4 link/shock setting???

[ky mustang]

My lower bar is 2* down, the bar spread is 12",,, the center of the upper bar is 4 1/2" to the center of the housing tube,, and the center of the lower bar is 7 3/4" to the center of the housing.... Now I can move the upper bar 1" closer to the axle tube and can move the lower bar 3" closer to the tube...thanks for your time Mr Mustang Your help is appreciated...

Just doing the math on your measurements I am getting 12 1/4 " spread. Are you taking into account that (in most cases) the top of the bracket is forward of the center of the axle ? I know it is a pain to measure.

When you say you can move the lower bar 3" closer ,that is not the distance of one hole up is it ? I guess what I want to know is the distance between holes in your brackets front and rear.
I am going to say try moving the bottom bar up one hole in the front and rear and try to set the bottom bar at about 1.5 - 1.7 degrees down in the front. Then move the top bar up one hole in the front.

I would first (before moving anything) check your shocks to make sure your adjustments on them are working like they should be if you have not. You can put a bolt through one end and clamp the bolt in a vise , change settings and extend and compress them to make sure there is not a problem there.

[ky mustang]

Remember: The closer you get to 100% antisquat, the less significant are shocks and springs. And, at 100% antisquat, the shocks and springs are just going along for the ride. All weight transfer is being carried through the links and there is no relative motion between rear axle assembly and the rest of the car.

Your IC location indicates antisquat less than 100%, so you certainly wouldn't want to put it further out at the same height. Page 13 of my site has a spreadsheet for determination of IC location AND percent antisquat.

Page 38 has a spreadsheet where you can play around with spread and see its effect. You might be surprised to see that spread has no effect if the IC remains in the same location. That is, the car "sees" the same force regardless of spread. Spread does, however, have an effect on link loads.
http://www.racetec.cc/shope

Billy I agree that less suspension movement close to 100% a/s is good , but you are going to have an initial hit (it wants to separate) , I know it has some to do with the speed of it also, it all works together .

I just feel like the distance from the center of the axles at the rear brackets has a lot to do with the speed of that hit. I think the farther away the bars are the quicker the hit the closer the slower.

I am no engineer and am not pretending to be , but I have had my 4 link bars in several different holes and I have payed attention to what happened.

[bracketracer]

My lower bar is 2* down, the bar spread is 12",,, the center of the upper bar is 4 1/2" to the center of the housing tube,, and the center of the lower bar is 7 3/4" to the center of the housing.... Now I can move the upper bar 1" closer to the axle tube and can move the lower bar 3" closer to the tube...thanks for your time Mr Mustang Your help is appreciated...

Just doing the math on your measurements I am getting 12 1/4 " spread. Are you taking into account that (in most cases) the top of the bracket is forward of the center of the axle ? I know it is a pain to measure.

When you say you can move the lower bar 3" closer ,that is not the distance of one hole up is it ? I guess what I want to know is the distance between holes in your brackets front and rear.
I am going to say try moving the bottom bar up one hole in the front and rear and try to set the bottom bar at about 1.5 - 1.7 degrees down in the front. Then move the top bar up one hole in the front.

I would first (before moving anything) check your shocks to make sure your adjustments on them are working like they should be if you have not. You can put a bolt through one end and clamp the bolt in a vise , change settings and extend and compress them to make sure there is not a problem there.

Shocks are good.......here is a pic's of the rear suspension....the holes on the rear brackets are 1" apart that is on center...The lower housing bracket holes are also 1" apart. So just moving the lower bar up 1" is going to somewhat slow the action down...Right??

[BillyShope]

You need to get to the track sometime and look around.........

What you see in the pits is the result of copycat thinking. Somebody ran well with the lower link angled down, so now everyone has the lower link angled down. As you'll see with the spreadsheet on Page 38, you can put those links anywhere, with any spread, and, so long as they point to the same instant center, the car will see the same net force moving it forward. And, the hit "speed" to which you refer will remain unaffected.

You talk about "hit," but that's normally associated with separation and, so long as your percent antisquat is less than 100, you're a long way from getting any hit.
http://www.racetec.cc/shope

[ky mustang]

Billy can you show me some proof of a competition 4 link that the first reaction is not separation , video etc , something that I can actually see a 4 link go up at the first hit of power ?

