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Author Topic:   4-link z-link bar angle help
Mr.C
Dirt Newbie

Total posts: 2
posted June 29, 2004 09:23 PM  
I need some suggestions on bar angle for my DW9
4-link Left side and z-link right side.
What angle should the bottom 4 link bar be?
I have seen guys run it down 5 degrees and some guys run it in the top hole with upward angle.( I don't understand why upward angle, maybe because of the z-link on the other side?)
Can someone explain this to me and the pros and cons of each (upward or downward angle of lower 4-link bar).
I'm running the top 4-link bar between 20-25 degrees.
The bottom bar is the one I would like explained on the 4-link side.
Thanks

NJantz
Dirt Forum Champ
Total posts: 755
posted June 30, 2004 05:51 AM  
Any time you put more upward angle in your 4 bar you will produce more rollsteer and more forward bite. However, there is a trade off.

With the rollsteer you have put into the car with greater positive bar angles, you will cause the left rear tire to move forward and the right rear tire to move rearward during chassis roll. This is why your car will get loose in the middle of the corner. So like most set up changes it's all a compromise.

The reason guys will run a right rear zlinked on a slick track is to keep the car tighter in the middle of the corner. A zlink has a more vertical travel path unlike a 4 bar where the wheelbase is always changing do to a more elliptical travel path.

That vertical travel path that the zlink generates keeps the right rear from moving rearward like a 4bar would do when the car rolls over on the right rear. So since your right side wheelbase is not increasing during chassis roll, your car will stay tighter with a zlink on the right rear.

Also, the more pos. bar angle you put on a link, the greater influence that tire will have on driving the car off the corner. Theoretically speaking, if you were to put a lot of pos. bar angle in your left bars, you would induce left rear bite causing the car to want to drive to the wall on corner exit much like a stiff left rear spring will do.

Hope this makes sense, feel free to ask questions or add to this.

Also, 4bars get kind of crazy on rough heavy tracks. That is another place a zlink might help calm the car down and keep it pointed in the right direction.

[This message has been edited by NJantz (edited June 30, 2004).]

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 30, 2004 07:29 AM  
Thats one of the best explanations of 4-bar and Z-link rear suspension i ever read. Good work.

I prefer 4-bar with alot of bar angles for killer steering going and thru the middle, but z-link is nice on slick and rough tracks.

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