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Author Topic:   4-z setup to 4 link for track conditions
rpm20
Dirt Freak

Total posts: 338
posted June 10, 2005 04:30 AM  
do any of you guys running a 4 -z setup convert to and from 4 bar both sides and back to 4-z to tune for varying track conditions.

if so then what conditions prompt what changes and what else needs to be done to balance the setup??

on my car it would be a fairly easy change,
what would cause you to make the change and would you use 4 bar for tacky and 4-z for rough , dry or what?
just a discussion , more pondering.

[This message has been edited by rpm20 (edited June 10, 2005).]

rpm20
Dirt Freak

Total posts: 338
posted June 10, 2005 05:17 AM  
also, lets talk about doing this with long lower bars and with short lower bars with plugs in the frame.

on the model that i use to check this out it really looks like the advantage would be good forword bite (due to bars pushing the rearend under the car on both sides under power) coming out and a small amount of roll steer on the rr with a 4 link rr and

with a z rr less lr bite coming out and a more stable low rear steer entry.

so.... that said........maybe a z link is better suited to tacky tracks and a 4 link better for a slick track ???

opinions, gentlemen???

it also seems that you can tune most any bite / rollsteer, etc into either one of these by varying the bar angles, but 4 link looks best for all around rear bite.

right ? wrong ? i know this topic will open a can of worms so lets hear it boys

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 10, 2005 07:31 AM  
This is a good subject.

4 Links to me are superior in the traction department. The two top links, couple with the lower links make alot of mechanical traction.

Although there hard to tune, hate rough tracks. We ran one last year and if the track was smooth there car was fine, but if it was rough the car got stiff and began to pogo stick around the tuns.

As well most have hard time realizing that a 4 Link needs to be loose in, or dont like the feel of it. They have to be free in the corner, or by the time you get to mid turn you might as well stop and then pivot.

Me personnaly i like 4 Links on smooth tracks, and bigger higher speed tracks. They just feel fast when you roll into a corner and the car is right, little loose in so you just cant saw on it, but when it starts to come around and lays over, you can roll back on it, and it hikes up and goes.

We switched to a Z-link this year thou, rougher tracks around here. Time will tell if it stays on there very long.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 10, 2005 08:15 AM  
WE have switched to 4 link RR and so far it has worked well. Really we havent noticed a lot difference excpet the driver likes the feel of the 4 link better. And we have had some pretty rough tracks this year and hasnt hurt too much if any over the z link. Its all in getting it tuned right. You can minimize roll steer with 4 ink just like z link the only thing is you get more indexing so if you have the spring in front of the BC it gets loaded more that way.

As far as length of bottom bars goes. If you keep the angles the same the longer bar on the LR increases indexing adn reduces roll steer, On the RR it decreases indexing and increases roll steer. typically with a longer bar you can run a little more angle on the LR and a little less angle on the RR to get the same effect.

rpm20
Dirt Freak

Total posts: 338
posted June 10, 2005 08:28 AM  
krom, do you think if you took some bar angle from the upper on the rr, it would still pogo??
you would lose some fwd bite ...but?

also , now that you have run both.....do you feel the z link helps on the rough or not??

hows the sidebite on the two differ?

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 10, 2005 08:46 AM  
We always had trouble getting the car to turn on the bottom of the track with a 4-bar. Up high it would fly, we race on a steeply banked 1/4mile and it just had trouble getting around the middle of the corner down low.

You gotta pass on the Lowside on our track, so we need it to pivot and go and still have the FWD bite to get the pass done.

4-Link to me has more sidebite, but again we run Hoosiers so side bite is not usually an issue. IMCA tires i think i would be pretty exclusive with a 4 bar car.

Your probaly right on the bar angles, i think we should of been running less on the RR lower bar to get it to loosen up for the low line.

