Follow these steps to square the axles in the chassis, and set up the front end.  Note: These instructions are specific to a 40" car.

Rear End      Front End      Helpful Hints      Feedback

Rear End

Squaring The Rear Axle ...
 

1. Put the rear end in the car; using a 5” block on the left side, and a 6” block on the right side.
2. Bolt the torque tube in place.
3. Put on the left and right bird cages.  At this point, do not attach any of the radius rods or torsion bars.
4. Using spacers, put on the axle nuts, and secure the bird cages on the axle.
5. Lightly insert (just) the torsion bar bolts into the bird cages.  Do not tighten, just get bolts started two or three round.
6. Put the (greased) torsion bars in the car.  At this point, leave the stops and arms off.
7. Roughly center the rear end in the car.  This can quickly be accomplished by:

a)       Measuring from a (centered) bolt on the read end cover plate to the frame rails.

b)      Measuring from the machined back of the torque tube to the frame rails.  Approximate measurement should be 10 1/8”.

c)       Line up a (centered) bolt on the read end cover to the torsion bar gusset in the middle of the rear torsion tubes.

8. Pick a side, and measure from the leading edge of the rear axle, to the front edge of the motor plate.  Move the axle forward/back and side to side until this measurement is 38 5/8”.
9. With the opposite side, measure from the leading edge of the rear axle, to the front edge of the motor plate.  Move the axle forward/back and side to side until this measurement is 38 5/8”.
10. Repeats steps 6 and 7 until both sides of the race car measure 38 5/8” from the leading edge of the rear axle to the front of the motor plate.  Note: this will take numerous attempts to accomplish.

Important Note: Every step after this assumes the rear end remains completely stationary in the car.  If the rear end moves in the least, undo each step completed, and start back at step 7.

Leveling the Bird Cages ...

   Method A - Using A Tape Measure

11. Attach the (rear) radius rods on each side of the car to the bird cages.
12. Pick a side, and measure from the leading edge of the torsion bar bolt (in the bird cage) to the front of the motor plate.  Wind the radius rod in/out until the measurement is 39 3/4”.
13. With the opposite side, measure from the leading edge of the torsion bar bolt (in the bird cage) to the front of the motor plate.  Wind the radius rod in/out until the measurement is 39 3/4”.

   Method B - Using A Digital Level

11. Attach the (rear) radius rods on each side of the car to the bird cages.
12. Zero the scale to a bottom rail of the chassis. Pick a side, and place a digital scale on the bottom edge of the birdcage.  Wind the radius rod in/out until the scale reads 0 degrees.
13. With the opposite side, place a digital scale on the bottom edge of the birdcage.  Wind the radius rod in/out until the scale reads 0 degrees.

Attaching the Torsion Arms ...
 

14. Remove the torsion bar bolts from the bird cages.
15. Attach the left and right torsion arms to the torsion bars (and tighten).
16. Pick a side, and without moving the birdcage, adjust the rod end so the (lower) birdcage bolt slides freely through the rod end and into the birdcage.
17. With the opposite side, and without moving the birdcage, adjust the rod end so the (lower) birdcage bolt slides freely through the rod end and into the birdcage.

Attach the Ladder ...

18. If the Jacobs Ladder is not in the car, put it in (being careful not to move the rear axle, birdcages, etc).
19. Adjust the rod end (in the right side birdcage) to the correct length so that the Jacobs Ladder attaches to the birdcage without moving the axle or birdcage.  This is simply a case of putting the Ladder into position, and aligning the holes in the Ladder with the eye on the birdcage rod end.  Keep adjusting the rod end in the birdcage until the two line up.
20. Put in the Jacobs Ladder bolt.

Recheck and Tighten ...
 

21. Recheck all the of the measurements above to ensure nothing moved during squaring.  If any measurement is not accurate, undo all the steps, and restart the entire process at step 7.
22. Once all measurements are correct, tighten all jamb nuts (being careful not to move anything until all jam nuts are tight), and Ladder bolt.

Front End

Put Front Axle in the Car ...
 

1. Put the front end in the car; using a 3” block on the left side, and a 4” block on the right side.
2. Make the two right front radius rods the same length.  Make the (single) left front radius rod (apporx) ½” shorter than the right side rods.  Leave the jamb nuts loose.
3. Hook up all three radius rods, and the panhard bar (tightening all nuts/bolts enough so none of them are loose).

Offset 50" Front Axle 1” To The Left ...
 

4. For a 50" front alxe ... offset the axle 1” to the left by:

a)       Pick a side, and measure from the king pin (center) to a straight edge that runs vertically from the top rail to the bottom rail.

b)      With the other side, measure from the king pin (center) to a straight edge that runs vertically from the top rail to the bottom rail.

c)       Increase/Decrease the length of the panhard bar until the measurement on the left side is 1” more than the measurement on the right side.

Square The Front Axle ...
 

