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Old 05-13-2000, 08:48 PM   #1
wolve80
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Post Passive Rear Steering

Can anyone explain this? It's vaugely (sp?) explained in the Impreza pamphlet, but I'm lost. I tried doing a search, but nothing came up.
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Old 05-14-2000, 02:21 AM   #2
cvalle-sd
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The suspension mounts are set up in such a away that nder fairly heavy loading, the rear wheels toe in/out, depending on which way you're turning - helps the car pivot, and probably prevents breaking the rears loose a little. My SVX had it, you could tell more on a heavier car.
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Old 05-14-2000, 05:19 PM   #3
HRE | giulio
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think of it as driving a shopping cart backwards
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Old 05-14-2000, 07:56 PM   #4
Snoopy
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Which model year Impreza is this passive rear wheel steering available on? I have a '99.

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Old 05-14-2000, 10:13 PM   #5
kelley nelson
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AFAIK, that geometry is part of all the roadgoing Imprezas.
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Old 05-15-2000, 12:57 AM   #6
Tarmac RS
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I have felt it a few times, its rather annoying if you ask me. The car seems to change its attitude in the corner just AFTER the point you think you have it set. It kindof disrupts the feel of the car. Seems less noticeable after the change of tires, maybe cuz the car is staying flatter on the road...

It would be interesting to see a technical article from SOA on it, Im wondering it they engineered it or if its an inherent characteristic of the chassis. Could be a better way of marketing a term called bump-steer.
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Old 05-15-2000, 07:35 AM   #7
ColinL
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It's a transverse link that counteracts the strut suspension's natural tendency to go to major toe-out on the outside rear wheel.

That's it, IMO.
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Old 05-15-2000, 08:55 AM   #8
cvalle-sd
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when it kicks in probably has a lot to do with your setup - It seems obvious that Subaru figured things out based on what we know as the stock setup, but after changing tires, springs struts, sway bars, etc. - it'll no doubt work diferently as well.

How - is another thing
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Old 05-15-2000, 10:25 AM   #9
Scooter
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Ok, for my discussion on this, please refer to the PowerFlex Bushings web site (see links page) and the drawing of all the suspension bushings for the Impreza.

I believe what Colin is refering to as a Transverse link is referred to as a Tie bar at the PowerFlex site. Instead of trying to get all the names right to keep all the gurus happy, just refer to the drawing and the list of the different bushings for the Impreza.

To the best of my knowledge, the Passive rear steering works by virtue of having bushings of differing hardness in the right places. The bushings I'm referring to are #4 and #5 in the PowerFlex bushing list for the Impreza. Each "Tie bar" has two bushings and there are two "Tie bars" each side. If at least one of the bushings of the rear "Tie bar" is softer than the bushings of the front "Tie bar", then that softer bushing will compress more under lateral loads. This greater compression means greater deflection, which results in the wheel turning slightly out or in. Since the Subaru brochure states "...the rear wheels turn with the car...", I would take this to mean that the wheel on the inside of the turn turns in a bit (toe-in as others call it) and the outside wheel turns out a bit (toe-out).

Tarmac RS,
I agree, it's affects can throw you off a bit at times. Just when you think you going to hit the point you're aiming at, the passive steering kicks in and you have to make some steering adjustments. However, I think the passive steering actually helps you steer with the throttle a bit. I find, that if I go into a reasonably sharp slow speed turn, then give it some gas once I've turned in, it seems that the car starts carving a sharper arc without additional steering input.


Just for arguement's sake, when both rear wheels do this \ /, I would use the termnology toe-out. When both wheels do this / \, I would use toe-in. However , when both wheels do this / / or this \ \, I would not use that termnology. I would just refer to it as steering. I think saying one wheel toes in a bit and the other toes out, though basically the same thing, may confuse us noivces that don't have




[This message has been edited by Scooter (edited May 15, 2000).]
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