Currie Front UCA Install ?s

[aw12345]

2 bolts 2 holes one big stir. Tighten the bolts and go wheeling, end of problem

[Schmo]

You will notice that the hex part doesn't come into contact with the surface being clamped together. There is a very slightly raised ring on the underside of the head. That surface is what comes into contact with whatever is being fastened together and is/are the faying surfaces.

The end of the bolt sleeve in the bushing is another faying surface as is the area on the side of the control arm U that comes into contact with the end of the bolt sleeve.

All cap screws that we use, with rare exception, are engineered to operate purely in tension. In other words, once you apply the correct torque value, the fastener is stretched and clamps the connection together. The friction developed amongst all the faying surfaces is what keep the body of the fastener from seeing any shear force. Once that tension is lost and the shank of the fastener and it's corresponding connection components see any shear force, the connection has failed or it's design parameters have been exceeded.

Trying to visualize here . . . let me see if I can get my words to make sense! So the faying surfaces use tension/friction to clamp the connection together which makes sense, but when I picture the set up in my head, I'm getting confused as to where the movement goes when the axle drops. I'd alway thought that the U shaped part of the UCA was turing on the bolt and against the sleeve, and the bushing simply took care of the lateral movement . . . but that would make for a very weak connection as only the strength of the bolt would be keeping everything together. So if the bushing sleave, UCA, and bolt/nut are all compressed together, that movement has to be going somewhere else right? Does the bushing spin or does the sleave spin inside the bushing? Did that make any sense?

Regardless, I'm going to leave that bushing alone and go with the 10mm and keep close watch on the torque until I replace the bushings with JJ's. I noticed that all my CAs from Currie use washers whereas the stock set up does not . . . would it be best to find new bolts, washers, and nuts or simply reuse the stock bolts and just bend the metal flap on the nut out of the way?

[mrblaine]

Trying to visualize here . . . let me see if I can get my words to make sense! So the faying surfaces use tension/friction to clamp the connection together which makes sense, but when I picture the set up in my head, I'm getting confused as to where the movement goes when the axle drops. I'd alway thought that the U shaped part of the UCA was turing on the bolt and against the sleeve, and the bushing simply took care of the lateral movement . . . but that would make for a very weak connection as only the strength of the bolt would be keeping everything together. So if the bushing sleave, UCA, and bolt/nut are all compressed together, that movement has to be going somewhere else right? Does the bushing spin or does the sleave spin inside the bushing? Did that make any sense?

Regardless, I'm going to leave that bushing alone and go with the 10mm and keep close watch on the torque until I replace the bushings with JJ's. I noticed that all my CAs from Currie use washers whereas the stock set up does not . . . would it be best to find new bolts, washers, and nuts or simply reuse the stock bolts and just bend the metal flap on the nut out of the way?

The OEM bushing is composed of three parts. An outer steel sleeve, a rubber isolation element, and a bolt sleeve.

The inner and outer sleeves are bonded to the rubber element. When the bolt sleeve is rotated, it twists the rubber and then relaxes back to neutral.

That's why you should never tighten up your control arms if they have OEM style bushings when the axle is drooped.

They are only designed with a specific amount of rotation before the bond breaks. If you tighten them with the axle drooped, you are already at close to their max and you still have the distance of your uptravel to the bumpstops that will over rotate them and break the bond.

Also why you should always float your uppers instead of setting them to the same length.

[mrblaine]

I noticed that all my CAs from Currie use washers whereas the stock set up does not . . . would it be best to find new bolts, washers, and nuts or simply reuse the stock bolts and just bend the metal flap on the nut out of the way?

Your stock bolts do have washers.

[Schmo]

The OEM bushing is composed of three parts. An outer steel sleeve, a rubber isolation element, and a bolt sleeve.

The inner and outer sleeves are bonded to the rubber element. When the bolt sleeve is rotated, it twists the rubber and then relaxes back to neutral.

That's why you should never tighten up your control arms if they have OEM style bushings when the axle is drooped.

