By: Ron Lee
Anyone who has driven a 5.0 Mustang knows that the car needs more traction, especially if the engine has been modified at all. There are several different ways to increase the available traction of your Mustang. The first step is to weld in a set of subframe connectors. These should be required before you do any other suspension modifications. They cost less than $100 to buy and then another $30 or so to have them welded in. Don't bother with a set of bolt in subframe connectors, they will elongate the bolt holes quickly and become worthless. Most subframe connectors come with a cross brace which provide more lateral support for the car; get them. Before the welder starts welding the subframes on the car, make sure the car is sitting level and the weight of the car is on the tires (or equivalent). You will notice a big difference in the way the car handles after having a set welded in and traction will be marginally improved, but everything will stay straighter when you're pressing the car to its limits which is very important.
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For a dedicated drag car, a roll cage, four link rear suspension with coil over springs, drag struts, special drag front springs, and slicks would be in order. Slicks will make a huge difference on any car but may only be used on the drag strip. Slicks will improve your quarter mile times by at least 0.5 second even in a stock Mustang. There are other types of tires available which may be run on the street but are much improved over normal street tires. They all have softer tread and softer side walls while still having at least some tread. Tread wear numbers are down around 060 or less versus roughly 200 for the typical Z rated tire. They won't make 10,000 miles versus 30,000 miles or more for normal street tires. Some of the tires won't make 1000 miles. Drag radials are the latest type of tires to come out which offer greatly increased traction over normal street tires at the cost of reduced handling and tread life. Do not expect to take a hard corner (or a medium hard corner) with drag radials on your car. Tires will make as much or more difference in traction than any other suspension modification you can make. However, these type of tires do it at the cost of reduced handling and tread life. There are ways to greatly increase traction and maintain your handling, however, for a true drag car, handling is sacrificed to achieve maximum traction.
Installing a torque arm rear suspension is probably the best way to increase both traction and handling. Torque arms are not meant for serious drag race cars, but rather for road racing cars. Repeated hard launches with slicks will break a torque arm in time. For a street car on street tires, a torque arm is a huge improvement in handling and traction, but ground clearance can be an issue. Installing a torque arm requires installing a panhard bar and removing your rear upper control arms. A torque arm acts somewhat like a single long ladder bar. The torque arm is bolted to the center of the rear axle housing and pivots on a bracket attached to the subframe connectors roughly in the middle (underneath) of the car. The rear upper control arms must be removed because otherwise the rear suspension will bind when you hit bumps that will end up in you being out of control and spinning off the road (very, very bad). The panhard bar must then be installed to control lateral movement of the rear axle that is part of what the rear upper control arms do. The panhard bar does a much better job of lateral movement control and you will think that your rear tires are now glued to the road in corners (caution, they are not). Buy a good, heavy duty panhard bar, particularly if you like to take hard corners. Some panhard bars are intended to be used with the control arms in place which does not load the panhard bar nearly as much. You should change to a boxed (or tubular) rear lower control arms at the same time with polyurethane bushings. Ideally you would also go to a stiffer rear spring rate (about 350 pounds/inch) at the same time. Traction will be more than doubled. Brake anti-dive (force against the tendency of the front end to dive when braking) will also be greatly increased. You will be surprised how the car reacts when you hit the brakes. The front end will barely dip at all and the rear will also basically not rise up. The car will be much more neutral in its handling at all extremes. Griggs Racing makes one of the better set ups around for a torque arm suspension, and I highly recommend them. The torque arm and panhard bar will cost you about $850 (without installation). Good rear lower control arms will set you back roughly another $200. Installation is not easy, but can be done in your driveway. Be careful working with the rear springs and ensure you have them unloaded before unbolting the lower control arms. A loaded spring is like a loaded gun, it can kill or maim. The panhard bar can be very time consuming to install correctly. Take your time and do it right. The bar should be parallel to the ground with the car at normal ride height. Weld the brackets to the frame, even if they do bolt to the frame. One final caution is that you will lose ground clearance, and things like speed bumps may become impassable to you.
