How do a choose a proper swaybar for lapping? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 24 Old 01-06-2011, 08:46 AM Thread Starter
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How do a choose a proper swaybar for lapping?

I have a 1990 gt with some heavy springs in the front..DECH 1000-1200lbs.. with a stock gt swaybar, rubber pivot bushings and shorter urethane end links.. on the street it drives fine but i find a the track it has some understeer, I was told by a some people who really know these DECH cars that I should get a smaller front bar, and at the track, totally remove the rear bar.. my car is a fully loaded gt with MM road&track box with the DECH springs, anti-squat brackets, and single adjustable Koni's.. I was thinking of going with the '93 cobra bar or the Steeda road race bar.. but.. not sure if this is the proper fix.. looking for some help..

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post #2 of 24 Old 01-06-2011, 09:09 AM
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What do you have for rear springs? If they are stock, then I would think stiffening them up would help the most.

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post #3 of 24 Old 01-06-2011, 09:44 AM Thread Starter
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^^^ I have the DECH 280lbs springs in the rear with the DECH anti-squat brackets and a DECH panhard bar..MM lower CA's and FRPP uppers...oh and the Koni single adj. shocks..stock swaybar

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post #4 of 24 Old 01-06-2011, 10:06 AM
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First, you take it to the track and see how it behaves, and tune from there.
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post #5 of 24 Old 01-06-2011, 10:14 AM Thread Starter
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^^^I have, mosport during the summer, and there was understeer issues..thats where i was told to try a smaller bar.. I just dont have the money to buy different bars to swap out and test y'know...was wondering if there was any way to find out what i need before i buy.. I honestly was thinking of just buying new rubber pivot bushings but cant seem to find any anywhere.. so was thinking a smaller bar with urethane bushings might fix the problem but again, kinda expensive if it doesnt fix the problem..
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post #6 of 24 Old 01-06-2011, 12:03 PM
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I used to run the stock V8 bar when I had 800-lb front springs. With the springs you have, I'd consider finding a 4-cylinder bar, they're cheap and not hard to change. See how it behaves, and you don't have much invested. I would NOT remove the rear bar, based on how the car felt when I did it for an autocross once, but I guess it wouldn't hurt to try.
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post #7 of 24 Old 01-06-2011, 12:38 PM
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Not sure I follow removing the rear bar on an understeering car...

I agree with trying a smaller front bar. Usually better to try to find more grip on the end that isn't working, before giving up grip on the end that is, imho. Also, are those SA Konis off the shelf? If so, that is a ton of spring to ask them to deal with...

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post #8 of 24 Old 01-06-2011, 01:11 PM Thread Starter
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Konis were brand new this summer, Koni yellow SA struts/shocks and red sport quads.. It was my understanding that the DECH cars came with this set up as a package, but Ive heard that the Koni's they used were specifically valved for their springs, but that was a long time ago..However, they feel fine on the street/track...mind you i aint no rocket out there either...
...I think the idea of removing the rear bar was to "...allow more body roll to plant the outside rear tire to help excelerate on exit"... or something, im paraphrasing, lol..its been awhile since i had talked with the guy..
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post #9 of 24 Old 01-06-2011, 01:31 PM
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How much camber are you running on track?
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post #10 of 24 Old 01-06-2011, 02:06 PM Thread Starter
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Quote:
Originally Posted by MFE View Post
How much camber are you running on track?
-2 camber, 0 toe in/out.. I had it set like this for street driving and cause thats what was suggested to me.. 3/4's of my driving is street driving so..

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post #11 of 24 Old 01-06-2011, 02:38 PM
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Understeering would require more rear stiffness. Bigger springs and/or bar. Or smaller front.

The anti-squat kit also has an effect. When a side goes down the arm pushes the tire backward, steering it.


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post #12 of 24 Old 01-06-2011, 02:56 PM
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Needs more camber. I assume you have adjustable plates, just measure where they are and put them back when you're done. Give it 3 degrees for the track.
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post #13 of 24 Old 01-06-2011, 07:05 PM
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Use a 1.125" or smaller front swaybar.

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post #14 of 24 Old 01-06-2011, 07:43 PM
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Quote:
Originally Posted by kreg90 View Post
Konis were brand new this summer, Koni yellow SA struts/shocks and red sport quads...
Why do you have quad shocks on it when you have a panhard bar? Why do you have FRPP rear UCAs when you have a panhard bar? Fix that uber-quadrabind (penta? due to PHB) first: remove the stiffer-bushinged UCAs and put 1 stock one back in (aka, PM3L). Get stiffer rear springs to match. Alternatively, get a torque arm (and stiffer springs). Ditch the anti-squat brackets once this is done.

What size wheels/tires are you running front and rear?

I agree re: picking up swaybars cheap from the parts yards. I now bring the tech:
http://www.miracerros.com/mustang/sway2.htm

I ran Koni yellow SAs with 1000#/in. springs for years with no problems, just fyi. Not saying they are faster than running a different shock/strut, just that they were able to work fine on my car.

