Sway Bar Drop Links
 

I needed to replace my rear sway bar drop links. Rather then spend $75 for an OEM set or $100 for an aftermarket set I decided to source and buy my own heim type drop links. Well after spending twice as much money I finally got a set to work.
http://forums.pelicanparts.com/uploa...1090884776.jpg
Now my question is, how do I and do I want to preload the sway bars? I can adjust the drop links to be tighter and pull the bar up or I can make them looser and push the bar down. Which do I want to do and what is the end result? I would assume by preloading the effective spring rate would be higher.

Also, I've got enough parts for at least another set. If anyone is interested send me a PM.

John

There is no sprung load on a sway bar. It is neutral. The only "loading" you can do is to weight-jack the car. You should keep it neutral.

What I'm saying is, there is no reaon to have two adustable links. One side is all you need. Install the first side and adjust the 2nd side to slip on with the car on level ground and rolled into place to settle the suspension.

The fact that you made up your own links is clever.

I don't want to diminish your work, but youv'e made a nice set of adjustable drop links that aren't going to change anything from the stock ones as far a stiffness. To change the stiffness in the rear (and front) you need some way of changing the point were the droplink attachs to the sway bar. The adjustable drop links are a way of getting the same degree of stiffness on each side and making up for any deviations. The farther out from the fulcrum, the less torsional force. Perhaps there is a way to alter your stock ones? Better yet, John, youv'e come this far, why not build a new bar and arms yourself. You do nice work!

They are the later style Carrera bars 21mm vs 18mm in the rears. I really wasn't looking to have a project to stiffen the rears, I just needed to replace my worn out drop links. Anyway, I guess I don't understand why I couldn't tighten the drop links equally on each side and thereby preload or prestiffen the sway bars. Either way the heim drops look much nicer.

John

I'm working on my sway bar too, but replacing with oem parts. Looking at your links, is there a jam nut there to lock the pair together or will the threads be expected to hold by themselves? Once adjusted/set, I would think a jam nut or even welding would ensure a longer lasting marriage of those two pieces.

No jam nut now, but thinking of shortening each end to allow for one. There is no way for them to really turn or loosen so I'm not sure it's necessary.

John

Springs provide a constant resistance (the spring constant). You won't alter the stiffness by doing this. You might limit the amount of movement available tho. (a bad thing).

Maybe I don't understand what you are thinking. If your sway bar is in the car and no links are attached, you should be able to move it up and down, the friction of the bushings being the only resistance. It is a free floating device. Connect it and all it does is move the weight back to the light side by forcing the light side to somewhat follow the movement of the heavy, or outside wheel in a turn. The amount of weight transfer is adjustable as 88911 describes.

Unless you're cornering in one direction (ala Nascar), you will want your car to handle equally well both left and right. Therefore, you should install the sway bar so there is no preload on either side. Minimally, one drop link works for this purpose.

Although you may not have increased the roll resistance (since the distance from the drop-to-sway bar remains the same and you haven't increased the bar OD), if you corner balance your car, the adjustable links will allow slightly difference individual corner heights (the rear anyway) to arrive at a "balanced" chassis without introducing any suspension preload - impossible with fixed-length drop links.

The length of the new drop links doesn't have to match with the factory ones. You should be okay as long as the angle of the bar ends is close to perpendicular to the drop links and you have adequate road clearance. A thin jam nut might fit if you have to shorten them more.

Hope this helps,
Sherwood

I used the same setup for my 993, and it worked fine. No preload on the bar when flat on the ground.

Sent you a pm on the spares!

I attended my first DE a couple weeks ago. My instructor (Randy Wells) drove my car a few laps & he mentioned that I had all the right components for a good suspension, but he felt that they weren't working together properly. After reading this thread I think I may need to unattached my adjustable links from my sway bar & adjust them so I can reattach them while the car is sitting on the ground.

