Sway bars / Anti-roll bars. A highly invited discourse.

[500AMM]

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Question: When there are ALL heim joints, will it move with the same fluid ease through the *entire* length of travel? Or do you find some resistance at either extreme of travel?

A thought exercise & spatial relationship processing challenge: If the relative length of a link between two points changes (during wheel movement), and that causes compression (lateral, not rotational) in a bushing, that bushing would have greater resistance to further movement in that direction (duh) - yet continue to allow full compliance in other directions. That, in turn, would allow the use of softer or larger bushings than would otherwise be possible, because you are able to limit *specific* relative movements by the rising rate of the bushing *in that direction only* AND *only* during specific wheel displacement.

IF those type of kinematics were being used, then IF you were to remove all compressible components, the suspension would not have full free movement and would bind at certain points as it tried to bend metal (links or pickup points) to comply with the geometrically dictated kinematic path – where normally it would have rubber to pick up compliance and allow the displacement/interference to be ‘absorbed’.
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You are into something here. I guess at one point when the suspension movement is in the extreme positions it will probably produce bending forces, but that may not (hopefully) be in the suspension operational range during driving. That would cause major wear on the rubber or mechanical fracture, which the 124s has proven not to have.

The question about keeping the SLS or replacing with other shocks/springs is in my opinion not the big issue, because it's only a two different ways of damping. The challenges starts, as you are explaining very well IMO, when lowering the car and changing the geometry - tweaking the suspension intentional operating range. Next is to find proper dampers, springs and swaybars to fit for that situation.

The wheel grip surface during hard curving is interesting. I recall from being a guest mechanic once in a race team, we measured the tire temps and pressure during dialing in the suspension. First the driver warmed up "tasting" the track, then it was "re-gearing"(?) the transmission for optimal shift points on the track, and finally the suspension. It is amazing how accurate it could be set.

-a-

 

[Rouven036]

I think a slightly bigger rear bar will work well in the 036 chassis, since the serial product was made in a time when the "Mercedes rules" here more evident then nowadays (even if Porsche had its hands on the setup). Comfort had still a high priority, so the installed suspension components have not been more than a compromise to meet a sporty comfortness.
Nowadays the AMGs have different bushings for stiffer "elasto-kinemtics" as well as stronger control arms for less flex which improves control but reduces comfort and possibly increased sound transition.

In regards to the SLS system, the first ADS system,installed in R129 Chassis, had a valve block in between the shock absorber and the sphere, the valve controls the flow and therefore the stiffness. There was a switch with a damper sign in the center console to actuate the valves...Theoretically it could be retrofitted (but in all 4 corners) since the control unit also controls the vehicle level in all 4 corners, as well the speed depending lowering. Which was in the W201 16V a complete mechanical/hydraulic system.

For best results of suspension performance after lowering, and to give the axle itself and rubber bushings the full ability to work as they are deisgned for, it is absolutely mandatory to open all fasteners of the control arms to give the bushings the possibility to return to neutral position (with the vehicle on its wheels), then retighten the whole thing. That step is often overlooked....

 

[gsxr]

Glenn, I do not fully understand the SLS internal design. All I can add is my observations. When removed from the car, the SLS shock extends/retracts with little resistance, as there is no fluid and no pressure. I don't know if there is any valving inside... my suspicion is "no", based on the information above. The 500E (and E60) SLS shocks have the internal rebound limiting springs, which again are ride-height dependent, and become less effective when the car is lowered. It's unknown if the AMG E60 SLS shocks have different length internal springs. Ron would have to send me one of his new ones so I could compare it to a stock 500E SLS shock.

On a related note, the SLS shock has a foam stop buffer, same as all other 124 shocks, but sadly it is not replaceable like the buffer on the front struts. And, the buffer can deteriorate over time and literally crumble apart. Photos attached below showing a bad one and a good one. You can check yours by removing the circlip at the bottom of the shock and lifting the accordion boot. The standard 124 had Sportline versions of the SLS shocks (for sedan & wagon). I'm suspicious that the only difference between standard and Sportline is the height of this stop buffer, and/or the firmness. Again, we'd need a good one of each to compare... the total travel/length could also be reduced.

The attached photos also show why you can only lower the car so much, before it's sitting on the stops. Based on my measurements, if the rear is lowered more than ~1 inch from stock, it's likely to be sitting on that foam buffer. At that point, you could remove the rear springs from the car and it still wouldn't go any lower.

 

[runningtoohot]

Thanks for the input & photos!

