Aluminum LCAs and the locknuts which ate them

[Bill Waters]

A number of you fellas are using the aluminum LCAs from 2006 WRX sedans in your build. I wanted to post what I consider a dilemma and see if any of you have thought about/solved/pursued an issue I am facing.

In preparing the LCAs to receive the steel lower coilover mount, I have drilled the through-holes as directed. However, while the flanges of the provided bolts sit squarely on the base of the mount, the bottom or underside of the LCA sweeps upward such that the underside is not parallel to the top surface of the LCA and the shock mount which sits on it. This means that the locknuts securing the whole affair tighten into the underside of the LCA at an angle. As a result, the clamping force of the nut is expressed only on a fraction of its surface, which should otherwise be square to the surface. Another way of saying this is that the nuts - if fully tightened- would dig into the LCA significantly.

It is hard for me to imagine that this would not create a stress riser or otherwise weaken the LCA (beside just being bad form for a lad with OCD tendencies like me). It may be, however, that this is more a theoretical than real concern. I have thought of a couple of possible remedies, including milling spots which are square around the bolt holes on the underside of the LCA or fabricating an offset washer which compensates for the angle.

I will be sending Jim and the guys a picture of this with an email and we'll see what they say. By the way, i can't find how to post pictures on here - anybody point me to the directions for that?

Have any of you encountered or though about this?

Thanks,

Bill

[RM1SepEx]

go advanced when you post and you can add photos

[TahoeTim]

wondering if you have to drill the holes at a slight angle to match the backside

[Xusia]

I used a combination of grinding and a washer to help ensure a more even clamping distribution.

[michael everson]

Thats why I drilled and tapped my holes. Then loctited the bolts.
Mike

[Bill Waters]

wondering if you have to drill the holes at a slight angle to match the backside

If you did, you would create the same lack of flush fit on the top side


go advanced when you post and you can add photos

Thanks; will do. Can you download directly or do you have to use Photobucket or similar repository


I used a combination of grinding and a washer to help ensure a more even clamping distribution.

Yep; I may be able to true up bottom with an end mill.

Thats why I drilled and tapped my holes. Then loctited the bolts.

Mike

Good move.

Thanks, folks, for your thoughts

Bill

[Goldwing]

As far as pics go, look along the formatting options at the top of the window you type a comment on. Bold , italics, etc. keep going to the right until you see the tiny picture with four dots, one at each corner. Hit the icon and a window pops up to search your pictures. I use that in the quick reply feature. The earth and binoculars icon helps properly embed a web link as well.

As far as the LCAs go, I used washers on bottom. I also used a little JB weld on top to fill the little bit of gap between the LCA and the shock bracket.

[Bill Waters]

Thanks, Rich