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Author Topic:   4-z theory , correct or out to lunch
rpm20
Dirt Freak

Total posts: 338
posted May 02, 2005 11:14 AM  
so my mod has a push entering the corner and as i gas it then it gets loose and tight again with the worlds worst push,

heres what i think happens ,

i enter the corner ......get off the gas breifly.....the car angles in then pushes.......so then i gas it , the rear end comes up from rear steer , the crossweight goes up dramaticly from the rear steer, the rear tires break loose from too much throttle.....................boom major push up the track and wall is comin fast......
driver gets off the gas, car straightens out and driver again on the gas but now pointed out of the corner.....somewhat

is the push on the gas pedal , creating excess lr bite a huge contibutor to the problem??

i assume it is but would love for you all to take me to school on this please.

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 02, 2005 11:39 AM  
I think i read on here you were running the LR clamped in front. Well, i've never run it and seen and talked to those that have, and from what i see and hear they are just tight off period.

If you pick up the throttle to soon or to fast it pushes bad, so you gotta be really carefull coming out / off a corner. You just cant drop the hammer and expect it to turn, roll on the throttle.

Thats the reason for the DW cars running some RR bite, to reduce the effect of the LR clamped set up, i believe anyway.

Your core issue is the push in, you solve that and your tight off may start working to your advantage.

Do us a favor, post your entire set-up and weights, and tire pressures to get a better picture off what you got please.

rpm20
Dirt Freak

Total posts: 338
posted May 02, 2005 12:11 PM  
krom,
heres what i had whebn this happened

lf650 3030 rf 680 4545
lr220 on coilover with 4040 clamped up in front, short 4 bar on steel bc with lower plug 12"& 14"up
bottom hole bottom bar 9* upper bar middle hole 17*

rr170 on top roller brg bc 19" swingarm @5* up lower 3050 shock on bc front
and 20"upper z bar 5*up hill to rear

spring pullbar with 800 spring at 14* angle centered on rearend with 10/90 bilstein

19"j bar 1" below pinion and 5" higher on frame
3/4" rear stagger and 3/4" front stagger

57 rear,53.5 left,49 cross,77lb bite (with driver) 20 gal fuel 2500lb with driver

problems...j bar hit rear at full rear steer,
little body roll (1.5"), major push in, through on gas and off

changes made for next session, 600lf spring,
put 225 lr spring on slider behind bc and clamped 3030 shock in front (no mount)
raised j bar 1.5" on pinion side and lowered 1/2" on chassis side, added 1.25" stagger (2" now),
lowered cross to 47 with driver and no bite.

too far????? my thought was to get it to turn then tighten it up where i want it.

[This message has been edited by rpm20 (edited May 02, 2005).]

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 02, 2005 12:28 PM  
Put the top RR bar 5* down from the BC to the frame this will put more drive in the car under throttle, may need more than taht even. Also puts alittle rear steer in it so that it turns a llittle better.

You say the car angles in then pushes? Is it a push or a skate? Does the car slide up the track or you just cant get the front to turn? You might be transferring to much weigh to the right(too much sidebite) which maked the car tight, try putting more left% in or raising jbar.

How do you have the rear aligned? You might need to trail the RR a little bit. That will free it up a little bit on the gas. I would make sure you are not leading the RR any. I have never talked to anyone who could make it work by leading the RR. Typically trailing 1/4" up to 1" even if track was really tacky.

We had problems with ours clamped up always being tight. pretty much same setup as you have, except we only ran about 30#LR and a lot more rear%.

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 02, 2005 12:34 PM  
225 lb srping /slider, behind and shock clamped in front is going to be better, but i worry about it not having enough dampening when you get off the gas, going in. It may drop down hard. Anyway to float the shock off the birdcage?

Try to leave the stagger where it is for now, the 3/4". Change one thing at a time till you get a handle on it.

Your set up with the LR clamped in front doesnt look to bad, i think i would try it again with a few changes.

Add some stagger, maybe 1.5" or so.
Remove that 90/10 off the rear end.
and maybe trail the rear end abit, 1/2" or so.

All that should loosen it up enough, to get the car in, and turned but remind yourself to not hammer it coming out, roll on the throttle.



rpm20
Dirt Freak

Total posts: 338
posted May 02, 2005 12:51 PM  
i do have another roller bearing type bc i could use that does have a front mount for the shock. i wont put it on until after our play day tomorrow, what effect do you think it might have and do you think i need to put my cross back at 49 or will the 46% with no lr bite work as a starting point.
what will pulling the 10-90 do for me ??

