My testing with rear bars

[ft_sjo]

Due to pretty much all production cars, including the 86, understeering (according to ISO test methods), I decided to test a few rear bars on my car and share my experiences.

Test environment were a variety of British roads. I am not talking about tracking, flying around a parking lot, or otherwise driving on a smooth, flat surface. British 'B' roads are usually narrow, bumpy, lots of camber changes, etc. A pretty good test for all-round driving. You arguably would want more bar than this on a flat surface, but that comes down to personal opinion.

Car = stock suspension, 225/45/17 AD08 tyres.


Stock (14mm)
Understeering monster. Entry into a bend, understeer. Once the car has rolled, understeer. Pushing out of the bend, understeer. Lifting off deep into the bend results in a mild reduction of understeer, but not neutral or oversteering. Very safe for the average consumer, what i'd expect.

WRX (16mm)
Much better. Car rotates better, less steering input required. Has more initial front bite going into the corner but still understeers on the limit. Heavy lift-off at < 40mph speeds results in almost a perfect sideways drift rather than oversteer. I did some high speed testing and lifting hard + turning at ~80 mph does result in over-steer, but the degree depends on your driving ability - light correction required. Generally fairly neutral when pushed hard. Allows rapid change of direction without upsetting the balance of the car. All in all a much better balance.

STI (18mm)
This is where personal taste will come into it. In my opinion this bar is too stiff and is throwing the balance of the car (with a 16) off. Initial entry into a bend now exhibits slightly more understeer than the 16, which tends to mean the rear bar is too stiff reducing grip on the front. As the car rolls more and more into a turn you notice the effect this bar has progressively. With this bar it doesn't take much throttle in the bend for to overload the rear tyres. It's still pretty safe with quick direction changes. You do get lift-off oversteer with this bar, if that's your bag. In a RWD car though it's not typically a characteristic you want, unlike FWD. You need the driven wheels to be able to pull you out the bend.



So I will most likely stick with the 16mm bar. I actually tested a 16mm whiteline bar using the OE drop links (perfectly acceptable, Subaru use the same end links for all their Impreza bars up to 19mm on a heavier car). I was using the middle hole on the bar as this gave the best geometry with the end-link and was closest to the OE mounting position. The Whiteline bar has a bit of a design fault though where they've extended the lever arm to the point where it can foul things on the car under serious suspension compression. I'll most likely grind off the end of the bar I don't need/want, unless I can find a cheap WRX bar quickly.

Some may argue that uprating the front bar may work well with the 18mm rear, but to be honest the car doesn't roll much (on the road) so it's a bit unnecessary.


I hope this information proves useful to some people . I'm not interested in FUD and bullshit from people who don't actually understand what understeer and oversteer is.

[Calum]

Well, that deescalated quickly.

[ft_sjo]

Originally Posted by Calum

Well, that deescalated quickly.

.. and without any moderator involvement!

[celica73]

You've described corner entry and mid corner, what about corner exit? Particularly slower corners where the ability to put the power down is already a bit traction limited?

[ft_sjo]

Originally Posted by celica73

You've described corner entry and mid corner, what about corner exit? Particularly slower corners where the ability to put the power down is already a bit traction limited?

If you're talking about first gear stuff, then that's probably more to do with the slipper than the suspension.

[evil_1998]

What year WRX & STi rear sway bars are compatible? Are these straight bolt on? Any modifications to mounts/bushings?

Also are the front compatible too?

[ft_sjo]

Originally Posted by evil_1998

What year WRX & STi rear sway bars are compatible? Are these straight bolt on? Any modifications to mounts/bushings?

Also are the front compatible too?

Please see my thread here for part numbers:

http://www.ft86club.com/forums/showthread.php?t=28221


I don't believe the fronts are compatible, but i've not tested it myself.

[ft_sjo]

Edited the 16mm description with some detail on high speed testing..

[Keenercarguy]

Sorry to bump an old thread... But the brackets and bolts on the stock BRZ/GT86 fit the bushings on the WRX 16mm sway bar, right? Or do you HAVE to get the WRX brackets?