Interesting is the fact that the Porsche guys once again decided to use rebound limit springs. I won’t beat that issue to death any further.

If there is only about 1” of wheel movement prior to engaging the bump stops, then they are using the bump stops as an adjunctive spring. (Why not just use progressive rate springs one may ask?) That seems verified by what looks to be a cup-like upper section. That cup looks like it is being used to keep the bump stop from blowing out radially, thereby also making the bump stop material act in a rising-rate manner. Some may see that as an elegant solution, but I see it as being a bit chintzy. MBZ knew that those bump stops were not going to last 1,000,000 miles, like all the parts of their cars are supposed to.

Are there any valve stacks inside the actuators? If not, where in the system *are* the damping characteristics controlled? Are there (strictly?) linear rate damping limitations with SLS? What are the nitrogen sphere’s influence & characteristics? Who knows. I’m certainly not going to guess because I don’t have *any* solid baseline knowledge to draw from.

 

[Glen]

The valving is all contained inside the actuator, similar to a conventional shock. I don't know enough about shock valving to make any changes but it's very easily accomplished. It's been about 14 years since I last disassembled one but basically there are discs with either holes or slots, I forget, that are at the end of the piston. There is a single nut that holds them on which is peened to prevent it from loosening in use.

I think I may have an old broken actuator laying around someplace...when I have some time, I will disassemble it and post pictures.

 

[gsxr]

If there is only about 1” of wheel movement prior to engaging the bump stops, then they are using the bump stops as an adjunctive spring. (Why not just use progressive rate springs one may ask?)

The photo is misleading. The internal rebound limit spring is "pulling" the shaft inward a fair amount. The photo shows the "off the car" resting position. On the car, fully extended, there is a lot more play. The photo shows the APPROXIMATE position when the car in "ready to drive" position, and probably 1.0-1.5" of total travel from that position. Which is why if you lower 1.0-1.5, it's on the stops. This is more difficult to determine with SLS because the boot hides the stop and travel. On conventional shocks, you can stick tape on the body (click here) and easily view the travel available by peeking under the car.

That seems verified by what looks to be a cup-like upper section. That cup looks like it is being used to keep the bump stop from blowing out radially, thereby also making the bump stop material act in a rising-rate manner. Some may see that as an elegant solution, but I see it as being a bit chintzy. MBZ knew that those bump stops were not going to last 1,000,000 miles, like all the parts of their cars are supposed to.

Clarification: The bumper on the SLS shock is in the LOWER end, not the top. And yes, MB designed the suspension front & rear to use the bump stops as a rising-rate damper. The front strut bumpers are available in various lengths and at least three firmness levels (click here). Only one was offered on the 500E/E60.

 

[runningtoohot]

The valving is all contained inside the actuator, similar to a conventional shock.

Oh good... Now we're back to (relatively) "normal" - and away from concerns about SLS being some sort of Roswell-grade alien technology. Conventional rules apply once again. For the most part, anyways.

Clarification: The bumper on the SLS shock is in the LOWER end, not the top. And yes, MB designed the suspension front & rear to use the bump stops as a rising-rate damper.

Well, even if they mounted the actuator rod side down primarily for plumbing purposes, it's still better from an unsprung mass perspective. (said half-jokingly)

Perhaps the cup around the rear bump stops was an attempt at making them last longer as a primary purpose rather than taking advantage of the additional (radial) compression factor? We'll never know...

 

[runningtoohot]

Off on another tangent again:

Again going back to early Rabbits & Sciroccos: I remember there was one company (name started with an “A”) that made ridiculously thick front anti-sway bars for those cars, plus it had HORRIFIC geometry issues. It attached to the unibody underneath the front bumper horns, and the forces generated were enough to twist and sometimes even tear the front structure apart on heavily abused cars. But boy, did those cars “handle” great with their go-kart transient response. (Sarcasm fully intended.)

 

[Glen]

Addco?
I think I had an addco bar on my Datsun 510 way back in the 80s.

 

[runningtoohot]

That’s it! Addco. They actually had a decent reputation, so they may have made good equipment for other cars; they were around for a long time.

However, this particular engineering gem looked to have been contrived by someone with both a hangover AND a hemispherectomy. Perhaps even two hemispherectomies.

