your regular PMs.
You’ll notice that the form allows you to track tread depth,
inflation
pressure, mileage and fuel consumed, along with other helpful
data for each wheel position.
 |
If
you collect fuel economy data during PMs, you can record
it on a form like this one.
|
|
Summarizing
your results
Once you’ve reached the end of your long-term test, a summary
form listing each tractor, its total test mileage, fuel consumption
and mpg will help you evaluate the effect of the tires you’ve
tested.
 |
Test
forms like these are available from your Bridgestone
representative.
|
|
Short
trem Vs. Long Term
A tire you buy today may still be on the road four years from
now. A tractor or trailer may be on the road longer than that.
Tire and truck fuel economy will continue to improve. And, any
fuel-saving purchase that fails to give you a satisfactory return
on investment over its useful life can become an expensive mistake.
| Long-term
Test Sequence |
- Standardize
inflation pressures and maintain throughout test
period.
- Set
toe and check and adjust alignment as necessary.
- Begin
record keeping.
- Observe
all normal maintenance practices.
- Replace
failures with a like product.
-
Return any tires repaired during the test period
to service.
|
|
In
short, large truck fuel economy is a combination of many factors.
Pay attention to as many as possible, and you’ll end up paying
less at the pump.
|
