front sway bar

[frog]

Hello,

I've been brain storming about the under steer in 1g DSM's and it seems like the problem all comes back to this.

The front suspension doesn't gain any camber at all. Well the proper way to fix this would to change the front suspension geometry to add camber as the suspension travels. It also seems that just increasing the front roll stiffness would solve the problem albeit not as good as a new front suspension design.

The use of stiffer front sway bars has proven effective on Impreza's which have a very similar front suspension design. They are moving up to around 22mm sway bars.

What are your thoughts on this? It seems obvious that correcting the positive camber a 1g see's on the front tires while cornering is needed to actually fix the problem. Not just decrease rear traction to make the car rotate.

Cheers,

Chris

 

[MNGSX]

Umm look at RRE's 1g front camber plates.

Ask them about their swaybars too.

 

[90AWDTalon]

Hello,

I've been brain storming about the under steer in 1g DSM's and it seems like the problem all comes back to this.

The front suspension doesn't gain any camber at all. Well the proper way to fix this would to change the front suspension geometry to add camber as the suspension travels. It also seems that just increasing the front roll stiffness would solve the problem albeit not as good as a new front suspension design.

The use of stiffer front sway bars has proven effective on Impreza's which have a very similar front suspension design. They are moving up to around 22mm sway bars.

What are your thoughts on this? It seems obvious that correcting the positive camber a 1g see's on the front tires while cornering is needed to actually fix the problem. Not just decrease rear traction to make the car rotate.

Cheers,

Chris

This is exactly what I've been thinking lately, I haven't bought a front sway bar yet to try it out. I was thinking the added roll stiffness would decrease the amount of negative camber needed to keep a good contact patch.

 

[frog]

Umm look at RRE's 1g front camber plates.

Ask them about their swaybars too.

Adding static camber is again a klugde almost and hurts your straight line and braking preformance.

 

[MNGSX]

You'd need to alter the pivot points of the LCA... Since there is no UCA.

Like raise the inboard pivot..

 

[DG-FNR]

The lack of camber gain in roll is a "feature" of McStrut suspensions. There's nothing you can do about it; it's a side-effect of the design.

The way you compensate for this on a race car is to add enough front roll resistance so that you get 100% front lateral weight transfer, and then add static negative camber until you get the outside front wheel into its happy place at full roll. I have seen Speed WC cars with 9 degrees of static negative camber before.

Look at any picture of a BMW M3 at full roll, and you'll see the inside front up in the air. The idea is that a single tire with a lot of load and the happy camber angle produces more grip than a pair of equally-loaded, but camber-unhappy, tires. In many cases this is true (depends on the tire, and is typically more true of wide 7 sticky tires than narrow & hard tires)

Unfortunately, on an AWD car, it's Not This Simple. The issue is the differentials - what happens when the inside front is up in the air and the driver punches the throttle? Generally speaking, nastiness.

So an AWD car must compromise roll resistance to make sure that the tires (at least) keep contact with the ground at all times. And if you do this, you need to compensate with increased static negative camber.

This is one of the reasons that make 2Gs much better race cars than 1Gs. 2Gs have SALA suspensions that produce camber gain in roll. A 2G doesn't need to have a lot of either static negative camber or front roll resistance - the suspension naturally keeps the outside front in its happy place, so you can run the tire straighter and with less lateral weight transfer and pick up grip *and* keep the diffs happy.

All else being equal, for the same tire size, a 2G will always produce more lateral grip.

DG

Learn: http://autocross.dsm.org/books.html

 

[frog]

The lack of camber gain in roll is a "feature" of McStrut suspensions. There's nothing you can do about it; it's a side-effect of the design. [/qoute]

s/feature/flaw/

The way you compensate for this on a race car is to add enough front roll resistance so that you get 100% front lateral weight transfer, and then add static negative camber until you get the outside front wheel into its happy place at full roll. I have seen Speed WC cars with 9 degrees of static negative camber before.Unfortunately, on an AWD car, it's Not This Simple. The issue is the differentials - what happens when the inside front is up in the air and the driver punches the throttle? Generally speaking, nastiness.

A clutch type I would imagine would go along way to cureing the the up in the air nasistness. Or if you could get enough droop travel a torsen could stiff be effective. But it does still seem this is obviously less than optimal. This all stemmed from an arguement if a front sway bar would allow the car to handle more effectivly.

All else being equal, for the same tire size, a 2G will always produce more lateral grip.

DG

No doubt about that. But not everyone has a second gen and a few lost soles are trying to make frist gens turn

So lets reask the question being a little more specific. Is the frist gens 19mm front sway large enough to be effective esp when coupled with sticky tires and stiff springs all around like 400F 350R and would you see a even greater befit with a stiffer front roll with a front LSD. (obviously the LSD would make a huge difference no matter what, but do you think it is absoultly nescary if you wish to control camber with roll rates.

