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Discussion Starter #1 (Edited)
Same song, different verse for this thread. A recent discussion got me thinking about how many different types and brands of rear lower links are out there, so I decided to come up with another list much in the same way as this thread: http://www.fjcruiserforums.com/forums/4x4-off-road-tech/485257-rock-slider-comparison-guide.html

Hopefully if anything, this list will help those looking for lower links to be able to find the ones that suit their needs and wants.

Why would you even want a pair of aftermarket lower links might you ask? There are various reasons:
1) Strength: If the OE links are hit on rocks, they have a tendency to bend or break, leaving you stranded.
2) Adjustability: While this is not usually a problem and maybe not even noticeable, if you run 35" tires you might find that your rubbing is located in the wheel wells towards the front or rear of the vehicle at full stuff. Having an adjustable length lower link will make it easy to space your axle back further and reduce rubbing.
3) Wheel travel: Most people won't see this benefit unless your running long travel shocks in the rear. With a long travel or "superflex on the cheap" setup at full droop the stock lower links will contact the axle housing, limiting your travel. If you get offset lower links you will gain more travel and not hit your axle at full extension.

Notes:
-Do not call these simply lower control arms or LCA's. Most people are right into thinking you mean the front lower control arm. This has a tendancy to confuse the **** out of people. :lol: These are "links" or be specific and call them rear lower control arms.
-The differences in joint types is kinda just personal preference. The Heims are more prone to failure in a corrosive environment while the Johnny joints act as a rubber cushion to reduce vibration transfer. Heim are less maintenance but Johnny are rebuildable. Google for more info.
-Please don't buy any of the solid aluminum ones thinking they are stronger than the steel. They definitely have a nice bling factor though.
-Look into Wild West offroad if you want to be different.

Please feel free to tell me to add something to the list if you know any other brands etc....
As usual, suggestions welcomed. :bigthumb:

Click on the attachment below to see it bigger.
 

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Discussion Starter #2
I have the metaltech lower links. I think they are one of the best heavy duty options of the bunch, especially for the price. I got lucky and picked up a pair used for a greater discount. If your afraid to do the install, don’t be. If you can change a tire you can install these, just need a few more tools. Here is great write up + video. I didn’t use any straps and mine lined up with little fuss.

FJ Cruiser Rear Lower Control Arm Installation | Off-Road Adventure
 

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Yes! Finally a thread calling them lower links! Good work on the list ... I'm sure people will chime in with others ... I know the two frog racing links aren't being made anymore ... You can add ricochet unobtainium links to the list ... Only a few of those though.
 

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Discussion Starter #4
Yes! Finally a thread calling them lower links! Good work on the list ... I'm sure people will chime in with others ... I know the two frog racing links aren't being made anymore ... You can add ricochet unobtainium links to the list ... Only a few of those though.
Thanks for the info. Ricochet made lower links?! If they are not being made anymore I may not add them, you have any info/links on them though? I'm interested! A quick search finds nothing.
 

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LoL i like the name " Un obtain ium"
 

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Out of curiosity, has anyone ever done the math to see what sizes actually make sense for the lower links? You could make a 3" O.D., 0.5" wall link but, is it possible to actually put enough stress on the links to require more than, for example, 1.75" O.D. 0.188" wall? I get that it's cool to have beefy and mean looking lower links but, at what point do you start to see diminishing returns? If you look at the Light Racing links, they look kinda wimpy compared to other links but, SPC tends to design stuff to be as strong as it needs to be. Are other links crazy overbuilt or are the Light Racing ones underbuilt?
 

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Discussion Starter #14
I know the light racing DOM lower links are advertised to be "2x stronger than OEM" which I'm sure is plenty, but I am also curious on the strength of others. An interesting thing I've always wanted to compare would be solid aluminum vs. some of the steel tubing. It would actually be simple to calculate this. Basic beam bending, moment of inertia, stress is about all you need to know along with some Greek. :lol: I'll see what I can come up with #'s wise when I've got some free time....
 

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Discussion Starter #15
One thing that would be difficult to figure out, how much load will these see? The weight of the FJ? Half the weight of the FJ? We can compare their relative strength all day long, but we need to figure out the maximum possible force they will see if we really want to determine if they are "strong enough".
 

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One thing that would be difficult to figure out, how much load will these see? The weight of the FJ? Half the weight of the FJ? We can compare their relative strength all day long, but we need to figure out the maximum possible force they will see if we really want to determine if they are "strong enough".
I've been thinking about this tonight and I was thinking to maybe compute 3000lbs on each end of a 2ft tube dropped at 1ft onto a point. That seems like an extreme condition and the variables could be backed off to find approximate failure points from there. Having said that, I'm not a materials engineer so, my methodology is likely to be naive or just plain wrong.
 

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Discussion Starter #17
I've been thinking about this tonight and I was thinking to maybe compute 3000lbs on each end of a 2ft tube dropped at 1ft onto a point. That seems like an extreme condition and the variables could be backed off to find approximate failure points from there. Having said that, I'm not a materials engineer so, my methodology is likely to be naive or just plain wrong.
That sounds close, usually with basic beam bending for this type of scenario you calculate the force it will see (in this case directed towards the middle as worst case scenario) and treat the ends as 100% statically supported. After this is completed, another interesting thing to look at in the system is the strength of the bolts they are attached to:

Some links and link skids come with 9/16" Grade 8 bolts. Grade 8 minimum yield strength = 130,000 psi (this is the force to bend, not break) Shear strength is approx 60% tensile strength: 130k x .60 = 78,000 psi. Tensile stress area for 9/16 bolt= .182" squared. Multiply this area by 2 because of two bolts, and by 2 again because they are in double shear= .728 in sq of area.

Ubiquitous formula:
Force (lbs) = P (psi) x A (sq in)
F= 78,000 x .728
F= 56,800 lbs to bend the bolts that mount the lower links given an evenly distributed force.
Divide this # by two to see what a single bolt can do if the load was on one end.

Now the factory metric hardware should be close to this # too.
There is yall's basic statics lesson for today. Part two is the strength of the lower links...
 

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That sounds close, usually with basic beam bending for this type of scenario you calculate the force it will see (in this case directed towards the middle as worst case scenario) and treat the ends as 100% statically supported. After this is completed, another interesting thing to look at in the system is the strength of the bolts they are attached to:

Some links and link skids come with 9/16" Grade 8 bolts. Grade 8 minimum yield strength = 130,000 psi (this is the force to bend, not break) Shear strength is approx 60% tensile strength: 130k x .60 = 78,000 psi. Tensile stress area for 9/16 bolt= .182" squared. Multiply this area by 2 because of two bolts, and by 2 again because they are in double shear= .728 in sq of area.

Ubiquitous formula:
Force (lbs) = P (psi) x A (sq in)
F= 78,000 x .728
F= 56,800 lbs to bend the bolts that mount the lower links given an evenly distributed force.
Divide this # by two to see what a single bolt can do if the load was on one end.

Now the factory metric hardware should be close to this # too.
There is yall's basic statics lesson for today. Part two is the strength of the lower links...
Rock on.
 

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