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Author Topic:   Z-Link Question
msnead
Dirt Forum Racer

Total posts: 77
posted July 01, 2005 08:17 AM  
DW9, 4LR/ZRR...

I know that changing the top bar on the RR can be used to make minor handling adjustments. (The bar that goes to the back of the car.) First off, what does moving this bar up or down do? In what situation should I move it?

Secondly, I had the car set up by a local chassis builder to DW's specs. (He did some other things to it, also.) Everything seems to be in order as far as the percentages go... The problem is that the top bar that goes towards the back of the chassis on the right side is touching the bottom bar--which means that the only adjustment that I could ever make to this bar would be to move it up. Does this seem normal?

Any help would be appreciated...

Thanks,

m

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 01, 2005 08:52 AM  
So it has alot of angle in it, pointing down towards the ground, from the birdcage ?

I cant picture what this bar would be that its hitting thou, that sounds like it could be an issue.

Moving it down usually provides some roll steer sooner, so moving it will take some out. Which should tighten the car up, in and off.

dirtmod0
Dirt Maniac

Total posts: 143
posted July 01, 2005 08:55 AM  
are u running brake floaters not understanding what ur saying top bar is hitting the lower bar? when u lower the top bar down it creates more rear steer when u raise it takes away rear steer.
raising it will tighten coming off and lowering will free u up thru the corner.
actually the top bars create more of a driving change than the lower bars.

[This message has been edited by dirtmod0 (edited July 01, 2005).]

msnead
Dirt Forum Racer

Total posts: 77
posted July 01, 2005 09:25 AM  
I guess I should have done a better job explaining myself...

In the back of the chassis, there is 1-1/2" steel tubing that makes up the "framework" of the rear of the car. Attached to this framework is the fuel cell, battery bracket, etc.

The Z-Link mount is attached to one of the vertical pieces of steel tubing on the right side of the chassis. (The Z-Link bar is attached to a bracket that clamps onto the steel tubing.)

On the top and bottom of this steel tubing, there are pieces of tubing running horizontal back across to the other side of the chassis. The Z-Link bracket is all the way at the bottom of the vertical tubing so that it is touching the piece of tubing that is going across.

Sorry to over-complicate things...I'm trying my best to use the term "bar" to refer to the bars of the rear suspension and steel tubing to refer to the chassis.

Anyway, the Z-link clamp bracket is all the way to the bottom of the tubing that it is attached to so it cannot go down any further.

Thanks for your help.

PS-If you go to the DW Tech Page you can see the bar I'm referring to...
http://www.dirtworksracecars.com/printtech.html

msnead
Dirt Forum Racer

Total posts: 77
posted July 01, 2005 09:31 AM  
One more thing...

The z-link bar appears to be angled down toward the rear of the car. The angle doesn't appear to be too excessive. Should it be level?

Another question: DW shows a 4-bar baseline setup and a z-link swingarm baseline setup... They don't show a standard z-link baseline...is it the same as the 4-bar setup? Is it really simple to convert the z-link to 4-bar? (I know you turn the bar around--but does the rear end move when you do that?)

Thanks,

M

dogwalker
Dirt Full Roller

Total posts: 65
posted July 01, 2005 09:40 AM  
With the bracket moved all the way down to the intersecting chassis tube, how much angle do you have in the top bar? You probably don't need much if it's dry.

If you wanted, you could also put in a shorty bracket for the rear to allow for a little more room and angle, but the reaction would be a little quicker.

Usually I'll start with a little angle in the top rear facing bar early and move it to flat on dry.

[This message has been edited by dogwalker (edited July 01, 2005).]

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 01, 2005 09:53 AM  
Everything sounds fine with the rear suspension. Dont worry about that angle it sounds ok, just remember that if its loose off flatten it out. Level the bar at ride height, but for now leave it.

Your running a Z-Link with the coil on the housing then, some run the coil on the birdcage (bolted to it), on an eliminator, and some like me run a swing arm for the front link and the coil connected to the arm via and elimintor.

