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Discussion Starter · #1 ·
Been looking over a lot of post about ladder bars and i see guys talking about the "anti-squat line" how do you figure out where that is on ladder bar cars?
 

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Ladder Bars really do not squat...

No compound leverage on the chassis, I would think you would have to have the ladder bar pointed down at a Drastic angle to pull the chassis down on the tire.

But there are two rules of thumb that are applied to ho to determine the line...

Run a line from the bottom of the rear tire through an intersection point that is equal to the height of the camshaft and

Theory 1, Camshaft height at the front wheelbase Centerline

Theory 2, Camshaft height at the center of the weight balance front to rear.. (a car that has a 100" wheelbase and 50/50 weight balance would be 50" in front of the rear tire)
 

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Discussion Starter · #3 ·
So if your above or below this line what would it effect or change on the chassis.
 

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So if your above or below this line what would it effect or change on the chassis.

With a Ladder bar not much.. unless, like I said, it is drastically above or below...

With a 4 link you have got two attachment points on each side, the lower bar pushes on launch and the upper bar pulls back a bit. they have leverage on the chassis depending on where they are mounted affects that leverage or push/pull.

Ladder bars have a single attachment point, it pushes and lifts through the same point. even with the ladder bar being pointed way down, the rotation of the housing will still try and pick up the front of the ladder bar.
 

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Discussion Starter · #6 ·
Ran a string line on the car and it intersects right through the center of the hole above where me bars are mounted, so i guess i should move it up a hole? or is plus or minus a hole close enough?
 

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Viewing the car from the side, picture a large number of lines, each passing through the rear tire patch. Each line represents a particular value of percent anti-squat. The 100% anti-squat line also passes through a point directly above the FRONT tire patch and at a height equal to the center of gravity height. If the rear axle assembly is rotating about a point below this 100% anti-squat line, the car will squat; if above, it will rise. With a ladder bar, this "point" is the front pivot. So, yes, it's not at all uncommon for a ladder bar car to squat. With a 4link, the "point" is determined by the intersection of a line through the pivot points for the upper link and the intersection of another line through the pivot points for the lower link. With deflection of the suspension springs, this intersection moves, so it is referred to as the "instant" center.

Note that, with either a ladder bar or a 4link, the right side IC (instant center) does not have to be the same as the left side IC. This sort of adjustment is not at all "weird," but, in fact, can be used to counteract the unloading of the right rear by the driveshaft torque. If done properly, it is possible to have equal rear tire loading for any value of driveshaft torque. See my site for further information.
 

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...it's not at all uncommon for a ladder bar car to squat.
Misspoke above. Should have been IMPOSSIBLE instead of UNCOMMON. You'd need very long ladder bars or, as race9899 points out, the shorter ones would have to be pointed down quite a bit to get the pivot below the 100% anti-squat line.

Some of the altered wheelbase cars of the sixties had ladder bars extending almost to the front wheels, which would definitely open the door to squat.
 
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