Running no rear sway bar on track?

Norm Peterson

corner barstool sitter
Joined
Feb 5, 2011
Posts
3,615
Reaction score
316
Location
RIP - You will be missed
Don't suppose that the 302R/S Torsens' bias ratio of 4.0 vs the more street-oriented Torsens' 2.7 has anything to do with it ??? If you can put even more power to the outside rear wheel the car should yaw (loosen up) even more aggressively under power.


Norm
 

Pentalab

forum member
Joined
Mar 5, 2013
Posts
5,216
Reaction score
1,104
Don't suppose that the 302R/S Torsens' bias ratio of 4.0 vs the more street-oriented Torsens' 2.7 has anything to do with it ??? If you can put even more power to the outside rear wheel the car should yaw (loosen up) even more aggressively under power.


Norm

Are u sure ? I was positive the optional kilobuck torsen was 2.7:1 ratio. It was an option on the 13/14 GT-500's and also the boss. The 4.0 was more for autocross. The eaton tru-trac is 3.5 and half the price of the torsen. Anything is better than the oem ford traction-lok, with its melting CF plates.
 

Norm Peterson

corner barstool sitter
Joined
Feb 5, 2011
Posts
3,615
Reaction score
316
Location
RIP - You will be missed
Street cars
2014 FRPP catalog said:


2012-2013 MUSTANG​
BOSS 302 TORSEN​
®

DIFFERENTIAL​
M-4204-MB​
31 spline

• Fits 2005-2014 Mustang GT and​
2007-2014 Shelby GT500 with​
8.8" axle and 31 spline​
• 8.8" Torsen​
® differential

• 2.7 bias ratio​
• Features full-time torque-sensing,​
torque-biasing differential​
• Standard on 2012-2013 BOSS 302​
Mustang Laguna Seca package​
• Will accept anti-lock exciter ring​
• Does not fit IRS applications



FR500S
↑↑↑ ditto said:

8.8” T-2R TORSEN​
®

DIFFERENTIAL​
M-4204-T31H​
• 8.8" differential​
• Fits 31 spline axles​
• Torsen​
® T-2R (Race) type differential

with high bias 4.0 ratio​
• To achieve the higher bias ratio​
the assembly is more complex and​
designed for race durability​
• Service part for the Mustang FR500S​
race car​
• Can be used for performance street​
or road race applications​
• Not for use in drag race applications​
• Does not fit IRS

A page near the beginning of that same catalog identifies the T2R (with 3.73's) as being the rear end spec for the Boss 302S. I had to go back a year to the 2013 FRPP catalog to find the same spec for the 302R but it's there.


Norm
 
Last edited:

Pentalab

forum member
Joined
Mar 5, 2013
Posts
5,216
Reaction score
1,104
The 4.0 version won't survive drag racing. " Not for use in drag race applications"
The 2.7 version in the 13-14 GT-500's won't survive drag racing either. A few months back, somebody on s197 posted a pix of the blown to bits rear end on a 2014 GT-500..used in drag racing. The crown gear was missing teeth left and right. The pinion gear was a complete mess..and the torsen 2.7 blew it's brains out. That's happened a few times now on the 2.7.

The eaton tru-trac appears to be a little more robust for that application. With it's 3.5 ratio, its at a midpoint between the 2.7 + the 4.0
 
Last edited:

Whiskey11

SCCA Autoscrosser #23 STU
Joined
Feb 24, 2012
Posts
1,644
Reaction score
2

58658297.jpg
 

Norm Peterson

corner barstool sitter
Joined
Feb 5, 2011
Posts
3,615
Reaction score
316
Location
RIP - You will be missed
The 4.0 version won't survive drag racing. " Not for use in drag race applications"
The 2.7 version in the 13-14 GT-500's won't survive drag racing either. A few months back, somebody on s197 posted a pix of the blown to bits rear end on a 2014 GT-500..used in drag racing. The crown gear was missing teeth left and right. The pinion gear was a complete mess..and the torsen 2.7 blew it's brains out. That's happened a few times now on the 2.7.
Not likely that the ring gear or the pinion was to blame. All it takes is for some other hard bit to come loose and wander around inside. Lost a C-clip in a different car once, a transaxle input shaft bearing disassembled itself in another one, and final drive gears took the beatings.


