Hellwig sway bars installed

[Paul G]

I finished installing the Hellwig rear sway bar. I got the front bar for super cheap on CL last year, just bought the matching rear bar on cyber Monday for a good price, $201 shipped to the house. 

The ride is a just a little bit firmer with the rear bar installed. 

With no sway bars, the car would lean horribly in turns. Very sloppy. Lots of tire squeal.

With just the front bar, cornering was flattened out and much more stable through the turns. The car would corner at higher speeds and be stable. When cornering hard the rear would want to swing out a lot though. That is the set up last year at the MATS Auto Cross.
 
Now with the rear bar installed the car stays very flat around the corner. At higher speeds the front of the car wants to push through the turn, understeer? The rear stays in the rear where it belongs, not swinging out like before. We will see how I do this year at MATS Auto Cross.

What corrects the understeer?

BTW, KYB shocks in all four corners, SS springs in the rear with 1" lowering blocks which you can see in the pics.     

[cdr]

adding a rear bar should have made the car looser,,over steer .

[cdr]

i dont know how tight you have the front sway links,but i would loosen them so that the bushings have very little load on them & drop 2 psi on the front tires.

[MSRacing89]

Your increased under steer does go against logic, but sometimes you end up putting load on other areas when make changes. The KYB shocks are not going to do you any favors and most importantly tires/ grip will go along ways.

I suspect you are overwhelming the front shocks and tires. I would really look at adjustable shocks.

[Paul G]

Well, maybe the understeer I am experiencing is an anomaly on a unique street corner. That was on my first trip out with the rear bar on the car. I didn't drive it much, or get on it really. I will find a big empty parking lot next weekend to get squirly a little and see for sure.

[HPP]

Your increased under steer does go against logic, but sometimes you end up putting load on other areas when make changes.

Could be tire mis-match. Looks like at least some 275s on the rear from the pics. What is your front tire size? If its 235 or less, you may have a contact patch understeer condition.

Well, maybe the understeer I am experiencing is an anomaly on a unique street corner. That was on my first trip out with the rear bar on the car. I didn't drive it much, or get on it really. I will find a big empty parking lot next weekend to get squirly a little and see for sure.

That could be as well. An on/off ramp sized radius is a large enough turn to give you a feel for over/understeer from an overall perspective.

[Paul G]

275/60-15 on the rear, 255/60-15 on the front. The front end alignment has never been checked since I have owned the car. Both front tires appear to "lean in" at the top, just slightly. They aren't wearing badly? At the Autocross I noticed that the pro built cars also have the same "lean in" at the top of the front tires. Just more pronounced than mine.   

[myk]

Hmm...but if a rear sway bar is supposed to flatten a car in corners isn't that understeer in itself? 

[Paul G]

Of all the things I have done to the 72, the big sway bars have been the most enjoyable. Improving the handling makes the driving experience so much more enjoyable. The big front bar by itself made world of difference. I dont have much seat time in the car with the big rear bar yet.

I have a Grant knock off Tuff Wheel. I took it off and went back with the big stock steering wheel becuase it just didnt look right. The smaller diameter wheel does make a difference in how the car feels though. I will probably put it back on before the next drive. 

[HPP]

275/60-15 on the rear, 255/60-15 on the front. The front end alignment has never been checked since I have owned the car. Both front tires appear to "lean in" at the top, just slightly. They aren't wearing badly? At the Autocross I noticed that the pro built cars also have the same "lean in" at the top of the front tires. Just more pronounced than mine.   

That isn't a bad match size wise. The lean is negative camber. It helps keep the tire face on the ground as the body leans over in a turn. A slight negative amount is good so long as it does not wear the inner tire ribs excessively. The opposite is positive and it reduces the tire contact patch when cornering. Radials will tolerate a wider range of camber before showing unusual wear. Bias plies will not tolerate this as well so that is why radials have provided a big step up in handling performance since the 70s.

Hmm...but if a rear sway bar is supposed to flatten a car in corners isn't that understeer in itself? 

No, actually it is oversteer. Cars out of the factory are built with understeer because if you are out of control with an understeering car, you have to slow down to gather it back up. By contrast, loosing control of an oversteering car means you heading backwards into something you can't see.  Adding the rear bar to flatten the car has added more rear rate to offset the inherent understeer so it may produce a more neuteral balance. See my response on the Cal-Track/TVS topic for more info.

