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Alkendesign’s Performance Glossary will be your source for a down-to-Earth explanation of the most popular modifications and products. Let us educate you before you make any purchases.

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Aftermarket: This term refers to parts and accessories that are not from your vehicle's manufacturer. Most upgrades and modifications are considered 'aftermarket' parts.

Autocross: A driving event where participants navigate a small race course temporarily setup in a large parking lot or paved area. The course is created with orange traffic cones and is designed to test both the skills of the driver and agility of the car. The event is run one car at a time, and is timed. Driver's are separated into classes based on the car they are driving. After every event, drivers are ranked by their fastest times in their respective classes. Autocrosses (often abbreviated as Autox) are typicall hosted by local car clubs such as regional chapters of the BMW Car Club of America and the Sports Car Club of America.

Big Brake Kit (BBK): Perhaps better called a 'Performance Brake Kit' or PBK, this collection of parts replaces your car's brake system at the wheels. Available in two or four wheel configurations, the kits main components are larger calipers and rotors, hence the nickname 'big brake kit'.

Consider this modification if:
1. You are using aftermarket wheels that are a larger diameter than the factory-installed wheels.
2. Your driving habits (performance driving/track/autocross) increase demand on your brakes.
3. You have modified your car for performance (speed).

Click here to learn more about brakes and brake upgrades.

Caliper: The component of brake system that applies force, squeezing the brake pads onto the rotor which slows the rotation of the wheels.

Cams: This part controls the opening and closing of the engine's valves. The valves allow air to enter and leave the combustion cylinder. As the cam is turned, its oblong-shaped sections move the rockers that push the valves open or closed. Aftermarket performance cams are designed to alter the duration valves are kept open and closed. This changes the air mixture in the combustion chamber, which in turn produces more power.

Camber Plates: These add-on components are installed as part of the front suspension and allow the angle of the assembly to be adjusted. The adjustment affects the lean of the front wheels – this is called ‘camber’. This can be beneficial for adjusting uneven camber, as well as fine-tuning camber to better suit performance driving.

Consider this modification if:
1. You are modifying your car for track or autocross use.
2. You would like to correct uneven camber.
3. You are upgrading your suspension and would like the ability to make adjustments in the future.

Chip: This term refers to a modification of a car's computer for purposes of improving performance. Modern cars use a computer to manage engine functions. Some cars' computers have a removable microchip that stores the basic programming commands. Aftermarket tuners sell replacement chips with altered commands that may improve engine performance. Other cars may require different means of programming the computer, as they do not have a removable chip. Though the term chip is generally accepted, though some simply call this type of upgrade 'software'.

Consider this modification if:
1. You would like to alter your car's engine management.
2. You have introduced other performance equipment that requires a change in engine operation to properly function.

Clutch: The component that transfers (or interrupts) power from the engine to the transmission. When a clutch is engaged, a disc is pressed against the flywheel that is being rotated by the engine. This then turns the input shaft of the transmission, allowing power to be sent to the wheels. When the clutch is disengaged, the disc is lifted from the flywheel, interrupting the rotation from reaching the transmission. Upgrading to a clutch that can withstand more force is a common modification.

Consider this modification if:
1. You have increased your engine’s power output (turbo/super charger, etc).
2. Your driving habits (track use, performance driving) put a greater demand on the drive train.
3. You are upgrading to a lightweight flywheel.

Clutch Delay Valve: This is a component installed by the factory in some models. It restricts the flow of hydraulic fluid that controls the clutch operation. The result is a slow, smooth engagement of the clutch. This is good for everyday driving, but bad for performance driving. Most experienced drivers will appreciate the improved feel if this valve is removed. This modification is simple and does not damage anything.

Clutch Line / Stainless Steel Clutch Line: The hose that delivers hydraulic fluid to the mechanism that engages and disengages the clutch. Typically, the factory-installed clutch line is rubber, which may stretch or degrade. Upgrading to a stainless steel clutch line is a common modification.

Consider this modification if:
1. You would like a more accurate feeling clutch operation.
2. You are changing your clutch components (best time to make this inexpensive upgrade).

Clutch Stop: This very simple and inexpensive part reduces the travel distance of the clutch pedal by acting as a bumper. It replaces the very small, factory-installed pad, which allows the clutch pedal to be pressed to the floor. The benefit of this reduced travel is a more accurate and faster shifting sequence.

Consider this modification if:
1. You drive a stick shift! Everyone can appreciate this quick upgrade.

Coilover Suspension: This suspension setup consists of a shock absorber with a coil spring encircling it. Typically, suspension referred to as coilover is adjustable for ride height and quality (harsh/stiff) by using a simple threaded spring perch which changes the position and compression of the spring.

Consider this modification if:
1. Your car is used for both track and street. 2. You intend to alter ride height everytime you change driving situations.

