Unequal length A-arms

elcaprerunner

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I am very curious, what is with unequal length A-arms? Every time I read an ad for an A-arm sandrail they describe the arms as being unequal length. For example.... Quicksand and Buckshot both describe their buggies this way. Anyway, my question is why do they make the arms unequal length? Is it the only way to get the geometry right because it's a full-tube car? DO they only do this on sand rails? Or does everybody make arms unequal length when using custom pivot points ( i.e. Trophy Trucks, class 1s & 10s, prerunners, etc. etc.) OR, are ALL A-arms made to be equal length meaning stock arms too? Or are stock arms equal length but if you put a long travel kit on does it make them unequal length? Or vice versa?

It doesn't seem right to have your A-arms made unequal length, it seems like the geometry would be wrong, or atleast different with each arm. Am I completely backwards with that theory? And how much differance in length is there between each side?

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BeastlyFord

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Are you thinking that means that they are different lengths on the passenger side as compared to the driver's side? What they are talking about is the upper arm being a different length than the lower arm. of course you could be asking a totally different question in which case i am an idiot who just had too much fun watching the Bucks kick the crap out of the Raiders!

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Dillon

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I think you are backwards, A-arms in principle are unequal length. I think you are confusing things, Unequal means the lower is longer then the upper. Go look at a car site with brand new vehicles w/ A-arms, the specs with say either double wishbone or unequal length control arms.
 

elcaprerunner

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That clears it up, thanks. I got the impression that the A-arms on one side ( both upper and lower) were different lengths on each side. I knew that didn't seem right, but you never know unless you just straight up ask right? :) But yes, I did know that the lower arm is a longer length than the upper, but I thought that it seemed too obvious to me by looking at the picture of the car to state that the uppers and lowers were unequal length......

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Dillon

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I see what you are saying, but I have never seen such a thing, there is no reason to do longer arms on one side then the other like on an I-beam system since all things are equal on each side of the truck with A-arms. I know unequal I-beams is to compensate for the mounting method so (while debatable, but I buy the theory personally) both wheels have equal (relative) proper wheel movement through their travel.
 

elcaprerunner

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Yeah, I understand it now. With the impression I got I was figuring that some how the pivot points were at different spots than eachother for whatever reason, I cound't figure out why but now it makes sense. Of course the upper and lower arms couldn't be the same length ( depending upon pivot points of course), otherwise the geometry would be totally, totally wrong. You would have camber change like I-beams if you did that, am I right?

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Dillon

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Technically you could have equal length arms. But IMO its not the best way. First off, travel is good. Having a track width of a B52 tho isn't always good. So ideally center mounted lower arms with short upper arms and a uniball is best way cuz you keep track width wider but not too wide. You also have to remember most A-arms trucks will have the engine compartment in front, so you can't fit to long ass center mounted arms cuz there is the engine in the way.

The only time you could have a clean traveling equal arm setup would be if the pivot points were exactly the same length from the points to the balljoint/uniball to spindle pivot. Make sense? But there is limited travel in that unless they are center mounted or you don't want much travel.
 

ntsqd

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Short upper arms at a steeper angle than the lower arms both generates a decent camber curve & puts the Roll Center almost where it needs to be.

Doing an equal length A-Arm car would offer no camber curve improvement over a VW beamed car.

TS

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