Squaring the Front & Rear Axle: The Foundation of a Sprint Car Setup
- TiBill
- Oct 12
- 7 min read
Updated: Oct 19
In this post, we’re diving into one of the most overlooked but absolutely critical steps in sprint car performance: making sure your front and rear axles are squared. Yes, we’ll keep it in plain English without too much jargon. If your axles aren’t square, the car won’t track straight, the suspension won’t work as it should, and you’ll spend the night chasing handling issues instead of racing.
What “Squaring” Really Means
When we talk about “squaring” an axle, we’re simply talking about alignment. Both axles need to:
Sit straight and true in the chassis
Be referenced correctly to the motor plate
Move freely without binding up the rods, birdcages, or steering arms
It’s the foundation for everything else. If the axles aren’t right, the rest of your setup is fighting against you.
Why Squaring Helps on Dirt
Dirt tracks change every lap. Ruts form, a cushion builds, and the slick line moves. When both axles are truly square, the car reacts the same way every time you hit those changes. When they are not, the car starts fighting you harder as the surface evolves.
Predictable handling
Straight axles keep the chassis’ thrust line pointed where the driver is aiming
The car tracks straight under throttle and brake, so mid-corner corrections are smaller and more repeatable
Consistent responses over bumps, cushion, and transitions make shock and bar changes actually behave as intended
Even loading
Both rear tyres carry load the way your setup intends instead of one side overworking
Balanced loading keeps crossweight targets meaningful and improves repeatability across a race night
More even loads mean more consistent tire temps and less fall-off over long runs
Freedom in suspension motion
Properly squared rear ends let radius rods, birdcages, the torque tube, and the Jacob’s Ladder move without bind
Free movement means shocks manage the bumps instead of the linkage locking up
Jacob’s Ladder geometry works as designed, with the roll centre moving predictably rather than spiking from a bind
Better steering balance
A squared front axle keeps caster split and toe where you set them
Steering feels centred and linear, which builds driver confidence on entry and lets the car “free-roll” to the middle
Rear axle thrust and drive off
Rear axle square to the motor plate equals a straight thrust line, so drive goes forward instead of crabbing the car
Matching left and right measurements within tolerance stops the car from stepping out under power on a slick exit
Fewer setup “ghosts”
When the axles are square, changes to shocks, bars, stagger, and wing angle show their true effect
Misalignment masks problems and wastes test laps chasing issues that simple squaring would fix
Practical payoffs you will feel
Cleaner corner entry, less steering input in the middle, and stronger drive off the bottom or cushion
Reduced shock heat because the linkage is not fighting itself
Tyres last longer because loads are shared instead of one corner doing all the work
Quick checks that catch most issues
Rear axle on setup blocks, car level, and both axle-to-motor-plate measurements matched within small tolerance
Birdcage bolts and Jacob’s Ladder bolts sliding in by hand with at least a hint of free play, not forced
Front axle on blocks with your chosen left offset, right-side measurement nailed first, then caster set and everything re-measured before tightening
Reminder: These steps are for a raised-rail chassis. If your car is not raised-rail, do not use a 1" smaller block on the left side of the axles when squaring.
Squaring the Rear Axle
Put the rear end into the car using a 5" block under the left side and a 6" block under the right side.
Bolt the torque tube in place.
Install the left and right birdcages, but do not attach the radius rods or torsion arms yet.
Use spacers and put the axle nuts on to hold the birdcages in position.
Lightly start the torsion bar bolts into the birdcages - only two or three turns, do not tighten them.
Grease the torsion bars and slide them into the car, leaving the stops off for now.
Roughly centre the rear end in the car by:
Measuring from a centred bolt on the rear end cover plate to each frame rail.
Measuring from the machined back edge of the torque tube to each frame rail (about 10 ⅛")
Lining up a centred bolt on the rear end cover with the middle torsion bar gusset.
On one side, measure from the front edge of the motor plate to the front edge of the rear axle tube. Adjust the axle forward or backward until the distance is 38 ⅝".
Repeat the same measurement on the other side and adjust until it also reads 38 ⅝".
Go back and forth repeating steps 8 and 9 until both sides measure exactly 38 ⅝" from the front edge of the motor plate to the front edge of the axle tube. It can take several tries to get both sides even.
Attach the rear radius rods on both sides of the car to the birdcages.
Zero your digital angle gauge on the bottom rail of the chassis.
