Stock upper control arms

I have a Rubicon Express 3.5" lift with Ram shackles on the rear, a 2" Teraflex coils spacer on the front, and drop brackets. I am using the RE lower control arms that came with the lift. This is all on a 2001 XJ.

My question, the lower arms measure, from bolt to bolt, 16 inches. The stock uppers measure 14 bolt to bolt. I need to replace the uppers. Am I ok with the stock uppers length or is it necessary to get longer uppers? I guess I'm asking, should both the uppers and lowers be the same length. Then, as a follow up, what would be the affect on my axle to get uppers that are, say 2", longer? I assume it would tilt it forward on its axis some.

I know the first answer out of the gate will be - get adjustable uppers. Well, that is in the plans...when the money is there. Right now though I need to get a different set of fixed in the Jeep in the next week or two so that I can make the Fall Flog.

Thanks!

Same length? No, I wouldn't think so.

This really is a Caster question. By adding 2" to the upper arms, you will remove caster. Is that the effect you desire?

-Ron

WB9YZU said:

Same length? No, I wouldn't think so.

This really is a Caster question. By adding 2" to the upper arms, you will remove caster. Is that the effect you desire?

-Ron

Click to expand...

The result I desire to get the damaged ones out and new ones in so that I can drive it again. Trying to determine if the stock uppers are my best bet in the immediacy, or if I need to find something closer to the length of my lowers.

I'm not all that versed in caster, camber, and toe, and everything.

caster changes the way the vehicle drives. You can google how. If you are happy with how it drives then go ahead and put stockers back on it.

If you are using drop brackets and the RE lower then you likely have a lil more caster then stock. That wont hurt anything as long as your happy with the feel.

I would go with adjustable uppers. Also, Pinion angle takes precedence over caster, but you should be able to maintain an acceptable caster with a good pinion angle at that lift height.

Cottontail said:

The result I desire to get the damaged ones out and new ones in so that I can drive it again. Trying to determine if the stock uppers are my best bet in the immediacy, or if I need to find something closer to the length of my lowers.

I'm not all that versed in caster, camber, and toe, and everything.

Click to expand...

Dirk, the answers are all on this interweb thingy and are covered in much more detail in other places

However, the Basic breakdown is this:

The Caster is the angle between the axle and the hub in a front/back orientation - think shopping cart. As with the shopping cart, this angle helps restore the wheel to the center position when you let go after a turn.

Camber is the angle of the wheel in relation to the ground in a up/down orientation. This angle has more to do with handling than anything else, however, if it gets too extreme, the vehicle will become laterally unstable and require constant supervision.

Toe is the angle of the wheels front to back and serves to make sure the wheels track straight when going down the road.

The car manufacture comes up with optimal figured for these items based on use - daily driving. Other uses require different settings for optimal performance.

Your fixed beam axle on your jeep has the relationship between caster and camber fixed at the factory (Inner knuckles are welded on) and in a factory configuration, if you zero your pinion to driveshaft angle (because it''s a double cardan shaft and that angle "Should be" zero) the caster and camber will be within spec.

As you move the suspension though it's travel (Ideally an arc), the caster and camber change because the axle has rotated.

When you lifted your vehicle, rotated the axle by moving the suspensions resting position down the arc, thus changing both caster and camber angles.

When you put on longer lower arms, you rotated the axle back toward the factory caster and camber angles (compensated for the new resting position). The pinion-DS angle gets a bit mushy here as you need to "Make lemon aid", or in other words, put up with some less than optimal DS angle to get the stability you want.

You can see now that if you extend the upper control arms 2", without also extending the lowers, you will be un-doing what you did when you installed the longer lower arms and the vehicle will become less stable.

As said, if you are basically happy with the handling, install a set of stock length arms (Always upgrade weak components ).
If you desire a bit better drivability, you can get adjustable ball joints for the top to adjust some caster and camber. Because these are oblong, you end up adjusting both (Remember - welded together).

Personally I think that with 3.5" lift, and RE lowers, you probably did about all you can with that configuration. If you want factory handling, install a set of drop brackets and stock length uppers and lowers to get the axle centered in it's travel again. You will get greater upper and lower travel than your existing setup.

-Ron