Wanting some 3-Link insight

[dirtplay18]

Running a car similar to an imca sport mod rules package. Solid 3-link, panhard bar behind the rear end, springs on top of housing. Wondering about the adjustment on the top bar. It is only about 16" total length, and about 10* angle. I've already adjusted it up on the front side, which seemed to help the car rotate better in the center on-throttle. It's currently 5-1/2" to center of heim from the housing, can't go any higher. I can move it down to 4-1/2" and 2-1/2" above and i'm wondering if I should try it, and, in theory, what it will do to the car. Has been driving great, won 6 out of 9 races this yr, but we run am racer kk 704's, so more forward drive would be a plus. Hate to back up, so I'm just curious what to expect if I try the adjustment.

[dirtplay18]

Hope I didn't confuse anyone, just wondering what dropping the bar on the top of the rear end will do.

[Duckhnter83]

I know the chassis side if you move it down or more angle it will provide you with more instant traction on the throttle exit but won't keep it as long down the straight and the less angle the farther it will hold it down the straight. I would assume the rear end would be the same adjustment just be more of that on the frame side because moving it up would add more leverage on the rear end. In my 3 link if I move it down on the frame I will get a slightly looser corner entry and in the tacky a tighter corner exit. If its dry slick I have to be a little more careful as not to just blow the rear tires loose on exit.

[Lizardracing]

That's true to some degree for a spring or biscuit spring type pull bar but for a solid upper link the generality goes, more angle=looser entry, tighter exit, less angle=tighter entry, looser exit. As far as moving the bar up or down without changing the angle you get into radias changes as the rear axle moves around under acceleration and deceleration. 11-12" above axle center line seems the popular starting point.

[let-r-eat]

Draw 2 circles on a piece of paper. 1 of them a 2" circle and the other a 4" circle. Look at the arc from 12 o'clock to 3 o'clock. Now look at the difference in the length of those arcs between the 2 circles. Think about how much traction the tire needs to move the pullbar those distances *think about a solid bar and forget the dampening devices, they just control when and not HOW MUCH is available*. ON ICE the pullbar would not react to the LONGER arc but may react to the smaller one?The pullbar may not be capable of transferring weight to the rear wheels if the surface is ice. We then must use static weight to create what traction we can and then help transfer through devices/pullbar/liftbar/bars/springs/CG migration.

[Duckhnter83]

I really don't understand the picture your trying to represent let r eat? Its kinda confusing. Can you explain better?

[let-r-eat]

Picture the center of the rear end from side view. Now picture pullbar mount closer to housing at say 8" from center of housing then another mount 12" from center of housing. Now as the pinion climbs the ring gear and the housing rotates until the driveshaft yokes align front and rear, picture the distance the 8" mounting point would move compared to the 12" mounting point.We have a circle that has an 8" radius verses a circle with a 12" radius. Circumference = 2*pie*Radius so we have...........50 1/4" circumference/360 degrees(360 degrees in a circle) = .139 inches per degree for an 8" radius circle and 75.4/360 = .209 per degree of rotation " for a 12" radius circle. So if the housing rotates 7 degrees then the 8" radius moves .139 X 7 or .973 inches and the 12" radius moves .209 x 7 = 1.463 inches. So there is basically 1/2 inch of additional distance the pullbar would pull on the front mount. So the farther downhill/or possibly uphill the pullbar is mounted the more potential to load the chassis if traction exists to do so. That is one of the reasons we look at the travel of a pullbar and why it's important.