4 link ?

[toddcalo]

I have a bracket car I race , Ill give a brief discription of the car Its a71 chevelle 12 point cage 355 small block car wieghs 2850 with me in car best et is 9.84 134mph 11 inch face on tire 29 tall 5.56 gear leave at 7500 rpm stick car 4speed lenco. best 60 foot time is 1.36. I recetly have been questioning my rear control arm angles after reviewing a video tape I noticed the rear tires are getting hit real hard. the rear suspension is basicaly a stock setup that has been made adjutable. cuentley the lower arm is at 4.5 degrees up in the front the top is pointing up 2 degrees in the front. [ lots of anti squat ?]Im going to move lowers to 3 degees up in the front and leave the top where its at. does any body have any sugestions, on angles?Ive been reading whatever I can get my hands on, one thing that Im still not quite understanding is the instant centers relationship to the neutral line , does it matter if the instant center is 5inches in front of the rear tire or 5 feet [provided they both intercect the neutral line at the same distane above or below]nobody makes this very clear. it woud seem control arm angels mean nothing and the instant center locaton is everything, help Im confused thanks.

[toddcalo]

Any one have any Ideas Thanks

[CoMaxRacing]

The instant center has everything to do with how hard the car hits the tires. The control arm angles set the instant center. Here is an explanation as simple as I can make it. As the instant center intersection gets shorter and higher up the car will hit the tire less, as the intersection point gets longer and lower it will tend to hit the tire harder. Finding those points is the real trick but at lease if you know which way to go you hopefully will find the sweet spot sooner.

Hope this helps

[toddcalo]

Thanks for the reply, anybody else care to comment?

[Ed-vancedEngines]

Comax,
Hi,
I believe that you may have unintentionally worded that backwards.

I di freely give by email a 4 link or suspension basics mini-seminar if you wish to see and to read it. Possibly you may not agree with my findings and theories but still it is a different writing by a different author if you wish to email me and ask for a copy, it is yours.

I would like to recieve some feedback from anyone who has received it and used the basic principles which I think I described in simple terms so it can be more easily understood.

To the original poster of this thread. The reason I have not responded to give you any suggestions and possibly the same reason others may not have is because the way you are describing the rear suspension reacting in a factory location chevelle rear suspension with all factory bar angles, just can not be. The normal instant center, or what I like to call the active instant center where you are drawing the imaginary line through the bar intersecting points to see the apex of where the actual instant center is is far beyond th3e front of the car. Be the theory it should give or cause front end lift, and possibly could if you are really over powered in horsepower. The almost parelell bar angles is why the first reaction at beginning launch for the factory Chevelles is to actually lift the rear end housijng upward into the fenders. That is why they squat. So to read in your post that the factory suspension is giving you a hard tire plant or hit just blows my mind. Even with raising your rear axle with shorter springs etc, at best you may get close to a neutral reaction. All suspension tricks that work on chevelles are for the purpose of increasing tire hit or tire plant or chassis separation etc. Too much with factory suspension has never to my knowledge ever been anyone's problem.

I would love to help but I can not understand how your problem could be. If it is in fact hitting the tires too hard, try increasing the rebound or extension friction or pressure on your rear shocks. If you do not have or can't buy adjustable shocks, put the meanset beefiest shoks on it you can find. IF it is like you say it is.
Ed

edvancedengines@hotmail.com

[toddcalo]

Thanks for the reply what I was trying to get across is that the suspension resembels a factory set up [ no panhard bar required ,arms are angeld] the front control arm mounts have 4 bolt hole locations to choose from to change angels on the upper and lower arms , the control arms are round tube with hiem joints on each end. I would love to get a copy of your seminar I will Email you tonight. Not to argue but isn't comax explanation backwards? what would you think would be a good starting point for a instant center location ? thanks

[Ed-vancedEngines]

If youhave capability to get the car professionally 4 wheel scaled at a chassis shop that gives you more information to begin with. BUT if you have to poor-boy it. In my little mini-seminar I tell you how to easily find your actual center of gravity and how to use that information to figure yoiur percentage of front/rear weight distribution. With that information and by knowing more about your car and full diriveline clomonation wheel size tire size and type etc, you will be able to at least get a baseline established as a starting point. After you take it to the track in my opinion getting good close up left side 3/4 angle video of your car doing a launch is a very good suspension tool or aid and all racers should video and watch thier cars in slow siingle frame advance motion. There are several reactions that will happen too quick for your eye to pick up or to register in your mind that the video will show.

