If someone can help a C3 guy out here, I'd be very grateful. I'm fabricating an aluminum LCA crossmember for my '69 (to pull some more weight off the car) and need some help understanding what keeps the LCA steel inner bushing from rotating relative to the attachment (camber adjustment) bolt in a C5 cradle. The previous C4 generation crossmembers are thin sheet steel that will crush/deform under the bolt torque, but what's the mechanism (aluminum deformation?) in the C5 cradle? I'm trying not to have to reinvent the wheel, as it were, to keep the LCA (I've got a C4 suspension under my '69) steel bushings from rotating relative to the through bolts.

Thanks for any help in understanding the cradle/bushing interface.

 

I don't understand the question. The lower a-arm bushing can freely move around the bolt and it should be able to move so the alignment can be set. Do you mean to keep the sleeve and bolt from sliding in/out when the bolt is tight? The alignment is basically held by friction once the bolt is tightened. Some places sell alignment plates to replace the eccentric washers on the bolts so the bolts can't slide in their slots.

 

My suspension experience is mainly limited to C3 and C4 parts. The factory chassis manuals for both of these models state that the LCA bolts be final tightened/torqued (after assembly or repair) while the car is at normal ride height (ie: not while on a lift with the suspension in full droop). I have heard through the years that this was to allow the rubber in the LCA pivots to be in the neutral position when the bolts were torqued. I only see the point of doing this is when the steel sleeve (that the bolts go through) is forced into a interference fit in the cradle when the bolts are torqued (at like 90# on a C4), and the rubber then either stretches in a spiral fashion when the LCA rotates up or down, or the rubber rotates/slides over the non-moving steel sleeve. If the steel sleeve was allowed to rotate around the bolt (in a non-lubricated fashion, no less), I see no reason for the need to have the car at ride height when the LCA bolts are torqued.

Short and sweet. I need to know if the C5 LCA steel sleeve is prevented from rotation (by the bolt clamping force) during suspension movement, and if so, I would like to know how the steel sleeve is prevented from rotation in the C5 aluminum cradle/crossmember, so I can duplicate that method in the aluminum crossmember I am fabricating for my '69.

 

Friction, as in the bolt clamps the frame down onto the sleeve.

 

That's what I was asking, whether the C5 setup uses bending/deformation of the aluminum ears on the cradle to control/stop rotation of the steel sleeves. Apparently it does.

My current design on my aluminum crossmember is substantially different than the C5 cradle, and more resistant to bending at the LCA bushing/sleeve area. I'll have to see what options I can come up with to get the clamping action I need on the sleeve.

I appreciate your input.