On one side, place the gauge on the bottom edge of the birdcage. Turn the radius rod in or out until the scale reads 0°.
On the opposite side, place the gauge on the bottom edge of the birdcage and adjust the radius rod until the scale also reads 0°.
Remove the torsion bar bolts from both birdcages.
Attach the left and right torsion arms to the torsion bars and tighten them securely.
On one side, without moving the birdcage, adjust the rod end until the lower birdcage bolt slides freely through the rod end and into the birdcage.
Repeat this on the other side, again ensuring the birdcage does not move.
If the Jacobs Ladder is not already installed, carefully put it in place without shifting the rear axle or birdcages.
On the right side, adjust the rod end in the birdcage so that the Jacobs Ladder lines up perfectly with the mounting hole on the birdcage rod end. Keep adjusting until the holes align without moving the axle or birdcage.
Secure the Jacobs Ladder.
Recheck all measurements to make sure nothing has moved during the squaring process. If any measurement is off, undo everything and restart from step 7.
Once all measurements are accurate, carefully tighten all jam nuts, ensuring nothing moves while tightening.
When this process is done correctly, the rear axle will be square to the chassis and aligned with the motor plate, allowing the suspension to cycle freely and giving both rear tyres consistent load and drive.
Hint: To make sure the rear axle is square, check that the ball doesn’t bind and can be turned smoothly by hand.
Squaring the Front Axle
Start by levelling the chassis on stands so that all measurements are accurate.
Block the front axle at ride height using a three" block under the left and a four"block under the right.
Install the radius rods. On the right side both rods should be equal in length, while on the left side the front rod is set about half an inch shorter. Leave the jam nuts loose so adjustments can be made freely.
Optional: Offset the axle to the left by using the panhard bar adjustment. On a 50-inch front axle, the left- side king pin to chassis measurement should be one inch longer than the right.
Square the axle to the motor plate by measuring from the motor plate to the back edge of the axle tube. For an 87/40 frame with a 2 ¼-inch axle, the figure should be 46 ⅜ inches. For an 88/40 frame, it is 47 ⅜ inches. With a 2 ½-inch axle, subtract one-eighth of an inch.
Apply the desired lead by reducing the left-side measurement. For example, on an 87/40 car with a 2 ¼-inch axle, a quarter-inch of lead equals 46 ⅛ inches. The left side should always be shorter than the right.
Set caster by placing an angle finder on the right-front steering arm. Adjust until the reading is between six and ten degrees, with eight degrees being a common baseline. for sprint cars.
To avoid upsetting squareness, 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.
Recheck all the measurements to make sure nothing has moved while squaring the front axle.
If any measurement is off, undo everything and start again from step 4.
When all measurements are correct, carefully tighten every jam nut, making sure nothing shifts while you do it.
Set the Toe
Determine the desired toe setting, which is based on driver preference and typically ranges between ⅛" and ¼”, with ³⁄₁₆” being a good starting point.
Loosen the jam nuts on the tie rod.
Run a tape measure through the frame near the radiator and measure the distance between the inside beads of the left and right front wheels at the back of the wheels (the area closest to the rear of the car).
Run the tape measure through the frame near the torsion tubes and measure the distance between the inside beads of the left and right front wheels at the front of the wheels (the area closest to the front of the car).
Adjust the tie rod by turning it in or out until the front measurement is ³⁄₁₆” (or the desired amount of toe) larger than the rear measurement.
Repeat the measuring and adjustment steps until the correct amount of toe is achieved.
Tighten the tie rod jam nuts to lock the setting in place.
Helpful Hints and Suggestions
Use tie-down straps looped over the shock tower and under the rear axle to stop the axle dropping if blocks move.
If short on spacers, 3" poly pipe works as a cheap substitute .
Side-to-side rear end centring may vary ±⅛"" – this is normal. The axle-to-motor plate measurements are what truly matter.
Always grease torsion bars in the middle as well as the ends.
Why This Matters
Squaring the axles is the foundation of sprint car setup. If the rear axle is out, the car will thrust sideways rather than straight ahead and no other adjustment will make the handling consistent. If the front axle is misaligned, caster and toe changes will not produce reliable steering feel, leaving the driver fighting the car. By setting both axles square and true, you create a solid baseline. Every other adjustment - shocks, torsion bars, wings, or tyres - will then behave as intended, giving predictable handling and repeatable speed.
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