Re: Lower control arm lenght??
[Re: '72CudaRacer]
#568373
12/31/09 11:11 PM
12/31/09 11:11 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Its done all the time with a chassis car that runs a A-arm set up... set the inner pivot points as the same length as the steering rack pivots
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Re: Lower control arm lenght??
[Re: '72CudaRacer]
#568374
01/01/10 09:25 AM
01/01/10 09:25 AM
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Joined: Aug 2004
Posts: 2,128 sweden
sshemi
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Quote:
Mopar lower control arms are much longer than upper.Why? Is it because of torsion bar placement? In a all drag car, is it possible to fabricate some that are closer to upper cont arm lenght, and still be stable at speed. It would seem to me that if the upper and lower cont arms were the same lenth and spaced apart the same distance as the spindle height, you would have a lot less problem with bump steer. Or am I missing something? Any chassis guru's have thoughts on this? Thanks, Brian
If they where equal in length you would get a whole lot of camber change throughout the susp travel. about the bumpsteer read Pbodys post
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Post deleted by Defbob
[Re: QWK_ENUF]
#568376
01/02/10 06:44 PM
01/02/10 06:44 PM
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Re: Lower control arm lenght??
[Re: '72CudaRacer]
#568377
01/02/10 09:59 PM
01/02/10 09:59 PM
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Joined: Dec 2003
Posts: 22,695 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
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I believe the answer you are looking for, they are unequal lenght becuase they want a certain amount of camber change, reason being as the car turns and body rolls, you would get positive camber, not good for turning, with negative camber as wheel compresses, additional negative camber keeps the tire in better road contact. Its all a big set of compromises anyway. bump Steer refers more to Toe changes as the wheel raises and lowers, due to cornering, braking, or accelerating or some combination.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Lower control arm lenght??
[Re: jcc]
#568378
01/02/10 10:15 PM
01/02/10 10:15 PM
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Joined: Aug 2009
Posts: 2,036 Mooresburg, Tn
'72CudaRacer
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Quote:
I believe the answer you are looking for, they are unequal lenght becuase they want a certain amount of camber change, reason being as the car turns and body rolls, you would get positive camber, not good for turning, with negative camber as wheel compresses, additional negative camber keeps the tire in better road contact. Its all a big set of compromises anyway. bump Steer refers more to Toe changes as the wheel raises and lowers, due to cornering, braking, or accelerating or some combination.
Exactly. In a drag race only car, none of that (except bump steer), matters, right? If I'm going to go to the trouble to do away with K member and torsion bars and use lighter upper and lower control arms and coil overs with a braced front frame section, wouldn't this be a good time to address the geometry? Most everyone that offers tubular K's have basicly duplicated the factory geometry (for street use, I assume?). Or am I WAY out in left field? Thanks, Brian
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Re: Lower control arm lenght??
[Re: '72CudaRacer]
#568381
01/02/10 10:30 PM
01/02/10 10:30 PM
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Joined: Nov 2004
Posts: 4,330 Lynchburg, VA
Leon441
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My lower control arms are shortened. The length is identicle to the upper control arms. And like Pbody said the tie rods are the same length also.
The length of the rack is longer than the distance between the pivot points of the lower control arms. This works to be an advantage. When you make up the steering arm the tie rod end needs to be further out from center of the car than the ball joints in order to have proper ackerman. This control which wheel turns shorter than the other when turning. How much is not criticle but if you have negative ackerman you are hurting the handling of the car. In a drag car if the steering whell needs to turn you are already in trouble. So it is important to have a car that will have stable manners. My car is narrower than the later A-bodies so it all works out fine. This is not going to be the case on 67 and later A-bodies as well as the others. So you may want that lower control arm a little longer. Builders of strut cars have a measurement between frame rails they use for all of the cars. The measurement has to do with the length of the rack. This is not written in stone because you can get a shorter rack it just cost more.
A drag car does not need as much suspension travel as a factory built car. You need to limit how much compression the front end has so you don't flatten your oil pan or headers. Depending on how much power you have you may not need a lot of extension either.
Leon
Career best 8.02 @ 169 at 3050# and 10" tires small block power.
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Re: Lower control arm lenght??
[Re: Leon441]
#568382
01/02/10 10:49 PM
01/02/10 10:49 PM
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Joined: Aug 2009
Posts: 2,036 Mooresburg, Tn
'72CudaRacer
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Well, back to the drawing board for me. I'm starting to believe an OLD racer friend of mine when he said, years ago I might add, "forget the weight, just build a bigger motor!" Thanks, Brian
Last edited by '72CudaRacer; 01/02/10 10:53 PM.
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Re: Lower control arm lenght??
[Re: '72CudaRacer]
#568383
01/02/10 11:21 PM
01/02/10 11:21 PM
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Joined: Nov 2004
Posts: 4,330 Lynchburg, VA
Leon441
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Bondobob he's got a nice kit. Bob's pro fab I think is the name.
Career best 8.02 @ 169 at 3050# and 10" tires small block power.
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