Question for the "You only need a stiffer front swaybar" camp
1/23/15, 12:40 PM
#1
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Question for the "You only need a stiffer front swaybar" camp
In stock form, the S197 is known to understeer. This observation has been shared in most, if not all the online/youtube reviews by pros/well-known industry publications alike when they take the car out and test it on the track. I've even experienced this when my Stang was stock.
Why do some reputable performance shops/experienced drivers recommend ONLY upgrading to a stiffer front adjustable swaybar? They say the stock rear swaybar is stiff enough. Stiffening up the front will only induce more understeer. I can see how playing with the front camber can help lessen understeer, but to discount a stiffer rear swaybar to balance out the car is counterintuitive.
Can someone in this camp explain?
Why do some reputable performance shops/experienced drivers recommend ONLY upgrading to a stiffer front adjustable swaybar? They say the stock rear swaybar is stiff enough. Stiffening up the front will only induce more understeer. I can see how playing with the front camber can help lessen understeer, but to discount a stiffer rear swaybar to balance out the car is counterintuitive.
Can someone in this camp explain?
Last edited by magnido45; 1/23/15 at 12:43 PM.
1/23/15, 01:39 PM
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Just got a very techinical explanation from a member from another forum:
"I can speak to my experience and understand, but by no means take it as gospel.
Thinking of the car as a connected unit (F/R), increasing the front roll stiffness relative to the rear means that the rear of the car will experience more load transfer in any given turn. Keeping the front tires in good camber position certainly helps, as even with 2 degrees of neg camber and coilovers I was experiencing rollover onto the outer sidewall before upgrading my FSB. The increased load transfer in the rear helps my car rotate, and takes some of the burden off the front outside wheel and transfers it to the back one. With the correct LCA geometry, you can utilize the roll steer of the solid rear axle to your advantage, increasing its contribution by making the front more of a "platform" for the rear to rotate on.
Just to give you an idea of my set-up and what I've been running out on the road course, I started with KW Variant 3's and the stock brembo bars. I then swapped to Eibach's adjustable kit, with the front bar being slightly stiffer than stock and the rear having a range of just about stock. I then added Sam's front bar, which is the same diameter but thicker wall tubing and thus effectively stiffer. Finally, I replaced Sam's bar with the new BMR 38 mm bar and I'm finally happy with the balance of the car. To give an idea, the KW rates are ~330ish front and ~180ish rear (working rates - progressive springs).
This is running a square tire set-up, btw."
"Keep in mind that the race teams likely have a VERY different setup, and true coilovers in the rear with different rates that may allow them to run with no rear bar.
I know Vorshlag and Terry/Jason are advocates of the stiffer front as well, with their coilover options coming with either 450F 175R or 550F 225R (correct me if I'm wrong) and they've found that to be the best balance as well. I don't have the rate to do that up front, so I turned to BMR for their bar.
I think csamsh (sp?) is also in the process of going up to 800 lb/in up front. It seems these cars really respond to increasing the front roll stiffness. I know it sounds counter-intuitive, but it feels good and lap times will drop
.
Yeah, I'm running the rates KW shipped with. They're odd-shaped to fit stock top hats so you can't swap them out like you can with an AST/MCS etc. that run Eibach or common diameter race springs.
Keep in mind, though, that sway bars are kind of a rob Peter to pay Paul thing at a certain point, and that they don't help in heave or situations like brake dive. I wanted to try something a little off the beaten path in terms of set-up, but there's a good reason why most serious track people don't do the whole soft-spring big-bar thing.
People rag on the solid rear, but one of it's benefits is that is stays relatively unaffected by rear roll, and thus you can get away with running a soft rear on the S197 chassis without worrying about the tire getting in a bad part of its camber curve, etc. Some rollover does happen, but not nearly to the degree as with a poorly designed multi-link, for example."
"I can speak to my experience and understand, but by no means take it as gospel.
Thinking of the car as a connected unit (F/R), increasing the front roll stiffness relative to the rear means that the rear of the car will experience more load transfer in any given turn. Keeping the front tires in good camber position certainly helps, as even with 2 degrees of neg camber and coilovers I was experiencing rollover onto the outer sidewall before upgrading my FSB. The increased load transfer in the rear helps my car rotate, and takes some of the burden off the front outside wheel and transfers it to the back one. With the correct LCA geometry, you can utilize the roll steer of the solid rear axle to your advantage, increasing its contribution by making the front more of a "platform" for the rear to rotate on.
Just to give you an idea of my set-up and what I've been running out on the road course, I started with KW Variant 3's and the stock brembo bars. I then swapped to Eibach's adjustable kit, with the front bar being slightly stiffer than stock and the rear having a range of just about stock. I then added Sam's front bar, which is the same diameter but thicker wall tubing and thus effectively stiffer. Finally, I replaced Sam's bar with the new BMR 38 mm bar and I'm finally happy with the balance of the car. To give an idea, the KW rates are ~330ish front and ~180ish rear (working rates - progressive springs).
This is running a square tire set-up, btw."
"Keep in mind that the race teams likely have a VERY different setup, and true coilovers in the rear with different rates that may allow them to run with no rear bar.
I know Vorshlag and Terry/Jason are advocates of the stiffer front as well, with their coilover options coming with either 450F 175R or 550F 225R (correct me if I'm wrong) and they've found that to be the best balance as well. I don't have the rate to do that up front, so I turned to BMR for their bar.
I think csamsh (sp?) is also in the process of going up to 800 lb/in up front. It seems these cars really respond to increasing the front roll stiffness. I know it sounds counter-intuitive, but it feels good and lap times will drop
.Yeah, I'm running the rates KW shipped with. They're odd-shaped to fit stock top hats so you can't swap them out like you can with an AST/MCS etc. that run Eibach or common diameter race springs.
Keep in mind, though, that sway bars are kind of a rob Peter to pay Paul thing at a certain point, and that they don't help in heave or situations like brake dive. I wanted to try something a little off the beaten path in terms of set-up, but there's a good reason why most serious track people don't do the whole soft-spring big-bar thing.
People rag on the solid rear, but one of it's benefits is that is stays relatively unaffected by rear roll, and thus you can get away with running a soft rear on the S197 chassis without worrying about the tire getting in a bad part of its camber curve, etc. Some rollover does happen, but not nearly to the degree as with a poorly designed multi-link, for example."
Last edited by magnido45; 1/23/15 at 01:40 PM.
1/23/15, 01:47 PM
#4
A Man Just Needs Some....
Just a matter of keeping the car flat as possible in turns. Say taking a left turn. Weight is already all forced to the right front. Left rear wants to come off the ground. Right rear diggs in. Caster/camber angles change and want to push. Keep the left rear down and right side up, less pushing against the turn. Best way I can describe it. Of course the developers and racers test so many combinations, sometimes what works and what seems to make sense differ. Stiffen that car up to reduce body roll is basically it.
1/24/15, 07:03 AM
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Some off this doesn't make any sense in support of the question. Regardless, this car is probably lowered, which changes the rc height and cg height which will change the balance of the car and therefore need to tune with springs and/or bars..not to mention the 2x increase in front spring rate and different dampers. Point is, this is not "only need a stiffer front sway bar" by far. If you are going big enough with a front bar to need a bigger rear bar, you should should be increasing spring rate instead...and therefore, you can leave the rear bar stock and only tune with the front bar.
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