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Scaling Properly |
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| Table of
Contents |
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- Race Ready
- Setting up the Scales
- Repeating the Process
- Documentation
- Note Taking at the Track
- Scaling at the Track
- Changing a Spring and Getting the Bite Right
- Verifying Your Changes Back at the Shop
- Battery or 110 Volt
- Common Problems
- Display Disappears
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| A. Race Ready |
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| In order to scale your car properly it must be ready to go. For the most accurate results the car must be fully prepared. If it is not "race ready" then any changes that you make will have an effect on your final setup and what you have put in your notes. So, what do you need to have done to be "race ready"? |
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Fuel Full
Radiator Full
Oil tank full and motor ran or too much oil can be in the pan
Gear oil full
Transmission full
Power steering full
Lead bolted in
Stagger set
Tire pressure set
Camber set
Rear end square |
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| "Race
ready" means that the next thing that the car will do is go around
the racetrack. Keep in mind the changes that will be made to the weights
if you attempt to scale the car before it is ready to go. |
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| B.
Setting up the Scales |
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| Now that you
have the car properly prepared you can get the scales our to begin the
scaling process. |
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Lay the pads flat at each corner and plug
in the corresponding cable. Double check that the cables are plugged in
correctly or you will waste a lot of time reading bad numbers. Let them
warm up for two or three minutes.
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| Once the cables
are plugged in and your scale system is turned on, press the zero button
and insure that each corner weighs zero with the pads flat on the
ground. The pads must be flat or you will not zero out the top casting.
Verify that the scales do not need charging. |
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| At this point
have one of your crewmembers stand on each pad. He should weigh within a
pound or two on each one. If all is well, then check that the scales
have returned to zero. At this point jack up the car and slide the pads
under each wheel. |
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| C.
Repeating the Process |
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| To insure that
you get the same results each time you must go through the same routine
each and every time. Since you just lowered the car onto the scales you
need to work out all of the chassis binds, hysterisis and scrub from the
tires by going through a settling routine. |
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| You can do this
by firmly bouncing the rear of the car, then bouncing the front, and
then shaking the roof bar above the driver's head. Try to let go in the
middle each and every time. |
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| Roll off type
trays help as well, but some very successful teams do not use them. For
example, Jeff Gordon and Dale Earnhardt do not use roll off trays, but
Rusty Wallace and Dale Jarrett do. Either way, if you go through the
same routine each time you will get great results. |
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| If you make an
adjustment to the wedge, move lead, adjust stagger or make any other
adjustment, you will need to go through the settling routine to insure
repeatable results. |
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| Once you get
your favorite set up in the car you are almost done with the scale job.
Write it all down in an organized fashion and now you are completed and
ready to win. |
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| D.
Documentation |
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| In order to be
fast each and every week you must keep good notes. Be sure to write down
your scale readings as well as the shock, spring, sway bar, Panhard
height, linkage angles, arm lengths, stagger and all other pertinent
information. It is one thing to be fast. It is another to know how you
did it and to be able to repeat the process. |
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| E.
Note Taking at the Track |
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| Once you get to
the track be sure to note each change and the results including lap
times and number of laps run. You should assign a person to this task
that is there every week and is detail oriented. Get a form to keep the
information the same way week in and week out. |
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| F.
Scaling at the Track |
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| When you scale
at the track you must find level ground or your readings will be off.
You can short cut the system by getting 2 strings and four guys. Have
the guy at the RF hold one string and another guy hold the other end at
the LR. Have a guy at the LF and another at the RR each holding another
string on opposite ends. The strings will now make an X in the center.
If the top string is higher than the bottom string then the other two
pads will need to be shimmed up. If the top string holds down the bottom
string then those two pads need to be shimmed up. By using this
stringing process the pads will be placed in the same plane. They may
not be quite level, but by being in the same plane your cross weights
will be correct. |
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| Another trick is
to find fairly level ground upon arrival at the track. Right when you
get there weigh the car. Mark the ground by tracing around the scale
pads with chalk. If your scales have memory you can get in the habit of
putting your shop set up in memory one and then put the track reading in
memory 2. You can now compare the bite between the shop and the new
reading taken at the track. If the track reading shows 1 percent more
bite you will know that the ground is out of level by that amount. By
knowing the difference you will have a baseline to return to if needed. |
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| Scales must be
exactly level in order to get perfect results. However, the two methods
described above are short cuts that get the job done without too much
compromise. |
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| G.
Changing a Spring and Getting the Bite Right |
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| Should you want
to change a spring at the track you will want to use the scales to
insure that you have made only a spring change and not a cross weight
change at the same time. Set your air pressure and then weigh the car
and take a reference height measurement from the fender or frame rail
down to the ground. Write the scale numbers and reference number down. |
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| You can then
change the spring. I like to measure the free height of the spring that
is going in and compare it to the one that is coming out. Lets say you
have a 400-pound spring in the RF and you are going to change to a 375.
The 400 is 12 1/8" and the 375 is 12" exactly. You can
estimate that the 375 will need about 1/8 more pre-load to maintain ride
height (1 turn on coarse thread coil-overs or 2 turns on fine thread)
then add in the free height difference. You will now be in the ballpark.
Verify your reference number to the ground and then weigh the car.
Fine-tune the adjuster until the scale numbers come back to the original
bite numbers. |
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| I even chart my
springs so that I know how many turns to put in or out when I go from my
numbered 375 to a different numbered 400. The chart allows me to change
springs when I am in a hurry and am unable to get the precision offered
by weighing the car to get the bite back. Basically, I do the work in
the shop to save valuable practice time at the track. |
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| H.
