Quote:
Originally Posted by WingsofWar
Iv encountered that same thing too with Subaru suspensions. I suppose it has to do working with AWD.
On a side note, I wonder if Subaru, being somewhat new to RWD will adopt a form of active rear steering.
|
I hope not. Subaru's current rear multilink suspension is great, with the exception of being miscalibrated for height (LOTS of droop available and not much bump, good for raised rally cars but not so good if you want to lower)
Subaru likes to mess around with diffs... I seriously doubt the normal version would have something fancy though. WRXs are still all dumb diffs, when they have them at all (08's and forward doesn't have a rear LSD just center).
For the STI, a variable-lock and/or active torque vectoring in the diff would be badass.
Quote:
Originally Posted by Dimman
bigbcraig:
When you are talking about the Subarus losing camber in corners, is that because of the big squishy rubber top mounts of the struts? Would proper bearings fix this?
(My Legacy's only a daily, but I'm accumulating some WRX/STI bits that may or may not fit. So far I've got some GD WRX struts and springs, and some STi front aluminum LCAs with the 'good' mounts/ALK part, whatever that meant...)
|
Perhaps stiffer upper mounts would help a little, but they should really just add precision and crispness. If they are loose /soft enough from age that you can wiggle the tops around then that would cause unpredictable camber change at load.
The loss of camber is almost exclusively in the Strut-type suspension: And I'l tryo to explain without pics because the internet in China is awful slow.
With a double-wishbone suspension, the hub is held in place with two sets of articulating arms. When you compress a bump, both of these move in arcs which means that overall, the alignment of the hub remains close to what it was. I hope that makes sense.
Struts only use a bottom articulating arm, that is stiffly connected to a 'strut', a heavy duty spring/shock combo that goes up to the top of the tower you're familiar with. On most struts and specifically subarus, the hub is hard-bolted to the strut and the strut aligns it. For instance, a camber plate that would replace your rubber mount will have adjustability to bring the top of the strut in towards the engine, so the struts and therefore the hubs are leaning in more... voila, negative camber.
When the strut compresses, the control arm ("wishbone) moves in an arc. Because we're in a relatively low passenger car, the arm is very nearly horizontal normally. In a bump, then, the outer point of the arm where the hub is mounted moves up and IN.
So, we have the strut compressing and straightening, as the bottom moves inward towards the vertical plane of the shock towers. This is where camber is lost.
The possible solutions are to raise your car or the control arm mounting points so the arms are below horizontal normally and actually move out a bit, adding camber under bump. But this is hard to do and people don't like the look of a raised car.
The other option is to increase (positive) caster. This makes it that when you turn the tire, it will actually also tilt inwards to the turn. This means that when you're turning and really need camber, the outside tire gains negative camber which is good. Too much can be goody but on a Subaru at least, you'll never really be able to get too much.
I'm not really familiar with what the ALK does in the older-style suspension (Legacy and 08+ Impreza ALKs are different), their main purpose is to change the tilt of the control arm around the axis of the axle (If that makes sense to you, I'll be suprised. Wish I had the time to make visual aids). This changes behavior under braking and acceleration that is complex but makes for the car to drive better in many ways. The new ones allow caster adjustment, and I think the old ones add some caster too. I'd have to look it up.
If you head over to motoiq.com, there's timely article about it that should still be on their front page as part of a 'ultimate handling guide' or something like that.
If you used to read SCC, a lot of the staff and friends are there writing the good technical / nerdy articles I used to love SCC for.