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Author Topic:   TOP A-FRAME POSITIONING/WHATS UP?
LITTLEMAN
Member
posted December 21, 2000 06:48 AM
I WAS JUST WONDERING...WHAT,S THE BEST ANGLES FOR THE TOP A-FRAME MOUNTING.SHOULD IT BE LEVEL WITH THE LOWER A?WHY DOES A CAMERO HAVE ITS TOP MOUNT ANGLED SO MUCH,WHAT IF ITS ANGLED THE OTHER WAY?

[This message has been edited by LITTLEMAN (edited December 21, 2000).]

[This message has been edited by LITTLEMAN (edited December 21, 2000).]

wfoondirt
Member
posted December 21, 2000 08:59 AM
it all depends on the type of frame your running, lower control arms, spindle,ball joint etc etc. There is alot more involved in front end geometry than most people realize and it has a lot to do with the way the car handles more so than the rear suspension. Many cars, even brand new ones from major manufacturers, that i have seen have obvious flaws in the front suspension geometry and a racer can gain alot by understanding and correcting front suspension on a race car. I reccomend to anyone to make a detailed drawing of the front suspension on a racecar and you'd be suprised what you can find wrong. There is really too much to explain in a post but want to look at one of stevie smiths books to get a good understanding, i also reccomend mark ortiz's web site, racecartech.com, he has some good posts on there reguarding front suspension geometry.


Strokin3
Member
posted December 21, 2000 10:45 AM
Littleman, one thing I know for sure is that
if your upper a arm doesn't travel in the same arc as your lower everytime you go into
bump or rebound your caster will change. The
position and angle of this component is the
hardest to get located correctly if you are
doing the work yourself. The last one I did
I used one of the books from Steve Smith and it still took a lot af trial and error in the designing phase till I got it right. As
the previous post said this is probably the single most significant component that effects front end geometry.Caster is only one
of the problems you will encounter, the list goes on.

[This message has been edited by Strokin3 (edited December 21, 2000).]

RICH
Member
posted December 21, 2000 12:18 PM
HEY RICH WHY DON'T YOU STICK TO THE TOPIC?I ALWAYS LIKE TO HEAR OTHER PEOPLES OPINIONS ON WHAT THEY THINK MAKES A GOOD RACECAR.DO YOU KNOW WHY A CAMERO UPPER A MOUNT IS TILTED LIKE IT IS?IT WASN'T COVERED AT MY WORK SO I THOUGHT I'D ASK THE DIRT FORUM READERS.SORRY IF I OFFENDED YOU.


Strokin3
Member
posted December 21, 2000 07:46 PM
Don't know why GM did it but it creates anti
dive in race cars and is usually an undesireable condition. I sure hope someone
will answer why GM did it cuz I have always
been curious. You know at our local dirt track warehouse they sell upper A arm brackets with the holes angled downward towards the rear???


LITTLEMAN
Member
posted December 21, 2000 10:24 PM
IF ANTI DIVE IS BAD FOR RACE CAR FRONT ENDS WOULD MOUNTING THE TOP A-FRAME WITH THE FRONT LOWER CREATE PRO DIVE AND HELP THE CAR GET OVER ON THE RIGHT FRONT?


RICH
Member
posted December 21, 2000 10:33 PM
i have followed the theory of mounting the upper plate at the same angle with the lower so they swing in the same plane without bind. also 0-2 degrees antidive. anti dive, how much you use determins how much caster change you want when entering the corners under braking. this can be good and bad. i have personally seen cars with the same frames built by different people with the uppers mounted at all kinds of angles and most of the cars ran good. i do not think there is any specific way of mounting them. some builders still use the stock mounts. most builders do what they think is best and make the changes till they are successful. that is why you see the variety in the way the mods are built. everyone has different ideas. that is what class so neat to watch and race in.


LITTLEMAN
Member
posted December 22, 2000 07:07 AM
I'VE HEARD OF BUILDERS TALKING ABOUT MOVING THEIR A-FRAMES TOWARDS THE FRONT OF THE CAR INSTEAD OF HAVING THEM ANGLED BACK AT 20 DEGREES.WOULDN'T THIS CAUSE THE FRONT END TO LOSE CASTER IN BUMP.THEY SAID IT MOVED THE ROLLCENTER TOWARDS THE FRONT OF THE CAR HELPING IT GET IN THE CORNER.

[This message has been edited by LITTLEMAN (edited December 22, 2000).]

CUSTOMPERFORMANCE
Member
posted December 22, 2000 07:17 PM
yes i know of one builder that does them that way. i still say anything can be made to work if you stick with it and work with it


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