When he first mentioned the car felt unsettled in the rear, I accredited to my rear tire pressure (40psi), but he felt there was something more to it so maybe this will be it. When I installed them I set them at the middle of their adjustment with the car on jack stands. I haven't driven any other 911 but my own & it feels much better with the new suspension I installed last winter. The car has a lot less under steer & stays really flat while cornering.

I plan to make this change tonight & will be curious to see what Randy's assessment is at the next DE. He will be my instructor again & can push the car a lot closer to it's limits on the track than I can. I want a good base to start to learn on before I start to make adjustments for my driving style after I learn to drive on the track. Perhaps after a while I'll get some adjustable sway bars after I learn to drive, but I don't think I want a tail happy car in the meantime. Thanks for the good input.

Paul,
Are YOU supposed to drive the car during the DE?

John

Just be aware that you should have the conical washers to go with those spherical rod ends. Otherwise they might bind. The binding is not a problem for your application but will affect lifetime of the part.

That combination works well but I would suggest a locknut or loctite.

Everyone is right, no preload on the bar. To stiffen you will not change the length of your drop link. You will just move the drop link closer to the pivot point.

John, I drove my car plenty, I thought it was a good idea to get some input on how my car felt from someone with a lot more experience. I want a good neutral base to start from & don't know what a neutral handling 911 is supposed to feel like. My next DE I should have a better idea as I think I preloaded my sways. I just want some reassurance that "yes this is how it's supposed to be", then I can go from there on what I like which very well could be a tail happy car because I hate under steer.

Well I just got through readjusting my drop links. I unbolted them from the sway bar then drove the car around a little to resettle the suspension. I had to extend them about half an inch to get them to line up with the sway. There is only about three turn out left on them. After, I drove around a little but couldn't push it. My first impression is that the back end is less stiff.

My question is why would Pelican & moreover Tarret market these if they are worthless. My next step may be to drill some more holes in the sway, but then again I don't want to devalue them because if I upgrade to fully adjustable sways I'll probable want to get my money back out of them, about $250.

Paul,
What year car do you have and what type of sway bars?

John

Paul are you sure you did it right. Can you adjust both of them up about half way and still have no tension?

Paul,
I assume you have a fully adjustable Tarret sway bar; adjustable drop links and adjustable sway bar arms.

Perhaps a drawing or photo describing the current setup would be more descriptive. Ideally, the geometry should be such that the drop links are close to vertical when installed midway through the total adjustment. That way, the drop links don't sit at an acute angle if the arm length is at full hard (short arm) or full soft (long arm).

IMHO, three threads is not enough engagement.

Sherwood

John, I have a 80 SC & I upgraded my sway bars to the larger Carrerra sways 22/21mm.

EW, I put the car on jack stands to unbolt the drop links from the sways & when I put it back on the ground, the holes still lined up. That is why I took it for a drive without the sways attatched to see were they would settle. I couldn't push them any higher by hand, so I figured that is were my drop links needed to attach.

I'll take the car out tommorow for a spirited run to see how it feels under hard cornering.

Sherwood, I only have the adjustable Tarret drop links on the rear.

Paul,
I've got the exact same set-up. Hopefully by Saturday I'll have my mounts reenforced and be able to play with the drop links.

John

Yesterday I had a chance to drive in a spirited manner & the old push is back. The car feels more like it did when I had the stock suspension on it with regards to balance. I like the fact that these adjustable rear drop links let me dial out under steer on my car. I know it may be safer to learn on the track with some under steer, as it's more predictable. But, I detest a car that pushes, I want to get on with it & I have a smaller steering wheel (270mm) to catch the ass if it misbehaves.

So tonight I'm readjusting the drop links to where they were, in the middle of there range. Perhaps when I get back from Canada I'll try the other end of there adjustment & see if I get massive overseer. I sure hope so.:D So at this point, although I'm not as educated on the dynamics of suspensions, I have to say I'm pretty happy with the adjustability these drop links afford me.

