Advanced suspension question

I have a good question(not that my Dad couldn't answer it) but I wanted some other views.

I have seen long and short torque arm cars do very different things when leaving the starting line, actually just opposite of what I would have thought they would do. A buddy of mine here locally has a 10 sec all motor LT1 car that has a short Global West type torque arm that is mounted on a square tube that is welded through the floorboard, this car leaves like a conventional(most) cars do, it will "get back on the tires" as me and my Dad say, or close the gap between the rear fender and tire.

Other long torque arm cars tend to seperate the gap between the tire and fender, like my buddies Buick GNX that also has a factory tq arm setup, it "hikes up" in the rear when leaving the line.

My question is why?, seems to me the longer arm would have the leverage the lift the nose and put weight back on the tires, and the short arm would not have the leverage and just plant the tires and seperate the rear from the car, but they work opposite of that.

Is it because most cars LCA's are parallel with the ground?


Thanks
]David

"Anti-Squat" geometry is the short answer.

Here's a similar thread:

http://web.camaross.com/forums/showthread.php?t=181649

To calculate % Anti-Squat you need to know locating points and do some some geometry. It's not the length of the arm, it's the angles that count.

FWIW, GNX had factory torque arm? I thought it was just the GM 4-link. Of course, this can be made to have lots of anti-squat by relocating pivot points. You don't actually need to have a torque arm. Any solid axle rear suspension has some % anti-squat (or squat, for that matter).


Is this about what Dad would say?

Yes the GN "X" had a torque arm setup. But only 547 I think were made. Guess I will have to figure out the angles once the car is closer to being finished.


David

Yes the GN "X" had a torque arm setup. But only 547 I think were made. Guess I will have to figure out the angles once the car is closer to being finished.


David

Thanks for the GNX info. I didn't realize ASC/McLaren also redid the rear suspension during the conversion. I learned something today! That makes it a good day.

Here's a good link:

http://home.att.net/~buickGNX/GNX/susp.htm

"Anti-Squat" geometry is the short answer.

Here's a similar thread:

http://web.camaross.com/forums/showthread.php?t=181649

To calculate % Anti-Squat you need to know locating points and do some some geometry. It's not the length of the arm, it's the angles that count.

FWIW, GNX had factory torque arm? I thought it was just the GM 4-link. Of course, this can be made to have lots of anti-squat by relocating pivot points. You don't actually need to have a torque arm. Any solid axle rear suspension has some % anti-squat (or squat, for that matter).


Is this about what Dad would say?


Dad done told him it was the angle,not so much the length.