By Roger Sitterly
This is the first of a couple of articles concerning how owners can improve the already excellent handling characteristics of their MINIs.
Caveat: I am not a suspension engineer, I am not a tire engineer, I am not an aeronautical engineer – in fact, I’m not an engineer of any kind whatsoever. I’m a self-taught automotive aficionado who has made an attempt to learn as much as possible about the inner workings and finer points of enjoying sports car ownership to the max. Therefore, if anyone finds errors of either fact or interpretation in what I write, I encourage them to explain their take on the situation and we’ll post it. I most assuredly do NOT have a monopoly on automotive truth.
As all owners know, the MINI has been very well designed, and provides exemplary road manners right out of the box. As a result, many owners (particularly those who have never before experienced the immense pleasure of driving a good-handling automobile) will be so smitten with the stock handling design and setup that they won’t feel the need to make any changes. For those people, I encourage you to continue reading because you may find a world you didn’t even suspect existed – and my goal is to make that world accessible enough for you that should you change your mind about upgrading your MINI’s handling you’ll know where to begin. For all others (who either have already made modifications or who intend to do so in the foreseeable future) my goal is to present information in an orderly manner so that you know where to start, how to define what you want to accomplish, and then how to go about accomplishing it.
Improving the way a car handles is a complex and often confusing thicket of thorns. Should you start with camber plates or a sway bar or new tires or urethane bushings or adjustable control arms or new strut inserts (shocks), or wheels or engine modifications or a limited-slip differential or an oil catch can or a short-shift kit or something else? And how do you select which of the many alternatives available from either MINI or aftermarket vendors will best accomplish what you desire?
Good handling is what makes driving fun; lousy handling makes driving a chore to be endured for the minimum amount of time it will take you to get from point A to point B. For as much enjoyment as a driver derives from a car with lousy handling, he/she might just as well be driving a kitchen appliance. We’re fortunate enough to own cars that are not cursed with “kitchen appliance” driving characteristics, but even so, there are ways to improve various aspects of a MINI’s driving characteristics to customize the car’s abilities to your driving preferences.
Handling involves every condition experienced while driving – acceleration, deceleration (reduced or no throttle – not with the brakes), straight-line stability, plus braking and cornering abilities on good and bad surfaces – and it means being able to deliver outstanding performance in those areas no matter what the weather conditions. A car that handles well will be controllable and predictable in all conditions and under all circumstances, and it will simultaneously provide at least a reasonable amount of riding comfort. The only excuse for having a car that handles incredibly well but beats your fillings loose and becomes a torture chamber after 300 miles is that you’ve got it set up so you can dominate the local weekly track scene and you value that more than having a basic level of comfort.
It is impossible to design one car that will provide ideal handling for every conceivable set of circumstances. Each and every car design is full of compromises in terms of its handling. My discussion in these articles will focus on how to improve the handling of a street car – I won’t be dealing with the preparation of an autocross specialty car, or a circle track car, or a race car that will be used on a road course, or a drag racer. MINIs can be and have been used for each of those types of racing, but the modifications made to a car for each of those events renders the cars essentially useless for normal street driving.
According to Fred Puhn, a successful race car designer, there are three stages to improving the way your MINI handles:
- Minor tinkering around the garage on weekends, costing minimal time and money;
- Suspension modifications (and I will include here engine and drivetrain modifications as well) which will have a moderate and possibly a significant effect on the health of your pocketbook; and,
- Designing your own car from the ground up.
Since we’re talking about MINIs that are already owned, option three will be disregarded. If you are capable of undertaking option three, you should be writing these articles, not me. Likewise, most of what I discuss won’t fall into the “minor tinkering” category unless you’re an exceptionally accomplished mechanic with a complete set of tools and a facility for using them.
MINIs, as well as every other car on the market today, are the result of an integrated engineering design that compromises some characteristics in order to emphasize others. For example, until fairly recently, virtually all domestic automobiles (GM, Ford, Chrysler) were designed to be very stable for driving on the Interstates and freeways in this country. As a result, they generally suffered from poor steering and suspension response. They felt kind of like riding down the road on a super-plush living room sofa. Taking a full-size American sedan around a cloverleaf exit ramp at more than 25 or 30 mph borders on the insane because the cars are simply not designed to perform at that level of handling response. Your MINI, on the other hand, is easily capable of taking that same ramp at 50 mph or more because it was designed that way.
As Puhn points out, very few production cars are an engineering design failure in the sense that they fail to do what the engineers and factory intended them to do (aesthetic failure is another story altogether – witness the Pontiac Aztek, which was lampooned by much of the automotive press as “creating a whole new level in ugly”). While an owner may be unhappy with the way his/her car handles, and may argue that it was poorly designed, in fact that’s not the case. Instead, the owner has expectations that simply are not met by the design of the vehicle he/she purchased.
If you have a car that does not handle the way you want or expect it to handle, you will have to change things about the car. When you change anything about the car (even something as apparently mundane as buying new tires when the old ones are worn nearly bald), you are changing the design of the car in some way. You are, in fact, imposing your design parameters on the vehicle in place of those of the engineering team and factory that developed and produced the car in the first place.
The change(s) you make may be so minimal as to be unnoticed, or can be severe enough that you find yourself doing a 180 the next time you briskly turn a corner. Changing one part of the overall design often has unexpected and unintended consequences if the process has not been thoroughly considered and the ramifications thoroughly explored. Before any modifications get made, the owner should answer to his/her satisfaction the following essential questions:
- What performance characteristics are you trying to enhance?
- Why do you want to improve those characteristics?
- What integrated set of modifications will enable you to achieve the desired result?
- Do you thoroughly understand the impact each possible modification will have on overall performance?
- For example, do you understand what happens when you stiffen or ease back on either a front or rear sway (or “anti-roll”) bar?
- What about the impact of changing strut inserts, or going further and installing coil-overs?
- What about tire design (diameter, tread width, weight, compound)?
- Will you be altering the car’s weight, center of gravity, polar moment of inertia, roll center, or roll couple?
- Will you be compromising safety with any of your modifications?
Well thought out and integrated design of planned modifications is essential to having a successful outcome. Every single modification that can be made to a car involves some kind of compromise – you give up some of driving characteristic “A” to get more of driving characteristic “B”. The articles to follow will explore the above issues and more.