After you get my paper and read and understand it, I can help you firther by phone or by mail and I am free. Maybe my suggestions are no goood. I give a money back guarantee with them. Meaning I will happily refund the ZERO Dollars my info will cost you. lol
Ed

[toddcalo]

I do have acess to wheel scales and I have a recent video as you descibed the tire wrinkels it makes one and ahalf revolutions before the car appears to move, the front tire lifts agout 6 to 8 inches , carrys them for about 10 feet , the back end lifts slightley this produced a 1.42 60 foot time. I may be wrong thinking its hitting the tires to hard but just looking for some input thanks.

[Ed-vancedEngines]

I would be happy to look at the video.
email to
edvancedengines@sbcglobal.net
or
Ed-vanced Engines & Performance
902 K ave # 102
Plano Texas 75074
972-633-0563

In the ideal world with a 4 link properly set up and adjusted, the very first reaction in the car at start of launch will be the bottom bar which is mounted in the rear a greater distance from rear axle centerline, and has more of a leverage motion, pushing the car forward. As the bottom bar is pushing forward the top bar which should be mounted a shorter distance up from rear, should be pulling against the front bracket which is pushing the rear axle and the tire/wheel downward quickly but should not cause much movement. All of this motion and reaction occures in just a split second.

Any tire rotation should be with the car moving forward and actually the car should initially react to the bottom bar pushing it forward as the first reaction at the hit. Almost as quick will be the top bars jerking on the brackets forcing the tire downward some.

Perhaps that is over simplying it but if your tire is rotating any with no car movement it is not good. I am also wondering about your burn out. Mabe you have not prepped the tires to be ready to initially hook. It is also possible to have the wrong tires for the car. Heavy cars mostly like a stiffer sidewall and I like to put tubes inside to stiffen them even more. After your burn out if you do a quick dry hop, the tires shoud be grabbing the track on taht quick test dry hop.

Hmm'
Ed

[toddcalo]

I do a hard burnout , about 5 seconds in 3rd gear ,the tires are not specificaly made for a stick but the good year rep said they should be fine Ive onley been to the track once with this tire Im running 11 1/2 #No tubes . Maybe I should raise tire pressure.

[Ed-vancedEngines]

Can we talk on the phone?

I love it that someone is still doing a clutch car.

I know some of the Goodyear compounds and the way they work. I would probably be doing high gear but that would depend on the tire and the compound and also to condition of the rubber. Never let off or roll out of the water by coasting and not under power.

There is an ancient video of me in one of my old cars on it's thrird time down a drag strip that has been circulating around the internet now. It is a little embarrasing because no one can know the car was new and the driver was not used to it either both car and driver was full of bugs but nonethe less someone found an old partial video clip of me from the early 1980's and it has gone everywhere.

I am bringing up that video tp make a point in this conversation. In taht vid I had to abort a burnout as quick as it begun because the car went immediately sideways. I hade to do several dry hops because of no burn out to get some heat inthe tires. IN the first dry hop you can see the tires turn appx two to three times, then they hook and I push in the clutch. Next quick hit the tires hooked and barely lifted the tires before I got the clutch in. Off the line there was zero tire movement not resulting in forward motion. The first dry hop was like you are describing your launch. Also are your tires sending smoke from only the bottom of the tire? If so the rubber can be dead. Dead rubber can be made to hook but it takes a lot of tire speed to get them heated.
Ed

[toddcalo]

When you say dead do you mean to many heat cycles? these tires have onley been to the track once since new Im supposed to be picking up wheel scales tonight Ill keep you posted.

[Ed-vancedEngines]

Sorry,
I was just grabbing at straws in the dark.

On this subject of too mny heat cycles, I might let everyone know that doesn't. Neer let your race tires be on the pavement or paved floor during any winter freezes. That will kill the rubber even on new tires.
Ed

[toddcalo]

I checked out your tutorial good reading and easy to understand sorry I did'nt notice you wanted to see the video Im not to great with computors so I will have to see if the kids can help I picked up scales so I will get some additional info over the weekend I would like to talk to you on the phone if you could email your # thanks

[katman]

Never let off or roll out of the water by coasting and not under power. Ed

Could you be more specific and or maybe a mini-course in burn-outs?