You should have about a 175 to 200lb spring on the RR, and about a 200 to 225 on the LR. Then some straight 3 or 4 valved shocks across the rear. The LR should be spring behind on an eliminator, and the shock in front. Then the shock on the RR should be behind the axle housing on the birdcage.

Everyhting sounds ok, what front & rear springs, and shocks you running and whats your %'s at?

[This message has been edited by Kromulous (edited July 01, 2005).]

msnead
Dirt Forum Racer

Total posts: 77
posted July 01, 2005 10:09 AM  
As I've said in other posts...I will get all of our setup information and post it soon. The "thrashing" until 2:30 a.m. this morning to get the car ready for our first race has taken the priority. (Actually, I worked on it on Wednesday night until 1:00 a.m., too.)

The rules difference between IMCA and our track are why I've had to change so much. We run a 2-barrel carb. on gas which meant that I had to change the carb., fuel pump and radiator. I also had to install a Battery Shut-Off switch to satisfy the track's safety requirements.

I don't know the angles, spring rates and percentages, but I do know that the LR has a slider mounted on the front of the BC (I think) and the RR has the spring/weight jack on top of the housing with the shock mounted on the back. Does this sound right? (I'm trying to picture it from memory--I could have it backwards.)

The guy that did the setup said that everything was right where it should be according to the DW beggining setup... The only number that I know from the setup is that we are running 31 lbs. of LR Bite and DW recommends 30 lbs.

Luckily, the only "problem" we had with the car was that the rear end was not square in the car. Once that was fixed, everything fell into place. We will see what happens when we hit the track.

Thanks for your help...

M

[This message has been edited by msnead (edited July 01, 2005).]

msnead
Dirt Forum Racer

Total posts: 77
posted July 04, 2005 09:41 AM  
I'm running out the door so I'll be brief:

LF: 502
RF: 424
LR: 690
RR: 659

LS: 52.4%
REAR:59.2%
X: 48.9%
LR BITE: 31 lbs.

New driver, wet track--hit the wall in practice (car pushed bad on a soupy track). Only had time to change 2 tires before the feature (j-bar bracket on frame and pinion both bent, tie rod bent, lower ball joint bent...)

In the feature the car felt good to the driver despite the bent stuff... I just need to know how to make the car turn when it's wet. (Rear brake didn't help...)

I'm going to record the spring rates and bar angles on here this week.

Thanks,

M

WPP
Dirt Freak

Total posts: 451
posted July 04, 2005 12:10 PM  
Take angle out of the left upper bar add all the angle to the right rear upper bar

msnead
Dirt Forum Racer

Total posts: 77
posted July 04, 2005 07:48 PM  
Now that I have a little more time to write...

The upper bar on the right side (the "Z" bar) is level at ride height. As I said before, there is no room to adjust it down because it is all the way to the bottom of the bar that it is mounted on. When you say add angle, do you mean angle it up from the rear end to the back of the car?

I bought an angle finder today so I will be able to give you all the setup specifics as soon as I can get over to write them down.

We are off next week so I'm planning on putting it on the scales once I fix all of the damage. (In addition to the other stuff, we trashed 2 brand new wheels. One of them was another driver's fault... I feel good about that.)

On a positive not, the car looked good in traffic and our driver got the hang of the car despite having too tall of a gear. (The proper gear will not be in until this Thursday.) I know there are arguments about the benefits of this...but we even lifted the left front off of the ground coming out of the turns. That's pretty impressive since a bunch of stuff was bent and we are on a fast 1/2 mile momentum track.

Thanks for the advice...

m

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 05, 2005 07:31 AM  
If the track is always really heavy like you described, your gonna need some rear steer. Moving that RR upper bar down will help some (add down-ward angle to it).

Also, you can run more stagger to help it out or off the corner. Maybe adding about .5 to 1" until the tracks becomes more smooth, and cleaned off.

You sound pretty close, and it sounds like things went pretty decent for your first time out. Now you just need to make some smaller type changes, to get the car inline with what the track is giving you.


msnead
Dirt Forum Racer

Total posts: 77
posted July 05, 2005 10:48 AM  
This is the confusing part to me. Right now, the RR Upper Bar (the "z" bar that goes to the back of the chassis) is level at ride height and as far down on it's mount as it can possibly go. How can I move it down any further?

