I know this is a bit older but there is lack of information on what these sway bar kits do for our cars the 79-04 Mustang. First off the rear bar is probably not worth upgrading alone for most people on these cars. I am sure there are cars and situations where this might be a good move, yet on a 79-04 Mustang, it's generally not something you would do. In fact, the aftermarket kits all come with rear bars the same size or only slightly larger than the stock ones on is on 99-04 GT. The front bar is the one that will make the real difference for most people on our cars as it reduces body roll and helps get rid of understeer. It just seems to make sense that you buy both in a kit that was designed to work together. You would only mess around with one or the other like that if you knew what you were doing and were trying to get the car to behave a certain way for a certain type of racing situation.
To anyone pondering buying them I suggest a kit and I highly recommend them, I promise you will never regret it, the difference is that big. Keep in mind the results will vary slightly between a Fox, SN95 and New Edge as there are differences in chassis stiffness, weight and the original bar size/stiffness. With that said the Eibach aftermarket sway bars on my friends 02 GT and the SR performance on my 1999 GT were well worth the 280-350 bucks. They were the single most transformative change I have ever made. Keep in mind I have SLP long tube headers, so yes, I have many mods. The difference is apparent from the first time you pull out the driveway or off the lot at the shop. The car is stiffer and it tightens up the ride a bit, even turning in a parking lot it just feels tight and it’s nimbler. As you get it out on the road you will notice how you can cut turns extremely sharp, it just feels amazing and will make anyone who has never had a serious sports car feel like a kid in a go-kart. Things like quick lane changing at speed, or a bob and weave in traffic will demonstrate what they mean when they say it reduces body roll. You will notice that it just feels amazing, it stays flat and it’s as if you no longer have a big boat on the road. It literally feels like a new car and I have owned my car since new in 1999 so I know how it “feels” to drive. As you take some hard turn particularly on/off ramps you will find it carries speed so well and you now feel more confident taking turns at higher rates of speed. You will come to understand what all the people who road race, are talking about with understeer vs oversteer. Take your time and build your experience, your Mustang is now closer to a sport car and behaves like it. So, don’t just jump into turns at extreme speed, you may get into trouble because the rear end will now come around somewhat (oversteer). Work your way into it and gain some experience before you push it. As I said before even if you are not interested in road racing or pushing the limits the benefits in daily driving make it well worth it to buy one of these sway bar kits. After all handling is more about how the car feels in your hands and this applies at all speeds and not so much about ultimate grip. I can’t say enough about them and I recommend them to anyone but a hard core drag racer, of course you can always loosen the end links on drag day. Anyone who has never had them on their car and is downplaying them or considering them a second-rate mod is kidding themselves PERIOD…… The bottom line is that sway bars are used to reduce roll, but more importantly to tune the way cars handle and are used to adjust it so that it will oversteer, understeer, or be neutral.
People have talked about a PHB so I want to address that. A PHB does not serve the same purpose as a sway/anti-roll bar. Like sway bars a PHB is a major improvement for any 79-04 Mustang. Yet the sole purpose of the PHB is to locate the rear axle and keep it from moving radically side to side, which anyone who has owned a 79-04 Mustang knows is a huge problem with our cars. As I have come to understand it the benefits of PHB are things like reduced bushing deflection and keeping the car at the proper angle with the road which will maximize the tire contact patch and so on. This is a huge benefit to both road and drag racers, as well as the casual driver. Why would the average Mustang owner want one? Well for less than 400 bucks plus install it makes our solid rear axle cars ride nearly as nice as the independent rear axle Cobra cars do, while keeping the cost and strength benefits of a solid rear axle. Many including myself see it as the best of both worlds. When you add a torque arm which is used to set pinion angle and found on the full Maximum Motorsports setup you can remove your upper control arms and quad shocks. This setup literally makes a Fox Body, SN95, or New Edge handle better most Ferrari’s or Porsches. A Watt's link also provides the same function as the PHB and can be used in its place. In fact, with the Maximum Motorsports full setup, a PHB and Torque arm along with all the other goodies on a 1990 LX 5.0, Motor Trend tested this setup in 1998 and was able to attain the third fastest 600ft slalom times of any car they have ever tested this included some pretty exotic automobiles. Maximum Motorsports Suspension Kit - 5.0 Mustang & Super Fords Magazine