Sway Bar Drop Links - Page 2

North Coast Cab · North Coast Cab's Garage

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

Schrup · Schrup's Garage

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.

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.

911pcars · 07-30-2004, 11:05 AM

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

Jeff Alton · 07-30-2004, 01:10 PM

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

Schrup · Schrup's Garage

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.

911pcars · 07-30-2004, 02:31 PM

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

Jeff Alton · 02:46 PM

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

Schrup · Schrup's Garage

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.

Jeff Alton · 07-30-2004, 03:49 PM

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

Chuck Moreland · 03:57 PM

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.

Eagledriver · 07-30-2004, 04:18 PM

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

Jeff Alton · 04:56 PM

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

Schrup · Schrup's Garage

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.

Jeff Alton · 07-30-2004, 07:51 PM

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

Jeff

Schrup · Schrup's Garage

Jeff, next week is the Rain Forest Round Up, I hope you can make it.
2004 Rainforest Round-Up...R U Ready?

Jeff Alton · 07-31-2004, 08:48 AM

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

KTL · 07-31-2004, 09:40 AM

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)

Quote:

by jpnovak:

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.

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

North Coast Cab · North Coast Cab's Garage

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