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Author Topic:   4 bar converted to Z link RR
Umpmod18
Member
posted April 16, 2003 11:32 AM
All we are concidering taking our dirtworks four bar and putting a z link on the RR. however before we do this would like some input from our friends on the dirt forum for their expert advise in regards to pros,cons, how long should rear bar be, what angle of bar, what changing of angle does to handling of car ect. Please help!!!!!!


bengee6
Member
posted April 16, 2003 03:05 PM
The guys around here love 'em. Out last year track champ has been running it and says on a slick track its the only way to go. I've been told it does make the cars a bit tight on a tacky track tho.


MD
Member
posted April 16, 2003 10:21 PM
You will want to set the length depending on how much roll steer you want. I would make the angle of the rear bar adjustable. If you want roll steer, equal lengths, increase angle gives you more roll steer and increases RR load. If you don't, 2 inches longer seems average, with a little angle.


Dustejr73
Member
posted April 17, 2003 01:08 PM
I didn't think that was detailed, but point taken. I do run on at times.


dirtracer14
Member
posted April 17, 2003 11:46 PM
I will remember that lol he he


Umpmod18
Member
posted April 18, 2003 08:35 AM
Oh come on Dust, MD was just using this board for what it was meant for, racers helping racers. Hey I see you guys are in Oregon I raced at Lebanon Speedway for ol Clair Arnold back in the good ol high scool days.
Anyway,we have installed the Zlink bracket this week and if we don't get rained out we'll give it a try. MD we did make the bracket adjustable and the way I am understanding your comments is the longer the link is compared to your lower link the less roll steer you will have, however you can increase roll by raising the upper link correct? I do appricate all comments positive or negative come on guys almost 200 views and only 6 replys I know more of you have some thoughts on this!!!

[This message has been edited by Umpmod18 (edited April 18, 2003).]

devil wrench
Member
posted April 18, 2003 10:55 AM
One of the biggest assets of this type of setup is when the track gets rough. Due to the decreased roll steer of the RR tire, when the car hits a rut with this setup, it won't try to dance all around like a 4 bar will do in the same situation.

One adjustment we did have to make was to change the RS mount for the lower link. The old mount for the 4 bar only had 3 holes. We got new brackets from A&A with six holes allowing us to raise the rod up more.

We made the rear link the same length as the front(so we could just flip it over to make a Z link), but I'm adapting that mount to be a bolt-in, so I can try some longer links. Rayburn's rear links on his LMs are 30". We'll see how that works.

WPP
Member
posted April 18, 2003 01:47 PM
I run the rayburn bar on the rr with a 12 swingarm 4 bar lr with the spring behind the lower bar on the 4-bar is 12 inches and the upper bar is 15 inches but i have ran the car twice during the day light hours at pratice and really like it easy to drive and it really seems good i can not wait to run it at night


Dustejr73
Member
posted April 18, 2003 02:12 PM
The only way to eliminate roll steer entirely is to run equal lengths and equal angles. If you put down angle in the back, you gain roll oversteer. Most manufacturers use a longer bar in the back with some angle. The longer bar reacts slower decreasing roll steer. There is a time for and not for roll steer. Driver preference is the key I think.


devil wrench
Member
posted April 19, 2003 11:25 AM
I agree...but you also have to take into account the fact that the drive forces created by the angles of the suspension links are usually MUCH more imortant to the handling than the amount of roll steer. Too many people get caught up in adjusting roll steer to fix an ill-handling car instead of balancing drive forces. This is why so many people have trouble with 4-link & Z-link type suspensions.


washeduptoo
Member
posted April 20, 2003 11:37 PM
Devil Wrench, when you say balancing driving forces, could you explain alittle what you are talking about? It would be very helpful because we have an ill-handling 4-link lr and a z-link rr. Car is very tight on tacky, but has alot of bit, drives ok on dry slick with hardly any bite. We have done what chasis builder has suggested, but so far hasn't helped alot. Thanks


devil wrench
Member
posted April 21, 2003 12:03 PM
First, we need to define "bite". You're talking about the track (not the car) having bite, correct?

Let's focus on the tacky, because you seem to be alright on the slick. First thing I need to know is where the car begins to push. On corner entry, or when the driver starts to get back into the throttle?

If it's just a throttle push, try more angle in the links on the RS. If you have no more adjustment in the car, make more. Add on to the link mounts so you can get more angle in the links. There's no Black Magic in a racecar; it's just a pile of pipe.

What you want to do is get more drive force on the RR tire, thus driving the car around the corner. Too many people will take force away from the LR instead of adding it to the RR. Catch my drift?

