This article was first published in 2003.
The five part series I recently put together on making a GC8 Subaru WRX handle has really highlighted the subtleties of chassis tuning. Wandering into a suspension shop and telling them something like, "I want you to fix my Goggomobile's understeer" is nowhere near specific enough to achieve a good result. What's more, judging from emails we've received and forum postings around the place, it seems a lot more people know to make a car hoot in a straight-line than 'round corners.
The key question is where to start if you want to improve your car's handling - irrespective of what type of vehicle it is.
The first step should be to get a proper grasp of the car's standard handling characteristics - and there's no better approach than to head onto the road with a pad'n'pencil. Take notes covering everything from straight-line stability, tram lining, ride quality and, of course, the behaviour of the car through a variety of corners. The more corners you assess - everything from tight roundabouts and hairpins to flat-out open corners with bumps - the better you'll be able to decide what changes to make. Make a half-day of it; take a lunch.
You should be able to describe the car's behaviour at a number of different sections through the corner - the primary sections are turn-in, mid-corner and exit. Note that you can also break each of these points into early and late stages - the more stages you can describe, the better. Next try taking some 'what if' notes as well; what happens if you suddenly haul on an armful of steering lock, what happens if you lift off the throttle mid corner and what happens if you get on the power too early? It's good to know how your car behaves outside of normal conditions.
Your handling description should include words such as oversteer, understeer, stability, instability, yaw, roll, dive, lift, balance, lateral and longitudinal grip, response and accuracy. If you dedicate half a day to exploring your car's handling, you'll be amazed how many notes you'll come back with - and these notes are extremely valuable. Lock them in a vault.
After you've returned from your handling test session have a close look at each individual tyre. Really get in there and check their wear patterns - if the tyres are wearing on either the outer or inner shoulder you can see where most of the cornering forces are being sent. This comes in handy for optimising tyre pressures and wheel alignment, and - further down the track - suspension hardware and settings.
Tyre pressures and a wheel alignment are a great way to start off your mods. Depending on the specific wear pattern on the tyres and the sort of driving you do, it is possible to both reduce tyre wear and improve handling.
When it comes to tyre pressures you generally want to pump 'em up fairly high (typically around 35 psi) - this reduces tyre distortion through corners, improving handling grip, accuracy and eases shoulder wear. Note that, in some situations, it may be of benefit to run disproportionate front-to-rear tyre pressures. The end of the vehicle with lower pressures will be slightly more unstable, which can be useful where you want to offset or balance a relative lack of grip inherent at the opposite end of the vehicle.
And wheel alignment? From a handling point of view, negative camber gives you more grip through corners, but - in everyday situations - wear will be focussed more on the tyre's inside shoulder. Straight-line stability may also be affected. Each wheel's toe angle can also be adjusted to give a specific handling characteristic. Toe-in is good for straight-line stability, but toe-out makes that particular end of the car more eager to change directions - rear toe-out is great for encouraging turn-in oversteer or, at least, offsetting inbuilt turn-in understeer.
With just tweaked tyre pressures and a tailored wheel alignment you can expect a considerable improvement - at virtually no cost.
From hereon you really need to sit down and work out where you want to go with the car and its handling. Aftermarket springs, dampers, swaybars, bushes, adjustable strut tops and more are all available but which to choose will depend largely on your ride, handling and tyre wear ideals. This is where expert guidance should really come into the picture for most of us. Make sure you give your trusted workshop those notes you took earlier and tell them where you're at after fiddling the tyre pressure and alignment - this info should be pinned up as a platform to select the most beneficial hardware given your budget. Go somewhere else if the workshop ignores the notes and comments you've presented.
Obviously, we can't suggest you should start with X swaybars or X springs because every car is different.
Oh, and one area where we've seen a lot of people get confused is distinguishing between grip and handling - particularly when a set of sticky tyres are involved.
All else being equal, changing to a set of four ultra sticky tyres does not change the overall balance of a car - only its grip levels are improved. This can be deceptive, because those existing handling characteristics are buried a little deeper and - without pushing harder to find them - you may think everything is fixed. Wrong.
Let's take a scenario we've heard many-a time. You've spent $1000-plus on a set of Yoko A032s road-legal slicks to replace your car's whailin' ol radials. You drive outa the tyre shop and corner after corner on the way home you can't believe how much better the car 'handles' - it doesn't move around at all
. You can now haul on the wheel and the front-end won't scrub wide and you can jump on the power early without having the rear-end oversteer wildly. You're a convert; who needs aftermarket suspension bits when all you need is claw-like tyres?
You'll soon discover, however, your newfound religious beliefs in semi-slick tyres are flawed when that supposedly 'fixed' handling problem reappears - this time at a much greater speed or when the road surface is slippery. That mid-corner understeer you had forgotten suddenly pops up through a corner - which you now take at an insane speed thanks to the 'security' of those sticky tyres - and the chance of having a major accident goes through the roof. Believe us when we tell this story - we've seen it happen!
Needless to say, burying an existing handling flaw so that it appears only at very high limits or in slippery conditions is not a very wise approach. First, you should balance the car's chassis so that it won't do anything untoward - only then is it safe, and wise, to raise the level of grip with some serious rubber.
That's how it should be done folks.