I can move it up on the chassis side so that there is a downward angle from the chassis to the rear. Is this what you mean?

I guess I could take some pictures since I'm not explaining myself very well.

On the 4-bar car I was helping with, we would move the RR lower bar up and down 1 hole to create more rear steer...we'd add rear steer for when the track is heavy and take it away for the features when it slicks off.

Thanks for the help!

m

WPP
Dirt Freak

Total posts: 451
posted July 05, 2005 06:57 PM  
SO you have your upper bar all the way down on the right rear and it is still level right Look at it this way from your bc the rear bar needs to go down hill change your mounts on the rear i can go to 15 degrees on my rr bar down hill from the bc in the lower hole and top hole is level with mine

autoshop
Dirt Freak

Total posts: 298
posted July 06, 2005 08:13 AM  
WPP is correct, I would make two more holes in the birdcage if there is room to get more angle in the bars.

msnead
Dirt Forum Racer

Total posts: 77
posted July 06, 2005 08:29 AM  
I will look to see if it is possible to add holes. (They may already be there--I've never looked.)

Assuming that I do have the adjustability, when do I move from level to the lower holes on the BC?

Will moving to the lower holes on the BC add rear-steer to the car? (If not, then what will it do?)

Will moving the bottom right bar up or down add/remove reer steer? (It does on the 4-bar car.) I'm trying to come up with a better qualifying setup when the track is wet.

Thanks,

m

washeduptoo
Dirt Maniac

Total posts: 155
posted July 06, 2005 09:39 AM  
I'm not too good at explaining things, but with our 4-z, from the top of the bc, your rearward running link should angle down to the chassis. I believe if you can't drop down on your chassis anymore, you might have to redesign your bracket to get more drop or your bc. You would have to put holes on your bc above existing one to get your negative angle to the chassis. On ours you increase negative angle and it increases roll steer and lessen angle has increased side bite. There are alot answers in the archieves on z-link if you do a search. I've picked up alot by looking there. Hopes this helps.

msnead
Dirt Forum Racer

Total posts: 77
posted July 06, 2005 09:49 AM  
I realized after I posted that if I put holes below the existing ones in the BC that the bar would be angled upward, not downward.

The car is a DW9 with a standard looking z-link sliding clamp bracket mounted to a piece of steel tubing.

Is it normal to not be able to angle the bar downward towards the chassis on the DW9? (Could the BC be smaller or is there something else that could cause this?)

Thanks for the posts!

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 07, 2005 07:06 AM  
Double check your ride heights, it could be to high and causing this issue.

Also what kind of birdcages are you running?

A pic is worth a thousand words, post one if you can.

msnead
Dirt Forum Racer

Total posts: 77
posted July 07, 2005 08:13 AM  

 
Due to other obligations, I will not be able to work on the car until Saturday morning at the earliest. (It feels strange that I haven't even seen our car since it left the track on Saturday night.) I will try to take a picture of it then.

To get us through, I sketched a drawing of it... Attached is a drawing that shows the setup of our rear. (This is for illustration purposes only...I don't know the actual angles or sizes of the bars.)

This drawing is showing the position of the rear bar at ride height. Notice how the rear bar is level, and mounted to the bottom of the tubing that it mounts to? In this case, how can I add downward angle to the bar? (By downward, I mean...how can it go from the bird cage downward to the back of the chassis?) That is why I was asking about the angle...if it needs to go down from the bird cage, it is impossible.

The ride heights were set to DW's recommended setup. (I don't have them in front of me but it doesn't appear to be too high.)

Let me know if you need any more information...

Thanks,

M

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 07, 2005 08:51 AM  
Anyone run one of these DW9's? you got any insight to this problem?

I cant imagine them designing a Z-Link with no room for adjustments to get downward angle in the rear bar. Sounds like something i would do, LOL.


