Control arms: What is the benefit to bushing at one end and flex joint at other?

Don Bulee said:

so.. considering this... I would not be gaining a lot from having a JJ in only one end? since the other end would impede the twisting of the arm? or the gains will be barely noticeable? I understand that the best way is to have both ends with a JJ, but in this case is out of my budget... and I'm not sure if the fixed end can be upgraded to a JJ as well..... I would assume yes, since the crawl series its pretty much the same end but with a JJ.. I already asked them but I havent had any answer

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The benefit would be statistical only - you would have half the mounts exposed to the risk of ripping off, instead of all of them. As far as which end to put the poly bushing on, I would consider which end is easier to repair, and which end, if broken off, would cause the least collateral damage.

FWIW, I have JJ's on both ends of my UCA's, and one end of my LCAs, which have Clevites or similar in the other end. I have the JJ's on the frame end because I'm not worried about one breaking off and that puts the jam nut where I can get to it without removing a wheel/tire.

freedom_in_4low said:

Sorry, yeah I follow now.

The thing is that straight poly bushings have two issues and having a JJ at the other end only solves one of them.

Misalignment in the form of the arm twisting around the centerline of the arm tube/body, the flex joint will take it and the poly will do ok. However, misalignment in the arm swinging laterally around the mount, doesn't matter what's in the other end. You're still trying to twist the mount off. The arms want to swing in this motion as the axle follows the arc of the track bar.

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It is easier for most if you explain it from the perspective of the track bars push and pull the axle back and forth sideways as the suspension moves. Poly is notorious for not wanting to let that happen and is responsible for more than a few rear upper control arms being ripped off of the frame. The other issue I've seen with a ton of poly bushings is the bolt sleeve is pretty thin wall and tends to let the ends wear into the slots at the lowers on the front axle mounts. Makes them very hard to keep tight. If the wall thickness goes up, that problem goes away.

mrblaine said:

It is easier for most if you explain it from the perspective of the track bars push and pull the axle back and forth sideways as the suspension moves. Poly is notorious for not wanting to let that happen and is responsible for more than a few rear upper control arms being ripped off of the frame. The other issue I've seen with a ton of poly bushings is the bolt sleeve is pretty thin wall and tends to let the ends wear into the slots at the lowers on the front axle mounts. Makes them very hard to keep tight. If the wall thickness goes up, that problem goes away.

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you mean like this? (skyjacker expensive shitty bushings after 1 year and a few months...)







BTW I just hung up with Core 4x4 team, and the cruise series cannot be upgraded to a JJ end in the fixed part of the arm only in the adjustable end, so Cruise and Camp series would only be able to have 1 end of the arm with a JJ (the adjustable one), if you want both ends with JJs you will have to get a Crawl series.. (around $445 for each pair..)

mrblaine said:

It is easier for most if you explain it from the perspective of the track bars push and pull the axle back and forth sideways as the suspension moves. Poly is notorious for not wanting to let that happen and is responsible for more than a few rear upper control arms being ripped off of the frame. The other issue I've seen with a ton of poly bushings is the bolt sleeve is pretty thin wall and tends to let the ends wear into the slots at the lowers on the front axle mounts. Makes them very hard to keep tight. If the wall thickness goes up, that problem goes away.

Click to expand...