Rear sway bar

Dale Teague from Teague's Auto is considering doing a run of rear sway bars for the SVX. Here's the deal: If we can all agree on a size for the sway bar and we get at least 10 - 15 people interested he "could push it to the top of the list." So how many people are interested and what size would you guys want?

[1994SubaruSVX]

I would love a rear sway bar. it would perfectly compliment my koni's and ground controls. but i have no idea what sizes they come in or what size determines as far as performance or chasis stiffness. I will need a little more information on what different sizes can offer. but definitely count me in on the sway bar. what would the cost be? I am guessing around $250-350? keep me posted on the progress of this project.

I wouldn't think they'd cost that much.... The Impreza 20mm rear sways from FHI run $90. Personally, I'd like to see the rear sway bars @ 20mm. Good size.

[svxboy]

Joel at JC is supposed to be working on one too. Whoever gets it done first and for a good price gets my money as I sure as hell am getting a larger sway bar. This car needs it! -Greg

Counter me in. What about a front sway bar too?

Kevin

The rear one is key to reduce "plow" and help the thing oversteer a little bit. This is the prescription route to reduce understeer in the 2.5RS.

I'm not sure if a front one is necessary. I guess we'll find out after people start driving with a rear one on and see how the balance is.

In either case I'm pretty excited, that's my only complaint about the SVX's handling (the plow).

cheers
mbs

Man, when are you JC Sports lovers gonna get it? I've posted it many times here. They don't deliver. They have a group buy on Turbo kits from September of last year that they haven't delivered kits on for gods sake. I wouldn't buy something from them if they gave it to me for free!

They have engaged in business tactics that are extremely bad, including but not limited to: lying, not delievering products that, not refunding money, and selling incomplete parts.

Wake up people. JC Sports will screw you like the have screwed hundreds of Impreza owners on the I-Club. If you want to give them that chance, then go for it. But don't freaking complain on this board about it when you get screwed.

-/my .02
/me off soapbox

im confused it sounds like youre saying the svx doesn't have a rear sway bar if youre talking about upgrading it then i understand
if the price is reasonable ill be getting one

Originally posted by KEVINL
im confused it sounds like youre saying the svx doesn't have a rear sway bar if youre talking about upgrading it then i understand
if the price is reasonable ill be getting one

Yes, I'm talking about an upgrade. That's why I asked what size you wanted

Anyone else have a suggestion on size? Anyone know what size the stock sway bar is?

I just looked at my svx and the sway bar is pretty small somewhere around 16 milimeter. I think at least 20 probably 22 on a car this heavy

Count me in for one.


Chris

Guys,
What's a sway bar?

From Sport Compact Car Magazine May 2001, pg296: "Terms like anti-sway bars, roll bars, stabilizer bars, or even sway bars are incorrect. An ANTI-ROLL bar does not have ANYTHING to do with sway, nor does it stabilize anything on the car. It simply reduces lateral roll of the vehicle's sprung mass."

You guys need to do a LOT of reading before you start throwing your money around. If you can't even call it by it's proper name, how are you going to be able to handle it once it's mounted to your car?

Those things can be dangerous because they can drastically change the way the car will handle. I would really recommend you get that issue of Sport Compact Car Magazine. There is a 4 page article explaining exactly how an ANTI-ROLL BAR works. I might join you guys in a group buy once you all have a better understanding about how one works, and how it will affect handling.

FYI, my SVX doesn't really "plow" (understeer) that much. In fact I'm able to even get the car to go "loose"(oversteer) in a corner! Maybe I drive it differently than you guys. Maybe you're going into your curves too hot (fast). Increasing the tire pressure in the rear tires, can be enough to get rid of that "plowing."

I can see how having a SLIGHTLY stiffer anti-roll bar would be beneficial though. I suggest that there be some adjustable holes built into the U-legs of the anti-roll bar, to satisfy you "sliders" and to pacify the "complainers" by being able to change the pick-up points at the end of the U-legs. That'll give that last bit of adjustability, so we're not all stuck with having to deal with same exact stiffness.

