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Author Topic:   What lenght trailing arms on a 4 link?
chickenlittle
Dirt Full Roller

Total posts: 67
posted November 16, 2005 03:17 PM  
I run on a short dry track with little forward bite. I was thinking of running a plug on the lower LR bar. What length would be best to use to get the most bite? RR is a straight Z. Springs are mounted on cages LR behind RR in front. Springs LR 250 with RR 225. Around 200 lbs or bite. Also, what would be some recommended bar angles be?

zeroracing
Dirt Forum Champ
Total posts: 1894
posted November 16, 2005 03:37 PM  
Many modifieds have too short of bars put on them from the builder, some cars came out with 14 upper and 12 lower. That short of bars can lead to a pogostick race car, jump all over the place erratic and hard to drive. Fast by themselves but beast in traffic.
Too get the most out of a 4 link then you should not be afraid to use long bars on it. A good set up that is popular would be 17.5 upper and 15.5 lower, this will work goodfor most track conditions. If the track is tacky you could remove the plug and run a long lower link, this will keep the car from loading to quickly, and help the car become more driveable on rough/tacky tracks.
But back to slick, if you go the 17.5 upper and 15.5 lower, then get a good set of birdcages with adjustment in them.
Start out with 18-20 deg uphill angle in upper, and level lower, birdcage straight up and down.
I might have some good birdcages for sale if your interested, bsb ones, pm me for info.
later
jason

GRTWallbanger
Dirt Maniac

Total posts: 198
posted November 16, 2005 04:43 PM  
I think some late model guys where trying longer lower bars.Suppose to give more bite and less roll steer.I noticed a few that tried this and they had a ton of angle in it because it took out so much roll steer the thing would not turn.The one I saw was on the LR.

[This message has been edited by GRTWallbanger (edited November 16, 2005).]

dirttrackin94
Dirt Forum Racer

Total posts: 77
posted November 16, 2005 04:48 PM  
my peirce car has 15'' upper bars and 17'' lower bars.

andykmod
Dirt Freak

Total posts: 364
posted November 16, 2005 04:58 PM  
My old car had equal length upper and lower links centered @ 15 1/4, When i would get crazy with bar angles we had a problem of it over centering the bird.

donslink1
Dirt Freak

Total posts: 322
posted November 16, 2005 06:57 PM  
what year Pierce do you have dirttrackin94?

shopboss
Dirt Roller

Total posts: 9
posted November 17, 2005 06:33 AM  
dirttrackin 94 are you shure your correct? 15 in. uppers and 17in. lowers, sounds like somethings monkeyed up

Kromulous
Dirt Forum Champ
Total posts: 810
posted November 17, 2005 08:03 AM  
quote:
Originally posted by GRTWallbanger:
I think some late model guys where trying longer lower bars.Suppose to give more bite and less roll steer.I noticed a few that tried this and they had a ton of angle in it because it took out so much roll steer the thing would not turn.The one I saw was on the LR.

[This message has been edited by GRTWallbanger (edited November 16, 2005).]


We have been running this all year, its hard at times to get it to turn but when it slicks off its game on.

18" Lower, and 16 3/8ths upper. Birdcage is on the edge of over centering, but hasnt yet. Same lengths they run on the Rocket LM's.

Personnally i would like to build a 4 bar car on a 17" lower and 14.5" upper on the LR, and a 14.5" lower and 17" upper on the RR, with a plug to swap the LR around on a normal track. 2.5" of split will help generate more indexing.

Krom.

WPP
Dirt Freak

Total posts: 454
posted November 17, 2005 08:51 AM  
I ran a 14.5 and a 20 3/4 on my dirtworks clamped it had bite but the car was hard to turn . Should have ran more angle on the rr z-link on both bar .This setup could have work if i spent more time with it . I now have a pierce my bars are not like the aboves lets here some more.

dirttrackin94
Dirt Forum Racer

Total posts: 77
posted November 17, 2005 08:55 AM  
my car is a 2000 peirce,and yes im sure the lengths are 15''upper and 17'' lowers.

dirttrackin94
Dirt Forum Racer

Total posts: 77
posted November 17, 2005 11:14 AM  
my peirce car has like i said 15'' bars on top and 17'' bars on bottom,same on the right rear also.my left rear is 4 bar and right rear is z-link,i have a 17'' long short strait panhard bar running from the bung on the left side,200lb springs across the rear with konig shocks and a spring loaded pullbar...

SMARTT
Dirt Roller

Total posts: 5
posted November 18, 2005 09:09 AM  
What lengths are most dirt works cars running?

dirtbuster
Dirt Forum Champ
Total posts: 2009
posted November 18, 2005 10:01 AM  
The newer Dw stuff is about 17 upper 15 lower with a plug.

On our old Dw9 we ran 17 uppers a 15 lower on the right and a 21" lower on the left. Like previous post mentioned it indexes a ton but keeps a lot of rear steer out. Typically I think you can run a little more angle in the longer bar to help it turn and hold bite in the car longer down the stretch. Driver said the longer bar was easier to drive as well, wasnt as erratic whether the track was slick or tacky.

FYI: GRT has a long LR lower setup for late models.

Kromulous
Dirt Forum Champ
Total posts: 810
posted November 18, 2005 12:42 PM  
Same results as Dirtbuster pretty much.

You run the LR behind?

Did your driver comment on how violent the car can come off the bars Dirtbuster? The long bar lower, indexes away from the spring on deceleration, so you better roll off that throttle pedal.

My younger brother come down the striaght at a 3/8ths paper clip (Mudlick Raceway in KY), let out of the throttle like a toggle switch and the car made dang near a 90* turn into the wall. He picked up the gas to save it. I gotta kick out of it.

He came back in and said he almost lost it. He asked me what caused that and i replied driver error, LOL. Now he rolls in and rolls out of the gas. Nothing like head on into a wall threat to make a guy devolpe a throttle foot.

Krom.

dirtbuster
Dirt Forum Champ
Total posts: 2009
posted November 18, 2005 01:13 PM  
We run the spring behind on a slider and the shock in front so that as the car unloads it actually indexes into the shock helpeing let the car down easier. There was another car doing the same thing with a single coilover unit behing the Lr and we ran it that way early in the year and really didnít have any trouble that way either. Theoretically it should work better with shock in front though. You cant run a soft shock like a 3 or a 4 though thatís for sure or it will fall hard.

WPP
Dirt Freak

Total posts: 454
posted November 18, 2005 07:45 PM  
I was clamped and the longer lower bar was level and i think i had the bar in the 4th hole with the 14.5 upper. The z-link was 34in on the rear and the lower was 20 3/4 with spring on top of rear spring rates was 175 lr 225 rr on top with 600/1200 hypercoil 50 pds rr bite it still had alot of drive off the corner .If i had to try this again i would add some angle to the left lower bar and drop angle on the 4-bar upper to the 3rd hole and i would add angle the both right side bars . I also dumped the throttle the first time my mistake 2nd drove in half throttle.I wish i could have drove the dw with this set-up a few more times.I was surprise the bite the car had down the shoot with rr bite .Makes you think some times uh uh

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