[myk]

Of all the things I have done to the 72, the big sway bars have been the most enjoyable. Improving the handling makes the driving experience so much more enjoyable. The big front bar by itself made world of difference. I dont have much seat time in the car with the big rear bar yet.

I have a Grant knock off Tuff Wheel. I took it off and went back with the big stock steering wheel becuase it just didnt look right. The smaller diameter wheel does make a difference in how the car feels though. I will probably put it back on before the next drive. 

It doesn't look right but as you've discovered the smaller wheel works better, especially for what we're interested in.  I didn't know you were auto-X'ing your car; that's great.

No, actually it is oversteer. Cars out of the factory are built with understeer because if you are out of control with an understeering car, you have to slow down to gather it back up. By contrast, loosing control of an oversteering car means you heading backwards into something you can't see.  Adding the rear bar to flatten the car has added more rear rate to offset the inherent understeer so it may produce a more neuteral balance. See my response on the Cal-Track/TVS topic for more info.

Ok let me see if I have a rudimentary understanding of this: when a car goes into a turn it will tend to roll into the opposite direction; this roll will reduce the turn-in and hence you have understeer.  If you install a sway bar, then the roll is reduced, the suspension is flatter and the car will follow the turn more precisely, which gives us more of a case of oversteering.  Is that correct?

[HPP]

Sort of. Body roll and turn in are somewhat separate from the over/under steer condition and in some applications are actually desirable conditions that will make a car faster through a turn irregardless of the over/under steer condition.

Plotting out the over/under steer condition is actually pretty easy if you know a few conditions and it can be achieved under a variety of weights and spring combos.  Think of it as a basic line graph.

First we have the front to rear weight percentage on the y axis. For most of our classics this range is 50-60%. Then we have roll couple percentage on the x axis. You can run these ratios across the X axis and they can be achieved in  multiple ways using spring and bar combos. Roll couple is that combination of T-bars, s-bars, leaf spring, or coil springs under a car. So if you have two 100# T-bars a 100# s-bar and 2 50# leaf springs you have a 3:1 roll couple, or 33%. You can get the same 33% result with two 50# T-bars and 200# s-bar, or two 150# t-bars and no s-bar, so on and so forth.

Simply find you weight percentage, you roll couple percentage and you can define if your car will over or under steer. Depending on where it lands, you can then decide how to bring it in to neutral through changing springs and bars.

Here is an example of the handling line here: http://heritech.org/cuda/mgcudah.html

[Mike DC]

Ok let me see if I have a rudimentary understanding of this: when a car goes into a turn it will tend to roll into the opposite direction; this roll will reduce the turn-in and hence you have understeer.  If you install a sway bar, then the roll is reduced, the suspension is flatter and the car will follow the turn more precisely, which gives us more of a case of oversteering.  Is that correct?

In very simple terms, with all else being equal:  

The end of the car with stiffer body roll resistance will break loose sooner.  If one end of the car is coming loose too easily, then you want to add more swaybar resistance to the OTHER end.  

[Paul G]

I have been reading up a little on over/understeer. Tell me if I have this right. If the car has understeer you can lower the front end to help correct it. If it has oversteer you can raise the front to help correct it. Is this true? I use the front end as the "fix" because we can adjust the ride height so easily. Raising and lower the front transfers weight to the rear, or away from the rear.

[Mike DC]

      
The ride height would have some effect on it, causing more body roll on the higher end of the car.  A tall building on wheels would lean farther over in the corners compared to a shorter building that weighs the same.  


But there is also the strong effect of camber change when the front suspension moves.  Pushing the front end of the chassis lower down splays out the bottoms of the front tires.  That increases the front end's grip in the corners, which would cause more oversteering.    

This camber effect would not be present on the rear end of a solid-axle car.  Only the center-of-gravity issue causing more body roll leverage would affect the back.    

[HPP]

If the car has understeer you can lower the front end to help correct it. If it has oversteer you can raise the front to help correct it.

It is not quite that simple, but as Mike points out, it is a part of the calculation as are spring rates, shock rates,  weight distribution, brake bias, tire stagge, wheel offset, camber curver, caster curve, bum curve, roll center height, roll axis location, moment arm length, and a few other things.

However, there are cars where a higher roll center and ncreased weight transfer makes it faster through a turn and the over/under steer is not determined by weight transfer. Think of dirt oval track cars compared to ashalt oval track cars. Big difference in body roll betwen teh two.