Think of your car as a shopping cart...as you stand behind it, your hands are drive force. If you push harder with your left hand than your right hand, what will the cart do? It wants to go to the right. Now, there are two adjustments that you could make to make the car turn left. You could:
A. Lighten the pressure in your left hand only, or
B. Keep the same pressure on your left hand, but put more pressure on your right hand.
Which one is going to get you around the corner faster?

I can be pretty hard to understand sometimes, let me know if you need it explained a different way.

washeduptoo
Member
posted April 21, 2003 10:22 PM
Devil Wrench, thanks for the info, I thought you did a good job explaining. The car pushes when you get on the throttle after entering turn on a tacky track. We are running rr with no indexing on birdcage and bottom link has about a 5 degree uphill. The link that goes to the back has no angle and it appears that it can't be adjusted unless you index birdcage.
Also when track is dry slick it handles ok at the start, but the longer you go the more throttle push you get, so that at the end of the race the push is about as bad as it is when its tacky. We have the j-bar about level and we have moved it around some trying to improve.
The chassis builder has us trying to get x-wt % and left side wt % the same. We are having to order some different off-set wheels to achieve this. If you can help us with anymore info it would be great. Thanks.


MD
Member
posted April 21, 2003 11:09 PM
I agree with Devil Wrench in regard to lateraly adjusting axle thrust. Add an adjustable mount to the RR and increase down angle in the upper rod. Sounds like what you need.


hm
Member
posted April 22, 2003 07:46 AM
DW is correct that you are using the LR too much if you have a throttle push. I personally wouldn't bother with adding mounts to the RR, I would just adjust the bars on the LR. On a tacky track the goal is not to put all the bite in the car as you possibly can, the bite is already there in the track, and there is only so much bite to be had. By decreasing LR bite you will increase RR bite and eliminate some or all of the throttle push. I'm not saying DW isn't right, its just not the adjustment I would make.
The same theory is true with springs (I know kinda off the subject....but so was the shopping cart, lol) Weight will transfer to the stiffer spring, so in theory a guy should be able to throw 300-400 pd springs under the rear and get a ton of bite, obviously it doesn't work that way that is why you have to adjust bite by what is available, its not ifinite.
Also your throttle push may be the track changing (there are a lot of factors it could be) but if your track takes rubber as the race goes along it maybe adding bite to the surface and your push is coming from the track itself. Dry/Slick has a tendancy to take rubber pretty quick.


devil wrench
Member
posted April 22, 2003 07:41 PM
hm...you're mostly right. When weight transfers to a pair of springs, it is distributed proportionally between those receiving springs as dictated by the ratio of their respective rates. BUT, the rates of those springs, in general, dictates the amount of weight that is transferred. If you put two 400# springs in the rear, only half of the weight is transferred that would be transferred with a pair of 200# springs. THAT is why excessively stiff springs don't work in the rear.

Also, I was talking about link angles, not springs. With link angles, and the use of the weight of the car and its acceleration, you can create more downward force on the tire patch than just the weight of the car being transferred.

washeduptoo
Member
posted April 22, 2003 10:12 PM
Thanks guys for the info, as we surely can use it. We've got the car pretty much like the chassis builder wanted, with x-wt and left side wt % almost equal. Before, we had the lf almost 100# heavier than rf with lr 140# heavier than rr. Might have been some of the problem, I don't how it got that far off. What springs wts. do you guys run. We have lf 750, rf 850, lr 175, rr 250 with 4-link top link 15% uphill, lower link 5% down hill as chassis builder has suggested. Does this sound about right to you guys. Again I want to thank yall for the info as this is our first time with 4-link, z-link, we had been running a swing arm car. Thanks.


Pa FastBoys
unregistered
posted April 23, 2003 06:08 PM           
Try (2) 800 in the front and (2) 200 in the back. Dropping your RR forward bar will tighten you up getting in the corner and not let the car roll in the corner. Also try 55 pounds in the LR. To loosen the car up drop your LR top bar down 1 hole on a heavey track and raise it for the slick. Remember you have to get up on the bars to get forward bite!!! Have fun.


devil wrench
Member
posted April 23, 2003 06:46 PM
Rocky....where are you guys racin now? And what happened at PPMS? Email devilwrench32@hotmail.com


Wauge28
Member
posted April 24, 2003 11:46 PM
MD and Dusty...keep going guys. I just got a re-fill on my pen to take more notes


Dustejr73
Member
posted April 25, 2003 07:38 AM
Why do you need a pen, we pit right next to ya? I always told you I would give you my honest opinion for what it's worth, or nothing at all. Of course the times when you don't need to ask is when I'd like to give you some advise. Try water in your tires, should carry more momentum and get you into the corner deeper. HEHE.

[This message has been edited by MD (edited April 25, 2003).]