Norm
 

2013DIBGT

I Hate Wheelhop
Joined
Jun 3, 2013
Posts
333
Reaction score
1
Location
The Ungreat North East
Originally Posted by Vorshlag-Fair
I don't know how you'd get an S197 setup to where it could handle "better" with no rear swaybar, unless it was really screwed up to begin with....

Yet the Ford Racing guys would run no bar if the rules allowed.

Heh..It appears that this character Carroll Smith (another keyboard racer?) has the same opinion of rear bars and mentions the concept of using enough rear spring instead as seen in this quote below.

Maybe, just maybe a car can handle well and not be "really screwed up" without one of these RSB contraptions we are speaking of? :poke:

CARROLL SMITH'S CAUSE AND EFFECT GUIDE

"My own opinion is that on most road courses a rear anti-roll bar is a bad thing. Anti-roll bars transfer lateral load from the unladen tyre to the laden tyre exactly what we dont want at the rear. I would much rather use enough spring to support the rear of the car. The exception comes when there are washboard ripples at corner exits, as on street circuits and poorly paved road circuits."
 

csamsh

forum member
Joined
Apr 9, 2012
Posts
1,598
Reaction score
2
Location
OKC
"My own opinion is that on most road courses a rear anti-roll bar is a bad thing. Anti-roll bars transfer lateral load from the unladen tyre to the laden tyre exactly what we dont want at the rear. I would much rather use enough spring to support the rear of the car. The exception comes when there are washboard ripples at corner exits, as on street circuits and poorly paved road circuits."

If you're on a track in Texas that isn't COTA, the exception is applicable.

Also....it's a solid axle. "Enough spring" in the rear makes the ride terrible.
 

Whiskey11

SCCA Autoscrosser #23 STU
Joined
Feb 24, 2012
Posts
1,644
Reaction score
2
If you're on a track in Texas that isn't COTA, the exception is applicable.

Also....it's a solid axle. "Enough spring" in the rear makes the ride terrible.

Are we talking about a racecar or a street car? Honestly, 275lbs/in rear springs was not that bad and is getting up there in what I'd consider for anything dual purpose. It was also probably more spring than I needed on street tires but I loved the way the car handled!

At the end of the day, everyone sets up their cars differently. Some people prefer a lot of bar and relatively soft rear springs, others prefer spring over bar. I opted for spring over bar and the car was an absolute riot that handled exceptionally well as noted by people who have driven the car.
 

Stephen31201

forum member
Joined
Jun 24, 2015
Posts
195
Reaction score
0
I am bringing back this post because I have been trying to tune the car using the sway bar at the track and the more I dig into knowing more about it the more I don't understand their purpose on a race car. From what I have read, sway bars were created to take the place of heavy spring rates (harsh ride) in order to reduce "sway" or body roll by increasing spring rate on the outside tire by robbing it from the inside tire. I hear people say "the car pushes like crazy when I remove the rear bar completely" yet they are still running a huge ass front bar so that explains it. I know it can be used for quick fine tuning, but why not run the correct spring rates in the first place and do away with both bars or fine tune with a small 5-10mm bar. They seem counter productive in the fact that they remove the weight on the inside tire which lessens traction (push and oversteer). A large front bar like we run on the S197 seems to turn it into a straight front axle. I see pics all the time of the inside wheel completely off the ground. I have never seen an indy car with the front tire off of the ground. I do not have a lot of suspension knowledge so I need help trying to wrap my head around this.
 

Norm Peterson

corner barstool sitter
Joined
Feb 5, 2011
Posts
3,615
Reaction score
316
Location
RIP - You will be missed
Time to start using some actual stiffness numbers for the bars as well as for the springs. Some load goes through the bars, and some goes through the springs, divided up according to their relative stiffnesses and the motion ratios (think "leverages") over which they act.

Sure, you could meet most any roll-per-lateral-g target with stiff springs and no bars or at most tiny ones, but I'll just about guarantee that you'll hate the ride. Typical "lowering springs" are in the 200 lb/in range. Front sta-bar stiffnesses typically add 500 lb/in or more to that, and there just aren't going to be many folks preferring 700 lb/in or stiffer front springs to a set of Steeda linear Sports and a decent front bar that gives essentially the same results. It'd be the same story with 500 lb/in coilovers and 475 lb/in or more bar, vs ~1000 lb/in C/O and no bar. You'd come to hate railroad grade crossings and most any other kind of 2-wheel bump.

