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A different long arm question... i think

Supermanxj

NAXJA Forum User
I have been throwing ideas around in my head and this one has got me thinking.

I am thinking about the Rock Krawler lower Long arms and then use adjustable upper control arms that are not long arms. bad idea??

I started thinkin about it while working on my r/c crawler and noticed that it has longer lower control arms and the upper arms are shorter and mount more towards the front.

Thanks for any input!

josh
 
check out teraflex's kit. that's their approach on the cherokees. i don't think that their kit is necessarily the best, but it works out pretty good...
 
In my eyes, that would defeat the purpose of the long arm system. It would limit the axle droop to that of a short arm system, I would imagine?

Long arms don't give more droop than a short arm system, it has nothing to do with travel. Long arms provide better arm angles, and so provide a better ride with less harshness. They also can help front climbing ability since the front tire doesn't have to move forward as much to climb. It's all about the angle of the arms and the arc of travel, not total travel.


check out teraflex's kit. that's their approach on the cherokees. i don't think that their kit is necessarily the best, but it works out pretty good...

Sorry, it sucks. The reason is too much pinion rotation, so the travel needs to be limited to avoid pinion bind.


Wouldn't you want upper and lower to be the same so the pinion angle doesn't change when flexing?

Bingo! Yes, the arms don't need to be exactly the same, but reasonably close in length. When the upper arms are a lot shorter, their arc of travel is more severe than the lowers, meaning that at the same amount of droop the axle end of the upper arms move further rearward, which rotates the top of the axle housing back and increases the pinion angle.
 
A radius arm setup would be different though... With a radius arm setup, the "uppers" are much shorter by necessity...
 
Ok...just clarifying... :)
 
x2, i think the arms need to be parallel for them to work at all actually.

Why??

Sorry, not true.

Using shorter uppers, like the Tera kit uses, does work, you just have to limit travel so the pinion angle doesn't change enough to bind the u-joint. Lot's of designs work, but some designs work very well and others don't work so well.
 
The ideal setup on an XJ for pinion angle is a Y link setup that links close to the transfercase due to the front shaft having a double cardian joint. This keeps the front pinion pointing towards the TC like it should. This setup (IMO) is best for a daily driver/trail rig.

The ideal setup on an XJ for consistant castor is a 3 or 4 link. The upper and lower links (assuming they are roughly the same length) will keep the axle from rotating as it moves through it's travel. This keeps castor more consistant and overall more predictable to drive at high speeds, thus making this the best setup for a jeepspeed or highspeed offroad rig (again, IMO).

In a "nut shell" so to speak.
 
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