Impreza top hots???

[.Kyle]

I am uncertain. My statement is from data I inferred from killing a set of Whiteline Com-C that were spec'd as a proper fitment for this chassis but have incredibly high failure rate. So much so that Whiteline has backed out of providing them as a "confirmed fitment" for this chassis. What I was able to tell when comparing to my old bugeye was that the 86 strut wants to bind the bearing in the strut mount in the max caster/camber position but does not in the GD. The max camber/caster is the position they always get mounted in so it doesn't make sense to use a part that is known to be bound in that position.

[churchx]

People tried even with adding washers so to explicitly for spring perch to contact only inner ring of bearing. They still failed/started binding rather soon for those that experimented back then with Com-Cs, so imho shape of spring perch contact with bearing is only part of story. My second guess, that maybe also on imprezas strut is angled at a bit different (/lesser?) caster/camber angle vs plane of topmount then on twins, so maybe that may add extra wear due not expected by design extra sideloads? 3rd guess, that they also have more weight on front due FWD/AWD nature, that also may decrease chances to bind, no?
Anyway, as whiteline gave up, to get -3 camber with rubber mounts, i used camberbolts in both strut holes +adjustable powerflex bushing for front LCA.

[.Kyle]

All of your points are what my thought process was. I had done the STi conical washers and a bunch of other BS. Thus why i walked away from them and went to a eibach unit with pillow ball and serrated/corrugated top plate for anti slip.

Back to the topic at hand; the top hat will physically fit but it's operation is suspect.

[churchx]

Pitty that Whiteline instead of just trying out different bearings in subsequent revisions, simply could have tried out those other things. For example - redesigning mount so to preset bearing at angle initially, for suspension with more angled struts. Reduce a bit offset. Sell optional washers for cars with too flat & wide spring perches. But that's just unprobable what-if scenario, as they need to make money with large enough batches to get costs down via economies of scale, and making custom Com-Cs just for twins probably was unprofitable. If they didn't fail that quickly, Com-Cs would have been my goto choice for extra camber, as i want more track-fit camber but still not willing to live with extra NVH from pillowballs .

[wparsons]

Originally Posted by jamal

Is the OEM frs/brz top directional and/or is the bearing set at an angle?

Nope, totally symmetrical.

[jamal]

Yeah here's the thing. The SAI or caster may be different between the impreza and brz, but the tower is angled so that the strut and top are perpendicular to each other either way.

I don't know what the deal was with the whiteline tops and these cars. They did have some issues with bearing choice and supply so there were some that failed prematurely on imprezas too, and others that were fine.

I guess one thing that comes to mind is that the distance from the top to the upright mounts is shorter, so that small change in the position of the bearing would creates a larger change in angle, especially when the car is lower or near full bump. Maybe that is just enough to cause more failure especially since the rubber is a good amount stiffer.

[churchx]

It would be nice if someone with both twin & impreza to take some measurements (eg. strut lengths, actual angles, actual tower angled or not placement, angle between strut & topmount and so on) to strengthen or remove some credibility behind this theory. Otherwise this might be just guesswork/mind game with no data to back it.