Something that I have not seen you address is the shock and recovery of a drag slick as a car leaves the line. I know that this can be controlled with the leverage applied by the 4 link in most cases , but if the tire is hit to hard it will bounce right back up and unload the suspension.

You have to keep in mind some of us are hitting the tires at around 5-6000 rpm with 900 - 1000 hp. I think you want as little separation as possible to hook the tire, with plenty of power the the mechanical leverage of the 4 link keeps the tires hooked, you just take the mechanical advantage away as the power increases.

You are not going to be able to do this with the bars running up hill and a lot of power ,the tires will want to run right under the chassis. I have seen back half cars that have a high ride height with bottom 4 link bars running up hill and they are usually wheel standers and In my opinion that is not what you want with a 4 link. You want a suspension that uses as much energy as possible going forward not lifting the front end planting the tires etc.

[BillyShope]

Billy can you show me some proof of a competition 4 link that the first reaction is not separation , video etc , something that I can actually see a 4 link go up at the first hit of power ?

You're asking 2 or 3 months too soon. I'm presently preparing a DVD in which I'll take the viewer through the development of the spreadsheets at my site. I'm working on the script and the DVD will obviously be many hours long.

...if the tire is hit to hard it will bounce right back up and unload the suspension.

Oh, how true! Life would be so much simpler without those pesky tires. In this case, however, we can learn a lot from racers engaged in other motorsports. Wheel hop during braking is a major concern with both sports cars and oval track cars. In other words, you don't want oscillatory loading in a friction application. This is yet another reason to seek an instant center location with 100% antisquat. Any other location means more oscillatory loading.

Shake is another tire problem, but it's pretty much restricted to dragracing. Not entirely, but pretty much. I can explain what triggers tire shake, but solutions are far more difficult. Again, reduction in oscillatory loading (100% antisquat) can reduced the incidence of tire shake.

I have seen back half cars that have a high ride height with bottom 4 link bars running up hill and they are usually wheel standers....

With a high ride height, this shouldn't come as any surprise. I'll bet they all have their batteries in their trunks, too. While wheelstands might get your car into Hot Rod, it's an embarrassment to a real racer, for it shows insufficient thought in the original design. (Unless, of course, the car is being built for wheelstand competition or as a Shriners clown car for parades. Those are the only 2 other times it might be desirable.) Much of this goes back, again, to the copycat thinking I mentioned. The "battery in the trunk" trick started half a century ago and it's still being copied. There's been quite a bit of traction improvement in tires since then.
http://www.racetec.cc/shope

[ky mustang]

My lower bar is 2* down, the bar spread is 12",,, the center of the upper bar is 4 1/2" to the center of the housing tube,, and the center of the lower bar is 7 3/4" to the center of the housing.... Now I can move the upper bar 1" closer to the axle tube and can move the lower bar 3" closer to the tube...thanks for your time Mr Mustang Your help is appreciated...

Just doing the math on your measurements I am getting 12 1/4 " spread. Are you taking into account that (in most cases) the top of the bracket is forward of the center of the axle ? I know it is a pain to measure.

When you say you can move the lower bar 3" closer ,that is not the distance of one hole up is it ? I guess what I want to know is the distance between holes in your brackets front and rear.
I am going to say try moving the bottom bar up one hole in the front and rear and try to set the bottom bar at about 1.5 - 1.7 degrees down in the front. Then move the top bar up one hole in the front.

I would first (before moving anything) check your shocks to make sure your adjustments on them are working like they should be if you have not. You can put a bolt through one end and clamp the bolt in a vise , change settings and extend and compress them to make sure there is not a problem there.

Shocks are good.......here is a pic's of the rear suspension....the holes on the rear brackets are 1" apart that is on center...The lower housing bracket holes are also 1" apart. So just moving the lower bar up 1" is going to somewhat slow the action down...Right??

That pic helps alot. I personally think the top bar has more to do with the speed and leverage of the hit at the housing. The reason I am suggesting to move the bottom bar up is because my car was acting about like what you are describing not too long ago.

