sway bar versus torsion bar

[dgc2]

suspension upgrades for a '87 non-turbo g50 carrera offer many upgrades. so far i believe i have read over 20 blogs on this topic. my question addresses handling improvements when going to larger torsion bars versus larger sway bars, from those who have done either or both. these options will require front/back matching. however endpoint effects are not clear. vehicle is primarily for street use. while i want firm handling i do not want to jar the fillings of my passenger. note that bushing upgrads are a given.

thanks

[drabels]

Sway bars are you friend then... A thicker/bigger sway bar can be added to flatten handling when cornering without significantly altering ride quality. I've done this on all my previous (sporty) cars.

Larger torsion bars (or stiffer springs) can definitely make the ride more jarring by comparison.

As you mention, if you stiffen one end, you want to do the other or you can alter the car's handling balance. A rule of thumb would be, stiffer on the rear for more over-steer, stiffer on the front for more understeer. I like adjustable bars.

A quick google on the topic, I find this (seems like a decent write-up)

https://www.streetmusclemag.com/tech-stories/brakes-suspension/lateral-grip-sway-bars-actually-theyre-important/

[PeteKz]

I've experinmented with different sway bars and springs on many cars. In general, a stiffer sway bar will make the car stay flatter in corners, however, it also WILL increase the jarring from bumps that one wheel hits but the other doesn't, like potholes, some frost heaves, and the like.

Stiffer springs will also make that car corner flatter, but will not transmit as much impact from potholes (it will transmit some more, but not as much as stiffer sway bars). I've found that, say, 50% stiffer springs do make the ride a little harsher, but not 50% harsher, whereas 50% stiffer sway bars do.

What makes a bigger difference than either the swaybars or springs is stiffer shocks.

I have moved towards the view that softer shocks, combined with slightly stiffer springs (no more than 50% increase), and keeping the stock sway bars provides the best tradeoff for STREET driving. On a racetrack, which are almost always relatively smooth (no potholes or heaves), stiffer swayers DO help significantly, without making he suspension harsher (well, for a race car, that is).

Bottom line for me: Make the springs moderately stiffer, keep the swaybars stock, the shocks soft, and keep the car at "Euro" ride height but not lower, for STREET driving. For the track, stiffen up everything and then let the stopwatch be your guide.

Warning: only make ONE change at a time! Do not add stiffer swaybars, and stiffer springs, and stiffer shocks at the same time.

[na2ub]

Um. The shocks work together with the springs. If you have stiffer springs you need stiffer shocks. The shocks control the 'bounce' of the springs. The bounce of the springs is related to the weight of the car and the stiffness of the springs. If you stiffen the springs and not the shocks, you have negatively affected the symbiotic relationship of the pair. The (relatively) soft shocks will no longer be strong enough to control the bound/rebound of the stiffer springs. i.e. it will be closer, in effect, to running no shocks at all.

I agree with drabels. For a sportier ride without making the car to jarring, swaybars would be your first addition. The sways just transfer the suspension movement from one side to the other, keeping the car from leaning in corners, without adding the more jarring effects of stiffening springs and shocks. If it is still not sporty enough, then I would look to springs and shocks (together).

[MyFlat6]

I agree with this ^. suspension setups are meant to be a package of components designed to work together to accomplish your goals. the weight of your car, the size of your wheels and tires, ride height, shocks/revalving, springs/torsions, sways, bushings, etc all need to be contemplated together. i see many threads calling out a single item (e.g. shocks too stiff) and the community making broad statement about that component, but the reality is that components and setups cannot be compared in a vacuum. for example, my setup in my early hotrod feels different than other very similar setups that i have driven - purely because of wheel/tire size.
Here is my setup - I find it sporty with good grip and handling characteristics for street use - but purposely a bit 'vintage' feel (ie tire size). Ride input/feel is also subjective.

