Downside to relocating macpherson top to reduce caster?

OK, bit of a long setup here...

When you 5 lug swap an E30 using E36 parts there is a very specific set of control arm parts that will work together to make it pretty close to correct. This is well documented in E30 circles but those are mostly street cars and the solutions tend toward the aesthetics of centering the wheel in the opening and using off-the-shelf BMW parts. I don't feel like paying $200 a piece for those control arms when I have a perfectly good set of E30 arms, an already highly modified car, and the skills/tools to move things around. I have good camber plates so slight inaccuracy can be adjusted for - meaning I can be with-in 10ths and still make everything even when aligning.

The problem: I have -15 caster which wreaks havoc not only in steering effort but geometry with the wheel turned. I cannot move the bottom backward to solve the issue as there is insufficient room for the wheel to turn.

Is there any downside to relocating the top of the strut forward to reduce the angle? It also helps put the tie rod closer to "flat" to help reduce bump steer and seems to be a silver bullet here. I honestly can't think of a single reason not to lop off the strut tower and move the entire mount point forward.

Also - my strut towers are triangulated into the cage so lopping off the dome and plating it isn't going to weaken the structure's ability to handle loads. Its just going to fix my geometry.

Is there something I am overlooking?

The only downside I can think of, is that after the moving kit is installed, the McP strut top can slip if the bolts get loose. But that can be dealt with. I say go for it.

Nothing I can think of.

how far are you looking to move it? i'd think it to be easier to slot the bolt holes to slide forward (and possibly weld shut once located or just drill new holes if its far enough) if there's enough room for the strut assembly to not hit the tower. except that since the mount is at a slight angle sliding it would technically lower the front a very small amount.

WilberM3 wrote: how far are you looking to move it? i'd think it to be easier to slot the bolt holes to slide forward (and possibly weld shut once located or just drill new holes if its far enough) if there's enough room for the strut assembly to not hit the tower. except that since the mount is at a slight angle sliding it would technically lower the front a very small amount.

It needs to move pretty far... 10 degrees - with the control arm at ride height the right triangle math says 1.475 inches... so if I go 1.75" to the center it will buy me a +/- 2 degrees of adjustment on the plate. So - from around -4 to -8 which should be right in the sweet spot. I have all but convinced myself that this will be fine. I just need to position it there and run the suspension thru its travel to make sure I'm not going to bind a ball joint with steering input and then its off to the hardware store for cutoff wheels!

If you've got negative caster and want more positive caster, the strut top needs to go rearward, not towards the front of the vehicle. Or did I read you post correctly?

Well it will pivot the steering arm some so bump steer will change, may be better maybe not..

fifty wrote: If you've got negative caster and want more positive caster, the strut top needs to go rearward, not towards the front of the vehicle. Or did I read you post correctly?

You read it correctly - I wrote it wrong. I have +16 degrees inclination.

44Dwarf wrote: Well it will pivot the steering arm some so bump steer will change, may be better maybe not..

It brings the tie rods back pretty close to level and slightly forward. I have approx .5" of horiz. adj in the rack so I can compensate for the forward movement if it is an issue.

I didn't cut anything yet - but I have it all positioned where it needs to go at ride height. I can't articulate the steering without having it all fall apart but it looks pretty good for going straight so far.

Since the upright and tie rods had a similar relationship on the donor car I expect everything should work out well with the possible exception of full lock needing to be restricted a few degrees to prevent rubbing.