Control arms.....can someone give me a quick run-down on the basics of
control arms? Advantages/disadvantages of replacing
LCA's as opposed to UCA's and vica-vera.
When it comes to construction, boxed mild steel, tubular mild steel, and billet aluminum are all stronger than the factory stamped steel arms. Tubular chrome-moly is the strongest of all. This is relevant because
control arms take a lot of abuse!
The factory bushings are soft rubber, but most aftermarket
control arms use polyurethane bushings which are stronger, more durable, and have less deflection than the soft rubber. This translates to less rear end sloppiness and more traction! (in corners and in a straight line) Some companies use delrin for the bushings and it's supposed to be better, but I've never noticed the difference between polyurethane & delrin from the seat of the pants feel.
Above 500hp or so, the service life of polyurethane and delrin bushings becomes limited. Basically, the harder the
suspension hits (like from mega power or even low power launching slicks) the bushings deflect too much and can become damaged. The recommendation above this power level is to go with spherical bearings (also called heim joints). The spherical bearings allow the
suspension to move very freely and they offer the best traction out of all of the options, but they're a less popular choice than the other bushings because they are solid metal. Solid metal bearings transmit all of the vibration from the road and the drivetrain into the body of the car. It doesn't bother me a bit, but some people really dislike the extra road feel coming through the car.
Sometimes in an attempt to create the best of both worlds, people will choose
control arms that have polyurethane bushings on one end and spherical bearings on the other end. It's a reasonable compromise, but I prefer going with sphericals all the way around. My '89 LX has spherical bearings (or heim joints) on the LCAs, UCAs, and even the front a-arms! In the interest of fairness, I should confess that I just picked up a set of
control arms for my 2006 daily driver that has polyurethane bushings all the way around... but that's another story.
(they're for a tech project... not all out racecar performance)
Some people will tell you to replace the lowers but not the uppers. That's crazy to me because the uppers cause plenty of sloppiness, and I don't buy into the whole
the uppers cause bind philosophy that some people profess. They say the uppers cause snap oversteer. In my experience, the snap oversteer is caused by bushing flex when the arms are side loaded by the weight of the car, and the best ways to eliminate snap oversteer are to run solid
control arms (spherical bearings) or run a
panhard bar.
I'm also a strong proponent of replacing the factory uppers & lowers to eliminate wheel hop, which then allows you to remove the factory quad shocks. (win-win scenario) However, this too has been heavily debated on all of the forums.
Another item to consider is the adjustability of all of the arms. Typically, adjustable lowers are only used to set the wheelbase of the car. The adjustable uppers are used (with or without adjustable lowers) to set pinion angle and pre load. Fine tuning your pinion angle can improve traction on the launch, but I don't think it's as monumental as some people make it out to be. -4° pinion angle for
control arms with polyurethane bushings or -2° for solid
control arms are good places to start with the adjustment.
Lastly, some people will recommend using a torque arm which allows the removal of the
upper control arms entirely. These torque arm setups have advantages and disadvantages. But I'd only use a torque arm if I was building the car for HPDEs. Don't get me wrong, torque arms are perfectly streetable... I just don't think their benefit is worth their added complexity on a street car.
With that statement, now is a good time for a disclaimer. Nothing I've said here is like universal law. These are merely my opinions based on 25 years of working on Mustangs and my ownership of literally dozens of different Mustangs with different
suspension setups.
One last comment, anyone with a 79-04 Mustang should consider torque box reinforcements, especially when upgrading the
control arms. The "torque boxes" are the control arm mounts on the body side (not axle side) of the car. From the factory, these mounts are tack welded sheetmetal... not very durable even with factory horsepower levels. When you start modding, they can literally tear apart!
The torque box reinforcements are just this metal plates that are bolted and/or welded in place to support the factory mounts.
Phew. That was a lot of typing. I hope this helps. Feel free to swing by the vendor's forum to see what the different site sponsors carry to improve the handling and durability of your Mustang.