Kromulous
Dirt Forum Champ
Total posts: 796
posted May 02, 2005 01:13 PM  
Removing the 90/10 will loosen it up in.

With the LR behind, you can run alot more LR bite, take the cross back up to about 49-50%.

hoganhomer
Dirt Full Roller

Total posts: 53
posted May 02, 2005 01:35 PM  
Could the second push condition (world's worst) be the car getting off the bars after the driver lifts due to being loose? I know last week I lost two positions because I let off the throttle to keep from nudging the guy in front of me and the car turned straight right. I realized what I did because the car hiked up again when I got going.

[This message has been edited by hoganhomer (edited May 02, 2005).]

rpm20
Dirt Freak

Total posts: 338
posted May 02, 2005 01:45 PM  
doesnt the suspension cause a ton of lr bite when throttle is applied? would a low crossweight work given that thought?

GRTWallbanger
Dirt Maniac

Total posts: 196
posted May 02, 2005 02:01 PM  
Is it ok to remove the 90/10 with a pull bar?I know you can do it with a lift bar but i thought you need it with a pull bar?
Why did you not like the clamped up in front set up?I tried the spring behind on the LR all last year and never got it to work very well.Very hard to drive unless you start on the front row.
Your Z-link bars dont seem right?If i am picturing this correct?Your front bar is angled uphill from birdcage to frame?And the rear bar is angled uphill from birdcage to rear of car,so the rear mount is higher then the birdcage mount.

[This message has been edited by GRTWallbanger (edited May 02, 2005).]

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 02, 2005 02:03 PM  
I have pretty much come to the conclusion that Lr bite is only good up to the point the car is on the bars. At that point it doesnt really matter. Also I think it is more important on a clamped setup than a LR behind setup. A clamped setup that stays on the spring until throttle application will be tighter with more bite. Once it goes up and gets locked down again I dont think itmatters.

I personally would leave the 90/10 on. It will help control the rearend and settle it easier on deceleration. IF you want to loosen the car try moving it to the left or take some angle out.



donslink1
Dirt Freak

Total posts: 318
posted May 02, 2005 05:35 PM  
I would soften the lf spring, and take some bar angle out of the lr upper link.
Get the car freed up in the corner, Then worry about getting down the straights

rpm20
Dirt Freak

Total posts: 338
posted May 03, 2005 04:54 AM  
i think i need the 90-10 also.
the reason i went away from the spring in front is because it was contributing to my tight condition, also i had it on a coilover and didnt think it was working that way, maybe a slider would work better but i dont know how it would fit.
we ran lr behind last year and were just starting to get a handle on it at the end of the season.
why didnt you like it, does clamped up work better for you and how do you run it.??
you were right on the z bars but now i angled the rear one down to the rear about 5*. to add some rear roll steer on entry.

quote:
Originally posted by GRTWallbanger:
Is it ok to remove the 90/10 with a pull bar?I know you can do it with a lift bar but i thought you need it with a pull bar?
Why did you not like the clamped up in front set up?I tried the spring behind on the LR all last year and never got it to work very well.Very hard to drive unless you start on the front row.
Your Z-link bars dont seem right?If i am picturing this correct?Your front bar is angled uphill from birdcage to frame?And the rear bar is angled uphill from birdcage to rear of car,so the rear mount is higher then the birdcage mount.

[This message has been edited by GRTWallbanger (edited May 02, 2005).]



dirtbuster
Dirt Forum Champ
Total posts: 2007
posted May 03, 2005 07:43 AM  
Teh thing to remember going from LR clamped to LR behind you have about 10X the adjustments available so it is easier to get dialed out. WE ran clamped LR last year and it was ok but seitched to Lr behind this year and I feel the car is by far better, at least for us. But I went into it last year knowing more about the LR behind deal and kind of had to work backwards to see what worked on the LR clamped. I have heard people say that the LR behind setup will really tighten the car up all the way out, but it has been the opposite for us. Teh clamp was way tighter, this year with the LR behind we cant seem to tighten it up, everythign we do just increases fwd bite but hasnt really tightened the car any, which is good i guess.

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