5. Determine the amount of desired right side lead.  A good starting point for most tracks is 1/4".  This will vary depending on driver preference and track shape/size.
6. With the right side of the car, measure from the leading edge of the motor plate to the back edge of the front axle.  This measurement will vary depending on front axle diameter as follows:

Adjust the right side radius rods evenly (each rod turned the same amount) until the above measurement is achieved.

7. With the left side of the car, measure from the leading edge of the motor plate to the back edge of the front axle.  This measurement will vary depending on front axle diameter and amount of desired lead as follows:

 As an example for a 87/40 with 1/4" lead, the measurements would be (depending on the size of the front axle):

2 1/4" Front Axle = 46 3/8” - 1/4" = 46 1/8”

2 1/2" Front Axle = 46 1/4" - 1/4" = 46"

Adjust the left side radius rod until the correct measurement is achieved.

Note: Another (less accurate) method to accomplish the same result is measure:\

  - 13 1/2" from the center of the right front torsion tube, to the center of the front axle.

  - 15 1/2" from the center of the left front torsion tube, to the center of the front axle (this includes a 1/4" of lead).

8. Repeat steps 6 and 7 until both measurements are correct.  It’s important to note this will take multiple attempts, as the opposite side measurement will change each time an adjustment is made.

Set the Caster ...
 

9. Measure the (current) angle of the car front and back by putting a angle finder on the bottom rail.
10. Mark the top of the right front radius rods with a sharpie (and any other pencil, pen, etc).
11. Place the angle finder on the right front steering arm.
12. Adjust the radius rods until the angle finder reads between 6 and 10 degrees, compensating for the (current) angle of the car.  The exact amount of caster will vary depending on driver preference.  A good starting point is 8 degrees.  Generally, the more caster in the car, the better the car will feel to the driver. 

To adjust the caster, turn the right front radius rods exactly opposite amounts.  This can be accomplished by keeping track of the number of turns done to the top rod, and doing the opposite on the bottom rod.  Use the marks on the radius rods done in step 10 as a guide.

By turning the top and bottom right side radius rods equal and opposite amounts, you will not alter the squaring of the front axle, just the caster.

Recheck and Tighten ...
 

20. Recheck all the of the measurements above to ensure nothing moved during squaring.  If any measurement is not accurate, undo all the steps, and restart the entire process at step 4.
21. Once all measurements are correct, tighten all jamb nuts (being careful not to move anything until all jamb nuts are tight).

Set the Toe ...
 

13. Determine the amount of toe required.  This is a driver preference, usually between 1/8” and 1/4".  A good starting point is 3/16”.
14. Loosen the jamb nuts on the tie rod. 
15. Putting a tape measure through the frame (close to the radiator air box), measure the distance between the left side and right side wheel beads at the inside bead at the back of the wheel (the portion of the wheel “most” towards the back of the car).
16. Putting a tape measure through the frame (close to the torsion tubes), measure the distance between the left side and right side wheel beads at the inside bead at the front of the wheel (the portion of the wheel “most” towards the front of the car).
17. Adjust these measurements by turning the tie rod in/out until the front measurement is 3/16” (or the desired amount of toe) larger than the back measurement.
18. Repeat steps 15 to 17 until the desired amount of toe is reached.
19. Tighten the tie rod jamb nuts.

Helpful Hints and Suggestions

• Use motorcycle tie down straps (or ratcheting tie down straps) to go over the shock tower (bar) and under the rear axle (in a big loop) on both sides of the axle/chassis.  Keep it loose so as to not lift the axle, but snug enough to stay in place.  This will prevent the axle from falling down and hitting the lower frame rail should the setup blocks move in the car.

• If you do not have enough spacers when tightening the bird cages on the axle with the axle nuts, 3” poly (drainage) pipe available from your local hardware store is a cost effective alternative.  This is also an easy solution to having to put 10 + spacers on the axle when squaring the rear end.

• The measurement of the rear end side to side in the car after it is squared may differ by as much as a +/- 1/8”.  This is consistent with all chassis and should be expected.  The single most important measurement to square the rear end is the measurements for the leading edge of the rear axle to the front of the motor plate (on each side of the car).

• This method is very useful, as it does not assume the chassis is level, and still squares the bird cages.   Thus, it can be done at the race track, or on any surface.  It is also much more accurate, as there is no estimating if the bubble in the level is at the top.

• Torsion bars should be greased in the middle as well as on the ends.  During racing, they will twist up and contact the torsion bar tubes.  Grease allows them to be free in the tube.
   
• When adjusting the toe, do not use the tires for obtaining the measurements.  Tires are not constant, and a bulge or imperfection in the tire will cause the toe measurement to be inaccurate.

• A quick and reliable method for checking the centering of the front axle is to ensure the center of the panhard mount (bolt) is directly above the center of the lower frame rail.
   
• Another method for checking the centering of the front axle is to measure from frame to radius rod brackets (on the axle).  This measurement should be 2 1/4".

Feedback

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