On the chopping block and into the weeds
Jul 14 '00
If you want to go fast on the track or autocross, here are a few steps you might find useful. Depending on the type of car you have (front wheel drive, rear wheel drive, all wheel drive) there are many things you can do to breathe new life into an aging suspension and make it feel like new again, and in some cases - even better than new.
Step 1: Stiffen the chassis
Chances are, you've never replaced the bushings on your car. If your car is a few years old and you're noticing more squeaks and rattles as time marches on, it could be that your suspension bushings have lost their elasticity. You can fix that with a new set of polyurethane bushings for the front and rear suspensions (including sway bar mounts), a set of motor mounts, and transmission mounts. For more aggressive stiffening try a strut tower brace (front, rear, or both), lower chassis brace (g-load or K-member brace), and a rollbar if you have a convertible or are considering some on-track drivers education schools.
If you have a Mustang, the single most important suspension upgrade would be to weld-on a set of subframe connectors with crossbraces. The difference in handling is simply astonishing. Check out http://www.bcmustang.com for more information about Mustang suspensions.
Step 2: Shocks and Springs
There's a lot of murky territory here with the advent of the import drag racing influence who would probably tell you to chop it as low as it goes and bounce it on down the road. I find that most of the people who do this to their cars have a terribly difficult time actually driving them. You can find them going so slow over speed bumps, even taking them sideways, that they're disrupting the flow of traffic. Then there's the complete destruction of the car's suspension geometry resulting from chopping the factory springs or getting a set of springs that are far too stiff for street driving. Anyway...
Go with a reliable, well known brand like Tokico or Eibach, both of whom have excellent customer service, great warranties, not to mention superior products. This is key - Get a KIT! Get a system of shocks and springs that work well together and that have been tested on your car. Trust me - don't go generic on shocks and springs, and don't mix and match - you'll regret it.
You'll need to decide if you want to get linear or progressive springs. What's that? Linear, or specific rate springs are designed to respond with a specific rebound rate whether you run over a pebble in the road, or if you happen to jump across a canyon. Linear springs are probably best for road racing, autocrossing, and some drag racing applications.
Progressive rate springs which are better for the daily driver as well as spirited street driving have a measured response when encountering road hazards. These offer generally a more satisfying ride overall, yet respond suprising well when thrown into a hard corner.
Step 3: Advanced Front Suspension
Another popular, yet often misused and abused suspension upgrade component are caster and camber plates. These attach at the top of the shock towers and offer the capability of drastically adding to the vehicle's positive caster (front wheels forward) and negative camber (tilting the wheels inward toward the vehicle's centerline). Both of these are highly desirable in the world of autocrossing and road racing, but can lead to some big problems if not properly used on the street. When specifying your settings, monitor the car for excessive and abnormal tire wear and "nervousness" or "twitchiness" which results from lots of negative camber. You can wear a set of tires out in a hurry this way!
Another thing that's very important to account for when lowering a car and using caster and camber plates is that you may increase the likelihood of adding too much bump steer - that is, the suspension is altered such that the angle of the steering rack contributes to a bumping sensation when maintaining a constant steering angle around a very sharp corner. One thing you can do to mitigate this problem is to install offset rack bushings which attempt to restore the proper angle of the rack (only applicable to some cars).
Step 4: Advanced Rear Suspension
Well, I can tell you from personal experience that replacing the rear control arms on a Mustang can leave you grinning all the way to the paddock. I also recommend installing a set of upper and lower control arms of the same brand - get a kit that works together. There's another component which I don't have any personal experience with called a Panhard Rod which can be installed on the rear of some Mustangs and F-body cars (Camaros and Firebirds) which also serves to "hook up" the rear end, i.e., makes for nice burn-outs at the drag strip and awesome grip coming out of corners at the track.
So, there you have it - a prescription for ultimate handling. Again, some of these upgrades won't be appropriate for all vehicles, but attend a local club racing event and start talking to people that drive the same car you do. They would be glad to show off what they've done to the car, and more importantly, tell you what worked and what didn't. That's the surest way there is to avoid the headaches associated with suspension tuning - find a local expert!
Happy Motoring...
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