Sway Bars: What's The Trade Off?

[whataboutbob]

Buy this book and read it before you do anything else. Seriously.

[Captain Snooze]

Okies. Approximately 17 seconds ago I placed an order for that book. If I can't pull 18g around corners after reading it I'm going to ask you for a refund.

[CSG Mike]

Originally Posted by Captain Snooze

I have read that increasing roll stiffness using sway bars is less harsh (read more comfortable) than increasing spring stiffness. I have also been told by a suspension shop ( I am taking this as a hypothesis because I have no other examples to back this up) that sway bars should provide a certain percentage of the total roll stiffness. (I cant remember what they said and it was a ball park figure.) So according to this hypothesis because I have increased the spring rate the sway bars should be upgraded as well.

Your thoughts?

All theory that we've not extensively tested, since it would ultimately be a band-aid fix for the underlying characteristic we're trying to change.

An easy way to think of it, is that a stiffer sway transfers more of the load to that end of the car. A stiffer front sway will make the front lose traction faster relative to the rear, and a stiffer rear sway will make the rear lose traction faster than the front.

In other words, stiffer front sways cause more understeer (or less oversteer), and stiffer rear sways cause more oversteer (or less understeer).

[CSG Mike]

Originally Posted by Captain Snooze

Perhaps what I am wanting is not possible: an increase in cornering performance without making daily driving tedious/unpleasant.

All comes down to budget...

[Captain Snooze]

Originally Posted by CSG Mike

All comes down to budget...

I have read in these forums a few times that a well damped stiff spring can feel more comfortable than a poorly damped soft spring. I like to think that the dampers I have fitted to my car are of reasonable quality (they are not Ebay specials). Given that I have already purchased dampers I am not going replace them any time soon but when I read your above post dampers are the only thing that come to mind. Could you please elaborate on that?

Thanks.

[wparsons]

Originally Posted by Captain Snooze

Perhaps what I am wanting is not possible: an increase in cornering performance without making daily driving tedious/unpleasant.

What do you mean by "cornering performance"? Are you measuring corner entry/midpoint/exit speeds or logging g forces generated? Just because there's less body roll doesn't mean the car actually has more grip. If you're after less body roll so it feels sportier, sway bars will give you what you want. If you actually want a quantifiable improvement in corners you'll need a baseline and other measurements (tire temps, etc) before you can make a decision.

What tires and alignment settings are you running? Those are two things you can change that won't make daily driving annoying that will definitely give you more grip.

[xwd]

Originally Posted by Captain Snooze

I have read in these forums a few times that a well damped stiff spring can feel more comfortable than a poorly damped soft spring. I like to think that the dampers I have fitted to my car are of reasonable quality (they are not Ebay specials). Given that I have already purchased dampers I am not going replace them any time soon but when I read your above post dampers are the only thing that come to mind. Could you please elaborate on that?

Thanks.

Once you read that book you will understand, but simple terms poor dampers are either over damped or under damped and rebound is what affects things the most.. Under damped won't control the spring so it oscillates making the car bouncy. Over and the car will ride very harshly not absorbing bumps which then get transmitted into the chassis. Tuning for both street and track is difficult, tracks are relatively smooth minus curbing, the street is not.

[Captain Snooze]

Originally Posted by wparsons

Are you measuring corner entry/midpoint/exit speeds or logging g forces generated?

I've been using Trackmaster (Android app) and I know it is a rough tool at best. Aim Solo DL on order.

Originally Posted by wparsons

What tires are you running?

Originally Posted by Captain Snooze

wearing Kumho V700.

Originally Posted by wparsons

Just because there's less body roll doesn't mean the car actually has more grip.

Ah!! *5 Watt light bulb blinks on above head*. Thank you.

[Captain Snooze]

Originally Posted by dwx

Tuning for both street and track is difficult, tracks are relatively smooth minus curbing, the street is not.

Thank you, that's want I wanted to know.

[Captain Snooze]

Thanks everyone for your educational replies.
(When I become ruler of the universe I am banning compromises.)

[CSG Mike]

Originally Posted by Captain Snooze

I have read in these forums a few times that a well damped stiff spring can feel more comfortable than a poorly damped soft spring. I like to think that the dampers I have fitted to my car are of reasonable quality (they are not Ebay specials). Given that I have already purchased dampers I am not going replace them any time soon but when I read your above post dampers are the only thing that come to mind. Could you please elaborate on that?

Thanks.

Anything that is under ~4k or so is a street damper. There's only so much you can do with a damper when cost is the major constraint. Typically at under 4k, you have dampers that damp really well at either low piston travel speeds, or at high piston travel speeds, but not both. One results in good street comfort, but underdamped-ness at the track, and the other results in good damping at the track, but harsh ride on the street. Once you get into the high end stuff, you can do both well.

We have more than a few people who have had sticker shock when they ask us for a "top of the line suspension setup".

[wparsons]

V700's are also very sticky tires for lighter spring rates, they'll be generating more grip than the springs you have can control. If you don't want higher rates you'll probably have to run more camber to keep the contact patch flatter in corners.

IIRC, CSG runs almost double your spring rates and they're running 140+ treadwear tires vs your 50.

[Captain Snooze]

Originally Posted by wparsons

IIRC, CSG runs almost double your spring rates and they're running 140+ treadwear tires vs your 50.

12k springs? omg!

[Racecomp Engineering]

There's always been a couple different schools of thought on swaybars in the subaru world. Some guys go for big bars, soft springs, others soft bars, stiff springs.

Definitely advantages and disadvantages to both.

Yes, ideally for a dedicated track car I would use swaybars more as trim device and get more of your roll resistance from your springs.

However, depending on your tire choice you might want a lot of roll resistance. To get that from just springs requires firm coilovers, and it would be nice if they had a great damper. That's a bunch of money. Or get less expensive coilovers with poor damping and deal with the crappy ride quality and performance.

The alternative is to run bigger bars so you don't need need super stiff springs. You'll get better ride quality and it's a heck of a lot cheaper. There are drawbacks as mentioned elsewhere (loss of suspension independence etc.) and you can go TOO big for sure.

I don't strictly think one way is the only way...it really depends on the user and application.

Regardless...it's very important (and I've said this a lot on here as have a few others) to try to pick springs and bars with your tire choice in mind.

- Andy