Moparts
4 link preload
Posted By: eds dart
4 link preload - 06/30/11 10:53 PM
am scaling the car today due to launching to the right last weekend. i had 50 lbs more on the right rear than left, was expecting to see less than that due to launching right. am thinking to increase preload to 60 or 75 lbs. is that to much or ballpark ok?
Posted By: Bigcube
Re: 4 link preload - 06/30/11 11:59 PM
That's not out of line. Usually the more HP it makes, more preload will take. Shouldn't take more than a flat or 2. Little bit will go a long way if you already have 50# in it. How hard was it pulling to the right? Do you have a AR bar? With a AR bar you can usually get away with less pre-load. I still have a bit in my car to get it to launch nice and straight. Not exactly sure how much because my car needs to be re-scaled.
Posted By: eds dart
Re: 4 link preload - 07/01/11 12:38 AM
car does have an AR, i had it disconnected when weighing. i run it with just taking the slop out of it. i found that a quarter turn either way on top bar was worth 30 or so lbs of preload. it didn,t pull very badly it just ,made an initial move to the right then went straight. going to try my luck at Muncie this weekend. Car ran pretty good last weekend and i was tearing the tree down, wish me luck, lots of hitters will be there .
Posted By: Guitar Jones
Re: 4 link preload - 07/01/11 01:16 AM
I've never scaled my car so I don't know how much preload is actually in it but I have two full turns on the top right bar, no AR bar though I know I need one.
un-hook the anti roll bar on one side, set rear wheel weights as close as possible left to right with the car at race weight (with driver). After setting the corner weights, adjust the anti-roll links until the bolt will slide in without force.
Posted By: Bigcube
Re: 4 link preload - 07/01/11 01:48 AM
Sounds like you know what the do
How did is sixty?
Posted By: eds dart
Re: 4 link preload - 07/01/11 03:34 AM
been out pumping fuel and loading the truck up. 1.40 and 1.41 when it would go right. didn,t seem to matter which lane which made me think i was pretty close and a little more preload would help.car definately doesn,t like equal rear weights.
Posted By: Leon441
Re: 4 link preload - 07/01/11 04:32 AM
Do you have someone equal to your weight sitting in the drivers seat. If not you are lost when it comes to starting line corner weights. I set my car neutral. Then get someone equal to my weight to sit in car. Then I dial in however much preload it takes to make the car go straight. My antiroll is then installed neutral as it does not take on any part of the preload, just maintianing the stabilitly in the rear of the car.
Leon
Posted By: moparmxz
Re: 4 link preload - 07/01/11 11:56 AM
My car takes 1.5 turns from neutral driver seated in car no antiroll. Good luck at muncie.
Posted By: moparmxz
Re: 4 link preload - 07/07/11 03:45 AM
Did you get this deal straightened out, just curious what the cure was.
Posted By: Leon441
Re: 4 link preload - 07/07/11 06:46 PM
Quote:
My car takes 1.5 turns from neutral driver seated in car no antiroll. Good luck at muncie.
1.5 turns or 1.5 flats?
Leon
Posted By: moparmxz
Re: 4 link preload - 07/07/11 10:26 PM
Quote:
Quote:
My car takes 1.5 turns from neutral driver seated in car no antiroll. Good luck at muncie.
1.5 turns or 1.5 flats?
Leon
Turns ,it will go straight with less but then it would smoke one tire a little quicker than the other. A little extra and my tires wear even and it still goes straight.
Posted By: eds dart
Re: 4 link preload - 07/07/11 10:49 PM
The high heat and track temp just killed the car. It wouldn,t 60 foot at all, it was all over the place. On Monday tried some throttle stop launch and that worked pretty good. Am going to try this again at INDY this weekend.
Posted By: Leon441
Re: 4 link preload - 07/08/11 02:20 AM
You ever tried checking the thrust angle on the car. There is no way that car should need 1.5 turns of preload. You are compensating for something. Probably rear steer or dishrag frame.
Leon
Posted By: moparmxz
Re: 4 link preload - 07/08/11 01:36 PM
Quote:
You ever tried checking the thrust angle on the car. There is no way that car should need 1.5 turns of preload. You are compensating for something. Probably rear steer or dishrag frame.
Leon
I assume you are talking to me,this is why i almost never post advice on here to much criticism. My frame is fine,and i,m a certified frame and body man. So i am positive the rearend is square and straight.I do have a short unequal 4 link,i do not have a frame stiff enough to run your kind of et,s. But i don,t think my car could be flexing much as the paint is 16 years old and the body has no stress cracks. I work with what i have and make the best of it. I just replied to Ed because i have talked to him and i like his car. Also i was not the one asking for advice. Now if you have some good advice for Ed i,m sure he would appreciate it. 
Posted By: eds dart
Re: 4 link preload - 07/08/11 05:20 PM
This car has been a continuing challenge to get it to hook in the high heat of summer. I realize heat affects all cars but mine seems to really change drastically for the worst. Much faster cars don,t seem to have as much trouble as mine getting down the track and that adds some frustration to the equation. For example over the winter made some changes to the 4 link, i shortened the bars and lowered the brackets to be able to get some lower IC points.This spring With outside temp of 66 tracktemp 97 car runs 1.36 60' 6.487 103.27 IC @ 41 long 6.5 high. that generated big wheelstand almost to the 60ft beams. fast forward to high heat last weekend 60,s detreriate to 1.43 with some really bad spinning 1.46 and high 6.55. No changes were made to the car and thats where my frustration comes from. I,m going to keep swinging at it but my hair is getting grayer.
Posted By: MR_P_BODY
Re: 4 link preload - 07/08/11 05:39 PM
Where's the CG of the car... but if it was wheel standing
the IC was most likely forward of the CG.... also
whats the weight bias
Posted By: eds dart
Re: 4 link preload - 07/08/11 06:02 PM
I honestly dodn,t know the cg location. The weight bias is 55% front 45% rear. Just scaled car last week, see previous post, 1755 lbs front, 1423 lbs rear. lf 937 rf 816 lr 669 rr 754. left side total vs right side total was 50.5% left and 49.4% right. when i built the car i kept the engine/tranny factory offset. all numbers with driver weight in seat.
Posted By: gregsdart
Re: 4 link preload - 07/08/11 07:58 PM
With that much weight over the nose, you will probably have to compensate with a more aggressive hit. Will probably also want as much front travel as you can muster, and loose.