If you're not going to do a torque arm suspension, the next best way to increase traction is to install a set of rear lower control arms which lower the pickup points. Some available brands include Megabite Jr, Megabite Sr, Texas Turbo, and South Side Machine Lift bars. Another choice, especially if you've already installed aftermarket rear lower control arms, is the TracKit from Kenny Brown ($65) which lowers the pickup points by 0.875 inch (not as much as the others, but more balanced for better handling). The TracKit will also lower your rear by about 0.75 inch which to me eliminates the need for lowering springs. These rear lower control arms will increase your traction from 50 percent to 135 percent, so they do make quite a difference. They will also improve your anti-dive percentages which will improve handling as well. Prices vary roughly from $175 to $300. Installation can be done in your driveway, but it is not easy. Drilling the holes through your rear axle brackets is a pain. Be very careful with the springs. They must be unloaded before you unbolt the control arms. See the warnings in the above paragraph. Welding of the brackets is preferred to bolting.
Also if you're not going to do a torque arm suspension, you should install a set of heavy duty rear upper control arms. These will improve traction and handling a great deal. To me, they are probably the number one suspension modification I would do. They make the rear suspension much more predictable and sure footed. Most of them come with polyurethane bushings in the rear and harder rubber bushings in the front. Some come with spherical rod ends which are far superior, but require more maintenance versus bushings. One more comment is that if you use ones with spherical bearings, you should completely weld the body seams for the bracket that the upper rear control arm bolts to. Otherwise they will eventually rip out of the car. Prices vary roughly from $100 to $200. You can install these in your driveway, and you do not have to touch the rear springs. Removing the old bushings in the rear can be a pain, but the results are worth it. I ended up drilling mine out.
Another option that is not as good as the torque arm suspension, but which improves traction over what you already have is the Trac-Link Kit available from Global West and Ford SVO (or whatever it is called these days). It is basically a short torque arm in that it bolts to the center of the rear axle and attaches to a bracket that bolts to the floor pan. It does not require the removal of the rear upper control arms and therefore does not require a panhard bar. Larger exhausts may not clear the bracket (I've read numerous complaints about this). The price is about $375. This kit can be pain to install but it will improve your traction when you get done and will work in conjunction with your other suspension modifications. It will also improve your anti-dive percentages which will improve handling. Make sure the car is sitting level and with the weight of the car on the tires before you install the bracket.
One final thing that can make a difference is to shift the center of gravity of the car, preferably higher (lower for handling) and rearward. The easiest way to make a significant change is to move the battery back to the trunk/hatch area. Another option is to move the engine back. That is not as bad as it sounds. Cars with 5 speeds can move the engine back up to an inch without huge problems while automatic cars are limited to about 0.5 inch. Either way will require shortening the exhaust by a like amount. The driveshaft probably should be shortened, and may have to be shortened. Be warned though that some things may rub, so this is not the best idea for an everyday street car.
Most of the other ways to increase traction are more applicable to the race track than to a street car. Several companies make drag springs for the front which basically are softer and taller to allow the front end to rise more. Your car's handling will suffer. Several companies also make drag struts which do the same thing, allow the front end to rise more. Drag struts are not meant for the street and if you hit a pothole with one, you will understand why (you may damage a wheel). Another popular thing is to install an air bag in the right rear spring to help equalize traction in the rear.
One more comment is that as you increase traction, you should install a driveshaft loop to ensure that you will not pole vault your car if the drive shaft breaks in the front. Some exhaust systems may prevent the driveshaft from hitting the ground, mine does. But if there is any doubt, install the driveshaft loop. They are cheap.
My last comment is that if you are running slicks you should have your torque box seams welded completely, or otherwise strengthened. Several companies make kits which reinforce the torque boxes. Over time the torque boxes will tear out and trying to put them back in correctly can be very difficult. Welding them up front will prevent this future problem.
©Copyright 1998 Ron Lee