Adding bigger sway bars obviously reduces body roll but (and please correct me if I'm wrong), also reduces the grip on which ever end of the car that you're attaching them. Add a heavier rear bar and the tail will come around. Add a heavier front bar and it will plow like a wrong wheel drive Honda.
My guess is that there's a happy medium...enough to stabilize body movements which would allow more crisp transitions and improve driver confidence...but not so much as to restrict suspension articulation and reduce mechanical grip any more than necessary.
So assuming your car came with a sway bar (as many of them did), how critical is it to go bigger when upgrading the suspension? Wouldn't stiffer springs and firmer shocks also help control body movements?
Does anyone with performance handling in mind leave them off the list of upgrades all together? I recently swapped in Bilstein shocks, Eibach lowering springs into my 2011 Mustang GT and despite leaving the stock sway bar alone, body roll was subjectively reduced just from the shocks/springs.
I'm just trying to figure out where to prioritize this mod on the Mopar. Any thoughts are welcome!
You have to match your spring rates with the amount of traction you have. So, adding a sway bar should add cornering ability and help grip, not reduce it, if you've sized them correctly. And the right size depends on a lot of things, your tire compounds and the amount of traction you have, the weight of the car, the front/rear bias for your center of gravity, how stiff your springs are already. And as mopar92 pointed out, optimal rate even depends on weather conditions, because it all comes back to how much traction you have.
It's true, sway bars can effect your overall wheel rate even in a straight line. If one side hits a big old pothole and the other doesn't, the sway bar could definitely come into play. How much depends on the amount of suspension travel and how the sway bar is mounted and actuated. If you've got big soft end link bushings, the sway bar may not add resistance right away. If you have a relatively small amount of suspension travel, it can effect how much and when the sway bar comes in.
So, yes, if you run super stiff springs, you may not really need much in the way of sway bars. Body roll will be reduced, you have to compress the springs. But your ride quality will suffer
all the time. The idea is that by running sway bars you can have the wheel rate you need when cornering hard, yet still have a more tolerable rate when just driving around casually. Sure, sometimes the sway bars will come into play and add that wheel rate in, but not
always, like it would be if you just made the spring rate the same as the overall wheel rate you wanted. And it depends on your tires. If you have super soft tires designed for handling, you can load them a lot more in a corner than you can just driving around, so there could be a big gap between the wheel rate you want just cruising around and the wheel rate you need when you're pulling .9G on the skid pad.
As far as when to add them, you can wait, you don't have to install everything at once. In fact it's probably better to wait. Install the springs and shocks you want, then see how the car handles with that combination. If it's a soft, floppy, body rolling mess you'll want to add sway bars. If it's already loose, you may already have more wheel rate than traction to go with it. As for the front only bar, that had a lot to do with the factory spring rates. The front was super soft, very undersprung. But in the back, the leaf springs were much closer to the ideal wheel rate than the front was. So, adding just a front sway bar to a car with factory spring rates could balance the car better. Weight balance effects that too, these cars are nose heavy so you can run higher rates up front. The other thing is that with a RWD only car you can control rear traction with the throttle, so, it's better to be a little undersprung on the wheel rate in the back because you can throttle steer if you've got enough power, and making it too stiff in the back will make the thing tail happy with any throttle inputs.
When you set up a car's suspension, you really have to start with the tires. If you're going to run hockey puck hard all season radials, you don't need huge torsion bars and giant sway bars, you'll end up loose because you don't have the traction (although you can still run more than the factory rates because they were for even harder bias plys!). On the other hand, if you're going to run 200 treadwear, modern compound tires designed for handling you'll need those big torsion bars AND big sway bars. Depends on where your drive too, if its all street you'll want softer springs than something that's mostly for track use, not just for comfort but because you want your tires on the ground. If it's all track, you can go super stiff with the springs because tracks are super smooth. Well, at least compared to public roads anyway. Remember that what you really want isn't the stiffest springs you can find, it's actually the
softest springs you can get away with for a given amount of suspension travel and handling. The whole idea is to keep the wheels on the road, so the softest springs and the most suspension travel you can get while still handling well is what you're shooting for to keep the wheels in contact with the road all the time. Of course that's a balance too, with a given suspension design the travel is usually the limiting factor, so your minimum wheel rate is the one that keeps you off the bump stops most of the time, and the max is where the car goes loose from lack of traction on smooth road and ideal conditions. Where you end up between those two depends on application, road conditions, personal preferences and driving style. How far apart the minimum and maximum wheel rates are mostly depends on how much grip the tires have.