When you move the bottom bar up at both ends you are changing its relation to the cog of the car. Just think about if the bar was perfectly level you would have raised it say an inch. In my opinion this has a big effect on how the suspension is loaded , that bar is pushing at a higher point against the cog.

That bar is also not pushing at the ic location its pushing on the 4 link brackets. The ic is just a reference point , if you don't think so why do you have bolts in the 4 link bracket then

The angle of the bottom bar coupled with its height in relation to the cog has more effect on if the setting wants to push forward , under , or over the cog. This is the main mechanical advantage / disadvantage a 4 link has. It either wants to push the front end up , forward , or down.

The power level plays into this also , the power can slam the tire down too hard and cause it to bounce, not hit it hard enough and spin , or cause a wheel stand , or hit it just right and go forward with efficiency .

The top bar plays into this as well , but it is pulling and its angle / location does not change the angle or location of the bottom bar its the other part of the puzzle you fine tune with.

When you move it you are pulling at a different location and at a different angle its either easier on the housing to pull on the chassis or harder and its due to the angle and the location of the top bolt in the 4 link bracket not the ic.

I think your bottom bar is too low and maybe to much angle .

If you really read into this I think you could say Billy and I agree somewhat I really like reading Billy's post. I never disregard any information I read because I can always learn that I am thinking wrong.

[want-a-be]

My lower bar is 2* down, the bar spread is 12",,, the center of the upper bar is 4 1/2" to the center of the housing tube,, and the center of the lower bar is 7 3/4" to the center of the housing.... Now I can move the upper bar 1" closer to the axle tube and can move the lower bar 3" closer to the tube...thanks for your time Mr Mustang Your help is appreciated...

Just doing the math on your measurements I am getting 12 1/4 " spread. Are you taking into account that (in most cases) the top of the bracket is forward of the center of the axle ? I know it is a pain to measure.

When you say you can move the lower bar 3" closer ,that is not the distance of one hole up is it ? I guess what I want to know is the distance between holes in your brackets front and rear.
I am going to say try moving the bottom bar up one hole in the front and rear and try to set the bottom bar at about 1.5 - 1.7 degrees down in the front. Then move the top bar up one hole in the front.

I would first (before moving anything) check your shocks to make sure your adjustments on them are working like they should be if you have not. You can put a bolt through one end and clamp the bolt in a vise , change settings and extend and compress them to make sure there is not a problem there.

Shocks are good.......here is a pic's of the rear suspension....the holes on the rear brackets are 1" apart that is on center...The lower housing bracket holes are also 1" apart. So just moving the lower bar up 1" is going to somewhat slow the action down...Right??

Seems like I've seen this picture before. Looks just like one sent to me from a friend of mine who posts here. What car is wrapped around this rear suspension?

Don

[bracketracer]

Hey Don ......kymustang entered a no idea that no one else said anything about. That is by moving the 4 link bars closer to the axle center line ....It's working better but still having the hook,spin,hook and still having 1.16 short times...Please if you have some commits to add go ahead. This is a good discussion

[want-a-be]

Well...On my initial settings of the lower bar I like to have it's height about the same as the beads set on the rims from the ground. Bottom bar around level to pointing down just a tad. Then tune from there. I'm a believer of the top bar starting in the top hole on the rear end mount.

IC will be set to around 45"-48" long and 6-8 inches off the ground for small blocks.

With the Big Blocks I'll start off @ around 55-58 inches long for the IC with it about the same height off the ground....6-8 inches.

These numbers are just the initial set ups to start tuning from and are very generic. They are also for Normally asperated engines.

Shocks and springs depend on weight of the car and peak torque of the engine as to how I'll come out of the gate with them set.

I'm no mathematician...and not very confident in math being able to pick out the optimum set-up for the 4 link. How I decide to make changes on the chassis comes from a lot of track time spent on tuning cars who I have built engines for. Both Drag, which I cut my teeth on, and circle (dirt) track.

But I'm still no guru by any means. I just tune untill I get what I want. But I did have very good teachers.

BTW,...I'm no spelling bee champ or english major ether. So don't hold dat agaist me. lol

Don