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Author Topic:   swing arm/z link set up or four bar/z link
Wes #20 dirt mod
Member
posted February 03, 2004 04:33 PM
I wonder if anyone can get me good starting specs on bar angle for the upper bar on my z link. Also is there any advantage or disadvantage for this bar being longer or shorter? What about the top bar angle on the four bar, and would you run the slider in front or behind the axle on the four bar.


zeroracing
Member
posted February 04, 2004 12:27 AM
ok z link, 5-10 deg neg, will work to star on the rearward facing one. as far as longer or shorter, that will effect how fast the thrust angle changes, how fast the car reacts, and rearsteer.
on the four bar, 15-25 deg, 15 on most tracks, then 25 on short stop and go slick.
mount slider behind on the four bar. it will index ths spring and make it have more bite.


Azrace
Member
posted February 04, 2004 11:54 AM
Zero, I have read many of your posts on the forum and you seem to be fairly knowledgable on swingarm's and z-links. Do the front and rear bars on a swingarm z-link help promote forward bite. What do you think the starting points should be on the right and left side bars. Thanks


zeroracing
Member
posted February 04, 2004 01:22 PM
i love swing arms. both the front and the rear bars effect forward bite, the rearward facing ones make the biggest change though.

z link both sides(or swing arm), i would run on the left the front at about 10 deg angle, and the backward one about 10 deg neg, or 15. remember as the body rolls the z link or swing arm lr will loose forward bite.
on the right side i would go with the forward about 5 deg and the back about 10 neg. that should have alot of bite. as the body rolls the rr will gain forward bite.
rules of thumb are the rearward bars make the biggest difference and the more neg angle in them the more that tire will bite.
watch the rearsteer, when you get odd angles the watts linkage will start to rearsteer alot.
its imposible to out run a swing arm on a rough track. look under some big name late models, they have swing arms, especially on rough tracks.
if you run a four bar on the left then go with like 15 deg -18 in the upper and 0-5 in the lower. a four bar on the lr will gain bite as the body rolls. the upper bars make the biggest difference in both 4 bars and watts links.


Wes #20 dirt mod
Member
posted February 05, 2004 03:25 PM
Thank You Zero. The numbers and reason behind them are exactly what I was looking for.


Azrace
Member
posted February 06, 2004 07:25 AM
Thanks Zero. Another question I have is on bird cage indexing. Is there any advantage or dis-advantage to rolling the top of the bird cage backwards. For example, if I wanted to quickly lenghten the right side wheelbase and I just shortened the right upper bar pulling the rear end back would this create any problems? Thanks


zeroracing
Member
posted February 06, 2004 10:57 AM
Ok on a z link by doing that you will pre index the birdcage, and when the car rolls over, being a z link on the right side, the bottom will go backward(so a spring mounted on the back side would index)
by roatating the birdcage like you talk about you would make the front side go up. so when the car started to roll it would go to center then index the rear mounted ones. so if you do that make sure nothing binds up, and you would probally notice a little less right rear bite so it would tighten the car up some.
also if oyu adjust it like that you would have to check the ride height again, beacuase those may change because your moving the bottom spring mount. if you can i would keep from doing this. on a four link it can make a big deal on how good it works if the upper and lower mounts are in straight up and down, on a z link that will not make a big deal(you might notice less rr bite, and ride hieght change). also make sure it will not bind up at all. if you start with the birdcage at angles you increase your chance for binding.
long story short.
try to keep from doing it(like at the shop make the wheelbase change and write down the bar lengths, then at the track just change both to that length.
if your on a swing arm(z link with the springs on top of forward lengths) it will not make a huge difference as long as yet again nothing binds up. i have ran with my birdcages on my swing arm straight up and angled some and you can not tell a difference.