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Old 10-26-2006, 07:03 PM   #1 (permalink)
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Equal vs. Unequal Length Arms

since this forum has come about Ive been looking at cheap builds on other forums, mostly rangers. and some guys run unequal length front swing arms or beams, or whatever they call them. how and why is this desirable? to me i would build each arm cantilevering from as far across the frame as possible to alleviate so much camber change throughout suspension cycle.

i have an idea of how i would build a swing arm suspension, and i have not seen it done yet, more than likely because it cant be executed strong enough.

Callen
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Old 10-26-2006, 08:17 PM   #2 (permalink)
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Old 10-26-2006, 08:44 PM   #3 (permalink)
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There are companies that make equal length beams
Giant Motorsports is one of them.

The reason most people have unequal length is because that is how they come from the factory (Rangers and F-150/250 's)

Equal length beams cost about $5k because you need the custom beams and the custom steering. Check out Giant Motorsports website to see what I am talking about.

Most people are able to get away with different length beams which cost about $1800 and do not require a serious change in steering.

I'm new to the whole beam thing but I did a lot of research on it last month. Some of the desert racers might have more comments.
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Old 10-26-2006, 09:25 PM   #4 (permalink)
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oh, i didnt realize (ive never actually looked at a factory TTB or whatever, all this is in my head) that the beams were of unequal length from factory. it seems to me that you could make a swing arm that held its camber withing a degree or two jsut as easily as you could design a rear 4 link. i dont have any programs to explain myself better. ill see what i can muster up on Paint here in a min.

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Old 10-27-2006, 01:51 AM   #5 (permalink)
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Quote:
Originally Posted by Fawk Awph
oh, i didnt realize (ive never actually looked at a factory TTB or whatever, all this is in my head) that the beams were of unequal length from factory. it seems to me that you could make a swing arm that held its camber withing a degree or two jsut as easily as you could design a rear 4 link. i dont have any programs to explain myself better. ill see what i can muster up on Paint here in a min.

Callen
When you say "swing arm" are you talking about an A-arm suspension rather than beams? I can't imagine you using beams and keeping camber within a degree with any travel. The reason beams are popular are because 1, they're easier (sans the steering part) and 2, more travel. To get mass travel out of A arms you have to center mount them or have a stupid wide trackwidth.
Plus beams just look cooler.
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Old 10-27-2006, 09:40 AM   #6 (permalink)
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i was talking beams, but none the less how does having unequal lenth beams actually work?

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Old 10-27-2006, 10:54 AM   #7 (permalink)
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unequal = stock pivot points/ beams are extended
equal = pivot changed/ custom beams

notice the difference





Honestly I cant tell the difference in the two ride wise w/ coilovers...but hey Im a Ford arm guy
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Old 10-27-2006, 11:18 AM   #8 (permalink)
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un = length beams came about in the early 80's when ford switched from = length king pin to un = length king pin then to un = lenghth balljoint beams.
the theory behind it is that one beam pivots infront of the other but the radius arms pivot in the same spot (opposite eachother). if you draw a triangle from spindle to rad arm pivot to beam pivot for drivers and pass side un = length setups triangles intercet in the center of the truck where as = length setups intercet of to the side of the center. somehow ford deturmened that un = length setups handeled beter for street driving, thus the change

hope that makes sence
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Old 10-27-2006, 09:06 PM   #9 (permalink)
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fuck no that didnt make any sense!
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Old 10-27-2006, 09:25 PM   #10 (permalink)
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Quote:
Originally Posted by Halogrinder
fuck no that didnt make any sense!

haha, someone had to say it. maybe ill back through it and take out all symbols and replace them with words.

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Old 10-27-2006, 09:57 PM   #11 (permalink)
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Quote:
Originally Posted by BHTool
un = length beams came about in the early 80's when ford switched from = length king pin to un = length king pin then to un = lenghth balljoint beams.
the theory behind it is that one beam pivots infront of the other but the radius arms pivot in the same spot (opposite eachother). if you draw a triangle from spindle to rad arm pivot to beam pivot for drivers and pass side un = length setups triangles intercet in the center of the truck where as = length setups intercet of to the side of the center. somehow ford deturmened that un = length setups handeled beter for street driving, thus the change

hope that makes sence



i was talking about this clusterfawk
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Old 10-27-2006, 10:14 PM   #12 (permalink)
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Quote:
Originally Posted by Halogrinder
i was talking about this clusterfawk
I think I got it

He is saying the roll axis is off center with equal length beams. And that ford switched to unequal length beams to make the roll axis centered.
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Old 10-27-2006, 10:31 PM   #13 (permalink)
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Quote:
Originally Posted by BHTool
unequal length beams came about in the early 80's when ford switched from equal length king pin style beams to unequal length king pin style, and then to unequal length ball joint beams.

the theory behind it is that one beam pivots in front of the other but the radius arms pivot in the same spot (opposite each other).

if you draw a triangle from spindle to radius arm pivot to beam pivot for drivers and pass side unequal length setups triangles intercept in the center of the truck where as equal length setups intercept off to the side of the center. somehow ford determined that unequal length setups handled better for street driving, thus the change

hope that makes sense
Quote:
Originally Posted by Halogrinder
i was talking about this clusterfawk
so was i

i understand what hes saying though. i tried to do a rough sketch in paint.





Callen
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Last edited by Fawk Awph; 10-27-2006 at 10:32 PM.
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Old 10-27-2006, 10:37 PM   #14 (permalink)
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Here is another pic

Top view of suspension:
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Old 10-27-2006, 11:26 PM   #15 (permalink)
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Quote:
Originally Posted by TRD
Here is another pic

Top view of suspension:

how is that correct? that shows the beams being the same length, but not lining up in the center. is that to show how the center would be off if both beams were the same length and why for went with the unequal length beams?

Hell, you need to get some paint skilz, all that fancy shits killin me. ha.

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Old 10-28-2006, 07:22 AM   #16 (permalink)
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That is to show equal length beams do not have the roll center in the middle of the vehicle.

And if you imagine the left beam getting shorter you will see that changes the roll center to the middle of the vehicle.
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Old 10-28-2006, 10:26 AM   #17 (permalink)
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There's some good information on this topic in THIS DISCUSSION on desertrides.com.
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Old 10-28-2006, 10:29 AM   #18 (permalink)
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Here's ANOTHER ONE (there's also some good including about Radius arm mounting points in there).
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Old 10-28-2006, 03:11 PM   #19 (permalink)
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Callen[/QUOTE]

I know this is a rough sketch, but you really don't plan on having the beams cross like this do you? Just a thought, but there may be a bit of an interferance problem.
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Old 10-29-2006, 05:47 PM   #20 (permalink)
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how do you go about running equal length beams without crossing them? is just one (the rear beam) bent so the spindles end up in the same place?

in TRD's post is shows the spindle positions in different locations, is this difference compensated in the spindle or what?

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Old 10-29-2006, 06:01 PM   #21 (permalink)
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this is probably wrong but maybe ford figured they could save money and get the same results with different lenght I-beam arms
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Old 10-31-2006, 10:59 AM   #22 (permalink)
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....just subscribing to this thread
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Old 10-31-2006, 04:54 PM   #23 (permalink)
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found some pics on those links you gave me.

this is what i was wondering. it seems as though you mount the beam-ends in a different place than i was imagining.

these pics pretty much explain the differences pretty good.
EQUAL LENGTH BEAMS



UNEQUAL LENGTH BEAMS


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