Paul,
Regard the push; it's a matter of degree. I think most cars are set up (or wish to be set up) for slight understeer throughout the speed range. For the majority of drivers, understeer is the best setup for high speed stability and to minimize racing stripes in the shorts. For cars with rear weight bias like ours, throttle position is of utmost importance to control the degree of ultimate under/oversteer.

In your case, how much understeer does it have? Does it act like a FWD car? Is it impossible to induce throttle lift oversteer? If so, that may be too much understeer.

Has your suspension been adjusted? F/R wheel alignment, ride height and corner balance? If not, you may want to pursue those adjustments first. Adjusting sway bars should be reserved to fine tune the basic setup. Out of the box, 911s should handle pretty good, but that's relative and assumes everything is to spec.

As far as basic sway bar settings go,

For max understeer:
Frt: Short arm length, large sway bar OD
Rear: Long arm length or no bar, small bar OD

For max. oversteer:
Frt: Long arm length or no bar, small sway bar OD
Rear: Short arm length, large bar OD

When you think about it, on any level of road racing, it's the basic car setup that determines how fast a car will ultimately go - not necessarily power/torque. For example, the current F1 Renault machines are probably 70 HP down on the competition (MB, Ferrari, Honda, Toyota, Sauber and BMW-powered cars), but they make it up by having maybe the best balanced chassis in the field (assuming driver skill being equal); probably easier to drive as well. It's not enough to make them clear winners, but that and car reliability positions them closer to the podium at every race.

Sherwood

I am having trouble understanding how adjusting drop links on a non adjustable sway bar change the characteristics of a car. If you pre-load the bar, I can see it having an effect turning in one direction maybe. If you just change the lenghts of the drop links, you really are not changing anything. However, the whole point of having the adjustable links is to eliminate pre-load.

Jeff

Sherwood, my car has been aligned & corner balanced by Fordahl Motorsports & it is as low as as it can be without bump steer. I have upgraded to Carrera sways. I have felt the lift induced oversteer twice both with the droplinks set in the middle postion. The first time was at 70mph when I had to lift for a large dip that bottomed out my car & was able to catch the rear, the second was at 90mph when I (stupid) hit the rev limiter & had three lanes to drift out. With the drop links at their current longest length I haven't felt lift over steer because I haven't tried. The car pushes at least 2 feet on a hard 50mph corner. I can use the throttle to control this but I feel the car should be turning better. Perhaps after I get some good track time & learn how to drive I will appreciate under steer.

Jeff, why the difference in how my car feels when the rear sway is preloaded (no push) & not preloaded ( big under steer). I don't understand why they would make them adjustable if all they are designed to do is eliminate preload. So if I shorten them up, thus preloading my rear sway, am I asking for something to break because I'm not using them as they were intended or am I just risking more snap over steer? I did have my mounts reenforced.

I really appreciate the input, as I am new & have a lot to learn. Fact is my instructor thought something was amiss with my suspension & I really don't want to invite disaster, so if understeer is something I have to learn to embrace to keep my car in one piece than so be it.

Paul,
So as not to confuse those who might offer suggestions, you could ID which sway bar you're adjusting (front or rear) whether it be the drop links or sway bar arms.

In addition, Jeff is correct in that the length of the drop links has no bearing on the effect of the sway bar - that depends on OD, length of the bar and the length of the sway bar ends (distance from sway bar to drop link). To repeat earlier suggestions, make sure the sway bar doesn't impose any load on either wheel when the car is at rest on a level surface.

Sherwood

Okay, I have re-read this thread and have a couple of questions.

Paul, with the links unbolted can you move(rotate) the bar in the bushings? It should move fairly easily. This may have something to do with why things change when you adjust the links. I think I saw in other posts that you had 22/29 t-bars, is that correct? If so, your car should not understeer with the 22/21 sways.
Where on the track did it feel loose? How was it in the highspeed turn 2?
What about 3b at the bottom of the hill? Just trying to see what is going on.

Lift throttle understeer is more a factor of weight transfer and not roll stiffness. You lift off and unload the rear, around it comes.

