Sam Strano

I also don't necessarily agree with the notion the bars are way too small. I very much like a 35/22mm combination, and in fact I think the 24mm GT500 bar is a bit too much if a well balanced set of lowering springs is also in use (as the springs and bars both work on changing wheel rates).

All that said, it's horses for courses. You could run a car with all spring and no bars, and a TON of bar and very soft springs. I don't think either is really wise.... And while I tend to like to get a good bit of my front roll stiffness from a bar (being a high powered, RWD car I feel the benefits are better power down and tire compliance vs. really heavy springs), I don't think a monsterous rear bar is the right way to go, especially if the alignment can be used to enhance front grip.

Sleeper_08

I'm running the Steeda 1 3/8 (35 mm?) front and 7/8 (22 mm ?) rear with Steeda Competition springs front and rear. So where does that put me on the soft spring/stiff bar vs stiff spring/soft bar spectrum?

clintster77

In a way, front end alignment is adjusted when a set of sways are added to any car. Theres less roll and therefore less front end travel when turning which keeps the tires flatter to the ground.
Where the trade off is is during braking and acceleration . From what I understand the amount of weight shift available during braking and acceleration is more with softer springs. Which gives more of the front rear balance back to the driver. Like left foot braking in the middle of a corner to gain a little more oversteer without letting off the gas . What I mean is with supper stiff springs weight shift is more of an abrupt (yet less) because the car moves from front to back to front less and can give the driver less time to react to some understeer /understeer conditions . Not that a stiff spring setup can't be driven but this is one of the reasons that rally car drivers can drive a rally car like mad even on a smooth asphalt track with a soft rally setup . They are used to throwing the car into corners and using their feet to steer the car around the corner (not to be confused with drifting which is stiff yet way different goal) . It is a more active way to drive with any soft setup.
Just another point of view.

Norm Peterson

In a "first cut" analysis, weight does not move, and the amount of load transfer can legitimately assumed to remain the same during any given maneuver regardless of suspension ride stiffness. What changes is the amount of suspension movement, which is a consequence of load transfer, not the cause of it.

In a fussier analysis, all fluid weights do move due to sloshing, and load transfer may be affected slightly by what are normally quite minor CG movements. But the end result is still the same - load transfer happens and what you see as changes in the vehicle pitch or roll attitudes is a result of that load transfer with whatever suspension ride stiffnesses and anti's are present.


Norm

RodeoFlyer

Albuquerque

Sam Strano

That would be more soft springs/stiffer bars (though not the softest springs, or the biggest bars). To me a stiff spring/softer bar setup would be when you are getting into the 400+ range on springs in front and stay with stock bars or start to drop sizes.

Bear in mind that H&R sells their Race springs which are seriously stiff @ about 600 front, 500 rear... they also sell a 35mm front, 26mm rear bar. Teaming those up would be pretty much the stiffest of both other than the Hotchkis bars which are bigger in front, 1mm smaller in the rear, but the rear is also adjustable where the H&R rear isn't.

clintster77

The amount of suspension movement during trail braking or any other movement is more as you said. In general there is more potential for more load transfer with softer springs because a lower spring rate at the same ride height as a harder spring is compressed more . So the front will dive lower and the rear will raise higher up in the air and this is why I said weight shift.
Drag racers use the term weight transfer to describe putting a larger load on the rear wheels during launch . You don't see drag cars with stiff springs all the way around because of weight transfer. We may be saying the same thing in a different way

clintster77

This thread is great but I think I may of hit a snag in my hopes of using these sways . Here is the link to the install guide . what I see is that the rear sway hooks up different than the stock . Is the OD of a v6 rear axle the same as a GT. www.stillen.com/product_files/304100A~inst.pdf

Norm Peterson

I knew that sooner or later that would be mentioned . . . so I just sat back and waited. Here ya go. Yeah, I know it's a bit long and probably has more math in it than lots of folks will bother to struggle through.

It's still load transfer because except for the rather small contributions of rearward fluid slosh and a CG path that's curved a tiny bit backward as the car pitches nose-upward, no other actual weight movement relative to the rear wheels is happening. People call it "weight transfer" because their experience only tells them when you add weight to the trunk or take weight off the nose (lose the A/C, for example) that end of the car either drops or rises. Acceleration isn't a physical object that you can hold in your hand, so most people can't relate it very well to the suspension movement it causes. It may be "good enough" in nontechnical discussions. But it is worse than "not good enough" when you need to understand what is actually happening because it suggests wrong conclusions and leads to errors in understanding what is a cause and what is a result.

