long arm or no long arm

[resident e]

when should long arm suspenion b consided? how high can u lift a TJ before the angles become 2 much :?: would anything more then say 4.5" b 2 much, were would the point b :?: :?: :?: :?: :?: :?: :D :D

[Jumbo]

As an experiment we tried a set of 5.5 in coils on my TJ with just the rubicon adjustable uppers and lowers..Looked great but drove like a bag of 5h-t.The angle on the control arms was just a tad on the excessive side.. :roll: We found that with the front axle instead of trying to drive over the obsticle it actually tried to fold the axle rearwards.. not good from a stress point of view :(

so from what we learned about 4.5 in coil lift would be the max you could run and still have reasonable drivability.. :)

[Wooders]

Similar to jumbo - I've running 4½" which is what I feel is the max comfortable SA lift.
The other thing to remember as the height gets over about 4½" with short arms your droop is limited and you get much more axle steer....

[LEXX]

I really have been happy with my LA kit. The ride difference was noticable straight away, the ride is smoother and not as quick as with the standard SA.

The drivability of the TJ is great now and with a 5.5" coil lift she drives just fine, a few other things had to be done, but if I still had the SA I recon it would be almost undriveable.

[TJPete]

when should long arm suspenion b consided? how high can u lift a TJ before the angles become 2 much :?: would anything more then say 4.5" b 2 much, were would the point b :?: :?: :?: :?: :?: :?: :D :D

The OE geometry is "adequate" for the OE setup. Longer arms than OE should be considered immediately the suspended or sprung height of the vehicle is increased. Why? The working angle of the control arms determines the degree of bump steer and forces exerted on the tyre contact patch with the terrain you are travelling over.

In my experience I have not found there to be a "perfect" arm length. However, an operating angle of 6 degrees at static ride height is what I have found to be just about as good as you can get in providing a compromise between what is practical and what works best in terms of handling and traction. You cannot achieve this angle with OE length arms unless you lower their mounting points significantly. But to do so without increasing their length only achieves some of the geometric equation that leads to superior handling in very eXtreme situations.

An operating angle of 6 degrees at static ride height also contributes well to getting power to the ground without the vehicle sinking on its bum. When this happens, torque output from the motor is being absorbed by the vehicle and not transmitting to the ground for effective forward motion. A good example of this defect can be seen in a Yellow TJ that ran the TTC last year.

In a 4 link, 6 degrees applies to both upper and lower arms. In a 3 link the equation is different for the upper arms than it is for the lower arms. The 3 link is less stable than a 4 link and requires more effort on the driver's behalf to control the car when it is off camber. However, the 3 link if set up correctly, will generally out-droop a 4 link and this (combined with other correct suspension geometries) can result in a superior performance.

In a nutshell, the 3 link generally provides the most articulation but a 4 link is generally more stable.

The longer the arms, the greater the opportunity for decresed rigidity and an earlier moment of inertia (MOI). The moi is the point at which the arm will bend or elongate out of true. This is undesirable and can be avoided by choosing the correct materials of appropriate dimensions and correctly terminating them to transcribe their best elliptical arcs.

I have most likely responded too much here, your question is a simple one and deserves a simple answer. The simplest response I can give is this:

Yes, longer are better, but don't analyse only the requirement for length of arm, look at all of the suspension geometry and not just the arms in isolation. And never forget that the longer the arms, the greater their ellipses as the suspension travels from bump to droop. And don't disregard the pinion angle whicj you can make remain static during bump to droop cycle or you can make it rotate up as maximum droop is approcached.

All the best bloke!