More than likely we will be switching back, i do preferr the 4-Link. Although i have found that the Z-link is bad, thou we dont have alot of laps on it yet to make that decison.

rpm20
Dirt Freak

Total posts: 338
posted June 10, 2005 08:58 AM  
this topic is already brewing well.
its really got me thinking......and working with my larger than life model.

its pretty amazing how you can load and unload springs and change indexing on the bc.

makes you really think of what your wanting to happen, i can really see how the lower bar effect entry and the upper effect exit.

i think for instance that on my lr i had too much top bar angle last week (had about 22*)
and on the rough track when i was exiting on the bars it pogo sticked up the straight on the ls bars. now i see why. i may just lower my rear ride heights 1/2" and take some upper lr bar angle out to smooth it out.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 10, 2005 09:13 AM  
dont get carried away with angle on the RR side with a 4 link. 15degrees is a good place to start. raising it will free teh car some because you are putting drive in that tire with the angle and it puts more roll steer in the car as well, but can be jumpier on rough tracks. If you really need to free the car up around the bottom then you might think about trailing the RR statically, and leave bar angles alone.

With our 4 bar RR we have it set to where we get minimal rear steer at that side(about 1/8") through 3" travel. Keeping that wheel more stable through travel makes the driver feel better about the handling of the car, instead of having that wheel moving back and forth over ruts.

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 10, 2005 01:29 PM  
500th post ! wow i blather on to much LOL !

Anyway, thats the problem we have as well RPM, you want the angle for traction, but the ruts interfere with the whole deal.

If we do switch back to a 4-Bar, i want to try that AFCO pinion plate that places the pinion below the yoke. As well i want to alter my rod lengths on the RR (LR is already) i think i want to go to a 18" lower and a 15" upper to create more index.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 10, 2005 01:46 PM  
I dont know what your bar lengths are now, but assuming you have the typical bottom bar 2" shorter than the top bar. Then going longer on the RR bottom will actually take index out of the car. You want the bottom bar shorter to increase index on the RR. Just the opposite of the LR.


What I was getting at on bar angle is dont put as much emphasis on bar angle for traction on the RR. Concentrate on using bar angle to tune roll steer and indexing on the RR more so than actualy drive. On our car when the thing is rolled over the top bar only has about 5-8* angle left in it. That way you keep the RR loaded with the spring and it can float over the ruts.

[This message has been edited by dirtbuster (edited June 10, 2005).]

rpm20
Dirt Freak

Total posts: 338
posted June 10, 2005 01:58 PM  
your right krom ..........we do just go on...and on ...and on lol

i was thinking if i ever tried this ..that i would put the plug in the lowers and run 12" lower bars ans 14" uppers on both sides.
with the lowers shorter it seems that it doesnt effect the indexing so much as long as you dont use extreme bar angles. you can kind of choose what side you want to load and when, it looks on the model like its very tuneable once you understand it.

krom, i do have the pinion plate with the hole in the middle and i just made my own extension to my speedway plate. i only tried it once but that was in testing , before i discovered that front spring screw up ....so that really gave no good usefull info on that at all.

rrrrick
Dirt Maniac

Total posts: 192
posted June 13, 2005 10:30 AM  
Looking at some set-ups , it seems to me that it is the panhard bar and not the 4 bar that causes the cars to pogo on rough tracks.
The long panhard bar cars use more of the four bar to drive the tires down.
I found that my car did the same when I switched from long panhard bar to a short panhard bar.

the_one
Dirt Full Roller

Total posts: 49
posted June 13, 2005 04:12 PM  
i have a ? does static lr bite only help get the car in the corner or does it help get in and off the corner on a 4 link car

nyimcamod8t
Dirt Full Roller

Total posts: 67
posted June 13, 2005 07:31 PM  
it helps when you have the car riding along at ride height, other than that not really. I don't know about you guys but my car is never at ride height when i'm racing, so i really have yet to figure out what static lr weight does other than give you a baseline on spring preload when setting up the car. it used to matter alot on the two link cars, but i don't honestly beleive it makes much difference on a 4 link car.

