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Old 02-26-2013, 10:54 AM
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Troubleshooting my 4 link

Hello! New member here. I'm actually posting this for my father but he will be checking back and responding.

First, I would like to say that I have done a search and gone through many topics but most have dead links or did not answer this question directly. I would also like to add his url so you can check out the '36 Ford Roadster Hotrod. Untitled Document

It has a TCI chassis with the Pro Street (narrowed rails for wider wheels/tires & Pro-Street 4-Link) package. http://www.totalcostinvolved.com/p/9...-plain-package

It has a panhard bar but not from the axle to the frame. The panhard is diagonal, linking the bottom two 4 links. Basically, like |\| if that makes any sense.

Anyway, on to the issue. During a launch the rear end will kick out to the left. It is has been very dangerous at times. Most of the articles I have come across cover squat control. I have yet to find one that troubleshoots kicking out left/right (not sure if 'kicking out' is the proper term, please school me on the technical term).

As far as we recall the 4 links are parallel and equal length. We will be going out to work on it in a few hours to add lock washers to the panhard bar nuts because they keep coming loose. I will snap a picture and also double check my previous statement.

Any help would be great. Thank you!

EDIT: I didnt realize my fathers webpage is titled "untitled document" but it is legit. Also, I fixed the TCI link, I had http twice.

EDIT2: Had to remove the link to TCI so it way copy and pasted instead.

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Last edited by AJThor; 02-26-2013 at 11:20 AM.
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Old 02-26-2013, 12:00 PM
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Post some pictures of what you have. That is a common setup used on the street and strip and I had that myself. Effective system, so I am not sure how the rear could move unless something else is giving in.
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Old 02-26-2013, 12:55 PM
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Okay. If you please revist my father's site Untitled Document he just added some pictures we took. They're at the bottom, the top picture on the driver's side, the bottom picture is the passenger. The bars do look parallel and I tried to capture that in the pictures.

The brake caliper's are centered left to right based off of the frame.

EDIT: I should also add that it isn't the actual rear end suspension, it is the vehicle. As if I was steering right and hopped on it. Positraction, so both wheels do spin and leave rubber.
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Old 02-26-2013, 01:05 PM
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When I have had that type problem, it's usually worn Heims on the track bar, which is what that diagonal link is called, or the track bar is in a bind, which may be causing the bolts to come loose.

Another thing to check is if the rear end is square in the chassis, if it is not square, it will push to the side on launch.
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Old 02-26-2013, 02:19 PM
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Ok, so the rear end is not actually moving out of the car, the car itself is pulling to the right. Am I correct? If so, you may want to add good heavy sway bars. The engine will pull the car that way if there is enough power and traction to do it. If the rear suspension is soft, this could very well be the problem. Good for riding around, but under force, you need to have the weight come down even (as much as possible) on the tires. Also, did you have the suspension aligned (by someone that knows what they are doing)? The angles of the 4-link will also play a factor in how the car launches. This is why they are so adjustable.
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Old 02-26-2013, 02:44 PM
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"When I have had that type problem, it's usually worn Heims on the track bar, which is what that diagonal link is called, or the track bar is in a bind, which may be causing the bolts to come loose.

Another thing to check is if the rear end is square in the chassis, if it is not square, it will push to the side on launch."

The track bar is not in bind, it looks great. The bolts were comming loose so we just added some lock washers. The rear is square in the chassis (as far as our measuring goes). The bottom two links are all the way short. The tops are both different but ever so slightly. .691in passenger side, .673in drivers side.


"Ok, so the rear end is not actually moving out of the car, the car itself is pulling to the right. Am I correct? If so, you may want to add good heavy sway bars. The engine will pull the car that way if there is enough power and traction to do it. If the rear suspension is soft, this could very well be the problem. Good for riding around, but under force, you need to have the weight come down even (as much as possible) on the tires. Also, did you have the suspension aligned (by someone that knows what they are doing)? The angles of the 4-link will also play a factor in how the car launches. This is why they are so adjustable."