Though one easier(cheaper) way to get rid of that last bit of "push" would be to just get some polyurethane bushings for the stock anti-roll bar. Bronze/aluminum blocks would be even better, but road vibration would get pretty bad then. It's something to look into, and definitely should be part of the anti-roll bar group buy.

Just make sure that this bar won't lower our ground clearance even more. Sometimes these aftermarket anti-roll bars will drag below everything else and can even get ripped off of the car!

Good luck and subscribe to Sport Compact Car Magazine!!

Originally posted by blonde_man
Guys,
What's a sway bar?

Sorry, I didn't know this was such a confusing subject. Here's a quick definition I found:

Anti-roll bars permit two key functions:

1. They reduce body roll.

2. They provide a means for adjusting the car's handling by redistributing cornering loads between the front and rear wheels.

Keeping body roll under control is essential in a high-performance car, because doing so restricts the vertical suspension motions that occur when a car is subjected to extreme cornering loads. Due to limitations in suspension linkages, it's difficult to maintain proper wheel geometry (particularly camber and toe) when the wheels are flopping up and down over large distances.

Reducing body roll keeps the suspension links closer to their optimum zone of operation-in this respect, anti-roll bars serve to compensate for inadequacies in suspension geometry. Adding stiff anti-roll bars to a family sedan that features soft springs and prodigious wheel travel can yield particularly spectacular improvements in handling.

Reducing body roll also improves transient response, which is critical in racing. Transient response can be thought of as the amount of time required for the car to achieve full load transfer (that is,"take a set") following some steering input. Obviously, if the body rolls less, it takes less time for it to take a set-the car is ready to respond to the next steering input that much earlier.

From Sport Compact Car Magazine May 2001, pg296: "Terms like anti-sway bars, roll bars, stabilizer bars, or even sway bars are incorrect. An ANTI-ROLL bar does not have ANYTHING to do with sway, nor does it stabilize anything on the car. It simply reduces lateral roll of the vehicle's sprung mass."

You guys need to do a LOT of reading before you start throwing your money around. If you can't even call it by it's proper name, how are you going to be able to handle it once it's mounted to your car?

Yes, that is not the proper name, but you don't call rover "Canis familiaris" do you? Everyone else that responded to this thread seemed to know what I was talking about, sorry if you were confused.

Those things can be dangerous because they can drastically change the way the car will handle. I would really recommend you get that issue of Sport Compact Car Magazine. There is a 4 page article explaining exactly how an ANTI-ROLL BAR works. I might join you guys in a group buy once you all have a better understanding about how one works, and how it will affect handling.

Yes they can change the way the car will handle, that is the point I thought? Since you obviously researched the subject so well I would be interested to know what size you suggest for our cars.

I suggest that there be some adjustable holes built into the U-legs of the anti-roll bar, to satisfy you "sliders" and to pacify the "complainers" by being able to change the pick-up points at the end of the U-legs. That'll give that last bit of adjustability, so we're not all stuck with having to deal with same exact stiffness.

Though one easier(cheaper) way to get rid of that last bit of "push" would be to just get some polyurethane bushings for the stock anti-roll bar. Bronze/aluminum blocks would be even better, but road vibration would get pretty bad then. It's something to look into, and definitely should be part of the anti-roll bar group buy.

Thanks for the advice. I'm going to send another email to Dale when I get a few more interested and we can iron out the details then. Also, check out http://www.subaru-svx.net/forum/show...=&threadid=311

Good luck and subscribe to Sport Compact Car Magazine!!

Just what I need, another magazine to subscribe to I think I will go out and pick up this month's issue if not at least for the article you mentioned. Thanks for the help Eric.

[1994SubaruSVX]

i just raced the svx on a road course this past weekend at pretty high speed. it really takes a lot to make the rear of the car get loose. i am not sure if the anti-sway bar would help but it certainly could not hurt. more than that though i think stiffer springs and better struts would stiffen the car and help flatten it at when tracking out of a hard corner. the car handles really well even with stock suspension. but there is a delay because of the body roll and that causes me to have to wait for the weight of the car to transfer before i set up for the next turn. again some stiff springs would really help a lot more. i really did not detect the car getting really loose, in fact the rear of the car only came around on me twice and that is because i just pushed it too hard. too hot into a corner with all the weight on the front and then too sharp of a turn and around the rear of the car comes. but i saved her nicely. it would be interesting to see it the anti-sway bar would actually help. i would buy one just to see if it did make a difference. i mean we are not talking about a huge investment here!