Wauge28
Member
posted April 27, 2003 02:26 PM
LOL, I will try the water thing...See ya Sat.


MD
Member
posted April 28, 2003 01:16 AM
Another win saturday for Wauge28. I think it's time for me to get out the pen and paper. Or did the water thing work,LOL. Good job, sounds like it was a rough one to get through.


Wauge28
Member
posted April 28, 2003 05:55 PM
Thanks Matt! I suggest the water trick to everyone out there


dirtmod#2
Member
posted May 11, 2003 02:05 PM
hi guys any thoughts on how this setup works on different tracks from tacky to dry slick

any in would be nice

washeduptoo
Member
posted May 11, 2003 11:00 PM
Well guys, it appears they have gotten the corner entry tightness out of the car. It appears the 70lbs of weight on the rr was causing this problem, took it off before races and it worked better. The throttle push went away after getting car scaled and making adjustments. But the new problem is no side bite, has good forward bite on tacky or dry slick. Any suggestions guys? Thinking of going to a heavier spring on the lr, maybe 200-250, think it would help or should we stick with moving links up or down. Thanks.


devil wrench
Member
posted May 12, 2003 08:06 AM
Play with the panhard bar first.


washeduptoo
Member
posted May 12, 2003 09:25 PM
I forgot to mention, they moved the J-bar up about 1 inch on the chasis to give it more upward angle between the heat race and the feature and it was about the same with side bite, but track had changed from the heat race, so maybe he needed more angle. Do yall move both ends of the j-bar up? Thanks Devil Wrench for your help.


devil wrench
Member
posted May 13, 2003 03:53 AM
Can you drop it any farther on the pinion?


Wauge28
Member
posted May 14, 2003 03:36 PM
Drop it on both ends and flatten it out. I know, most people say that the angle will press down the rearend and make side bite but think of this. If the bar is angled, doesn't it act like a kickstand on a bike? When it is flat it lets the body roll much easier and that body roll will cause side bite. Lower it too much at first. Feel the effect then raise it from there. Too low will keep the car rolled over too long and forward bite will suffer. Mine is almost flat and level with the bottom of the housing at both ends.


devil wrench
Member
posted May 14, 2003 05:45 PM
Wauge...I thought you were a leaf man?


MD
Member
posted May 15, 2003 01:36 AM
Wauge's a link man now days and he's right about the adjustment. Lowering the roll center will tighten you up on entry and apex. You raised it. To much angle can make your suspension basicly ridgid as you "ride on the bar". Not very drivable.


Racer17V
Member
posted May 15, 2003 10:54 AM
Wauge28- what are the handling characteristics of too much angle on the panhard bar? Too low is too much side and no forward bite, right? What's too much angle do? Thx.


Umpmod18
Member
posted May 19, 2003 12:02 PM
I would like to thank all of ya for all the questions and replys on this subject. We have switched our car over to the Zlink RR and the car has been much more consistant and easier to drive with incredible forward bite. We have raced it 3 times since converting it and we have collected our first 2 feature wins of the year. You guys are GREAT!!!!!


racinrich66
Member
posted May 19, 2003 01:05 PM
Guys Id like to thank yall too. He's making it harder on me to catch him in the point standings..


washeduptoo
Member
posted June 02, 2003 06:17 PM
First I want to thank yall for all the info on 4-link, z-link. We've had some success with a 2nd and a 3rd and several other top fives, but we've also had some out of the top five. We would like to improve. Is it the nature of a 4-link, z-link car to be stiff? By this I mean, it doesn't appear to have as much chassis roll as our swing arm car did. Could be the springs or shocks causing this? LF 750, RF 850, LR175, RR 250.
The shocks are Bilsteins LF 7330,RF 7330,LR 9330, RR 9330. We've tried several different shocks without any major change. We have tried a 300 spring of RR, but driver didn't like it much and didn't help car. You know when you are warming your tires up prior to start of the race, you whip car back and forth and most cars body rolls with car, but this one doesn't. Is this a concern? Any help would help. Again thank yall.


Wauge28
Member
posted June 02, 2003 06:49 PM
Devil, I was and then tried to outthink myself and try this bar stuff. I have struggled for a little over 2 years now and really miss the mono leafs.

17v, MD said it above. I see it as too much angle as holding the car up too much (like the kickstand) When you run a short panard and even a j-bar, it is too easy to get the car up on the bar and at that point...right to the wall. More angle is OK on a flat smooth track but avoid it on the bumps. the car will fly up and get on the bar and won't come down until you get out of the gas; hince, throttle push.

Too low? Well, I have mine pretty low and keep going even lower. I love the way the car feels when it rolls over and grunts through the turns. I guess it is too low when everyone is leaving you coming off. It takes too long for the car to roll back over on the LR and you end up cooking the RR.