You can counter initial understeer by loading the front wheels prior to turn in. Either lightly tap the brakes, or lift slightly while the car is still pointed straight ahead.

Jeff

Thanks guys, I'm going to set my drop link a little further in so they have a few more threads to grab & leave them alone. It seems that the sway didn't rotate by hand but that maybe due to the new bushings. It sounds to me that the problem is with the driver. When I was getting the under steer it seems I was accelerating around the corners pretty hard to induce it. Probable to prove to myself that I'm right & everyone else that knows what they're talking about is wrong. I need to set them & forget about them & worry about seat time at the track as I've only been to one DE & am just getting started.

One more question, would having the drop links too short (preload) cause things to bind & this is what my instructor was feeling (amiss)? I just want to ensure my car is doing what it is supposed to.

Paul, if you can, grease the sway bar bushings so that the bar will rotate. If it binds it acts more like a spring and less like a sway bar. That alone could make the car loose feeling. Try to set the links so that they are a close as possible to 90 degrees with the sway bar arm. I guess if they were too short, things could bind a little.

I agree with Randy, from what I have read about your setup your car should be great. I have a very similar set up with the same sway bars and the car was very neutral on Seattle.

By the way, when are yo guys out there again? I would like to come down.


Jeff

Paul

Yes, having the links too short can bind. Especially if your car is lowered.

If the angle between the drop link and sway bar is severe, it will change the roll stiffness. In extreme cases it will bind.

With the car on the ground the angle between drop link and sway bar should be just about 90'.

Seperately, when you adjust your drop links the car needs to be on its wheels and on level ground. You can't do this on jack stands as the preload will be different.

edit: re-reading your posts, I think you may have pre-load confused.

Pre-load is not about the length of the drop links. It is a measure of the tension in the sway bar under static conditions. Zero preload means that the sway bar is completely relaxed when the car is on level ground, and not moving. That is what you want to achieve.

To expand on Chucks comments: Preload is when you have the drop links set to different lengths than each other such that the bar is trying to roll the car while it's just sitting there. Moving both drop links shorter or longer should have no effect (unless taken to extrem and causing binding). Spend a couple of minutes thinking about the purpose of sway bars (anti-roll bars) and the geometry of the system and you should be able to see what is going on. The sway bar should be able to rotate 360 with no restrictions if the lever arms weren't there to hit the rest of the car.

-Andy

Having the links at different lenghts does not mean that there will be preload necessarily. They are adjustable so that they can be set at different lenghts to eliminate the preload.

Jeff

Thanks again guys, the fog is starting to lift now. This Sunday I will get everything set proper including taking off the sway bar & applying some Weltmeister gorrila snot to the bushing to free up the bar. I don't know why I have to over complicate things, It's quite simple when I think about it.

Jeff, the next DE is August 27, hope to see you there.

Cool, good luck!! You mentioned you were going to be up in Canada. When and where?

Jeff

Jeff, next week is the Rain Forest Round Up, I hope you can make it.
http://forums.pelicanparts.com/pacific-northwest-us-wa-id-ut-hi-ak/169894-2004-rainforest-round-up-r-u-ready.html

Ah yes, Doug's Baby!! I wish, but I will be at work all weekend. Pretty countryside up there though, just watch your speed on the hwy 5!! Not sure of the route you guys are taking from the coast, but hwy5a from Meritt to Kamloops is worth the extra 15 mins it ads to the drive!

Jeff

John (North Coast Cab),

Are the rod ends you used Aurora Bearing Company brand? Those are the kind I intended to use because of the metric sizing. Specifically, the A-series metric rod ends (AM-M, AW-M)

Jamie, or anybody else, could you show an example of these conical washers in use?

I don't know the brand as I bought them from a distributor. I cur pieces of bronze sleeve bearings to act as spacers on each side. I reinstalled the drop links to the same mounting points as the OEM ones. I'd also like to see a picture of the changed mounting point using the conical bolt.

John