Backdraft Anti Squat

[Waitey]

My Squat geo issue.

Squat = Bad. Its essentially weight coming off the rears during acceleration (they are driving themselves upward into the body) along with the suspension compression adding camber to the rears. All of which gives less grip and more potential of doing a Mustang at a car show crash.



reen line - Front Spindle Centre line, which when under power the car wants to rotate around.
Yellow line - Centre of Gravity plane across the car.
Blue line - 0% Squat line, the interaction between the rear spindle and where the COG plane crosses the front centre line.
Orange line - Line from the rear spindle, through the trailing arm mount to the front centre line.

As you can see, the orange line is below the blue one. Ideally I want it to follow the blue one, or close to it. Below blue line = Pro Squat. Above blue line = Anti Squat.

To do so, I'll have to raise the front mounting for the trailing arm around 40mm (this should take into account driver weight lowering the car further than this photo too). Which given the space around how Backdraft make mount for the arm, should just be possible. Result.

[reynoldsgto]

rt3 or rt4?

[eschaider]

Your model is essentially correct for a four-link suspension, although the actual illustration of the anti-squat line and instant center (among other things) are not correct. The concept you are attempting to use will not work on an IRS-suspended vehicle. It requires a stick axle and a four-link rear suspension.

There is an excellent tool for setting this up available from Jerry Bickel Race Cars. Again, however, it is for a four-link, not an IRS rear suspension. When I get home this evening, I'll post up more info and pics from the Bickel tool.

[Waitey]

Originally Posted by eschaider

Your model is essentially correct for a four-link suspension, although the actual illustration of the anti-squat line and instant center (among other things) are not correct. The concept you are attempting to use will not work on an IRS-suspended vehicle. It requires a stick axle and a four-link rear suspension.

There is an excellent tool for setting this up available from Jerry Bickel Race Cars. Again, however, it is for a four-link, not an IRS rear suspension. When I get home this evening, I'll post up more info and pics from the Bickel tool.

If it were a 4 link, the anti squat neutral line would pass through the rear tyre contact patch as the Diff wouldn't be constrained.

Since it is IRS the neutral line has to pass though the spindle and intersect the COG and Front spindle interaction.

As seen here:

https://youtu.be/XuxhI4CBaNk?si=R8jnem_ewDjRAzSM&t=524