1972 911, 2,133lbs
Stock 15x6 Fuchs with 185/70 Pirelli CN36
Ride height at fenders F24.25 R23.75
Bilstein sports (front revalved)
Torsion 21/26
Sway 18/18
Elephant rubber bushings
Corner balanced
Turbo tie rods

[jac1976]

Originally Posted by myflat6

i agree with this ^. Suspension setups are meant to be a package of components designed to work together to accomplish your goals. The weight of your car, the size of your wheels and tires, ride height, shocks/revalving, springs/torsions, sways, bushings, etc all need to be contemplated together. I see many threads calling out a single item (e.g. Shocks too stiff) and the community making broad statement about that component, but the reality is that components and setups cannot be compared in a vacuum. For example, my setup in my early hotrod feels different than other very similar setups that i have driven - purely because of wheel/tire size.
Here is my setup - i find it sporty with good grip and handling characteristics for street use - but purposely a bit 'vintage' feel (ie tire size). Ride input/feel is also subjective.


1972 911, 2,133lbs
stock 15x6 fuchs with 185/70 pirelli cn36
ride height at fenders f24.25 r23.75
bilstein sports (front revalved)
torsion 21/26
sway 18/18
elephant rubber bushings
corner balanced
turbo tie rods

2.4?

[MyFlat6]

Originally Posted by jac1976

2.4?

It is a 2.54 MFI motor. 217hp / 201tq at wheels. Great power to weight ratio for the street with a lot of torque (necessary in my opinion on congested SoCal streets/highways).

[Bill Verburg]

Originally Posted by dgc2

suspension upgrades for a '87 non-turbo g50 carrera offer many upgrades. so far i believe i have read over 20 blogs on this topic. my question addresses handling improvements when going to larger torsion bars versus larger sway bars, from those who have done either or both. these options will require front/back matching. however endpoint effects are not clear. vehicle is primarily for street use. while i want firm handling i do not want to jar the fillings of my passenger. note that bushing upgrads are a given.

thanks

ideally you do not want to use a sway bar at all. Why? you ask.
A sway bar moves grip from the outside loaded wheel to the unloaded inside wheel, at less then 9/10 this is an ok strategy as the net max grip levels for either tire has not been approached, but as you near max side G, the available grip on the outer loaded wheel approaches max while the inner unloaded approaches min.( aka 0) so there is no where for the grip to be transferred to,


the stronger the sway the more grip is actually reduced at max side G at the end of the car where it is installed

The main positive thing that a sway does is reduce body roll, which makes the car more comfortable for a well strapped in driver and reduces camber & toe changes due to suspension compression

The way to set up a good handling car is to use the stiffest springs which are compatible w/ the ride quality you want. Of course this selection isn't in a vacuum and needs to be compatible w/ wheels, tires, shocks and chassis stiffness

The specs of all these components are then balanced f/r to give the desired handling characteristic


For a stock 87,
roll bars are 22/21, only improvement here would be adjustable at at least one end, the adjustment is just for fine tuning by the most demanding users

t-bars are 18.8/25, this gives roughly the same handling traits as an early Carrera, main negative is they allow for a lot of roll, but that also relates to the grip from the wheel and tire assemblies, 20/27 would eliminate a lot of the roll and slightly reduce low speed understeer, Bilstein hd front and sport rear shocks would be a good match but a better one would be to have a custom digressive revalve done on them.

after the above is done the wheels and tires are the weak link, stock 6 & 8 x 16 are a min for handling, 8 & 9.5 a max. This applies to 15, 16, 17 or 18. Better handling comes from shorter stiffer sidewalls, wider wheels, shorter tire OD
each wheel size has its merits, 16 is the worst for size choices, 15 best for acceleration 17s best compromise, 18s best for 100% track use

for any of the wheel choices a stagger of 1 to 1.5" in wheel width is desirable as is a stagger of 20 to 30 for tire width and a stagger aspect ratio. Unless some very specific goal is desired, For example less stagger and more less understeer is very desirable for A/X the opposite for big track use

[PeteKz]

Re stiffer versus softer shocks:

https://www.youtube.com/watch?v=JzSzoESEhCQ

[drabels]

Originally Posted by na2ub

I agree with drabels. For a sportier ride without making the car to jarring, swaybars would be your first addition. The sways just transfer the suspension movement from one side to the other, keeping the car from leaning in corners, without adding the more jarring effects of stiffening springs and shocks. If it is still not sporty enough, then I would look to springs and shocks (together).

My thoughts exactly.

