Another Sway Bar compilation, reconciling the data

[Bossdog]

I'm looking to upgrade my PP2 sway bars to compliment Steeda Sport springs for MagneRide.
There are 10+ sway bar threads already here on the MG6 Suspension forum. I've searched all the data I could find and found much of it doesn't mesh; claims of % increase don't agree with lbs/in performance.

I centered my search and calculations on the one thing most of us can agree is a fact:
1) PP1 say bars 295 lbs/in front and 123 lbs/in rear
2) Car and driver reports in 2018, PP2 has a 12% increase over PP1 in the front, 67% increase in the rear.
Manufacturer Claims: Steeda and BMR make claims of increased stiffness over PP1
Much of my reported data comes from a post from @shogun32 , post #6, Thread title "Sway Bars, Which Ones". thanks to Shogun32.

The PP2's significant increase in rear bar stiffness over the PP1 (67%) compared to only 12% in the front, I am assuming was an effort to dial out track understeer was successful! I do like the balance of the PP2 front to rear ratio as I don't have track understeer. (I also have Steeda Camber plate)

My goal then is to stay close to the PP2/Mach 1 bar front to rear ratio as I increase stiffness. I've reported front to rear ratio calculations in my spread sheet below. A first number larger than 1.6 will move toward adding understeer. Less than 1.6 will add over steer, compared to the PP2/Mach 1 bars.

If you have added stiff track springs, this info may be less applicable
Please feel free to challange any of my assumptions and "facts".

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[NightmareMoon]

What are you trying to do? Calculate what bar you want to buy or provide accurate info for posterity?

to calculate stiffness you need to know the inside diameter of a hollow bar, and many of these with the same outside diameters have different inside diameters (and the lever arm lengths too). I had a spreadsheet too but lost it recently in a HDD crash.

thats the bad news. The other bad news is there is no perfect swaybar balance. Its salt-to-taste, and depends on your driving style, preferences, tire widths, shock settings, etc.

the good news is rear bars at least are pretty cheap and super easy to swap, so if you buy a front bar /rear bar setup with adjustable bars, and you dont like the balance, it may be as easy as changing the setting, swapping back to your stock rear or at worst, swapping the rear bar. Most of these 35mm fronts are similar enough in dimensions that along with adjustments, you’ll be ok.

So back to the question. Whatcha looking for, or are we just playing with spreadsheets?

 

[Mikepol2]

The Steeda adjustable sway bars have been a nice upgrade for my car, which has the same stock front and rear sway bars and springs as your PP2. If you are tracking it, full stiff front and full soft rear is what I would try first. For public roads I found the stiffest front setting to be a hoot but too harsh, following every undulation in the road. 2nd stiffest front is good but the car does want to oversteer even with the rear bar at full soft. This is with 305/30 fronts and 315/30 rears.

 

[13GetThere]

Tell me more.

 

[NightmareMoon]

The Steeda adjustable sway bars have been a nice upgrade for my car, which has the same stock front and rear sway bars and springs as your PP2. If you are tracking it, full stiff front and full soft rear is what I would try first. For public roads I found the stiffest front setting to be a hoot but too harsh, following every undulation in the road. 2nd stiffest front is good but the car does want to oversteer even with the rear bar at full soft. This is with 305/30 fronts and 315/30 rears.

Steeda has a couple different rear bars.

 

[Oakley]

I have the steeda rear competition bar on its softest setting with dual rate spring sand pro action adjustable shocks. its thinner than the PP1 rear by a significant amount.

so far the combo is working out great.

 

[kz]

I second what Nightmaremoon said.

Everyone needs to quit thinking in terms that stiffer bar is an "upgrade". It's a tuning tool. Sometimes you may want a softer bar - depending on your spring stiffness and Steeda offers one as Oakley pointed out..

Also what feels like "nice upgrade" on a grocery run, may turn out to be a disaster in steady state cornering at the limit - especially super stiff rear bar.