No, pulling to the left (the rear end of vehicle). He says it is a heavy duty sway bar that is part of the TCI chassis Pro-Street 4-link, although I couldnt find any specific spec on their website. The suspension is probably too hard, it doesnt really squat at all. Unfortunately, it has not been professionally aligned. That will eventually happen if we can't figure it out.
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Old 02-26-2013, 02:55 PM
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Mine was doing that and I found that the wheelbase was not equal on both sides. Measure front wheel to back at the centers. It doesn't take much to throw it off if u have a hard launch.
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Old 02-26-2013, 03:03 PM
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Quote:
Originally Posted by Fang16 View Post
Mine was doing that and I found that the wheelbase was not equal on both sides. Measure front wheel to back at the centers. It doesn't take much to throw it off if u have a hard launch.
Will do, my dads asleep at the moment, will get back to you when he wakes up.
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Old 02-26-2013, 03:12 PM
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I am no drag race suspension set up guy so this is just a shot in the dark. But that "locator" bar is a joke in my opinion, first off it looks crazy close to the drive shaft. Your adjustments on your rear bars look to be equal front and rear, while it has a full range of adjustment for just this kinda of problem. Like I said, you need to wait for someone with this type of experience know how but those bars are usually set with the upper ones pointing down as I remember and this makes the car squat less. But that being said, that locator bar could be "pushing" that right rear so on lift of compression it is lessening the movement thus allowing the other side to move more and giving it an un-even hook up causing it to go sideways.

I don't like that locator at all, don't know what others think but I think from my limited knowledge in anything other than your general street stuff that looks like a joke to me.

Brian
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Old 02-26-2013, 03:22 PM
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Quote:
Originally Posted by MARTINSR View Post
I am no drag race suspension set up guy so this is just a shot in the dark. But that "locator" bar is a joke in my opinion, first off it looks crazy close to the drive shaft. Your adjustments on your rear bars look to be equal front and rear, while it has a full range of adjustment for just this kinda of problem. Like I said, you need to wait for someone with this type of experience know how but those bars are usually set with the upper ones pointing down as I remember and this makes the car squat less. But that being said, that locator bar could be "pushing" that right rear so on lift of compression it is lessening the movement thus allowing the other side to move more and giving it an un-even hook up causing it to go sideways.

I don't like that locator at all, don't know what others think but I think from my limited knowledge in anything other than your general street stuff that looks like a joke to me.

Brian
Unfortunately, we don't have any other options unless they hit the lotto without buying a ticket. It's not unsafe to drive and it goes like stink we just can't give it too much throttle. But, other than take it to a professional do you have any other advice? We don't mind messing around with it.
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Old 02-26-2013, 03:31 PM
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I don't have anything like I said, my knowledge is pretty limited on set ups other than general street. I know that the photos you have proved don't offer a whole lot. But someone with a lot of experience in this set up won't need any more I don't imagine. Just hang in there and see what others post.

Brian
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Old 02-26-2013, 03:37 PM
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body roll

With a lot of torque, the body-chassis will want to roll sideways, With a must II front . susppension you shouldn't have that much torque steer, One side of the chassis lifting more than the other. usually you have to turn the steering wheel to counteract it. and if the front end lifts and you pull your foot off the gas and hit the brakes the car will self steer off to one side. sometimes you have to preload the coilovers different on all 4 corners to keep it going straight under hard launches, just be carefull when testing to have plenty of road space when the front end comes up then down. A long and proper angled panard bar might work better. than the diagonal bar.
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Old 02-26-2013, 03:57 PM
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Quote:
Originally Posted by Fang16 View Post
Mine was doing that and I found that the wheelbase was not equal on both sides. Measure front wheel to back at the centers. It doesn't take much to throw it off if u have a hard launch.
By our rudimentary measuring the driver side wheelbase is about an 1/8th of an inch shorter that the passenger side.

Quote:
Originally Posted by timothale View Post
With a lot of torque, the body-chassis will want to roll sideways, With a must II front . susppension you shouldn't have that much torque steer, One side of the chassis lifting more than the other. usually you have to turn the steering wheel to counteract it. and if the front end lifts and you pull your foot off the gas and hit the brakes the car will self steer off to one side. sometimes you have to preload the coilovers different on all 4 corners to keep it going straight under hard launches, just be carefull when testing to have plenty of road space when the front end comes up then down. A long and proper angled panard bar might work better. than the diagonal bar.
The front end does lift *slightly* and as I said before the suspension is so stiff it doesn't squat at all. He hasnt let off and hit the brakes but when he does let off the the vehicle corrects itself.

Thank you all. Please keep helping if you can.
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Old 02-26-2013, 04:02 PM
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Here's a good article on 4 links.
BaselineSuspensions.com.........Launching A Drag Car
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Old 02-26-2013, 05:03 PM
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That 1/8 inch can make a difference. Check your tire pressures all around. If a rear tire is lower than the other by very much it will pull to that side on launch. Could you post a short video of what it's doing on launch? I think we're all confused on what it's actually doing.
I'm also thinking you don't have the links and shocks set for a good launch. I looked at the pix you mentioned and rarely do parallel links make for a good launch. To set them correctly you'll need to know the weight of the car in race trim. Ft. end weight and rear end weight as explained in the article link I posted.
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