|01-21-2004 12:02 PM|
This might help, whether you're running a ladder bar, 4link, or even a 3link:
Consider a side view of the car. Imagine a vertical line drawn through the front tire patch. Then, a horizontal line through the center of gravity. These two lines intersect at a point above the front tires. Finally, consider a line drawn, from that intersection, through the rear tire patch. Detroit calls this the "no squat/no rise" line. If the rear suspension instant center (pivot point of a ladder bar or the intersection of lines through the upper and lower links of a 4link) falls anywhere on this line, the rear of the car will neither squat nor rise on acceleration. If it falls above, the rear will rise; if below, it will squat.
Since the front suspension links do not carry similar dynamic loads during launch, there exists no similar trick. In other words, the front will always rise. By using "softer" (lower rate) springs at the front, you can get the front to rise even more, of course. This raises the center of gravity very slightly and thus increases the weight transfer.
There is a little trick available at the front which will affect rear tire loading, however. By using a lower rate spring at the left front than at the right, the left front will rise more than the right. This then forces the right rear down (compared to the left rear). The result is a dynamic loading of the right rear, tending to cancel the tendency of the driveshaft torque to unload it. It is necessary, of course, to have adjustable coilovers when taking advantage of this trick, as the lower rate spring will require more compression to support the same load. Note that this is NOT the same as a preload. The load is applied dynamically, not statically.
|03-11-2003 03:18 PM|
[quote]Originally posted by strawntech:
<strong>ok guys we will turn the spring nuts up they are very low right now
Most Coil over shocks have a recommended ride hieght. It is usually recommended that they be right in the middle of the stroke. Be sure you dont get so far up you have problems with topping out. If you have to set the shocks in the top 2/3 of the stroke, it might be a good idea to get some stiffer springs.
|03-10-2003 09:01 AM|
hey 4 jaw
what bar were you refering to
i hope not the ladder bars becouse we moved them down one from the center hole ( 5 holes)to the 2nd from bottom and seem to be making progress
|03-09-2003 11:49 PM|
|4 Jaw Chuck||
There should be an inch or so left in the spring travel during a full launch, you can use a short piece of rubber hose cut in a spiral and slipped over the shock shaft to tell how much it has moved after a good launch. Do both sides because they will be different.
Why not move the bar to the highest position?
|03-09-2003 08:46 PM|
ok guys we will turn the spring nuts up they are very low right now
|03-09-2003 02:51 PM|
|firstname.lastname@example.org||Turbo is right on. As soon as the suspension bottoms out, all bets are off. You need stronger springs to keep the wheels planted.|
|03-08-2003 07:27 PM|
Okay, I think you said it just then. You said it lifted untill the rear bottomed out. That is the problem. At that point the suspension bouces and and you loose it all. It sounds like the coil overs are not set properly or the springs are too soft for the car. The coil overs should be set so that they are mid stroke when the car is setting still. If the springs are too soft, this will not be possible. Also remember, if you reset the ride hieght to correct any spring problems, the ladder bar geomtry will also change. If if fact the springs are too soft or set too low and you raise them, the bars will be pointed more upward, and will hit the tires less. This might not be a bad thing if it is bottoming out rihgt now.
|03-08-2003 06:18 PM|
well we went out to the local rubber coverd go fast spot with the ladder bars lowered one hole (now second from bottom) took most of the preload out of the coilovers (7 threads showing about 25% up) and turned the adjuster knob on the QA1's down to two outa twelve
the car sat alittle lower and drove well
after a breif tire warming the car left realy realy hard lifted the front till it ran out of travel (8-10 inches ) ans slamed the rear till it bottemd out as well then spun a little and did this two more times (hook spin hook spin hook spin ) then grabed one last time witch planted the rears well and went the last 900 -1000 ft
so i figured the shocks were alittle loose and went up a click ......
next pass spun like hell
same line same tire temp etc...
went back to click #2 to verify and did similer to pass#1
so whats next? anyone? turbo..., willys
|03-04-2003 04:57 AM|
I guess I am just confused. I thought you were thinking this was an 11 second car. I am not trying to be a *****, it is just that there are alot of people who come to this site with imaginary cars or imaginary engines making imaginary power. I am not accusing you of this, but when this happens it makes it is misleading to those following along if all the details of the car or situation in question do not make sense. It can give people a false sense of the answer to problems that may not even exist. This could lead someone else down a path that is just plain wrong.
That said, I think if the car has never been to the track you really dont know how it will react. You said it unloads the tires after it moves a couple feet. Are you testing it on the street? Nothing will hook on the street. The only way you will know if this car will hook and launch is at the track. There is no substitute for a concrete launch pad covered in rubber.
You need to get to the track to do your testing. It is pretty much impossible to set up a car on the street to see how it will run at the track. The point is that a well tuned race car will roast the tires on a standard asphalt street surface.
[ March 04, 2003: Message edited by: TurboS10 ]</p>
|03-03-2003 07:42 PM|
for all the info
Il run some numbers tonite
this is not the first nine second car i have driven. my idea of spins alittle and your idea may be a little different
so sorry i was not so clear with my wording
i also run a low nine second dragbike so my conception of speed is a little alterd too
anyway after thinking about it and waching the car leave a few more times it seems toleave real hard and then unloads the tires after about 5 feet(mabie 10)
|03-03-2003 07:15 AM|
As previous posts point out, there are a lot of considerations in getting your nose off the ground. it isn't all hp or weight transfer, etc., rather it is the entire system. The thread below discusses this tropic in detail. I posted some basic equations which should get you into the ballpark of the setup you need. In summary, you need enough torque, enough weight on the rear tires, enough traction, and center of gravity far enough back or you can't get off the ground.
<a href="http://www.hotrodders.com/cgibin/ubb/ultimatebb.cgi?ubb=get_topic&f=15&t=004682" target="_blank">http://www.hotrodders.com/cgibin/ubb/ultimatebb.cgi?ubb=get_topic&f=15&t=004682</a>
|03-03-2003 06:06 AM|
If the car is making 680 RWHP as you say, it should run 9's if it is dialed in. If it just "spins pretty good" I am doubting you have that much power. It should "spin pretty good" at 120 mph with that much power to the ground and that small a tire.
[ March 03, 2003: Message edited by: TurboS10 ]</p>
|03-02-2003 08:17 PM|
thanks every one
i guess the bottom line is move the bars up and soften the shocks... right?
il keep ya posted
|03-02-2003 11:08 AM|
|4 Jaw Chuck||
Pull off the front sway bar and any other heavy unnecessary bits like bumpers (buy fiberglass) and steel hoods. The big problem is your car only weighs 3100 pds but probably 1800 pds of that is over the front tires, you need to get that car on a scale and dial in the chassis weights to get what your after.
No matter how you look at it you need to tune your chassis setup and get your weight distribution right, even wheel standing race cars have at least %50 of the weight on the rear tires to start. A four bar setup is a lot easier to dial in front end lift than a ladder bar, a ladder bar is setup to drive the car forward for quick times not for showing off. Instant centers for a ladder bar are in the wrong location for tire lift, it is too far below the CG of the car and not far enough forward.
I suggest you find a set of scales somewhere and do some math.
|03-02-2003 10:53 AM|
|roys63||we useto remove the front shocks and hit the gas hard and let off when the front end just comes down we hit the gas to the floor and lift the wheels that way just playing on the street, can you get more tire under the car? wider, shorter|
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