Whether it's through the bars or the springs that "weight" is getting transferred during sustained had cornering, or through the shocks and struts during transients, it's always a matter of load coming off the inside tires and being added to the outside ones.

When a car takes on a 'tripod' cornering stance, it's because the front and rear roll stiffnesses are out of balance with the car's physical weight distribution. And there may be a reason for doing this, even though all further load transfer can only happen at the end where both tires are still on the ground. Keep in mind also the matter of rearward load transfer if the car is also accelerating on the throttle. Effects from cornering and either braking or acceleration are additive, and it's common to have some of each when the driving does get hard enough to lift a tire.

It's unrealistic to compare what's basically a hopped up street sedan against a pure race car with its much lower CG. Though I do have to ask if those pictures you've been looking at involve the car rolling over an insde track curb and one or the other inside tires briefly becoming airborne (which isn't necessarily as upsetting to the car as it looks, BTW - inside tires are pretty lightly loaded at max lat-g as it is).


Norm
 
Last edited:

Stephen31201

forum member
Joined
Jun 24, 2015
Posts
195
Reaction score
0
Dang that is some heavy stuff. lol. As for the pics, I am referring to at the track. And I have seen this right in front of me on many many occasions at the track as well. I definitely understand the use of the bars for street cars, as most of the public wants a plush ride yet great cornering. I on the other hand am more about performance at the track and I don't care if it rides like a wood wagon on the street as I use this car mostly for the track. It just seems that the entire design of the bar is to simply add spring rate in corners, but removing weight off of the inside tire to do so seems counter productive. It would seem that using a sway bar for each wheel and leveraging it against the chassis on the opposite end would be a much better design at getting the torsion spring action that you want but without sacrificing spring rate on the inside wheel. Then the car would actually work like a true independent front suspension and maximum traction would occur at all 4 corners at all times. Again, I am no suspension guru and you obviously know more about it than me. I am just the guy who can leave shit alone and I am always trying to improve something.
 

Vorshlag-Fair

Official Site Vendor
Official Vendor
Joined
Nov 12, 2010
Posts
1,592
Reaction score
107
Location
Dallas, TX
I think some folks are confusing swaybars with bolt-on chassis braces, subframe connectors, torque arms and other useless doo-dads. You can argue and calculate and quote Carroll Smith and postulate online but that still doesn't change the fact that modern cars function better with swaybars at both ends. Just like they function better with dampers on each corner, tires on each corner, and brakes on each corner. They aren't magic, but they are necessary.

There's always going to be less-than-perfect suspension advice out there, but we have to all be vigilant to keep from falling into the trap of "that sounds so easy and cheap that it must work!". Like disconnecting ABS systems, or thinking that there's a cheap way to make your brakes bulletproof, or that you can get great handling with Chinese coilovers, or that those scrub race tires you got for cheap are as good as new race tires. NO.

51fx7UMlXUL._SX258_BO1,204,203,200_.jpg


Carroll Smith was a great race car driver, engineer, and author. He died 13 years ago. I've read all of his books cover to cover, and much of it still holds true, but most of his experience and writing had to do with small, lightweight, formula cars. And even those still have swaybars. He was not infallible, and some of his theories have since been replaced with better data. Again, on the whole his writing is excellent and insightful, but it is starting to become a bit dated. 4 of his 6 "...To Win" racing books were written in the 1970s-1980s, and a LOT of automotive technology has changed since then. The advances in tire technology alone since the 1980s is revolutionary, not to mention ABS systems, EFI systems, cylinder head design, damper design, and more.

I'm not trying to disparage folks form NOT reading his 6 books - you should buy them and read them, they are still very helpful - but you have to realize that much of his race car building career was in the 1960s GT40 program and into the 1970s with formula cars. An S197 Mustang has little in common with those when it comes to finite details like "running without a rear swaybar".

B61G1548-M.jpg


Seriously, don't try to remove your swaybar at either end of your S197 Mustang. It will turn your big, heavy, stick axle unibody cars into a big hot mess. You are welcome to test this, but again, most of the "internet testing" I've seen regarding running no swaybars is so poorly done and inaccurate that these outlier data points can be chalked up to internet folklore.