Verifying Your Changes Back at the Shop |
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| Many times
changes happen fast and furious at the track. Each week you should fill
your car with fluids upon arrival back at your shop. You have to fuel up
to do the setup for the next week so you might as well get in the
routine of doing that early in the week. Set the air pressure and weigh
the car. Take good notes and you will insure that you will get
consistency when you return to the track that you just ran over the
weekend. |
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| I. Battery
or 110 Volt |
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| Most scales are
designed to work on the battery as long as it is charged up. By running
on the battery you will extend the battery life. Battery design life is
two to four years. By running on battery power you will get a stable
consistent supply of power to your system. If you get a low battery
indication you can plug into 110 Volt power and finish the job. By
running on the battery you will extend the battery's design life. |
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| Should you
choose to plug in all the time this will work fine as well. However,
more heat will be generated in the battery thus reducing the battery
life span. I recommend running on battery power whenever possible. |
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| J. Common
Problems |
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| My wedge
changes? |
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| Wedge will
change due to a variety of things that are explained below. When you
notice a wedge change have a look at the total weight. If the total is
the same then odds are your scales are operating fine and there is
something in the car that needs correcting. If the total changes by more
than a few pounds then you could suspect a scale problem and should call
the manufacturer for more direction. |
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- Stagger effect
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Cars that run high amounts of stagger
and a locked up rear end can experience changing wedge due to the
tires getting read to "skip" like when you are push through
the pits around a tight turn. Weight will momentarily be miss-applied
as the tires excerpt force through the rear end gears. The axles
literally climb up the ring gear causing an occasional wedge
variance. To avoid stagger effect problems simply remove an axle cap
and pull the an axle out past the spline on the rear hub. You can even
see the stagger affect on cars with differentials however it is less
common.
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- Chassis binds
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I. A-Arms
Sometimes A-arms
can be in a bit of a bind to get the caster right. This usually
happens when more shims are used on one A-arm bolt than the other. You
can see wedge numbers change due to this added resistance. Try to
avoid uneven shimming and be sure to keep your A-arms greased at all
times.
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II. Ball Joints
Ball joints
have a fair amount of friction and need to be greased often. The
friction can cause wedge variations if the car is not settled
properly. Damaged ball joints should be replaced.
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III. Sway Bar
When weighing
your car or making spring changes you should always have the sway bar
disconnected. Many of the wedge variances I hear about are due to sway
bar binds. I connect the sway bar only after the weigh process is
completed. On late models I like to load the bar with 1/2% of wedge.
On Cup style cars I like the bar to be completely neutral. You can set
the bar to your liking but try to do it the same way each time and
note your weight readings with the sway bar load if it is not set to
neutral.
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IV. Camber Changes
When you
adjust camber you are changing the tilt of the tire. Adding camber
changes the wedge in the car to a small degree. Keep this in mind when
recording your weights. If camber is changed, wedge will change a bit
as well.
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V. Shock Rebound
Shocks
with high amounts of rebound can artificially hold weight in a corner,
especially when cold. Settling the car usually works the hydraulic
fluid to get consistent readings. However, high amounts of rebound can
make the weighing process harder. If possible, disconnect the shocks.
On coil over type cars settle the car thoroughly.
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VI. Tire Pressure Changes
Air
pressure changes moves cross weight and will change the numbers on all
four corners of the car. Be sure to have the air pressure set before
you begin the weigh job. I have seen slow leaking tires or bleeders
that are still bleeding cause the weigh job to be a real hassle as the
wedge keeps moving every time you check it. Be sure the tires hold air
before you begin.
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VII. Stagger Changes
Make
sure the stagger is set. More rear stagger takes bite out of the car.
Less rear stagger puts bite in the car. More front stagger puts bite in
the car. Less front stagger takes bite out of the car. Make sure you do
your shop set up including ride heights with the proper amount of air
pressure and tire stagger.
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- Total changes
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Total weight changes indicate that
something is interfering with the free movement of the top casting on
the scale pads or there is a problem with your system.
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I have seen Winston Cup teams make
leveling trays that rub the sides of the top castings on the scale
pads. The interference can cause weight variances in the 30 pound
range. Make sure that the top casting on the your pads is free to
move.
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- Scale numbers bounce
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I. Damaged cables
A damaged
or smashed cable can cause the numbers to bounce. Inspect the cable
for damage. If damage is found order a new cable. If you are in a bind
you can do a quick repair job. Insure that the system is off and cut
the bad section out of the cable. Splice the wires together color to
color and tape up. The quick repair will get you by until a new cable
arrives.
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II. Moisture in the connectors
If
water gets in the scale connectors the moisture interferes with the
scale signal and a bouncing will occur. The fix is to dry out the
connectors with a heat gun or put them over a heat register over
night. Usually, the system returns to normal when the connectors dry
out.
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III. Dead battery
A dead
battery will cause many different problems. If you experience any kind
of trouble then plug the scales into 110 volt and see if the problem
is cured. Extremely dead batteries might require some charging before
the system returns to normal operation.
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Old batteries can short out
internally and can interfere with proper scale operation even when
plugged into 110 volt power. Battery design life is typically 2-4
years.
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| K. Display
Disappears |
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| Liquid crystal
displays will disappear when exposed to direct sunlight. At times people
think that scale has suffered damage. Avoid leaving the scales or any
liquid crystal product in the sunlight. To cure the problem simply put
the item in the shade. When the LCD cools down the numbers will
reappear. |
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