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MG MGA - Odd steering with swaybar

Hi, I'm wondering if anyone else has experienced this. A year ago, I installed a Moss front (anti)sway bar on my '57 1500. Easy installation, but since then the steering has this odd, unsettling characteristic: entering a curve at any speed over, say, 30 mph, the initial 1/8th turn or so of the wheel doesn't give any resistance and doesn't translate into any change of direction, like I've hit a patch of ice. After that, it "answers the helm" rather quickly. Kind of scary. At parking-lot speeds, it steers the same as always. Have I altered the steering geometry such that I need to change camber/caster or something? I'm pretty dumb when it comes to suspension dynamics.

(BTW, I'm a member, but my employer's firewall keeps me from getting to the login portal. Sheesh!)
Dan Bradley

Hi Dan, It sounds as if something on your steering or suspension is loose. I don't know exactly what you did in installing the sway bar so can't suggest what it might be but I would not drive the car till someone who does know what their looking at checks it out. John
J.H. Hall

Dan, check for binding in the front end. You may have parts that are rubbing only when you go fast enough to apply a lot of side load when turning.
John H

Front anti-sway bars reduce under steer, the tendency for a car to go straight ahead rather than change direction when the wheels are turned. Sounds like what you're feeling is the normal understeer until the body roll compresses the bushings in the mounts and end links enough for the bar to become effective, then its resistance is felt and the under steer is reduced allowing the front tires to grip better. Under steer is a designed in feature which for most drivers allows speed to be scrubbed off by the tires sliding if they enter a corner too quickly. Most racers use solid or urethane mounts and link bushings to reduce any delay in the anti-sway bars effect.
Bill Young

Thanks, guys. John, I'll have a look-see under there when I get home. Subsequent to doing this installation, I read somewhere (not the shop manual) about putting the bar on with the front suspension loaded. I did it with the car on jackstands, because I was constantly having to turn the wheels while swapping-in the replacement A-arms. Maybe that makes a difference, or maybe, as you say, Bill, I'm just experiencing what's to be expected.
Dan Bradley

You don't mention the diameter of the sway bar. I have read cautions about installing too large a diameter. The claim is that doing that may actually accentuate understeer.
Good luck,
GTF
G T Foster

Sway bar should improve steering response. It should only require a small tweek on the steering wheel redirect it at speed. Sluggish steering response may be due to misalignment. Toe out can make a car wander like a drunken pig with slow steering response. Too much toe in makes it twitchy, wanting to dart back and forth actoss the traffic lane. MGA works good for street use with zero toe, both wheels straight ahead when loaded. Otherwise anything loose or worn can give it a sloppy feel.
Barney Gaylord

I agree with Barney. After reading his site countless times (and after almost crashing my A) I went for the sway bay. Steering response improved greatly. I am tickled ash green with the performance and wonder how I went so long without it. Ditto for too much toe in. One false move and disaster. Don't think I ever drove a car with too much toe out, though.
Tom Baker

Unfortunately, I need to disagree that adding a front sway bar reduces understeer - it in fact increases understeer, a rear stab bar would reduce understeer. What a front bar will do is reduce steering response times - the time it takes for the vehicle to react to a given steering input. This is why the vehicle feels (is) more responsive. Another factor is the reduced lean, which always gives one the feeling of improved handling (this last comment is my opinion since I dislike vehicle roll while cornering). I do agree that loose or soft link bushings can give you the two stage steering feel that is being described, although I'm betting on this issue being the toe set is not correct.
Michael Moder

Check the bar to be sure its not bent. I had a problem with two bars I purchased from Moss. They were both bent. I finally installed the second unit, but had to shim one side to have it not preload. It was a strange feeling when turning left was difficult, but turning right took no steering effort at all!
Jeff Schlemmer

Is it possible the rack is missing a tooth; or has a damaged or badly worn tooth? Or anything else in the rack assembly?

Gord Clark
Rockburn, Qué.
Gordon A. Clark

Check the end links and make sure they aren't contacting the steering arms during suspension travel. I fitted a 7/8" bar and had a similar problem because the links were too long.
Kemper

Ah, this is jolly good fun when I get to play guru.

Michael M, -- You may be missing some of the "subtleties zbout MGA suspension. You are right,in general terms, that increasing rear stiffness will in theory reduce understeer, but that must assume that it was somewhere close to being balanced to begin with, which the stock MGA is not. With stock MGA suspension the rear springs are so stiff as to lift the inside rear tire completely off the ground in a fast turn. See here: http://www.mgaguru.com/tales/3w_autox.htm

When that happens the outside rear tire ends up carrying half the weight of the vehicle, is relatively overloaded, and looses grip efficiency. End result is a sudden transition from initial understeer to dramatic oversteer, in which case it takes a lot of finnesse to keep the car from going sideways. Adding a rear sway bar only serves to get the rear wheel off the ground sooner, and higher, and makes the transition into oversteer happen quicker. When the car is on three wheels with a rear tire off the pavement, a rear sway bar cannot do anything to reduce body roll or to adjust oversteer or understeer.

The relatively large amount of body roll with stock suspension makes the outside front wheel lean out in a fast turn. Short radius turns at low to moderate speed are also a problem for the stock suspension. Because of the inward inclination of the kingpin, when you do a sharp turn the outside front wheel tilts even more in the outward direction. Combine that with the tall profile original size tires and you find the tire rolling partially onto the sudewall and lifting part of the tread off the pavement (narrow wheels being a contributing factor). This makes the outside front tire also loses grip, resulting in "plowing" or nasty understeer, and this will happen before the rear tire lifts.

Reducing body roll is very benificial, even when you have to do it with a front sway bar. The addition of a front sway bar reduces body roll enough to help the outside front tire stand up straighter, which improves the grip considerably.

With large body roll to begin with, I would not recommend softening the rear springs to keep the rear tire down. The first order of business should be to stiffen the front to reduce body roll enough to keep that inside rear tire always in contact with the pavement. Then when you have all four tires on the ground you can think about what a rear sway bar might be able to do for handling adjustment. As the pictures show, the 3/4" front bar was not quite up to the task when running the sticky race tires, but it is just the berries for use with modern radial street tires.

When you can keep the inside rear tire in contact with the pavement you have a chance to tune it to carry about the same load as the inside front tire in a fast turn. This gets you very close to the holy grail of neutral steering for spirited driving.

So in a round about way, the addition of the front sway bar can reduce initial understeer on the MGA, even though it first seems to fly in the face of theory. This is because of a combinaton of stiff rear springs, large body roll, front wheel tilt, and rollover of the skinny standard size tires. But too much front sway bar makes the steering twitchy and goes back to plowing in tight turns, which is when a rear sway bar can reuuce understeer.
Barney Gaylord

Barney,
Thanks. I see what you're saying. I was relaying theory and experience with more "modern" vehicles. I don't presently have a front bar on my 62 MGA. Now I may just consider it, although I never drive where I'd lift a rear tire, but I'd like the reduced roll.
Michael Moder

Bump steer bushings - Did you by any chance also lower the car? If an A is loaded up on the bump steer bushings it will also case the car to push. It's a fairly eash process to shorten them or take them out all together.

skip

Barney,
Love the music, it's my vintage
maurie prior

This thread was discussed between 18/04/2006 and 25/04/2006

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