 

[Bossdog]

What are you trying to do? Calculate what bar you want to buy or provide accurate info for posterity? . . .

So back to the question. Whatcha looking for, or are we just playing with spreadsheets?

I'm not looking to generate any new data, only understand the "data" that is out there. As I stated, the data out there doesn't really mesh. No surprise, manufacturers are not interested in publishing all their specifics so a "real" comparison could be done. I don't blame them for keeping their cards close to the chest.
For me, it is important to have as much info as possible before I go to the track. If its a "street only" vehicle, yes, you can drive around all you want and take time to make adjustments. With the cost of a track weekend at around $1500, combined with the difficulty of making changes at the track, I try not to make changes to the car that will diminish my enjoyment ( F-things up) before I head to the track. I generally only get 2 or 3 weekends each summer.

What I'm looking for: to analyze existing data on sway bars in an effort to make an informed selection of sway bars that will reduce body roll in combination with my current springs (Steeda progressive sport, Magneride) without adding understeer or oversteer.

Looks like the Steeda bars ( part # 555-1017) may be the best candidate for me.

 

[Bossdog]

I second what Nightmaremoon said.

Everyone needs to quit thinking in terms that stiffer bar is an "upgrade". It's a tuning tool. Sometimes you may want a softer bar - depending on your spring stiffness and Steeda offers one as Oakley pointed out..

Also what feels like "nice upgrade" on a grocery run, may turn out to be a disaster in steady state cornering at the limit - especially super stiff rear bar.

Hence, the reason for my analysis.

(I like to use the word hence whenever I can as it seems to irritate so many people)

 

[NightmareMoon]

Thanks for the info. As I said the data may not make sense until you have all the data including inside bar diameter aka wall thickness of those swaybars.

How do you evaluate your current setup? Does it understreer, oversteer, or neutral?

My PP1 GT definitely understeered from the factory, for example.

 

[GTP]

For me personally (and even though I am BSME) I simplified the whole thing and just changed out my 2019 GT-PP1-MR bars for Ford GT350R combo. I also changed front springs only for GT350/M1-nonHP spring rate.

My logic? I did not want a much stiffer ride than stock PP because of DD. I wanted the F/R spring rates to be close to GT350, and same for the sway bars. I just figured that Ford probably got things pretty close with the GT350R, and I did not want to overthink or overspend, especially since I'm an amateur HPDE driver.

Having said that, I felt that my car finally had good turn-in at slower turns once I graduated to 305 Cup2 tires. And it feels great in medium and high-speed turns (60-110mph). I think my car feels quite close to neutral because I can steer with the throttle just right. Again, speaking as an amateur.

 

[GTP]

In summary, I stiffened front springs while stiffening both bars, more so the rear bar. (I still don't understand why people recommend a real stiff front bar when our cars understeer as stock.)

 

[zenwhipper]

Good stuff. Definitely worthy of consideration.

 

[NightmareMoon]

(I still don't understand why people recommend a real stiff front bar when our cars understeer as stock.)

Most people arent able to drive an oversteering car and can’t gain time in the corner entry phase, so they double down on getting traction on corner exit.

i’ve done rear-bar only and front bar only setups in the past. They were different but ‘about the same’ in autox lap times once you mastered how to drive the setups. Both bars is superior, but you dont necessarily want a rear bar as stiff as some companies sell. (It depends). FWIW my front bar is never set on full-stiff.

 

[Bossdog]

Thanks for the info. As I said the data may not make sense until you have all the data including inside bar diameter aka wall thickness of those swaybars.

How do you evaluate your current setup? Does it understreer, oversteer, or neutral?

My PP1 GT definitely understeered from the factory, for example.

With Steeda magneride sport lowering springs, Steeda camber plates , Steeda roll center/ bump steer correction kit, it feels pretty neutral on the track, no under steer and the rear is not loose. My effort here is to keep that balance with a bit less body roll.

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