This is the simplest understanding of it:

The end of the car with stiffer body roll resistance will break loose sooner.  If one end of the car is coming loose too easily, then you want to add more swaybar resistance to the OTHER end. 

[myk]

Ok let me see if I have a rudimentary understanding of this: when a car goes into a turn it will tend to roll into the opposite direction; this roll will reduce the turn-in and hence you have understeer.  If you install a sway bar, then the roll is reduced, the suspension is flatter and the car will follow the turn more precisely, which gives us more of a case of oversteering.  Is that correct?

In very simple terms, with all else being equal:  

The end of the car with stiffer body roll resistance will break loose sooner.  If one end of the car is coming loose too easily, then you want to add more swaybar resistance to the OTHER end.  

?So...what's the point of controlling body roll if by doing so you just increase the vehicle's chances of spinning out of control?

[Mike DC]

  
Each time you stiffen one end of the car, it also raises the total average stiffness of both ends in the process.  If you add the same amount of extra stiffness to both ends then the car's cornering speed should increase overall without changing which end breaks loose first.  



It's an incorrect blanket statement for me to be saying that stiffer ALWAYS means faster.  Even if we're talking about stiffening both swaybars equally that probably won't always be true.    But when it comes to the swaybars of vintage stock-ish musclecars it is pretty much true in practice. 

Street cars err on the side of too soft for a comfy ride.  45yo street cars err even farther on the soft side because they were originally designed around tires with much less grip than we have now. 

Everything from the swaybars, to the springs, the shocks, the bushings, even the stiffness of the unibody itself - the car only needed to be built stiff enough to take advantage of the grip they could get out of 1960s tires.  Now a stock musclecar will flop all over the road on modern radial tires because it wasn't designed for them.  (Same story with the original geometry/alignment settings.  And the brakes.  And the gearing.  etc.)

 

[HPP]

So...what's the point of controlling body roll if by doing so you just increase the vehicle's chances of spinning out of control?

A lot of guys don't understand it but they just do it anyway. Plus you have the "I'm a great driver" perception that has some of us thinking we can control any sort of run away car because we're such awesome drivers.

This is like a statement I saw else where about putting an 850 double pumper on a stock 318. Same concept. Can a 318 handle it, sure its built to support it with different internals. Same with a suspension. If you improve its roll characteristics, it may necessitate other changes to maximize the effectiveness of the original intended change.

[Mike DC]

         
Yeah there is a lot of truth in that too. 

For the average joe on the street, I think tightly controlling a sports car's body roll is about instilling confidence & comfort as much as actually raising the car's limits.  What the stiffer car gains in higher limits is also lost in predictability/feel.  You get less warning when it's about to break loose. 

[Paul G]

Since I now have both bars installed, and have driven it more, my observation is that the car will stay flat around corners at higher speeds then pre- sway bars, and without tire squeal. This is driving on the street, normal speeds considered. Is the car more fun to drive. An astounding YES! I have not pushed the limits of the car yet so I cant tell where the break away points are. I don't intend to ever push the car that hard at high speeds anyway.   

Last Thursday I drove to our monthly club meeting with Reggie, we ride together taking turns driving each month. Reggie has not ridden in the car since the rear bar was installed, and I didn't tell him about it yet either. We came up on a green light, turning yellow. I was making a right turn at this intersection, our usual turn. Normally I would have stopped for this. Not this time, I rolled through it a much higher speed than I would have normally done. As we approached the intersection Reggie stopped talking and held on. He did not expect the car to handle that turn at that speed. It normally would roll and lean, and just not like to turn very well at that speed. The car made that turn without tire squeal, just rounded the corner more like a modern car would do. I was very pleased. So was Reggie.      

[myk]

Since I now have both bars installed, and have driven it more, my observation is that the car will stay flat around corners at higher speeds then pre- sway bars, and without tire squeal. This is driving on the street, normal speeds considered. Is the car more fun to drive. An astounding YES! I have not pushed the limits of the car yet so I cant tell where the break away points are. I don't intend to ever push the car that hard at high speeds anyway.   

