| Static Weight: Front Bias and Left Bias
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| | complicated. Front bias and left bias
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| The most fundamental way of changing the
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| | adjustments are made by actually moving
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| handling of your car is by redistributing
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| | components of the car around to try to
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| the weight. The weight distribution of a
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| | achieve the desired weight distribution
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| car is determined by literally placing a
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| | (e.g. moving the battery to the left side
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| scale under each wheel. When making
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| | or rear of the car). Cross weight is
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| weight distribution adjustments, you must
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| | adjusted by lowering or raising the upper
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| consider the weight transitions that the
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| | spring perches on each corner of the car
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| car experiences while you are driving.
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| | to raise or lower that corner.
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| For example, when you accelerate, weight
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| | To understand how cross weight works,
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| shifts toward the back of the car onto
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| | imagine a car that is perfectly level
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| the rear wheels. When you turn right,
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| | with the ground (equal ride height at
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| weight shifts to the left side of the
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| | each corner). If you raise the left rear
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| car. You can feel these weight transfers
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| | corner (increase cross weight), that
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| on your body while you are driving.
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| | corner now carries more weight because it
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| The most useful weight adjustment for
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| | is sticking up. In addition, the car is
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| road racing is front bias, or the weight
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| | leaning towards the right front (trying
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| distribution between the front and rear
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| | to compress the right front spring) so
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| wheels. The purpose of adjusting front
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| | that corner is holding more weight than
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| bias is to balance the weight of the car
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| | it did when the car was level. The left
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| evenly between the front and rear wheels
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| | rear and right front hold more of the
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| while the car is turning. If the front
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| | weight of the car than the right rear and
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| tires have more weight on them while
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| | left front.
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| turning, then they will have to exert
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| | If you lower the left rear corner of the
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| more force on the racetrack than the rear
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| | car, then the left front and right rear
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| tires to keep from sliding. The same goes
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| | corners are sticking up more than the
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| for the rear tires. This can be seen from
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| | left rear. Therefore, the left front and
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| basic physics:
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| | right rear hold more of the weight while
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| F = ma = (m * v^2) / R
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| | there is less weight on the left rear.
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| F = Forcem = massa = accelerationv =
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| | Since the left rear corner is lowered,
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| velocity
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| | the car leans in that direction, which
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| R = radius
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| | also takes weight off of the right front
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| It can be determined that the
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| | tire. In summary, by lowering the left
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| acceleration of an object of mass "m"
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| | rear (decreasing cross weight), the
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| traveling around a circle of radius "R"
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| | weight on the left front and right rear
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| with a velocity "v" is v^2/R, and the
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| | increases, and the weight on the right
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| force necessary to stay on the circular
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| | front and left rear decreases.
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| path with this velocity is just the
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| | Cross weight is usually measured as a
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| object's mass multiplied by that
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| | percentage of the total weight of the
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| acceleration. Let's assume that your car
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| | car. Take the following weight
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| has more weight on the front tires than
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| | distribution as an example:
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| on the rear tires. Looking at the formula
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| | Left front: 750 lbs., Right front: 700
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| above, we can see that mass is the only
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| | lbs.
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| thing that changes the force that the
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| | Left rear: 700 lbs., Right rear: 750 lbs.
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| tires must exert since the square of
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| | The cross weight is simply the left rear
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| velocity and radius are essentially
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| | right front (diagonal) weight divided by
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| identical for the front and rear of the
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| | the total weight of the car and
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| car. Therefore, since the front has more
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| | multiplied by 100 to make it a
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| mass, the front tires will have to
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| | percentage. In this case, the cross
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| provide more force than the rear tires to
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| | weight is:
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| keep from sliding. Eventually, the front
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| | [(2 * 700) / (2 * 700 + 2 * 750)] * 100 =
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| tires will begin to slip before the rear
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| | 48.3 %
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| tires, which is the definition of
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| | Cross weight will not change left bias or
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| understeer.
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| | front bias weight distribution. Using the
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| Making the weight on the front tires and
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| | example above, you can see that front
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| the rear tires equal in a turn does not
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| | bias is 50% ((750+700)/(750+700)), and
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| necessarily mean that the weight
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| | left bias is also 50%. Assume you
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| distribution should be 50/50 (50% front,
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| | decrease cross weight to 46.6 % with the
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| 50% rear) while the car is standing
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| | following settings (while keeping total
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| still. The type of track you plan to
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| | weight the same as before):
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| drive on determines the ideal weight
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| | Left front: 775 lbs., Right front: 675
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| distribution. If the track requires
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| | lbs.
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| getting on the throttle early in the
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| | Left rear: 675 lbs., Right rear: 775 lbs.
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| turns, then weight will be transferred to
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| | The front bias and left bias are both
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| the rear of the car while you are in the
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| | still 50%.
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| turn. Therefore, you should add weight to
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| | Decreasing cross weight adds oversteer to
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| the front of the car to offset the weight
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| | the car in left turns. The front tires
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| transfer when you get on the throttle.
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| | grip better since the left front starts
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| Instead of using a 50/50 distribution,
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| | out with more weight than the right
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| you might want to try 55/45. The front of
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| | front. In the turn, weight transfers from
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| the car will be heavier than the rear
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| | the left front to the right front, which
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| when the car is standing still, but when
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| | balances the front of the car and
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| you accelerate in a turn, weight will
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| | maximizes grip. On the other hand, the
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| shift to the rear and balance the car. If
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| | rear of the car is not balanced in a
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| you are driving on a track with short,
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| | turn. The right rear holds much more
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| sharp turns, then you will probably be
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| | weight than the left rear. Therefore, the
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| getting on the throttle late in the turn.
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| | rear tires do not grip as well as the
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| Therefore, you want a more even weight
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| | front tires, which creates oversteer.
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| distribution to start out with (possibly
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| | With the same kind of reasoning, you can
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| 51/49) so that the weight will be evenly
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| | see why increasing cross weight creates
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| distributed as you drive through the
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| | understeer.
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| turn.
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| | Cross weight is usually difficult and
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| Generally, if you are driving on a road
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| | time consuming to adjust on a street car
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| coarse with approximately the same number
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| | even if you have installed aftermarket
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| of left and right turns, front bias
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| | suspension components such as coilovers.
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| should be the only weight adjustment that
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| | Unless you are building a pure race car
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| you work with. However, there are two
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| | for oval tracks, you don't have to worry
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| other adjustments that can improve
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| | about cross weight adjustments. Remember
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| handling if you will be racing on an oval
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| | that the weight distribution of your car,
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| or a track with predominantly right or
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| | particularly front bias, is the most
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| left turns: left weight bias and cross
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| | fundamental characteristic that affects
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| weight. Left bias is adding weight to the
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| | how your car handles. Keep in mind that
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| left side of the car so that it will be
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| | the weight of the driver affects weight
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| balanced in left turns. The same can be
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| | bias. Placing parts on the right side of
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| done for right turns.
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| | the car will help balance the weight of
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| Cross Weight
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| | the driver on the left side.
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| Cross weight (AKA wedge) is slightly more
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