48modracer
Dirt Roller

Total posts: 12
posted July 07, 2005 11:24 AM  
My friends DW had that bar extended on the right side to get more angle on the rear trailing arm. You can do that or go ahead and weld a bolt on bracket there and be done with the DW slider mount.

msnead
Dirt Forum Racer

Total posts: 77
posted July 07, 2005 11:52 AM  
So, I'm not crazy! (I'm sure that is up for debate.) I'm going to have the car over at my chassis guy's shop soon anyway--I'll see what we can do to remedy the situation with the J-Bar mount. (Normally I'd take it back to the chassis builder but I live way too far from DW...I'm on the east coast.)

Ok, now that we've settled that... I have 2 more questions:

1. We bent 2 wheels and destroyed a 3rd. I'm getting ready to buy wheels (again). What offsets should we run?

DW says: LF: 4" BS, RF: 3" BS, LR: 3" BS
RR: 4" BS

I was having trouble with the RR rubbing the spring during qualifying so I changed from a 4" BS to a 3" BS wheel on the RR and that also seemed to free the car up a little.

What should I do for next week's race? (We are having the "big boys" on ESPN2 next weekend so I suspect the track will be dry-slick by the time we run.)

My personal preference would be to buy all the same wheels (3" BS) and then change the offset on a particular corner to help correct handling problems as needed. Does anyone see a problem with doing that? I was also told that these DirtWorks cars require the different offsets on different corners but nobody could tell me why.

2. Since I have no way of moving the RR top bar down on the frame side, what other ways can I compensate for the car being too tight? My thinking was that we needed some more rear-steer but I want your opinion. If you throw out a bunch of ideas, tell me which I should try first, second and so on. I want to make 1 change at a time so we can tell what the change is doing.

Thanks

Kromulous
Dirt Forum Champ
Total posts: 796
posted July 07, 2005 12:15 PM  
In my opinion, those DW wheel offsets are going to make the car tighter in and a little looser off. I always regard wheel offsets as a double change, what i mean is, if you move one in or out 1" it will effect the car in 2 ways, usually one is going in the corner and the 2nd coming out.

Putting the 3" on the RR confirms that, freed the car up in, which is good, because it tightened it out, or up off the corner.

Personnally i buy all 4" offsets, and use a wheel spacer to create a 3", by putting the 1" spacer on a 4" wheel. Its just to exspensive to have 40 wheels with good tires and all the different offsets. Plus if you cant get enough of an affect that your looking for with a 1" wheel change, you need to make bigger changes anyway, bars or wedge or something.

If you bought all 3" wheels, and had a few 4" to use here and there i think that would be good. Maybe start out, on a tacky track, with these offsets, and your base set up from last week.

RF = 4"
RR = 3"
LF = 3"
LR = 4"

Last week you said it had a bad throttle push, this should help. Also make sure the drivers knows that when the track is major tacky, he has to rotate the car in the middle, via brake or throttle it dont matter, just get it rotated before you want to head down the straight.

Other than that, your LR bars will be where i would look. If it still has trouble turning, raise the LR lower bar up one. After that, or when the track slicks off raise the top one hole (more fwd bite), and maybe even the RR fwd bar. But be leary of that top bar, dont raise it if the track is very rough, because it makes the car act stiff.

Your getting there, soon you'll have a good base set up and really be able to get in to tuning it for better & faster lap times.

What track do you run on anyway?

msnead
Dirt Forum Racer

Total posts: 77
posted July 07, 2005 12:37 PM  
As far as the push goes...here is what happened: The track was slick and had barely 1 groove. When he went in the turn a little hot, the car began to push up the track into the really wet stuff. He tried to gas it to get the rear end to come around and that didn't work--instead, he kissed the wall with the right side. (Bent the RF/RR wheels, lower ball joint, tie rod, j-bar mount on the frame and pinion...that is all that I could see without putting the car up in the air.) Keep in mind that the gear that wins at this track is a 5.29 and we were running a borrowed 5.00 just so we could race. (The car came with a 5.67.) Would the lack of gear prevent it from being able to spin the wheels to break the back end loose?

In the race (with the bent stuff), he said that even if he stabbed the brakes, the rear didn't seem to want to come around. For practice, the brake bias was set all the way to the rear--I'm not sure if he changed it for the feature or not. I guess our problem is that the car didn't seem to want to rotate in the middle with a wet track and it was still a little "pushy" with a good tacky track.