Cheers,
Chris

 

[DG-FNR]

Is the first gens 19mm front sway large enough to be effective?

I dunno. Test a bunch of different sizes and tell me.

The base concept - that increasing the size of the front sway bar may INCREASE front grip - is sound though - up to a point.

DG

Learn: http://autocross.dsm.org/books.html

 

[Xyloft]

stiffer front to correct understeer?

i may be wrong, but it seems that a stiffer rear end will keep the front tires on the ground. at least in most of the FWD cars i've heard about.

the problem is when the back flexes one fo the front tires lifts off, and the car understeers.

I drive a 2003 tiburon GT horrible stock understeer, and all we do is put on a rear sway bar, and it almost completley eliminates understeer. in fact on the stiffest setting, we are able to induce over steer.

we put a stiffer front on my friends comaro to help fix his oversteer problems.

now the camber stuff i dont know about so adjusting the camber up front may also do the trick.

 

[frog]

stiffer front to correct understeer?

i may be wrong, but it seems that a stiffer rear end will keep the front tires on the ground. at least in most of the FWD cars i've heard about.

the problem is when the back flexes one fo the front tires lifts off, and the car understeers.

I drive a 2003 tiburon GT horrible stock understeer, and all we do is put on a rear sway bar, and it almost completley eliminates understeer. in fact on the stiffest setting, we are able to induce over steer.

we put a stiffer front on my friends comaro to help fix his oversteer problems.

now the camber stuff i dont know about so adjusting the camber up front may also do the trick.

The problem is the fact that the suspension doesn't gain any camber as the suspension travels (aka body rolls) the wheels end up having positive camber realitve to the ground this is bad.

This makes fixing the understeer on a 1g DSM imo a counter intutive soultion. You have to stiffen the front to not decrease the aviable traction at that end but to increase it.

Increasing the front traction would obviously decrease understeer as well. The trick is as DG said to find the balance between increasing the front roll stiffness to the point where it has increased the traction as much as possible but before it starts giving any up. It would be nice if some one made and adjustable FSB for the 1g to make it cheaper to test. Also, solid endlinks I'm sure would help by making the bar more direct and effectivly increasing the rate. For this to be truely effective the car would be cornering very very flatly.

Cheers,
Chris

 

[neuralracing]

Not to hack the thread but I figured that my question may add to the discussion... I just purchased a JIC setup from RRE as welll as Poly Bushings... I am thinking of eliminating the Toe-Link in the rear (1Ga DSM)... what else can I do to help the car turn better. I also stripped allot of the weight off the car (AC, Rear seats, Radio, swapped out front seats for Sparco Revs).

This car will be mainly a track car and I say mainly because I would like to drive it to the track and not have to tow it.

 

[Kokomo]

I dunno. Test a bunch of different sizes and tell me.

The base concept - that increasing the size of the front sway bar may INCREASE front grip - is sound though - up to a point.

That point being when your coil springs are unable to keep a solid contact patch on the inside front tire and the sway bar just lifts the inside tire enough to break traction. That's a recipe for understeer city. Most FWD guys definitely can relate since the effect is much more pronounced since the front tires are receiving all the punishment.

 

[jtmcinder]

Reread and try to digest what Dennis (DG) was saying when he brought in the issue of differentials.

Before you throw money at the suspension, you need to decide whether you are staying with the stock diffs or adding a front LSD and maybe a center LSD (assuming AWD). If you optimize the suspension for the stock diffs, you will have to do it all over again if you upgrade the diffs.

With stock diffs in an AWD DSM, you are darned close to driving a FWD car with an open front (yuk!). Under these conditions, keep the front soft (and maybe even disconnect the front swaybar) and stiffen the rear to move a lot of the weight transfer to the back. Otherwise, you will just smoke the inside front at corner exit.

With upgraded diffs, especially with front struts, you can stiffen the front to maintain camber and let the diffs move the power to the rear, which, therefore, can be left soft. Keep in mind, however, that an AWD car with a soft rear will break driveline parts, such as transfer cases, on a super hard launch, as lots of power is sent to the rear.

The interaction between diffs and suspension is a huge issue. If you have been confused by some experts suggesting 500/450 springs for an AWD 2G (that would be me) and others suggesting 900/400 for the same car (that would be Dennis), then you are forgetting the issue of diffs. 500/450 has worked well on a car with stock diffs; 900/400 has worked well on a car with front and center Quaifes.

- Jtoby

ps. Dennis - take the olive branch; they don't come around very often - Jtoby