DSC_9127-M.jpg


There is some solid conventional wisdom surrounding swaybars - use them as a tuning tool and to help with transitional movement in the car, but not as a crutch for lack of spring rate. I see so many people discussing swaybars that still have OEM lowering springs on their cars. Those are too soft to even test with. Coilover springs are usually 300-500% stiffer than OEM springs, because that is what keeps are car from moving too far in roll, dive, or heave. If you don't even have proper monotube dampers, you aren't even in the ball park of good handling and you should stop trying to "overthink" shortcuts to proper suspension setup like removing swaybars.

DSC_9109-M.jpg


Like the car above - you don't need to think about Watts Links or control arms, you need REAL SPRING RATE increases (and thus real dampers) before you do anything else to the suspension.

DSC_4988-M.jpg


After you get quality coilovers on your S197 with proper spring rates (AT LEAST 4 TIMEs the OEM front rates) then you can experiment with swaybars effectively. Most times we see aftermarket front swaybars that are BOUND UP in the mounts. Out of the box virtually every aftermarket swaybar doesn't fit the chassis mount bushings, and it adds hundreds of pounds of roll resistance.

This is easy to check, and its happened to all of us. Disconnect both end links on a given swaybar and see if it rotates in the bushings with "pinkie finger effort". Most times I've seen an aftermarket bar it's so bound up that we can do pull ups on the swaybar... as in it takes 100-200 pounds of force to even move it. They NEVER fit well out of the box and the bushings and mounts usually need tweaks to get that "pinkie finger" low effort mounting. Not loose in the mounts, but FITTED PROPERLY in the mounts. It takes shimming the brackets, reaming the bushings to fit, or both.

DSC_9071-M.jpg


Our first V8 BMW E36 above was a classic case of this. With an H&R front swaybar added, at the next autocross test event (shown above) the car pushed like mad (massive understeer) because it had too much front roll stiffness. It was getting up onto 2 wheels in transitions - too stiff! We took it back to the shop, put it on the lift, unhooked the endlinks, and I could hang my 200 pound body from the end of the swaybar. Wouldn't budge. We spaced the bracket down, ground the bushing a bit, got the bar to pivot freely, and then took it to another event... night and day difference. It was now neutral and the DEATH PUSH went away. No parts changed, not even swaybar settings, just fixed the swaybar pre-load in the mounts.

So look at your swaybars for this "bound up" condition, because it is ALL TOO COMMON. I've probably seen this 50 times in our shop with customer cars. That's something to worry about with swaybars, not their total deletion, good grief. And yes, some of the internet folks that swear their "no swaybar" setups are faster were likely victims of a "stuck" swaybar. Don't let that data confuse you....

/rant :yuno:
 
Last edited:

Whiskey11

SCCA Autoscrosser #23 STU
Joined
Feb 24, 2012
Posts
1,644
Reaction score
2
I am bringing back this post because I have been trying to tune the car using the sway bar at the track and the more I dig into knowing more about it the more I don't understand their purpose on a race car. From what I have read, sway bars were created to take the place of heavy spring rates (harsh ride) in order to reduce "sway" or body roll by increasing spring rate on the outside tire by robbing it from the inside tire. I hear people say "the car pushes like crazy when I remove the rear bar completely" yet they are still running a huge ass front bar so that explains it. I know it can be used for quick fine tuning, but why not run the correct spring rates in the first place and do away with both bars or fine tune with a small 5-10mm bar. They seem counter productive in the fact that they remove the weight on the inside tire which lessens traction (push and oversteer). A large front bar like we run on the S197 seems to turn it into a straight front axle. I see pics all the time of the inside wheel completely off the ground. I have never seen an indy car with the front tire off of the ground. I do not have a lot of suspension knowledge so I need help trying to wrap my head around this.

The truth of the matter is that people need the ends of the cars to do more than just resist body roll. Resisting roll is important for steady state cornering which as Norm will tell you rarely exists in any pure sense. What I DO need the car to do is put power down and in order to do that I have to give up rear wheel rate to keep the axle compliant over bumps and allow some rearward weight transfer to happen in a much less abrupt sense. Same goes for braking events. I need the braking event to happen at a rate that the tires can handle. Too much and I get into ABS way early, too much rear springs and I blow the tires away instantly upon throttle application.

