Rod ends
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maxbraketorque
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Are you doing a 3-link or 4-link? DD or full offroad?
It's going to be a 4 link radius arm and a dd but I'm building it to be over kill for my needs and I'm wanting to set it up for when or if I need more flex I can remove a upper arm
maxbraketorque
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I can say from experience that 3-link radius arm is much more supple on the street than 4-link radius arm. No effect on drivability.
I guess people think that 4-link offers more safety or is somehow stronger, but it hinders axle tilt pretty strongly and puts very high loads on the bushings and arms during axle tilt. My guess is that the loads are higher than those associated with acceleration and braking. And if you are worried about safety, keep in mind that there is only one track bar keeping your front axle from sliding sideways out from under your XJ. Of course the suspension will keep it from sliding all the way out, but a broken track bar bolt would almost certainly result in a crash due to loss of control.
My primary suggestion for permanent 3-link is to go with larger bolts for the short arm mounting. I did 12 mm on mine, but could go even larger.
I guess people think that 4-link offers more safety or is somehow stronger, but it hinders axle tilt pretty strongly and puts very high loads on the bushings and arms during axle tilt. My guess is that the loads are higher than those associated with acceleration and braking. And if you are worried about safety, keep in mind that there is only one track bar keeping your front axle from sliding sideways out from under your XJ. Of course the suspension will keep it from sliding all the way out, but a broken track bar bolt would almost certainly result in a crash due to loss of control.
My primary suggestion for permanent 3-link is to go with larger bolts for the short arm mounting. I did 12 mm on mine, but could go even larger.
maxbraketorque
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After you attach the 4-link to your XJ, try flexing it with no springs or shocks. Then try with one upper link removed.
BTW, if you do run with 4-link, you absolutely have to run rubber bushings at the mounting points on the axle. Poly will bind up a 4-link even worse in flex. And of course Johnny joints at the axle are out of the question. With 3-link, you can put whatever bushings you want in the axle.
Why are JJ "out of the question" at the axle end?
maxbraketorque
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The ability for the axle to tilt/flex with a 4-link radius arm suspension relies heavily on the bushings at the axle having some compressibility. The way to envision the issue is to think about axle rotation as the radius arms move with a 4-link setup. As the long radius arms move, the axle not only moves but also rotates because the short arms lock the rotational orientation of the axle to the long arm. If both long arms rotate the same amount in the same direction, then all is good. Now think about what happens if one long arm rotates and the other doesn't. They both want to control the axle rotation which is impossible with stiff bushings at the axle such as JJs.
A little geometry will tell you how much bushing compressibility at the axle side is needed to accommodate the rotational difference between the two long arms. Most long arms are at least 30". If a wheel is flexed 8", this causes the long arm at that wheel to rotate ~7 degrees, and it will try to rotate the axle by same amount. But the rotation of the axle is also locked to the other long arm which nominally hasn't rotated. So the two long arms are fighting to control axle angle. If perfectly stiff axle side bushings are used, then one of three things will happen: the axle will take a permanent twist, an arm will break, or the suspension will not flex.
If compressible bushings are used, then axle flex is possible without destruction. Here's how much is needed. The 7 degrees of axle rotation causes the upper and lower axle mounting points to rotate relative to each other. I believe the distance between the upper and lower mounting points is ~8 inches vertically, so 7 degrees of rotation causes the fore/aft distance between these mounting points to shift by ~1" which has to be accommodated with compressible bushings. If the bushings equally share the necessary deformation, then each bushing needs to compress 0.25". That's for just 8" of flex. 16" of flex requires 0.5" at each bushing. That's pretty massive.
Overall, I think that while a 4-link radius arm can work on an XJ if the axle-side bushings are rubber, it places tremendous loads on the arms, bushings, joints, and axle during high flex offroading. The front suspension will also be unnecessarily stiff against flex. And as I said before, I can easily feel the difference on the street as well.
A 3-link radius arm does not have this issue because only one long arm is controlling axle rotation, and therefore JJs can be used at the axle.
Radius arm designs (long arms in general) are not as effective as a mid arm 3 or 4 link which work extremely well with JJ at both ends for all of the reasons you stated above - and their awful climbing abilty, axle unloading, loss of clearance, etc.
My last TJ was a mid arm 3 link front (technically a four link since it had a track bar) and a triangulated upper four link in the rear (with out boarded rear shocks) and it handled and performed the best out of all my TJs. It also ran the hardest rock trails there are routinely. I had JJs on all three of my TJs - short arm lift, J arm lift, and finally the mid arm.
Anyway - a properly designed front suspension doesn't need stiff bushings. There isn't a finer joint made then the JJ for actual hard off road use.
My last TJ was a mid arm 3 link front (technically a four link since it had a track bar) and a triangulated upper four link in the rear (with out boarded rear shocks) and it handled and performed the best out of all my TJs. It also ran the hardest rock trails there are routinely. I had JJs on all three of my TJs - short arm lift, J arm lift, and finally the mid arm.
Anyway - a properly designed front suspension doesn't need stiff bushings. There isn't a finer joint made then the JJ for actual hard off road use.
maxbraketorque
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Just to be completely clear, I was only speaking of radius arm with both short arms connected. Parallel (or nearly) arm suspension isn't as sensitive.
What do you consider a good mid-arm length?
What do you consider a good mid-arm length?
Whatever these are. This is the best "kit" for a TJ IMO. When combined with outboarded rear shocks and tuned shocks and a Swayloc your Jeep will driver better on the pavement then it did when it was stock, and perform far better off road - both at speed on whoops and rock crawling.
The guy that designed it knows a thing or two about TJs and since the front of a TJ is essentially a XJ the front stuff can be applied. Obviously a TJ has a frame, but most XJs are running frame stiffeners now so welding things up shouldn't be a challenge.
savvyoffroad.com
The guy that designed it knows a thing or two about TJs and since the front of a TJ is essentially a XJ the front stuff can be applied. Obviously a TJ has a frame, but most XJs are running frame stiffeners now so welding things up shouldn't be a challenge.