 

[gerryvz]

Again going back to early Rabbits & Sciroccos: I remember there was one company (name started with an “A”) that made ridiculously thick front anti-sway bars for those cars, plus it had HORRIFIC geometry issues. It attached to the unibody underneath the front bumper horns, and the forces generated were enough to twist and sometimes even tear the front structure apart on heavily abused cars. But boy, did those cars “handle” great with their go-kart transient response. (Sarcasm fully intended.)

I had a 1984 Rabbit GTI (last year of the Golf Mk 1 / Rabbit body) and I had full Neuspeed swaybar kit (front and rear) along with upper and lower strut bars underhood. It was lowered about 3/4", not horribly. Nothing could touch that car in the handling department. It loved to lift the inner rear wheel in tight turns and sudden maneuvers. The G's I was pulling daily also ate front wheel bearings at a prodigious rate. I finally bought the Snap-On press tool to press them out without having to remove anything from the car, as I was replacing 1-2 per year. Best $250 I ever spent.

I don't remember anyone who made quality aftermarket suspension gear for those cars outside of Neuspeed, but I'm sure there were several companies that did. My mechanical mods were all Techtonics Tuning. I knew Daryl and Collin there fairly well, both before and after their move from Riverside to Sheridan, Oregon which must have been around 1990 or so. That was back when the hot setup for the CIS was a Porsche 944 air metering assembly.

 

[gsxr]

Speaking of lifting the inside rear tire. My old 1981 Jetta GLI would do the same (also a modified suspension). While it looks way cool and is fun, I don't think it's actually desirable to have a tire off the ground under cornering. It was a neat car, but I don't miss it one bit!

 

[runningtoohot]

I had a 1984 Rabbit GTI (last year of the Golf Mk 1 / Rabbit body) and I had full Neuspeed swaybar kit (front and rear) along with upper and lower strut bars underhood. It was lowered about 3/4", not horribly. Nothing could touch that car in the handling department. It loved to lift the inner rear wheel in tight turns and sudden maneuvers. The G's I was pulling daily also ate front wheel bearings at a prodigious rate. I finally bought the Snap-On press tool to press them out without having to remove anything from the car, as I was replacing 1-2 per year. Best $250 I ever spent.

I don't remember anyone who made quality aftermarket suspension gear for those cars outside of Neuspeed, but I'm sure there were several companies that did. My mechanical mods were all Techtonics Tuning. I knew Daryl and Collin there fairly well, both before and after their move from Riverside to Sheridan, Oregon which must have been around 1990 or so. That was back when the hot setup for the CIS was a Porsche 944 air metering assembly.

I cut my teeth on the watercooled VW’s. Darryl Vitone – there’s a name I haven’t heard in many years. Or Bertils, Schrick, or Drake for that matter.

Neuspeed put together some excellent packages for the A1 cars. When set up properly like yours was, they were as neutral as you could conceivably make a FWD car be, allowing you to do an on-the-limit lift-throttle dance to rotate the chassis without too much drama. Or you could do a “Blomqvist” maneuver – keep your right foot in it, and quickly / sharply stab the brakes with your left foot to yaw the chassis. Not exactly the fast way around, but fun, fun, fun.

BTW, if it only lifted the inside rear wheel in low speed turns, you weren't going fast enough in the high speed turns. Or perhaps your sense of mortality developed earlier than mine. (JK)

Speaking of lifting the inside rear tire. My old 1981 Jetta GLI would do the same (also a modified suspension). While it looks way cool and is fun, I don't think it's actually desirable to have a tire off the ground under cornering. It was a neat car, but I don't miss it one bit!

Actually, having that wheel up in the air really didn't matter at all in the overall scheme of things with those cars. There was (obviously) no weight on it to allow it to lend any additional cornering grip - and the cars were still understeering, so no additional rear grip was needed. And, ironically enough, considering the primary issue of this thread, the tripod effect was caused by the rear torsion beam axle acting like an oversized anti-roll bar.

I used to tell people that when my Sciroccos or customer’s Rabbits were on up on three wheels, it was just like a dog lifting its rear leg to pee on the other cars.

 

[Hollybrook]

The 240Z in my avatar always lifted the inside front tire in slow speed corners. Freaked me out the first time I saw it in a photo, but you did not feel it from the driver's seat. We never figured out a way to fix that with a conventional anti-roll bar. My buddies with NASCAR style bars could keep it on the ground, but I had the biggest solid bar that I could find and never was able to, even with no rear bar and soft springs in the rear.

Great thread! I don't have time to read the last day's worth, but will on Monday when I get back in town. I am liking the idea of adjusting the viscosity of the SLS fluid to get more damping.