Swaybars come in to allow me to tune out the body roll while keeping those things compliant enough to not shock the tires in braking and accel. If anything, those two events are more important than the pure roll anyway since I'm usually blending the two all the time.
 

modernbeat

Jason McDaniel @ Vorshlag
Official Vendor
Joined
Jan 30, 2012
Posts
412
Reaction score
15
Location
Dallas, TX
Heh..It appears that this character Carroll Smith (another keyboard racer?) has the same opinion of rear bars and mentions the concept of using enough rear spring instead as seen in this quote below.

Maybe, just maybe a car can handle well and not be "really screwed up" without one of these RSB contraptions we are speaking of? :poke:

CARROLL SMITH'S CAUSE AND EFFECT GUIDE

"My own opinion is that on most road courses a rear anti-roll bar is a bad thing. Anti-roll bars transfer lateral load from the unladen tyre to the laden tyre exactly what we dont want at the rear. I would much rather use enough spring to support the rear of the car. The exception comes when there are washboard ripples at corner exits, as on street circuits and poorly paved road circuits."

If you really read his writings in context you will understand that he is first, out of date, and next, is usually writing about formula style aluminum monocoque chassis with 100% spherical ends in the suspension, lockers or spools in the differentials and mainly independent rear suspension.

Those are the Smith books under that stack on the left. There are better books on suspension design, but people keep coming back to the Smith books. Maybe because they are cheap and the good books are priced like textbooks. Anyway, keep in mind that what Carroll is talking about and what you are working with are miles apart and his advice in this case does not apply. Don't believe me? Test it yourself. That's what I did.

books.jpg
 

Norm Peterson

corner barstool sitter
Joined
Feb 5, 2011
Posts
3,615
Reaction score
316
Location
RIP - You will be missed
It would seem that using a sway bar for each wheel and leveraging it against the chassis on the opposite end would be a much better design at getting the torsion spring action that you want but without sacrificing spring rate on the inside wheel.
You just built the springing portion of Chrysler's front suspension from the mid 1970's through about 1990, aka "transverse torsion bar". Nothing but a torsion bar instead of a coil spring, and still not as effective at resisting roll as a real sta-bar. FWIW, Chrysler's earlier longitudinally mounted torsion bar arrangement was better in many respects.


Norm
 
Last edited:

Stephen31201

forum member
Joined
Jun 24, 2015
Posts
195
Reaction score
0
You just built the springing portion of Chrysler's front suspension from the mid 1970's through about 1990, aka "transverse torsion bar". Nothing but a torsion bar instead of a coil spring, and still not as effective at resisting roll as a real sta-bar. FWIW, Chrysler's earlier longitudinally mounted torsion bar arrangement was better in many respects.


Norm
See, I'm smarter than I thought. I am just 40 years late is all. I think I am going to try installing the proper spring rate and then install the smallest bars I can find in order to "fine tune" the set up. If people are in deed using the proper spring rate, then throwing a 36mm front sway bar on the front would clearly be way too stiff and in fact using the bar for spring rate instead of for fine tuning.

I know you guys at Vorshalg have probably tried everything under the sun, so I am curious what spring rates you were at and bar sizes with the 315 R6 tires. I would guess 700-800/275-300?
 

csamsh

forum member
Joined
Apr 9, 2012
Posts
1,598
Reaction score
2
Location
OKC
I ended up at 800's with a 315 A6 on the front. That was the first spring rate I ran where the sway bar needed to be moved off of full stiff to alleviate understeer.
 

Stephen31201

forum member
Joined
Jun 24, 2015
Posts
195
Reaction score
0
Well that must be nice. I have adjustable front and rear and cant run them more than full soft. I have removed the rear and it definitely tracks better out of the corner and I can put the power down earlier. Off throttle the rear does want to walk around at entry. But that is also using a 36mm front bar. The same bar that I used with the stock suspension before switching to coilover springs.
 

Latest posts

Support us!

Support Us - Become A Supporting Member Today!

Click Here For Details

Sponsor Links

Banner image
Back
Top