What is happening is that the CG is being permitted to rise enough to significantly affect how much load transfer is developed. The rear is held from dropping (squatting) partly by suspension linkage arrangements that provide various amounts of "anti-squat" and partly by rear spring and shock stiffnesses. Relo brackets increase the amount of anti-squat (and ideally at 100% anti-squat the tail does not squat from acceleration forces no matter what rear spring rates are). Shocks that are stiff in bump slow down any tendency for squat.

Up front, soft springs allow more upward movement there, there are no "anti" effects, and shocks are typically softer in rebound so that the rise can occur more rapidly. If the rear does not drop, or only drops a little while the nose rises substantially, the CG being somewhere near the middle will rise.
Bottom line,
[RearwardLoadTransfer] = [Acceleration] x [SprungCarWeight] x [SprungWeightCG_Height] ÷ [Wheelbase]
where
[Acceleration] = [Rear%] ÷ (1 - [Rear%] x [CGHeight]/[WB])

Here's a few (simplified) numbers to chew on. 3500 lbs car + driver, 107" WB, 21.4" CG height, 53%/47% weight distribution, coefficient of friction µ = 1.00, solid suspension (no springs at all). The numbers are reasonable, but only for the purposes of this discussion. They are not from any specific car or modification.

[Acceleration] = 0.47 ÷ (1 - 0.47*21.4/107) = 0.519g
[RearwardLoadTransfer] = (0.519 x 3500 x 21.4 ÷ 107 = 363 lb
Rear tire vertical load = 3500 x 0.47 + 363 = 2008 lbs

Now assume that due to front springs being installed (that are obviously softer than "rigid") that the nose rises 4", but the tail does not squat at all. The CG rises by 53% of 4" (2.12"), to 23.52"

[Acceleration] = 0.47 ÷ (1 - 0.47*23.52/107) = 0.524g
[RearwardLoadTransfer] = (0.524 x 3500 x 23.52 ÷ 107 = 403 lb
Rear tire vertical load = 3500 x 0.47 + 403 = 2048 lbs


Norm

clintster77

I wasn't referring to adding weight in the back or taking weight away from the front but someone could of interpreted it that way.(so I am glad you cleared that up.)
What I was saying using technical terms . IS...
[Weight shift] = [Acceleration] x [SprungCarWeight] x [SprungWeightCG_Height] ÷ [Wheelbase]

I will start using the term load transfer instead of weight transfer and Weight shift

The reason I used the term weight transfer with the Drag race analogy is to try to bring the CG raise to the light . But I was referring to its effects on acceleration as well as braking. think about the numbers in the example you used A:363 lb and B403 lb with softer springs. That is only a 40lbs difference in the rear axle . But in my analogy ( not the drag racing analogy )

Example : lets say you have two very neutral suspension setup that pulls a lot of Gs on the skid pad without oversteer or understeer (neutral).
One is the one with stiffer springs and the other is the one with softer springs . Throw braking and acceleration into the mix . Load transfer gets added into the equations .Effecting the oversteer / understeer manors of the car .
Not only is the car in the example A: putting 363 lb of load on the rear but it is reducing the load on the front axle by aproxx 363 lbthat is a 726 lb change. Example B: is +403 lb rear/-403 lb front for a total change of 806 lb for 80 lb difference in the two spring setups.

Now these numbers are way different when you add cornering into it but you can see that applying the brakes or accelerating changes the car into an oversteering or understeering machine . Depends upon driver input but also on the suspension stiffness.

Believe me I used to drive a 84 camaro that had worn out shocks and everyone knows that a 84 camaro has one of the most flexible unibodys out there. I raced it at the circle track and it was almost totally reliant on my input . So I went around the track pressing the gas and brakes . Oversteer hit the gas /understeer hit the brakes/oversteer hit the gas. over and over agian. I finnaly got to where I would go into the corner way hot and just downshift mid corner, the down shift was just enough to take some load of the rear axle. as soon as the rear would start moving out then I would floor it
and keep the front end pointed in the direction I wanted to go. It did not have posi so the rear would actually slowly start to tuck itself backin due to the scuff that the one non spinning wheel would give me.(I could of never done this with a posi because that would of put the rear out like a drifter due to more rear bind)

Wow that's the longest post I have ever typed .