Last Thursday I drove to our monthly club meeting with Reggie, we ride together taking turns driving each month. Reggie has not ridden in the car since the rear bar was installed, and I didn't tell him about it yet either. We came up on a green light, turning yellow. I was making a right turn at this intersection, our usual turn. Normally I would have stopped for this. Not this time, I rolled through it a much higher speed than I would have normally done. As we approached the intersection Reggie stopped talking and held on. He did not expect the car to handle that turn at that speed. It normally would roll and lean, and just not like to turn very well at that speed. The car made that turn without tire squeal, just rounded the corner more like a modern car would do. I was very pleased. So was Reggie.      

That sounds great, I'm glad you were able to feel the results of your modifications.

         
Yeah there is a lot of truth in that too. 

For the average joe on the street, I think tightly controlling a sports car's body roll is about instilling confidence & comfort as much as actually raising the car's limits.  What the stiffer car gains in higher limits is also lost in predictability/feel.  You get less warning when it's about to break loose. 

So...the more we "refine" our suspensions then the more capable they become, but the less predictable the car may be in extreme situations? 

[Mike DC]

 

So...the more we "refine" our suspensions then the more capable they become, but the less predictable the car may be in extreme situations?  

Yes.  Just ask Paul Walker & Roger Rodas.  


That is, if "refining" a suspension means trying to wring every last bit of cornering ability out of it.  And if by "predictable" you mean there is a decent margin in which to sense that the car is about to let go before it happens. 


Not everyone would agree.  The OEM designers would say refining a suspension is coming up with the best compromise between road holding, predictability/confidence, and ride quality.  It costs them basically the same money to make the springs/swaybars as stiff as a granite block as it does to make them softer.  They choose not to make everything 100% stiff even on their dedicated sports car models most of the time.  Paul Walker's Porsche was an exception to that.

As for predictable, even if the margin is tiny there is still the way in which it lets go.  Some cars with small margins are still more predictable than others. 

[myk]

So...the more we "refine" our suspensions then the more capable they become, but the less predictable the car may be in extreme situations?  

Yes.  Just ask Paul Walker & Roger Rodas.  


That is, if "refining" a suspension means trying to wring every last bit of cornering ability out of it.  And if by "predictable" you mean there is a decent margin in which to sense that the car is about to let go before it happens. 


Not everyone would agree.  The OEM designers would say refining a suspension is coming up with the best compromise between road holding, predictability/confidence, and ride quality.  It costs them basically the same money to make the springs/swaybars as stiff as a granite block as it does to make them softer.  They choose not to make everything 100% stiff even on their dedicated sports car models most of the time.  Paul Walker's Porsche was an exception to that.

As for predictable, even if the margin is tiny there is still the way in which it lets go.  Some cars with small margins are still more predictable than others. 

Funny you mentioned the accident.  This thread and discussion lead me to thinking directly about Paul Walker and Rodas' demise.  Here we have one of the greatest handling cars ever designed, the Carrera GT, and I'm thinking that the superb handling capabilities didn't allow these men to notice their car was about to lead them to their deaths.  If they had been showboating in a stock C body with a 440, then that wallowing tuna boat would've told them to STOP, long before anything could have happened.

This is an enlightening discussion.  I incorrectly assumed that the better a car handled the better your performance and your safety, too...

[Mike DC]

Funny you mentioned the accident.  This thread and discussion lead me to thinking directly about Paul Walker and Rodas' demise.  Here we have one of the greatest handling cars ever designed, the Carrera GT, and I'm thinking that the superb handling capabilities didn't allow these men to notice their car was about to lead them to their deaths.  If they had been showboating in a stock C body with a 440, then that wallowing tuna boat would've told them to STOP, long before anything could have happened.

The Carrera GT had a reputation for spooky handling even compared to other uncompromised race cars.  I don't know exactly what played into it but the Rodas/Walker wreck was probably a combination things.  The more recent suspicion is that they probably hit the center-lane reflectors sticking up in the road, which broke the car loose.  That seems very plausible to me.  It brings up yet another drawback of very tight suspensions: less tolerance for bumps in the road without losing traction. 

This is an enlightening discussion.  I incorrectly assumed that the better a car handled the better your performance and your safety, too...

It's all about where the compromises are made.  There is something to be said for avoiding an accident with better handling & braking.  But once you've made most of the low-hanging-fruit improvements to the car then you're better off not trying for every last bit.  At least if safety is your primary concern.  It's not as important how it handles on the best pass in the best possible circumstances, it's important how it handles in bad circumstances with a startled driver.