And finally, a quote: "[Fox body] Mustangs are at their fastest when they are just barely understeering." John Ames, multi-time SCCA Solo 2 National Champion during a conversation I had with him in the mid-90s. Not sure that anyone was ever faster in a fox than he was. Of course he was referring to auto-x'ing and not road racing, but just something I remember to this day.
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post #15 of 24 Old 01-12-2011, 07:34 PM
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1000lb springs! are we talking coilovers or conventional springs

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post #16 of 24 Old 01-12-2011, 09:49 PM
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Conventional. Car rode terrible. It's WAY better with 425 coil overs in the front.
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post #17 of 24 Old 01-16-2011, 11:48 AM
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jesus christ!

im gonna try 400lb springs up front and 300lb in rear (both coilovers)

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post #18 of 24 Old 01-16-2011, 11:59 PM
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I'm using a 4cyl swaybar with 425# coil-overs up front. The car felt quite a bit more willing to turn in going from the stock V8 bar to the 4cyl bar (which I got off a junk car for free ).

'89 GT convertible, N/A 357W, MM front susp w/425# coil-overs and Koni D/As, MM TA/PB rear setup (Koni Yellows, 390-430# springs), Stoptech 332mm / 12" Baers, MM 6 point rollbar, Maier 1.5" flared fenders & quarters, 18x9.5" front/18x10.5" rear Enkei RPF-1s (street), 18x10" CCW C-10s (track), etc...
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post #19 of 24 Old 01-17-2011, 10:26 AM
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Quote:
Originally Posted by Patrick Olsen View Post
I'm using a 4cyl swaybar with 425# coil-overs up front. The car felt quite a bit more willing to turn in going from the stock V8 bar to the 4cyl bar (which I got off a junk car for free ).
I really need to try that. My car still pushes a bit.

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post #20 of 24 Old 02-01-2011, 05:28 PM
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Going to a larger sway bar is like adding stiffer springs to that end of the car. The stiffer the bar the more tendency for the tire to slide in a turn. Hence if you have a bit of understeer you can soften the front springs, smaller bar up front, or softer springs in the rear or smaller bar in the rear to balance out the front. Of course shock compression/rebound has an effect also. When you purchase new stuff try to make it adjustable so you can adjust settings for different tracks and conditions. You will learn a bunch in a short time when you do this. btw 1000 in/lbs in the front help a great deal with brake dive. I suspect you dont need much of a front sway bar with those springs.

The advise about fixing the rear suspension is the best thing you can do for a fox style rear. That is the limiting factor on these cars. GA

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post #21 of 24 Old 02-01-2011, 11:02 PM
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Quote:
Originally Posted by aurdraco View Post
John Ames, multi-time SCCA Solo 2 National Champion during a conversation I had with him in the mid-90s. Not sure that anyone was ever faster in a fox than he was.
Can't think of anyone. He did amazing things with that car, even after he converted it to ESP trim.

I remember talking to Mark Daddio (driving a F/S coupe) at a Tri-State event in the early 90's. It was in late Sept. and I believe John had a terrible showing in ESP that year. I asked him what happened to Ames. All he said was....

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post #22 of 24 Old 02-02-2011, 03:06 PM
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Quote:
Originally Posted by Garyalp View Post
Going to a larger sway bar is like adding stiffer springs to that end of the car. The stiffer the bar the more tendency for the tire to slide in a turn. Hence if you have a bit of understeer you can soften the front springs, smaller bar up front, or softer springs in the rear or smaller bar in the rear to balance out the front. Of course shock compression/rebound has an effect also. When you purchase new stuff try to make it adjustable so you can adjust settings for different tracks and conditions. You will learn a bunch in a short time when you do this. btw 1000 in/lbs in the front help a great deal with brake dive. I suspect you dont need much of a front sway bar with those springs.

The advise about fixing the rear suspension is the best thing you can do for a fox style rear. That is the limiting factor on these cars. GA
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post #23 of 24 Old 02-04-2011, 03:30 AM
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Garyalp's comments are correct.

Total lateral load transfer is a function of cg height, track width and cornering force. It has nothing to do with the suspension. Gokarts manage to achieve 100% lateral load transfer (both inside tires off of the ground) yet they have no suspension at all.

Lateral load transfer is directly proportional to roll stiffness. If the front of the car has 75% of the total roll stiffness, then 75% of the total lateral load transfer is reacted there. This means that 25% of the total lateral load transfer will happen at the rear of the car.

Since a given pair of tires can generate the maximum amount of cornering force when they equally share the load, any load transfer between them results in a total decrease in cornering grip. This is the nonlinear (digressive in this case) grip versus normal force behavior that tires have.

If your car has balanced handling and you increase the roll stiffness at the rear of the car with a larger swaybar, you increase the amount of load transfer at that end, which makes the rear tire normal loads more unequal, which reduces grip at that end of the car, which causes oversteer.

This entire relationship is the basis for all suspension tuning. Without understanding it, you will be hopelessly lost.

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post #24 of 24 Old 02-04-2011, 09:46 AM
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Yes, but one big caveat to the whole discussion, especially as it pertains to most mustangs, is assuming proper camber control in the first place. By the rule of thumb, adding more bar to the front of a mustang makes it understeer more, or oversteer less. But in reality, when the car exhibits crappy camber control and the outside tire is going positive in a hard corner, the loss of traction caused by increased stiffness is more than offset by the gain in traction from keeping the outside tire cambered better, for a net gain in traction.

Last edited by MFE; 02-04-2011 at 09:48 AM.
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