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Chassis Lowdown: Get Square!
How To Find The Baseline Setting On Your Race Car
February, 2009
By Will Handzel
Photography by Will Handzel
 On Raudman&8217s Tour car,...  On Raudman&8217s Tour car, the A-arms have Heim ends to adjust their length. Raudman always checks this length, and the angle of the A-arm, before he starts doing any measuring on the car. We show him here measuring the length off the car so you can see how he does it, but he really measures it on the car. A digital-angle finder is a must for this job. Buy one and use it often. |  As with all measurements discussed...  As with all measurements discussed here, you should record them in a logbook and refer to it often. Record your track changes, what they affected, and more, so you can learn from each change. If you have a race car with stock A-arms, it&8217s not a bad idea to check this measurement since contact has a funny way of shortening parts. |  Since tire diameter is going...  Since tire diameter is going to alter the ride heights, it is important to check the diameters before you start, and get them to your baseline setting (at the track setting). |  If you have just bought a...  If you have just bought a chassis and bolted the suspension onto it, consult the chassis builder on recommended ride heights. If youve bought a used car, consult the original chassis builder, or the previous owner. You might change it later, but set a height and start there. This is your datum, or base starting point. If you get lost on the chassis, you can always go back to this. |  See caption with the following...  See caption with the following photo. |  Once the ride height off the...  Once the ride height off the floor is set, you can build blocks to hold the rearend at ride height (on an underslung chassis) as shown in photo number six. Then you can remove the front shocks, see photo number seven, and use stands or shock rods to hold the front wheels at ride height. |  With the ride height locked...  With the ride height locked on all four wheels, the car can be set up on jackstands so you can get under and around it easily. Raudman removes all of the wheels at this point for easy access into the suspension/chassis area. |  The next four photos show...  The next four photos show Raudman checking all the angles of the rear suspension. This procedure should be repeated whenever anything is moved on the rear suspension because these angles determine how the rearend steers while the car is running around the track. Photo number nine shows the trailing-arm angle being determined. Do this on both sides. |  |  The rear suspension on this...  The rear suspension on this car is a "three link"--two lower links, and one upper link in the center--so Raudman checks the angle on this lower link... and upper link. |  Then he checks the pinion...  Then he checks the pinion angle on the third member. |  See caption with following...  See caption with following photo. |  Raudman has a simple way to...  Raudman has a simple way to determine the Panhard-bar location. He recommends setting a tape measure upright to where it balances itself. Locate it on the center of the bolt on the higher mount, and read the tape where it enters the tape-measure body. Then, slide the tape over the other mount, and read the difference. Now you know the Panhard-bar setting. |  See the following photo c...  See the following photo caption. |  See the following photo c...  See the following photo caption. |  Victory Circle offers these...  Victory Circle offers these handy little plumb-bob hangers, which they call Zerk-o-Bobs, in a plumb-bob kit. They make it easy to locate the center of the ball joints. Just remove the zerks, screw in the Zerk-o-Bobs, and set the length of the string so the plumb bob barely touches the ground. Plumb bobs are also hung off the front A-arm frame mounts on each side so there will be four plumb bobs hanging down from the car on which to locate a straightedge. |  The next step is to lay a...  The next step is to lay a straightedge on the floor and line it up with the plumb bobs. On Raudmans Tour car, he knows the centerline of the ball joints should be 3/8 inch behind the straightedge located off the two plumb bobs on the A-arm mounts, and measures to ensure this is true. |  As per the dimension reference...  As per the dimension reference sheet given to each Victory Circle customer, Raudman measures from the straightedge back to the rear-frame kick, and then to a plumb bob hanging off the rearend on both sides of the race car to check that the frame is square; and then, to check that the rearend is square in the car. |  Once the rearend is square...  Once the rearend is square in the car, the side-to-side location of the rearend needs to be determined, and the rearend set properly in the car. To do this, put the tires back on the car and set it back on the ground. Run a string down each side of the car at spindle height. Raudman uses two jackstands to hold the string. |  The string is then located...  The string is then located a few inches away from the body, and set perpendicular with the rearend by positioning it equidistant from the front and rear portions of the rear rim. Now, the front wheels can be measured to determine if the rearend is located properly. Too much on one side or the other will tell you what you need to know. Just make a note if your rearend is shorter than the track width, because that will make one side shorter! |
There are plenty of circumstances where squaring a car comes in handy. Let's say you just bought a race car, and want to know where the suspension is on the thing. Or maybe you just got a brand-new chassis an need to set the suspension straight in the car to locate the body on the chassis. Maybe you're just ready to set up the chassis for the next week of racing, and need to find your baseline again. For all of these situations, you need to square up your race car--and here is where to learn how to do just that. We dropped by the Victory Circle Chassis and Parts shop in Bakersfield, California to talk with owner Craig Raudman about squaring a race car. Raudman also fields a full-on Southwest Tour effort and was getting ready for the next week's racing. Here's what he does to get ready and what he recommends to his customers. Before measuring, find the flattest space on the floor in your shop. Mark the four corners with tape, and always do your measurements in that area. If it’s not, he shortens or lengthens the trailing arms, and the whole process of checking the angles on all the rear-suspension components, and getting everything to the starting point is begun again. This is not a one-step procedure. You will find problems and you’ll need to solve them to get all of this right. If you need to slide the rearend one way or the other, make sure that once you move it, the frame mount of the lower-trailing arms is further inside than the trailing-arm mount on the rearend. This is important in ensuring against fouling up the rear steer of the car.
Victory Circle Chassis & Parts, Inc.
3818 Pierce Rd.
Bakersfield
CA
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Chassis Lowdown: Get Square!
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