Visit The Dirt Forum for More Information

Author Topic:   need help .....short 3 link .....late race handling probs.
JT54
Dirt Maniac

Total posts: 170
posted June 21, 2004 12:29 PM  
Ok. here goes ...I race on high bank 1/4 mile car is bad fast on tacky short runs I.E.heat races....but we are strugling with our dry slick set up.....it seems the first 10 laps of main car is fast as anyone but as fuel load burns off we pick up a bad throttle push and the last 5 laps we loose all side bite.......this is what I think....we are starting race with too much cross and as fuel load drops our cross gains 1.5 percent by the end of the race .....also as fuel load burns we loose rear percentage wich in turn changes ride hight slightly.....could this change in ride hight be moving the frame side of the J bar enough to affect rear roll center ,causing loss of side bite at the end?.....also I think the thrust angle of my links are increasing as fuel load drops....wich is probably why my left front is rising more and more as the race goes on......here is what I have for set up...metric chassis ....lf 900 rf 1000 lr 200 in front rr 175 on top lr link 17 " at20* angle and rr link 21" at 10* angle ...J bar 20" with pinion side 2nd hole up next to pinion 4 1/2 of rake .....D&M dual spring pull bar 23" long had it at 20* down for awhile but lost bite as fast as it would get it on dry moved it up to 15* or so and it seems to pull good now down the shoot...dont know the spring rate but it is moving 31/2 to 4 inches ....I think this is too much......the car is awsom and we only have 7 nights on it ....top 5 car but am lacking a little if I want to run with the big dogs on the slick......oh yea we start heat with about 58 % rear with me in car and main with 60% with me in the car ....with out me its about 59% and 54% cross......Help Please.

mod70
unregistered Total posts: 170
posted June 21, 2004 03:20 PM           send a private message to JT54   Edit/Delete Message   Reply w/QuoteBBBBBB
What jumps out at me are the front spring rates. They seem 150 to 200 lbs high. If you soften them up, either initaly, or before the feature (you'll have to figure reseting ride hights & weight in the shop so you know what to do at the track) it will really help the car turn. The fuel burn off could be part of the problem. The way to correct for that is to set your fuel cell to the left side of the chassis. That way as it burns off it will also take some cross with it.

JT54
Dirt Maniac

Total posts: 170
posted June 21, 2004 05:05 PM  
I have metric lower control arms ,thats why the high spring rates in front....cant move the cell....but I can move some ballast to the right .....what do you think?....anyone else have thoughts on this?

21racer
Dirt Full Roller

Total posts: 56
posted June 21, 2004 08:38 PM  
front springs to stiff i run 850lf 800rf my car is 4 link z link but i also had a leaf spring car a few years ago ran 800/850 both metric front ends rear set up sound ok

zeroracing
Dirt Forum Champ
Total posts: 1875
posted June 21, 2004 08:51 PM  
first off i run a metric with metric lowers and use those springs alot on the front your not too high.
changes i suggest..shorty bar with some angle. this will help on the dryslick and a 225 pound lr spring, this will tighten it up off the corner on the dryslick.
SWITCH TO GAS!!! burn alot less.
scale the car how you like the set up with a low fuel load and start the race heavy, take your time wait till 15 laps in and get on it.
you may lower your front links just a bit, and see if that makes it more drivable.
but i would go with the 225 lr(get a spring rubber like 6 bucks, and put it in when it turns slick, reset ride hieght, and jsut put it in your 200 lr). also try the short bar.
good luck


JT54
Dirt Maniac

Total posts: 170
posted June 21, 2004 11:29 PM  
Thanks zero,this is my first year with this suspension ....I used to have a mono leaf car....If I understand right if I lower my J bar ,say an inch and a half it will make the car roll more and create more side bite ,am I understanding this corectly?.....I dropped it to the bottom hole on the pinion with about 6 inches of rake and it realy rolled over and carried the left front down the straight away , I only ran it this way for about 2 laps then I slid up in the marbles and off the track durring my heat race ....felt pretty uncomfortable so I changed it back to where it is now for the main......after looking at the video it didnt look nearly as bad as it felt maybe I should give it some more laps and see if I can drive it that way?......Do you think that as the track dries out lowering the J bar on the chassis side only will maintain some of the side bite that is lost from the track loosing grip?.......I have the stuff to put the shorty bar on and the track has been smooth as of late but I dont know if it will be too reactive for me or not....I guesse there is only one way to find out!.....does even with the pinion and about 3 inches of rake sound like a good starting spot for the shorty?.....thanks for the help and I do appreciate the time people take to answer all the ?

JT54
Dirt Maniac

Total posts: 170
posted June 21, 2004 11:40 PM  
Ramble, ramble, I know but is 3 to 31/2 inchess too much movement on a 2 coil progresive pull bar? and if so would more prelode stiffin it up?.....how do you know when there is to much cross ,my car seems to like alot.....car works good with even weight accross the front .....this sound right ?

sdracer12
Dirt Maniac

Total posts: 180
posted June 21, 2004 11:56 PM  
Just a quick question regarding the above posts: When you say metric lowers, are you referring to 78-86 Big metric Impala, or 78-86 Monte Carlo small metric fronts?

Wondering if it makes a difference on spring rates? Thanks

JT54
Dirt Maniac

Total posts: 170
posted June 22, 2004 04:44 PM  
Small metric,they have a diferent leverage ratio than the big cars.......1000 lb feels prety soft when you jump up and down on the front bumper.

sdracer12
Dirt Maniac

Total posts: 180
posted June 22, 2004 08:25 PM  
Thanks now I see the difference!!

zeroracing
Dirt Forum Champ
Total posts: 1875
posted June 22, 2004 08:35 PM  
as far as pull bar, how far is it from your center of rearend, then you can fiqure what the pinoin angle is when the bar is wrapped up so to speak.

look for binds in the coils, you know missing paint, and looks like they hit each other. if they are hitting you may want a stiffer spring or springs.

as far as short bar to get used to it go second hole up on pinoin mount, and over the frame, then up 3.5-4 inches from level with the pinoin spot. if you have a 2x2 square tube mount with the holes on each side then you want to put the short bar in the far left hole that way you get a longer bar so it reacts slower, and you still get the good effects of the short bar.
but i would start there, then if you get used to that you can add some more and try it.
try the short bar on slick and smooth tracks though. smooth tracks, or you can end up on your head if your not careful.

good luck
jason

JT54
Dirt Maniac

Total posts: 170
posted June 23, 2004 01:00 AM  
Thanks Zero,no evidence of springs binding ...I think I will try some more pre load on the pull bar and see what happens ....Lifting the left front off the track is a new experience for me and it feels a little uncomfortable but I think It can be fast once I get used to it.....short bar is going in the parts box and we might try it if the track is smooth .......already been on my top the first night out (wrong place at the wrong time).....dont want to go there again !!

Back to the Archives