In normal circumstances, going over typical undulations on the road, it will not impact ride - hardly at all (IMHO.) But in the corners, one side "borrows" the spring rate from the other. Hence the name, "anti-roll bars"

If you're riding over potholes as a regular habit, then stiffening things up any which way you look at it is going to be a mistake. So there's always a compromise at hand.

Something worth mentioning here is the price of entry.

It's really simple to change the sway bars, very much in the realm of a DIY-er job on a lazy weekend, and with the newer underbody adjustable jobs from Eibach you can tune the car to your liking to boot - you don't have to change the body like earlier types.

Removing the torsion bars can, by comparison, be an ordeal. Particularly the rear. Then when you fit a stiffer torsion bar, you need to re-index them to get the correct ride height - you may need a few goes at it, because the suspension will also "settle" somewhat over time.

That's if you even get them out easily. When I refurbed my rear suspension, the left side came out in 15 minutes and the right side took 8 hours (with heat, grinders and gear pullers all in action.)

Then you'll need new shocks as well. Maybe none of that matters if you get a shop to do it.

We've yet to here back from the OP. He's probably more confused than ever!

Daniel

[icarp]

Some thoughts on softer suspension , Stock T bars and sway ,

https://www.youtube.com/watch?v=MPVV04V7Zcc&t=2077s

Ian

[911 SLANT]

I was wondering when you were going to chime in on this subject Ian

[dgc2]

thanks to all for your comments. have decided to take to 'safe' route and keep everything stock (sway and torsion) and replace only the bushings with rubber.
rear spring plates and sway bar is completed. as an aside, the torsion bar spring plates are a poor design. new spring plates were needed since original were sufficiently rusted and prevented any body movement relative to the torsion bar (which i believe makes the actual spring rate much higher). ideally a means to grease the rubber bushings would have helped.

since i am moving to the front, i would ask whether anyone has an opinion of eccentric versus low friction mounts from elephant. notable in the previous utube is mention of eccentric from mounts. since i found the 'soft' yet 'flat' cornering to be appealing. low friction mounts are much less expensive than eccentrics.

as an additional question, bilsteins verus koni classics for front shocks. comments suggest the latter for a softer ride. any comments woulkd be appreciated.

thanks again for the valuable insights.

[PeteKz]

Smart choice to stay with stock springs and swaybars. Get new bushings in there, THEN think about whether you want to stiffen up the ride.

I went with the Rebel Racing teflon A-arm bushings in the front of my 1973. I was concerned that they would transit more noise, vibration, and harshness (NVH) to the interior, compared to the rubber ones, but they don't because they work very smoothly.

Shocks: I used the Koni Sports (yellow) with the adjustment knobs at the tops. With these, I can make quick adjustments and play with the settings on different surfaces to see what differences the adjustments make. The red Koni Classics do not have the external adjustments--you have to detach the tops of the front shocks and rear shocks, then compress them by hand and twist the clicks to change the settings. Because I wanted the ability to easily change the settings from street to track, I went with the Sports. On the street, I run them at full soft, and I find the ride to be well controlled but not at all harsh. Remember, my car is a lightened 1973, so Koni Sports on your '87 Carrera will feel even less stiff than on mine. Unless you are willing to pop for the KW's, I recommend to buy the Koni Sports.

If you still choose to go with the Bilsteins, then choose the softest ones, not the stiffer "sport" or "heavy duty" versions.

I mentioned something above, and I'll say it again: The shocks make a bigger difference in harshness than the springs (torsion bars)! If you have adjustable shocks, you can prove this to yourself, and you can dial in the amount of damping you like, or even switch it for different driving.

The next step up from Koni Sports is something like the KW struts and rear shocks, which allow even more adjustability and have valving that allows the wheels to react to small bumps and road irregularities with less damping, but then increase the damping for larger chassis movements. But those are much bigger bucks.

[winders]

Originally Posted by PeteKz

The next step up from Koni Sports is something like the KW struts and rear shocks, which allow even more adjustability and have valving that allows the wheels to react to small bumps and road irregularities with less damping, but then increase the damping for larger chassis movements.

If you are talking about digressive or regressive damping strategies, these have increased damping for slow movements and decreased damping for faster movements.

Linear (increase damping as movement speeds increase) and progressive damping (increase damping at a faster rate as movement speeds increase) strategies fell out of favor in motorsports many years ago....