EA81 strut mount orientation question > EA81 coilover retrofit

[dfoyl]

According to the FSM, the orientation of the front strut mount on EA81 / MY vehicles is different from 4wd/PS/wagon to sedan/coupe. The position moves the strut top forward or backward. The question I have is - why was this designed in ?

 

 

(Sorry the photo is sideways, Photobucket and M$ are dicks)

 

Here's a photo of a stock MY strut top for reference :

 

 

And here is where my question is going. I am running stock EJ Impreza struts as part of my 5-stud setup and am now looking at coilovers. The best way to retain the adjustability of the coilovers for camber adjustment is to make a new plate essentially the same as the stock unit but with a center using this design :

 

 

The question I am trying to ask is ultimately, do I need to have the same offset design for my new plate or simply center it between the stud holes.

Edited July 30, 2016 by dfoyl

[carfreak85]

Since you've already got a FSM, flip to the suspension section and look at the caster angles between the two models.  You will see that the 2WD/Sedan has a bit more caster than the 4WD position.

 

For your camber plates, you will probably want to make it adjustable so you can dial in a little more than stock.

[dfoyl]

Thanks for the response - sorry I missed it earlier. I bounced the same question off a suspension company and they said it is better to offset as far back as possible (like the factory design) as it helps the power steering setup (I have EJ PS but MY PS steering rack)...

[carfreak85]

On the road, yes, more caster will be beneficial.  It will make more camber as you turn the steering wheel, the opposite is true of the 4WD chassis, they want less caster so that if you hit an obstacle, the wheel will be less likely to be ripped from your hands.

[bugster42]

I like where you are going with this. I've brainstormed about doing the same thing but the rubber strut tops seem to suck up some of the road vibration. 

This link helped me understand some of the steering angle principals.

 

http://aligncraft.com/terms/terms.html

 

When I lifted my lady's ea81 (with power steering) I added a couple degrees of POSITIVE caster into blocks (I.E. moving the strut tops rearward) in addition to extending the radius rods about 20mm forward. Overall the handling at highway speed seems more stable and long sweeping corners are manageable now. 

 

I hope that helps.

[dfoyl]

Agree on the rubber strut tops - with the move to pillowtops on the coilovers I will lose that insulation from the road, and combined with low (45 profile) tires I will probably have to go quite soft on the coilover setting.

 

What I have also found since mocking up is the coilover setup is I don't have enough length so will need to put a spacer in - essentially turning the stock MY strut top upside down. I will mill / turn it out of 6061 alloy with a sunken center and then mill in the coilover adjustment. Once anodised black it will look stock.

[dfoyl]

Slight change of plan to the above. Now I will press out the factory rubber center of the strut top, and use some decently thick (10mm-ish) steel with slots cut for the coilover camber adjustment (will lose some of the extreme adjustment points, but most camber will be done at the knuckle). Weld that to the top (now bottom) of the strut top, add a hard rubber gasket between the top of the strut top (was bottom) and the bottom of the vehicle strut tower to give me back some insulation, and it should all work. If I need more strut travel I can add a packing plate between the rubber under the strut tower and the tower itself - like a standard engine mount.

 

Just need to press the factory rubber center out on the industrial press tomorrow and cut those 10mm thick plates...