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Author Topic:   Pullbar Location
jkittleson
Dirt Roller

Total posts: 5
posted April 08, 2002 09:37 PM
What effects does the mounting position have on the car? I was running the pullbar in the top back location and the car was tight on entry and had ALOT of foward bite. I moved the pullbar to the front lower hole and the car became ALOT looser on entry and seemed to loose some foward bite. What made it looser on entry?

Thanx

wfoondirt
Dirt Freak

Total posts: 242
posted April 09, 2002 08:35 AM
Increasing third-link angle typically will loosen entry because the third link not only reacts accel torque it also reacts braking torque especially if your not running floated brake. The increased downward angle effectively unloads the tires on decel which results in a looser entry car. This can be counteracted to some extent by running a stiffer dampner shock on top of the rearend or increasing the upward angle of the dampner.

jkittleson
Dirt Roller

Total posts: 5
posted April 09, 2002 08:53 AM
I understand more angle makes the car looser on entry, but I have less angle now. Why did lowering the pullbar on the rearend and moving it foward make the car looser on entry? Does it have more leverage now?

wfoondirt
Dirt Freak

Total posts: 242
posted April 09, 2002 01:07 PM
Oops misread your post, lowering it on the rear-end effectively stiffened the rate of the spring which is probably the cause for the loss of forward bite. Lowering it on the rearend also changes the ic location, typically raising which will usually have the same effect as increasing the angle.
Imagine a line in side view from the rear tire contact patch to the center of gravity of the car, if the ic is above or below that line there are jacking forces in relation to rear axle torque and the farther from the line the greater the jacking force. Barring the use of brake floaters and some kind of dampner shock on the rearend, the higher and/or farther to the rear the instant center is the more the car rear will unload under braking, but it also increases anti-squat under accel. Now there is always a debate about the benifits/penalties of having jacking forces built into a race car, but it really comes down to what works best given the situation.

Robcat
Dirt Roller

Total posts: 22
posted April 09, 2002 02:10 PM
Also if for some reason you changed the position of the bar to centerline. The bar will pull harder on the rear tire it is closest to. A note if you need to tighten the car on corner exit.

[This message has been edited by Robcat (edited April 09, 2002).]

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