They are only designed with a specific amount of rotation before the bond breaks. If you tighten them with the axle drooped, you are already at close to their max and you still have the distance of your uptravel to the bumpstops that will over rotate them and break the bond.

Also why you should always float your uppers instead of setting them to the same length.

AhHa . . . it's all coming together . . . I'd heard that you need to tighten the bolts when it's resting on ground, but now I understand why . . . thanks! Seems like having the JJ on the other end should really lengthen the life of the bushing as the arm will just rotate on the ball on the other end and eliminate the stress on the bushing that could result in breaking the bond, right? Can you elaborate on the last part about floating the uppers instead of setting them the same length? I'm no pro and seeing that I'm not having any alignment issues, I was going to simply set the UCA's to whatever the stock arms are at now.

Your stock bolts do have washers.

I don't recall any seperate washers on the stock control arms for the uppers or lowers . . . do you mean that the washer is incorporated into the bolt/nut on the stock ones?

[mrblaine]

AhHa . . . it's all coming together . . . I'd heard that you need to tighten the bolts when it's resting on ground, but now I understand why . . . thanks! Seems like having the JJ on the other end should really lengthen the life of the bushing as the arm will just rotate on the ball on the other end and eliminate the stress on the bushing that could result in breaking the bond, right?

Only works if you have JJ's on both ends. Otherwise, the OEM style bushing will see exactly the same rotational stresses.

Can you elaborate on the last part about floating the uppers instead of setting them the same length? I'm no pro and seeing that I'm not having any alignment issues, I was going to simply set the UCA's to whatever the stock arms are at now.

Set both lowers the same length to start. At ride height, get someone to help you square the front axle to the rear if you know it's good, or level the rig and square up to a pair of points on the frame.

Use a floor jack to set the pinion where you want it for your caster/pinion angle with no uppers installed. You may have left a single upper in place to help you square up the axle with the lowers. Remove it now and adjust the pinion.

Also, be careful to not try and extend your wheelbase. You won't like having the interference this creates with your steering.

After you get the pinion where you like it and the axle centered side to side at ride height, adjust one of the uppers so the bolt goes in. While that bolt is relaxed in the hole, set the other arm in place and adjust the length on it until the bolt goes in. Now both arms are set to the correct length to have the same amount of preload on the bushings and neither is in a bind trying to tear up your bushings.

Remove floor jack and check the angle again when the springs load the uppers. A minor adjustment may be needed.

I don't recall any seperate washers on the stock control arms for the uppers or lowers . . . do you mean that the washer is incorporated into the bolt/nut on the stock ones?

Yes, the OEM control arm bolts incorporate washers into the heads. They are called washer head or flange head cap screws for this very reason.

[Schmo]

Use a floor jack to set the pinion where you want it for your caster/pinion angle with no uppers installed. You may have left a single upper in place to help you square up the axle with the lowers. Remove it now and adjust the pinion.


After you get the pinion where you like it and the axle centered side to side at ride height, adjust one of the uppers so the bolt goes in. While that bolt is relaxed in the hole, set the other arm in place and adjust the length on it until the bolt goes in. Now both arms are set to the correct length to have the same amount of preload on the bushings and neither is in a bind trying to tear up your bushings.
.

Seeing that everything is working well w/ the stock arms (no vibes, alignment, or steering issues), could I accomplish the same goal by setting one arm to the stock length that is on there now and then pick up where your instructions talk about putting that arm on with the bolt relaxed and then setting the other arm?

[mrblaine]

Seeing that everything is working well w/ the stock arms (no vibes, alignment, or steering issues), could I accomplish the same goal by setting one arm to the stock length that is on there now and then pick up where your instructions talk about putting that arm on with the bolt relaxed and then setting the other arm?

There is really no set or specific way to do it. There are many ways to skin that cat and as long as you understand what the end goal is, you're good.

You do not want to load your upper bushings differently by hooking up one arm and then prying, jacking, or lifting the axle because the internet told you all the arms need to be set the same.

[Schmo]

Thanks again . . . I think I can leave you alone for a bit!