Great post Matt!

That should clear things up a bit! This morning I took this sharp curve really fast and really rode on the outside tires!! Talk about body roll! Stiffer anti-roll bars should help, but I'd suggest upgrading both front and rear. My SVX really didn't understeer through it, so I wouldn't want to make the rear much stiffer than the front. Maybe because I loaded the car up right and was easy on the throttle. The rear LSD comes in real handy during hard cornering maneuvers! I've heard that if you autocross your SVX with sticky racing tires, you can corner so hard, that the inside rear tire will completely lose contact with the ground! I'm sure I was near that this morning! A stiffer rear anti-roll bar is in order!

How stiff should it be though? Last night I changed my front brake pads, and rotated my tires. While I had the rear tires off, I took a good look at the rear anti-roll bar, and took some measurements. The diameter of it is 17mm, and the U-legs go back 8 inches from the pickup point. That article in Sport Compact Car Magazine provided a few equations to determine the stiffness of an anti-roll bar.

One equation determined the change in stiffness by moving around the pickup points on the U-legs:

(change of size)/(original size)=(change of stiffness)

If we moved that pickup point inward by 2 inches (reducing the length of the U-leg from 8 to 6 inches, by adding a new hole 2 inches up it), the equation says that we would be increasing the stiffness by 25%!!

2/8=0.25 or 25%!

Moving it in 3 inches would stiffen it up even more!

3/8=0.375 or 37.5%!

Are both of those too stiff? How about just 1 inch:
1/8=0.125 or 12.5%


That's with the same diameter anti-roll bar. We could probably do it ourselves by just drilling out a hole!

Changing the diameter of the anti-roll bar will change the stiffness even more! In fact, it changes by the fourth-power of the bar diameter!!(SCC May 2001)

The equation for that is a little more complicated.

(diameter of new bar)^4/(diameter of original bar)^4=(change in stiffness)

So if we took out our 17mm bar and put in an 18mm bar the stiffness would increase by:

18^4/17^4=1.27 or 27%!

What about 19mm bar:

19^4/17^4=1.56 or 56%!
20^4/17^4=1.92 or 92%!
20mm bar:


And some of you hard core racers wanted even larger bars like 22mm?

22^4/17^4=2.8 or 180%!


Now these are just numbers, but I can imagine how this could change the handling of the car! So how much is enough to improve the car? Well what are your goals? What do you want to get out of this mod? What are the safety concerns?

Well the article in Sport Compact Car Magazine gives an example of how a 65% stiffer rear anti-roll bar would affect "a neutral, or mildly understeering car."(ala SVX) They said that you would "end up with a dangerously oversteering vehicle." The reason for this is because adding stiffness to the rear will put more "anti-roll" force on those rear tires during a hard turn, which will make them lose traction earlier than the front tires, and thus oversteer. That would not be fun if you enter a corner too fast! Your SVX would get mangled up!

Unless you guys also want to increase the stiffness in the front anti-roll bar, I would suggest a conservative upgrade in diameter of the rear anti-roll bar. As was shown in the equation, an 18mm bar would increase stiffness by 27%. That should be more than enough to dial out that understeer. If not, we should also request that the 18mm bar have multiple pickup points(1 and/or 2 inches up the U-legs), so we could tweak it even more, by increasing stiffness even more by 12.5% and/or 25%.

A package like that would give a total increase in stiffness of 27%-to 52%! I'd first set mine up in the softest setting(27%), and only increase it if necessary, or if I added a stiffer front bar later on. Add polyurethane bushings, which are stiffer than the stock rubber ones, and we'll be set!

What do you guys think? 18mm bar with 1" & 2" shorter pickup points sounds great to me!

A 19mm anti-roll bar with just stock pickup points is already 56% stiffer. That would be pretty dangerous, if you're only adding a rear bar! If you are adding a stiffer front anti-roll bar, then that's another story, and a higher price tag.