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> Suspension upgrades, Mass. confusion
wndsnd
post Jun 3 2012, 06:42 PM
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Trying to figure out what is the difference between sway bars, anti roll bars and torsion bars. Expensive stuff - Is it worth it for the road if I do no autocross?
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mepstein
post Jun 3 2012, 06:56 PM
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First decide what you want your car to do better or differently and then you find the parts or mods to accomplish.
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bulitt
post Jun 3 2012, 07:18 PM
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The Torsion bar is a spring, it replaces the typical round wound spring on the front suspension.

Sway bars and anti-roll bars are the same thing IMHO. Some are adjustable. They keep the body level and as you go through a corner when the inside wheel wants to lift off the ground they help to keep it planted.

I'm sure the experts will chime in shortly.
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Bruce Hinds
post Jun 3 2012, 07:34 PM
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QUOTE(bulitt @ Jun 3 2012, 05:18 PM) *

The Torsion bar is a spring, it replaces the typical round wound spring on the front suspension.

Sway bars and anti-roll bars are the same thing IMHO. Some are adjustable. They keep the body level and as you go through a corner when the inside wheel wants to lift off the ground they help to keep it planted.



Yeah, what he said.... torson bars and sway bars/anti-roll work the same way they get their spring from the twist. After noticing the other porsches you drive I doubt you'd be happy with out sway bars on the teener. It makes a big difference in the cornering.
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toolguy
post Jun 4 2012, 07:07 AM
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"Sway bars and anti-roll bars are the same thing IMHO. Some are adjustable. They keep the body level and as you go through a corner when the inside wheel wants to lift off the ground they help to keep it planted."

The purpose of a sway bar is to transfer weight of the car in turns. . Now think of all the pictures of racing Porsches going around a turn with the inside tire 3 inches off the ground. . .

Actually, the sway bar increases the lift of the inside tire, and pushes down harder on the outside tire. . . that makes that end of the car want to slide more. So a real stiff sway bar on the front will makes the front 'understeer" or "push"
. . . a rear bar will tend to make the back end want to swing around in a turn. .
So now you are thinking why would you want them if they make the car slide around?? the answer is complex. . . what they do is keep the car flat which is advantageous on faster turns.. the trick is to balance the stiffness of the front and the rear bars, so both ends slide an equal amount, IE allow you to drift through a turn sideways. This is in a faster turn only. . on slower turns, a lot of drivers will adjust the bars looser or even disconnect the rear bar altogether.

Even back in the 70's, racing Porsches had sway bars that were adjustable from inside the cockpit by the driver when racing. I remember it was a lever that controlled the position of the drop link on the sway bar end arm. . For it's time it was really slick.

The factory set up street 914s to be relatively neutral for ease of driving and safety, and then guys like us come along and want things to be better, as in we think we are smarter than the engineers that designed these car. . Well, we can be if we take a lot more than sway into consideration. . . change ONE thing and you affect something else- is the rule. . . so just putting on a front bar will make the front 'seem' better because you got rid of the nagging body sway a little. . . what you really want to do to control sway and keep the car's wheels planted is increase the torsion bars and rear springs stiffness. . . but this too comes at a price. . It rides like a go cart and beats you to death. . .

SO in essence, how much of a comfort ride are you willing to give up and how fast do you take turns ?? an autocross is a mild spring and sway bar set up. . . . time trials are a little more on the stiff side. . . Real race car are stiff as hell with little to no suspension give at all. . .

Just my 2 cents



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mskala
post Jun 4 2012, 10:00 AM
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QUOTE(wndsnd @ Jun 3 2012, 08:42 PM) *

Trying to figure out what is the difference between sway bars, anti roll bars and torsion bars. Expensive stuff - Is it worth it for the road if I do no autocross?


You're probably less than 10 miles from me. Sometime I can show you the feel
of stiff springs on the street. I use 180lb springs and roughly equivalent front
torsion bars, with very mild front sway bar, which works pretty well for autocross
but is near the limit of not fun for driving on crappy roads.
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wndsnd
post Jun 4 2012, 10:04 AM
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QUOTE(toolguy @ Jun 4 2012, 09:07 AM) *

"Sway bars and anti-roll bars are the same thing IMHO. Some are adjustable. They keep the body level and as you go through a corner when the inside wheel wants to lift off the ground they help to keep it planted."

The purpose of a sway bar is to transfer weight of the car in turns. . Now think of all the pictures of racing Porsches going around a turn with the inside tire 3 inches off the ground. . .

Actually, the sway bar increases the lift of the inside tire, and pushes down harder on the outside tire. . . that makes that end of the car want to slide more. So a real stiff sway bar on the front will makes the front 'understeer" or "push"
. . . a rear bar will tend to make the back end want to swing around in a turn. .
So now you are thinking why would you want them if they make the car slide around?? the answer is complex. . . what they do is keep the car flat which is advantageous on faster turns.. the trick is to balance the stiffness of the front and the rear bars, so both ends slide an equal amount, IE allow you to drift through a turn sideways. This is in a faster turn only. . on slower turns, a lot of drivers will adjust the bars looser or even disconnect the rear bar altogether.