My idea was to add some rear-steer to kick the back in around a little on entry...and then he could drive it off once it was pointed in the right direction.

We race on a 1/2 mile egg-shaped track in Virginia. (http://www.vamotorspeedway.com) It was purchased a few years back by the Sawyer family--the family that owned Richmond International Raceway (the NASCAR track). They have sunk a lot of money into this track...new stands, sky boxes, lights, electronic timing and scoring, etc. As far as I know, they are the only dirt track in Virginia to race Modifieds.

viper3244
Dirt Full Roller

Total posts: 57
posted July 07, 2005 09:07 PM  
Something sounds weird for sure. What do you see on your brake gauges when you have all rear brake cranked in? If your running a Willwood set up make sure you have enough space in between the master cylinder brackets and the pedal on the adjuster. The adjuster rod should pivot back and forth. If the bracket are to close to the pedal it will NOT pivot enough, so even though you have all rear brake cranked in when he jabs the brake you have even byass which will push the car straight the direction it is headed. I remember chasing a nasty push for several weeks till we checked brake temps with a pyrometer. If you have all rear brake and the car is sideways just a tiny bit it should tail out. As far as the z-link we run a dw8 and I always try to keep the same angle in both bars I have been all over the range of angles this is my take of what happens. 0 degrees on both bars (with birdcage indexed to zero wil hold RR limit the forward or back movement. Now if you put more angle it will allow it to move forward or back. So think about it if you have alot of down angle in the back it should allow it to come back. If you had alot of angle in the front it can come forward. IE Roll understeer or roll over steer. I usually run ours second hole up on the frame use the bottom bar to square the rear end, set the same angle in the rear facing bar and adjust just that bar to index the birdcage to zero. We float the spring on the birdcage (RR spring in front). The opions very and there are some knowledgable people on here keep trying. Another thing to remember, most all rookies will complain about a push, seat time is sometimes the best adjustment. good luck

msnead
Dirt Forum Racer

Total posts: 77
posted July 08, 2005 06:53 AM  
We don't have the gauges in our car--how hard are they to install? (I may do that for next season.)

I'm new to this, but looking at the top of the master cylinders...when we crank the brake bias adjuster, it doesn't appear to change the angle between the front and rear master cylinders by a lot. I assumed that was normal since this was the way it was run before--but I don't really know. I think the car came with documentation on the master cylinders/brake bias adjuster but I'm not sure. I'll see if I can find it...

Given the fact that the driver drove deep into the turn and then stabbed the brakes, you would assume that locking the rear wheels and centrifugal force would cause the back end to come around...that didn't happen.

I'll check the adjuster/bracket to make sure that everything is ok.

Thanks!

m

seabiscuit
Dirt Roller

Total posts: 15
posted July 10, 2005 08:17 AM  
As far as I know the Z link frame bracket is a problem with all dw9 cars. Apparently they didn't intend for you to run any downward angle in the bar. I added my own zlink frame bracket to my old dw8 and had plenty of adjustment but when I got my dw9 and started to set it up I noticed that I was not going to have near the adjustment that I had before. You'll need to cut that bracket off and weld on a longer piece of tubing or adjust rear steer someplace else.

seabiscuit
Dirt Roller

Total posts: 15
posted July 10, 2005 08:18 AM  
As far as I know the Z link frame bracket is a problem with all dw9 cars. Apparently they didn't intend for you to run any downward angle in the bar. I added my own zlink frame bracket to my old dw8 and had plenty of adjustment but when I got my dw9 and started to set it up I noticed that I was not going to have near the adjustment that I had before. You'll need to cut that bracket off and weld on a longer piece of tubing or adjust rear steer someplace else.

msnead
Dirt Forum Racer

Total posts: 77
posted July 10, 2005 11:39 AM  
I spoke with DW yesterday and the guy told me that my car must not be at the proper ride height in the rear because I should be able to get 10* of downard angle if everything is right.

I'm hoping to get a chance to work on the car today or tomorrow evening so I will be able to get a better idea of what is going on.

Thanks for the input--worst case, I'll get my chassis guy to put a new bracket on.

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