Keep playing with it. I think the J-bar/panard bar is the biggest adjustment there is on a car as the track changes (just my opionion).

washeduptoo
Member
posted June 02, 2003 09:16 PM
Are you guys running a panhard bar or a j-bar. We are running a j-bar and I don't think we can get it any lower on the pinion and if we lower it on the chasis it would be down hill, is that ok? Thanks, If we were to go to a short panhard bar to the left, what can we expect in handling changes?


devil wrench
Member
posted June 02, 2003 09:39 PM
Interesting turn of events this week...went to a different track with a buddy of mine. Big 1/2, smooth as a mirror. Seriously...you could see the reflection of the cars in the dirt! I really think I learned a lot here. He was running a straight shorty, now here is the strange part to me... the pinion side was about 2 inches above the pinion shaft with maybe 3-4 inches of angle in the bar. Kind questioned it at first...but the performance speaks for itself. Half lap lead to win the heat from an 8th starting spot. Started the feature 9th. Leading on 3rd lap running away from the field. The car looked absolutely perfect.


washeduptoo
Member
posted June 02, 2003 10:04 PM
Devil Wrench, was the bar running downhill or uphill on the car?


Racer17V
Member
posted June 02, 2003 10:25 PM
Wauge28- I follow your post, but when you say you have yours pretty low, do you mean little angle or low on the pinion? Or both? Thanks.

Devil- What surprised you? The fact he was up on the pinion side or that he had only 3 or 4 inches of angle? Trying to understand what was against the rational thinking here, thanks.

Wauge28
Member
posted June 02, 2003 11:27 PM
I think devil was surprised how high the bar was mounted. My guess was that the car was extremely top heavy. He probelby got a ton of body roll without lowering his panard bar.

The best side bite I have ever had was on a mono leaf car with no panard bar at all. If you think about it, the mono leaf is like having your panard bar mounted at the bottom of the axle tubes on both sides. Does that make sense??? Where the leaf mounts to the tubes it what controls your roll center. If you use lowering blocks, you can adjust your roll center just as if you were moving the panard to raise and lower your roll cener. I am sure you already know, that is what we are doing when lowering the entire bar. If you move just one end, lets say the end on the axle tube, you have to lower it twice as far to effect roll center as much as if you lowered both ends at the same time.

My preference...again, this is what I do...I leave my bar with a 2 in. downward rake. I rarely if ever change the angle. If the track is dry slick and smooth, I run the bar on the bottom of the axle tube on the RR and 2 inches higher on the left side of the chassis. If the track is heavy and smooth, I raise it about 2 inches on both sides. Anything in between gets adjusted in between those two points.

Now, with that said, chances are we not running the same chassis. Our fuel cells are probebly not in the same place and many mnay other factors will change how much roll you will have in your car. Like I said before, start with the bar too low and work your way up. You will find the sweet spot much faster than starting too high.

Man I hope that makes sense...

washeduptoo
Member
posted June 03, 2003 10:25 AM
Wauge28, by reading your post I take it that you run a long panhard bar. Are you running a 4-link on the left or are you running a straight swingarm left or z-link left. We are running a 4-link left with spring behind axle tube and don't know if there is enough room back there to run a long panhard bar. With the swingarm car we had we had the long panhard bar and adjusted just like you posted. With this new setup we are having problems getting it to roll. It maybe time to go back to swingarm setup. Thanks.


Wauge28
Member
posted June 03, 2003 10:40 AM
If you have loked at other post form my "friends"... they make fun of my 4 bar car. I hated it. I should have switched tot he Z link/Z link long ago. The 4 bar car (FOR ME) was never the same car. No matter what I did to it, it felt like someone elses car I had jumped into for the first time. The only bar I could ever make work even a little was the J bar. I had mine on the bottom pinion hole and about the same incline.

Assuming you are running a pull bar, try taking some angle out of it. Again, go too fla to start. What happens is when it is too steep, the car locks up and losses its suspension and won't roll, bounce or even move. When going slow, jump on the gas. If the back end jumps up, you have to much angle. If the car jumps forward and more flat, it is good. I had mine so steep at one point, if I got on the gas har in the parking lot, the underslung would hit the housing and the wheels would come off the ground.

washeduptoo
Member
posted June 05, 2003 08:55 PM
We are going to decrease the pull bar angle this weekend to see what it does to the car. Thanks, and I'll let you know what it does to the car.


washeduptoo
Member
posted June 09, 2003 10:31 PM
Well, we decreased the angle of the pullbar and the car had more roll. We were moving up in the feature and we spun out, finished next to last. Driver said car was too tight coming off. Any suggestions? This chasis sure takes alot of trail and error adjusting, but were learning. Thanks again for the info.