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two suspension q's - sway bars/bumpsteer

ok, searched and got lost.

1. how does a adjustable sway bar work? you basically change the length of the droplink? which rotates the SB and then what happens? preload?

2. bumpsteer; i got a bit of bumpsteer on mountain road drives. car is lowered, the washers installed to correct for this. if the car is flat on level ground, the tie rods need to be parallel with the floor? it would appear my ends go "uphill" a bit to the wheel. i will measure with a tape during daylight. i am thinking of scraping the washers, bringing the steering rack back down and installing the ERP adjustable tie rod ends. so i just level out the tie rods? i dont get it.

basically, i am feeling the urge to fiddle with the car. even with adjustable sway bars, how does the newbie even begin to mess with it?

i got: LSD, 21/27hollow tbars, brand new bilsteins, (sports in back)

TIA, cliff
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Old 08-14-2004, 10:39 PM
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1. no, you adjust where the droplink connects to the lever arm, which changes the mechanical advantage, see:



2. yes, tie rods should be about parallel. How much correction you need depends on your ride height obviously. Raise your rack up some more, or raise the car, or I guess get the ERP kit, which is somewhat adjustable, but really expensive. Here are the instructions, they also give a book reference for learning about bump steer:


http://www.smartracingproducts.com/pdfs/481210%20(Bump%20steer)WEB.pdf
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Old 08-14-2004, 11:18 PM
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Correcting for bumpsteer requires to tie rods to be parallel to the control arms, not the ground.

Problem with the rack spacers is you can't space it enough to solve the problem. The rack hits the floor.
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Old 08-15-2004, 07:56 AM
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Another alternative to set the tie rods correctly is to use these tie rods. I got these units from ERP .

Kurt Williams

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Old 08-15-2004, 08:04 AM
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Quote:
Originally posted by Chuck Moreland


Correcting for bumpsteer requires to tie rods to be parallel to the control arms, not the ground.

.
dam, I've been figuring it wrong. I thought that parallel to ground was conventional wisdom? Maybe it is and most guys have it wrong?

So that means that the angle of the control arms = the angle of the tie rods ?

thanks Chuck
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Old 08-15-2004, 08:35 AM
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Ron, you are correct.

You often hear that they arms should be parallel to the ground. That is wrong. Instead, you want the angle of the control arms = angle of tie rods.

For many cars that have made this mistake, don't worry too much. At about "Euro" height, the control arms are pretty near parallel to the ground with stock spindle height.


Ideally, you are trying to achieve a parallelagram with the tie rods and control arms forming the top and bottom.
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Last edited by Chuck Moreland; 08-15-2004 at 01:30 PM..
Old 08-15-2004, 09:04 AM
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thank you chuck. and thanks andy, i guess i get it now. i have a friend making his own, drop links, i have to tell him this.
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Old 08-15-2004, 01:02 PM
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Chuck:
You must know by now that I always try to learn more about suspensions/steering...and we've shared thoughts before on this board.

Hmm.....parallel to the control arms and not the ground. That also is a new epiphany for me.

However....is this correct if the "radius" of the lower A-arm and the "radius" of the steering tie-rod is different? Are they different? I submit to your thinking, Chuck, but wonder if this is true in all cases or only when the two pieces are the same length.

True enough...most of us would get it close enough because the A-arm is fairly horizontol in a "car-lowered" condition...so setting the tie rods parallel to the ground is almost the same thing.

Interesting stuff !! .......

--Wil
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Old 08-16-2004, 07:34 AM
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You learn something new everyday-hopefully.
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Old 08-16-2004, 07:47 AM
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Wil

The radius of the two arms is close to equal. The tie rod radius is
adjustable, so we aren't dealing with a true parallelagram. But close.

The difference in radius could be compensated by altering the angles slightly. If we can measure the lengths (and angles) with sufficient accuracy, that compensation could be calculated. But we are talking minor affects. Alternatively, there are setup tools that can measure the bump steer as the wheel moves up and down.

For guys with normal tools, you can get close to ideal just by setting the arms parallel.
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Old 08-16-2004, 08:13 AM
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Thanks for the clarification , Chuck.

Conversely...if the radius for the two pieces were markedly different...then I suppose the two pieces being parallel to one another wouldn't work...or would work only very well over a narrow range at near static ride height...

---Wil
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Old 08-16-2004, 08:29 AM
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ok, it is clearer now.

now with aftermarket bushings, i fear a harsh ride. (only from what i hear). how do bushings make the ride harsh? it just seems to make things rotate smoother, at least in my mind. but harsher?

cliff
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Old 08-16-2004, 12:42 PM
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The bushings are kind of like the "padding" where the A-arm connects to the body. I installed Chuck's poly-bronze bushings and the ride is great, not harsh at all, and so nice to install.
Old 08-16-2004, 12:52 PM
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Vash

You are right in thinking smooth rotation with low friction yeilds a smooth ride. The harsh ride you hear about is specifically with polyurethane type bushings.

In the best of cases, Polyurethane bushings create a moderate amount of friction. But in practice they are difficult to fit properly and require specialized tools (eg. a metal lathe). Fit incorectly (as most are), they do not move freely. With time the grease squeezes out and they run dry. The friction them becomes high and ride harsh.

Do a search on Polybronze bearings. These solve the problems and do not ride harsh. Pelican sells them.
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Old 08-16-2004, 12:58 PM
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your polybronze bushings have been in my sights for awhile now. thanks, that answers my que, since i am trying to avoid a harsh ride. i am looking forward to checking out, k911sc's car, he installed them.

cliff
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Old 08-16-2004, 01:22 PM
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Cliff,
You are welcome to take a ride in my smooth-riding, polybronze equiped car during autocross class in two weeks.

Call me vain but I just picked up a pair of Piloti driving shoes while attending the Historics at Laguna Seca this weekend. I'll probably be labeled a poser in class.

-Brad
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Old 08-16-2004, 03:27 PM
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too bad that ERP tie rod end kit is so expensive. What's the lowest ride height that the simple (cheap) rack spacers can compensate for?
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Old 08-16-2004, 08:04 PM
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I don't know the lowest -- and the error effect is progressive, but I understand that the rack spacers are fine for the Euro ht.
Old 08-16-2004, 08:28 PM
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Quote:
Originally posted by Randy Webb

the rack spacers are fine for the Euro ht.
absolutely
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Old 08-16-2004, 09:06 PM
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Did Euro Height 911's come stock w/ the rack spacers?
Old 08-16-2004, 10:25 PM
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