[This message has been edited by nyimcamod8t (edited June 13, 2005).]

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 13, 2005 07:44 PM  
LR bite will free the car in and tighten it out.

sdracer12
Dirt Maniac

Total posts: 180
posted June 13, 2005 10:34 PM  
I can switch back and forth between a Z-link and the 4-bar on my RR. My bars are 17 1/2 top, and 15 1/2 bottom on both sides.

We moved the RR spring on top of the housing this year, and have been running z-link on the RR. Last year we had the RR slider mounted in front of the birdcage.

I'm curious if running the 4-bar on the RR without the benefits of indexing will still give more forward bite than the Z-link on the slick? Or, will the 4-bar RR merely loosen up the car on the gas at exit?

rpm20
Dirt Freak

Total posts: 338
posted June 14, 2005 06:01 AM  
in theory.........the 4 bar offers the advantage of having the bars put downforce to the wheels on acceleration which causing mechanical traction to be increased at both rear wheels.

i am hoping to increase my forword bite and be able to better tune my sidebite.

quote:
Originally posted by sdracer12:
I can switch back and forth between a Z-link and the 4-bar on my RR. My bars are 17 1/2 top, and 15 1/2 bottom on both sides.

We moved the RR spring on top of the housing this year, and have been running z-link on the RR. Last year we had the RR slider mounted in front of the birdcage.

I'm curious if running the 4-bar on the RR without the benefits of indexing will still give more forward bite than the Z-link on the slick? Or, will the 4-bar RR merely loosen up the car on the gas at exit?



the_one
Dirt Full Roller

Total posts: 49
posted June 14, 2005 10:30 AM  
to free the car from middle off do you raise the rlb or lower the llb or im i way off

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 14, 2005 10:38 AM  
We got our 4-z car out last week, couldnt get it up to speed due to various carb and fuel pressure issues. Man i hate dealing with them issues.

Anyway maybe next week i will have more to comment on with this thread.

Middle off, on a Z-link RR i would raise the RR lower bar? or Lower the rear bar i think thats correct, maybe somebody could confirm.

Krom.

dirtmod0
Dirt Maniac

Total posts: 143
posted June 14, 2005 11:10 AM  
i would lower the top bar, before i would raise the lower bar, top bar will give more results than the lower

nyimcamod8t
Dirt Full Roller

Total posts: 67
posted June 14, 2005 02:32 PM  
quote:
Originally posted by dirtbuster:
LR bite will free the car in and tighten it out.

yeah, i understand that theory on paper, my point was that 99.9% of the time on the track the car is not at the ride height it was scaled at and thus is not even close on numbers.I don't get how 40lbs of LR make squat difference when the car jumps up in the air the minute the gas pedal is touched and has who knows how much weight on it then. i don't really notice much of a change from changing the LR bite, but change a bar angle or two and you notice a huge difference.

anyhow, back to the original question, it seems to me that as long as the bar angle are correct that a 4-4 has a little better fwd bite than the 4-z did. what i always noticed with a 4-z is that the car would get snug at the apex of the corner.right now our tracks up here are dry dry and i've been running a 4-4 with alot of success.


dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 14, 2005 02:55 PM  
nyimcamod8t,
If your LR spring becomes completely unloaded when the car hikes up then it might not make as much difference as if the spring stays loaded. But look at it this way, when you put static LR in the car you are putting more preload (or wedge) in the RF and LR compared to the LF and RR. Now when you are on the bars you have increased the wedge effect with the LR bars but you still have less preload on the LF and RR than before which should tighten the car some off the corner.

rpm20,
With a zlink you can use the bars to load the rearend just like a 4link. More angle in the rear bar will load the RR more on exit looseng the car up. Teh adjustments for 4link or z link are pretty much the same except that the top bar adjustments are backwards, move the 4 link up for traction whereas move the top z link down for traction. In general use the bottom bars for entry and top bars for exit whether for z link or 4 link.

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