How does a mid-arm suspension improve the climbing capabilities from the drivers seat?
- Thread starter mattcogdell
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Not looking for a fight!
Why is a mid-arm so wonderful yet a long arm is condemned completely?
If the long arm calculator is only good as a starting point (which it obviously is) then so would any length control arm calculations.
But I haven't seen any criticism for mid- or short-arm geometry.
Looking for explanations
not expletives 
Why is a mid-arm so wonderful yet a long arm is condemned completely?
If the long arm calculator is only good as a starting point (which it obviously is) then so would any length control arm calculations.
But I haven't seen any criticism for mid- or short-arm geometry. Looking for explanations
not expletives 
Long arm kits in general suffer from bad geometry due to packaging. The average owner doesn't weld but he can cut and grind. They attached the arms to the belly skid so it could be installed. There was little thought given to geometry, just installation.Not looking for a fight!
Why is a mid-arm so wonderful yet a long arm is condemned completely?
If the long arm calculator is only good as a starting point (which it obviously is) then so would any length control arm calculations.
Looking for explanations
Not looking for a fight!
Why is a mid-arm so wonderful yet a long arm is condemned completely?
If the long arm calculator is only good as a starting point (which it obviously is) then so would any length control arm calculations.
Looking for explanations
There is nothing inherently bad about longer arms, it's that they don't package well into a TJ which ends up causing all of the bad things you hear about long arms.
The key to start understanding why the mounting points matter more than the arm length is understanding what the instant center (IC) is. The locations of the control arm mounting points define where the IC is and how it moves through space. The arm lengths are largely the end result of where the mounting points are placed to create the desired position of the IC.
The first half is the important part where we learn how to find the IC. The second half that talks briefly about where to place the instant center is the start of the discussion how the IC (relative to the CoG) determines how the linked suspension will behave (antisquat) when loaded by the drivetrain. Antisquat describes how the suspension will rise or sink when loaded. Different applications will want the instant center in a different location relative to the vehicle's CoG to create the desired antisquat behavior.
For our purposes on an off-road Jeep, we ideally want the IC to be located in a certain range in space to make the suspension behave a certain way.
The first half is the important part where we learn how to find the IC. The second half that talks briefly about where to place the instant center is the start of the discussion how the IC (relative to the CoG) determines how the linked suspension will behave (antisquat) when loaded by the drivetrain. Antisquat describes how the suspension will rise or sink when loaded. Different applications will want the instant center in a different location relative to the vehicle's CoG to create the desired antisquat behavior.
For our purposes on an off-road Jeep, we ideally want the IC to be located in a certain range in space to make the suspension behave a certain way.
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Synergy DDB with custom Core4X4 arms for my short arm, I have not decided on what to do with my mid arm I may install in the front.
K. Got it. It isn't the arm length that is the problem, it's the lack of proper engineering that is. The frame side mounts are designed for ease of install and not located to maintain ideal axle location.
Thanks for the info.
Short of Ultra4 or similar, does anyone make a long arm kit with correct geometry, or is that the reason Savvy stopped at a mid arm?
Thanks for the info.
Short of Ultra4 or similar, does anyone make a long arm kit with correct geometry
, or is that the reason Savvy stopped at a mid arm?
the mid arm incorporates all the benefits that longer arms claim to provide, but "stopping at mid arm" keeps you from sliding on the arms ie: better clearance. longer arms generally have a shallower angle and run further toward the center of the jeep where breakover angle is most critical.K. Got it. It isn't the arm length that is the problem, it's the lack of proper engineering that is. The frame side mounts are designed for ease of install and not located to maintain ideal axle location.
Thanks for the info.
Short of Ultra4 or similar, does anyone make a long arm kit with correct geometry
Exactly, geometry is what is being corrected in the good setups like savvy mid. Arm length has absolutely nothing to do with it - that’s simply a byproduct of correcting the geometry and packaging.K. Got it. It isn't the arm length that is the problem, it's the lack of proper engineering that is. The frame side mounts are designed for ease of install and not located to maintain ideal axle location.
Thanks for the info.
Short of Ultra4 or similar, does anyone make a long arm kit with correct geometry
Geometry is compromised for packaging. That means they had to lower the forward end of the upper rear arms to get them to attach to the skid plate and to clear the cargo step for uptravel. If you want to correct the geometry, you need to hack some holes in the tub for the upper arms and mounts.K. Got it. It isn't the arm length that is the problem, it's the lack of proper engineering that is. The frame side mounts are designed for ease of install and not located to maintain ideal axle location.
Thanks for the info.
Short of Ultra4 or similar, does anyone make a long arm kit with correct geometry
The fact that you said "stopped at a mid arm" is because you believe there is some benefit to long arms, there isn't.
If the typical long arm kits had good geometry, their arm lengths and mounting points would more closely resemble the Savvy kit because that is where everything needs to be in order to do what it is supposed to do.
Watched this today. Can guys you break down what he's trying to say and what is wrong. I trust the knowledge on this sight but would like to see your arguments to help me understand both sides.
What’s going to go over a lot of heads in this video is his discussion of how geometry is the important part and not arm length. He states that - and it holds true. I’ll let the experts break down the other stuff.
I saw that last night. He has a point in some areas like climbing an undercut. He specifically built his front to maintain pinion angle over caster, if that hints at anything. Also notice that he never once addressed the rear. Beyond that, I am clearly among the crowd he criticizes in the beginning. One thing I notice in nearly every TJ long arm YouTube video is that they never discuss instant centers and antisquat. They never discuss the importance of shocks. They never cycle the axles and explain setup. Nate is slightly better than most on YT, but there are large gaps in his understanding.
As is typical in these things, Nate is placing emphasis on the wrong geometry.
I agree. I enjoy watching his fabrication but even the fact that he used the laser to show how much the axle doesn’t move when going down (which although true has little to no relevance when actually discussing pros and cons). He also falls short is saying that “long arms” (what does that phrase even mean) “ride better” - compared to what? Not a well setup “short arm” suspension (also a bad label)
Also - I knew he had no idea what he was talking about as soon as he said that tire size isn’t a factor.............you’re kidding. Tire size, wheelbase, and belly height are the three factors you build a suspension around.
His long arms don't get in the way because of his tire size and potentially the trails he runs. My mid arms get in the way because my tires are too small and because of the trails I run. Catching the rear frame mount is one of my complaints right now.
Large is an understatement. We have tested short and mid arm side x side on the same rig with no discernible difference in ride quality and that was two folks who are very sensitive to such things. For someone trying to explain stuff to folks, his front geometry is fucked. Caster is about 3.5 degrees, the arms are too close together at the frame simply due to length and he's running more money in that bypass shock than most will spend in a lifetime on shocks.