Even back in the 70's, racing Porsches had sway bars that were adjustable from inside the cockpit by the driver when racing. I remember it was a lever that controlled the position of the drop link on the sway bar end arm. . For it's time it was really slick.

The factory set up street 914s to be relatively neutral for ease of driving and safety, and then guys like us come along and want things to be better, as in we think we are smarter than the engineers that designed these car. . Well, we can be if we take a lot more than sway into consideration. . . change ONE thing and you affect something else- is the rule. . . so just putting on a front bar will make the front 'seem' better because you got rid of the nagging body sway a little. . . what you really want to do to control sway and keep the car's wheels planted is increase the torsion bars and rear springs stiffness. . . but this too comes at a price. . It rides like a go cart and beats you to death. . .

SO in essence, how much of a comfort ride are you willing to give up and how fast do you take turns ?? an autocross is a mild spring and sway bar set up. . . . time trials are a little more on the stiff side. . . Real race car are stiff as hell with little to no suspension give at all. . .

Just my 2 cents



This is a great explanation, Thank you. I just ordered 100 lb rear springs, and Billsteins all around. I am trying to decide on the front sway bar. Seems like the consesus is that would be a nice combination. BTW, I have never driven my 914 yet, but have owned many Porsches. This one is on stands as I sort it all out.
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URY914
post Jun 4 2012, 10:06 AM
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I'd say a front anti-roll bar will make the biggest single item differance in the handling of a stock 914.
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wndsnd
post Jun 4 2012, 10:21 AM
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QUOTE(mskala @ Jun 4 2012, 12:00 PM) *

QUOTE(wndsnd @ Jun 3 2012, 08:42 PM) *

Trying to figure out what is the difference between sway bars, anti roll bars and torsion bars. Expensive stuff - Is it worth it for the road if I do no autocross?


You're probably less than 10 miles from me. Sometime I can show you the feel
of stiff springs on the street. I use 180lb springs and roughly equivalent front
torsion bars, with very mild front sway bar, which works pretty well for autocross
but is near the limit of not fun for driving on crappy roads.



This I would enjoy! I appreciate the offer and would enjoy the friendship of a local 914 owner.
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toolguy
post Jun 4 2012, 10:44 AM
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100 lb rears are right at stock level. . 140 ones are a big improvement and not too harsh 160 is pretty stiff for a four cylinder 914 and what you'd want for high speed turns. .

140 rears with 19 mm front TORSION BARS is a good balance.
then around a 19 mm front sway bar and the factory stock rear 16 mm bar works well together. . the car will be flat through even the sharpest street turns, but it's going to be a much stiffer , as in a very bumpy' ride ...

This is just a guide from what I've used on numerous 914's over the years. . .. a lot of people will insist on no rear bar at all. . I like the rear to slide a little. . .

The other thing to remember that I left out of the big post was that a sway bar will in essence, transfer traction to the other end of the car. . . so a stiff front bar will make the front push out and make the rear seem to stick better. . . a rear bar will slide the rear while making the front a little more predictable.

This gets more complicated for the front of the car and what is called bump steer. . when the car hits a bump or leans in a turn, the change in the level of the wheel and A-arm, pulls on the steering arm and causes the toe alignment to change slightly. . Ideally, if the car stays flat, the tie rods stay the same level plain and the toe doesn't change. . . If the steering rack isn't properly aligned with the ride height of the car, any bump or sway makes a greater difference on toe. . . thats' why it's important when you lower the ride height from factory specs, you move the steering rack an equal amount to compensate. [I.E. the term steering rack spacers, which are really ust thick washers]
.

When set up properly for autocross, time trials and racing, a whole bunch of the steering is done by the right foot. . . as in, you don't take your foot off the gas when the rear starts to slide, you actually steer in the direction of the slide and give it a little more gas and drift sideways . . . takes a while to get the hand of it but it's the quick way around a course. .

Just another 2 cents worth from an old guy. . .
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ConeDodger
post Jun 4 2012, 10:56 AM
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If you're just looking for a decent handling car, the stock front and either no rear or stock rear sway bars are just fine. Your 100# rear springs are roughly the same as stock so I would just stay with what you have. My car came without sway bars and I initially went with stock front and rear bars (I am way beyond that now). It was probably one of the most dramatic changes I have experienced with the handling of my car. It went from feeling like you were seated on a big rubber ball and trying to stay on top of it while it rolled (think Ford Mustang handling) to being a fun car to toss around a bit. Not autocross ready but fun...

You may have heard the term 'slippery slope' tossed around as it regards modifications. Be careful with aftermarket changes on a car you just want to street drive. You might not like what's at the bottom of that slippery slope...
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