Cold Air Intake (CAI): This component replaces the stock air box – the factory installed intake and filter system – with a duct and filter that draws air from a location cooler than the engine bay, while allowing for a higher volume of air to be sucked into the combustion chambers of the engine. Cooler air is denser than hot air, and therefore contains more oxygen by volume. More oxygen = better combustion = better engine performance. CAIs come in many styles and configurations.

Consider this modification if:
1. You would like to increase your engine’s performance.
2. You are using your car for track or autocross where high engine bay temperatures can affect performance.

Direct-Fit: This term refers to components that are a direct replacement for factory parts. Though they may be an upgrade, they require no modifications to the systems they are installed into.

Driver's Education (DE): When discussed here, this term does not refer to the boring classes we attended before we all got learner's permits... Driver's Ed, or DE events are in fact driving 'schools' held at race tracks. These high-speed tracks are rented out by the organization hosting the event, and students pay to attend classroom sessions and on-track lessons driving their own cars. Every student is paired with an instructor who rides in the passenger seat and guides the driver as they negotiate the often intricate track. These events are also called High Performance Driving Events (HPDE). Car clubs typically host DEs at road tracks within a reasonable distance from their region.

Driver Input: This term refers to components the driver directly handles while controlling the car. These parts are used everyday, so upgrading or improving their performance yields very satisfying results that are appreciated anytime you drive.

Exhaust: The system that ducts air and gasses that are by-products of combustion from the engine to the back of the car. This vital assembly removes pollutants and muffles the loud noises produced by the combustion process. Most factory-installed exhaust systems are fairly restrictive by design. This allows for great reduction of noise, but may negatively affect performance. Upgrading to a less restrictive exhaust can improve performance by improving airflow through the engine. Beware – some aftermarket exhausts (mufflers and partial systems) only change the sound, but do not improve airflow. Understand what the exhaust you are shopping for has to offer.

Consider this modification if:
1. You would like to improve your car’s performance.
2. You enjoy the rumble of a deep exhaust tone.

Flywheel and Lightweight Flywheel: This component is connected directly to the output shaft of the engine. The engine turns the flywheel, which turns the clutch, which turns the input shaft of the transmission. Most factory-installed flywheels are heavy, requiring a lot of power to get them spinning. Upgrading to a lightweight flywheel reduces the rotational mass, requiring less power to reach desired speeds. This allows for quicker acceleration without increasing the power output of the engine. This is a fairly common upgrade, and often coincides with replacement/upgrading of the clutch.

Consider this modification if:
1. You are modifying your car for track or autocross use.
2. You would like to improve throttle response and acceleration.
3. You are replacing your clutch (flywheel is exposed and easily removed when this work is being done) and would like to improve performance.

Forced Induction: This term refers to the use of a turbo or super charger to 'force' larger volumes of air into an engine's combustion chambers. This creates more power by inducing more oxygen into the cylinder and therefore burning more fuel. Opposite of "Normal/Natural Aspiration." Handling: The term that refers to the ability of a car to turn at high speeds. Handling is a direct result of the type of suspension a car is equipped with.

Click here to learn more about handling and handling upgrades.

Harness: A system of straps/belts securely fastened to the frame of the car that is then 'worn' by the driver instead of a standard seat belt. Typically used in track cars and race cars, harnesses are secured to the car at either 4, 5, or 6 points. A harness that secures at 5 points is known as a 5-point harness. Harnesses can be tightened very securely around the driver's shoulders and hips, providing excellent stability when turning at high speeds. They also hold the driver securely in the seat in case of an impact.

Headers: This part replaces the stock exhaust manifold, which is generally a simple cast iron unit which collects engine exhaust and delivers it to the exhaust pipe. However, when greater performance is required, this restrictive tube is often replaced with individual headers which are tuned for low restriction and improved performance. There are two types of headers. Collector style headers use pipes that merge into a collector, and can be utilized with mufflers. Collector headers can be used for the street or for a race car. "Zoomie" headers have no collectors, and are used almost exclusively on race cars. Headers have been widely available from aftermarket sources for decades, and some manufacturers have begun using them as original equipment.

Magnuson-Moss Warranty Act: Legal precident staing that no aftermarket part or accessory that is properly installed on your vehicle will entirely void your original vehicle manufacturers warranty. According to the provisions in the Magnuson-Moss Warranty - Federal Trade Commission Improvement Act, It is the dealership's responsibility to prove that your modification directly caused or affected the failure you are trying to resolve.

O.E.M.: This acronym for Original Equipment Manufacturer refers to parts that were either on the car as a stock item, or replacement components sold by the car's maker.

Oversteer: This term refers to a car's tendency to loose traction at the rear wheels when turning. This results in the back of the car sliding sideways, commonly referred to as 'fishtailing'. The driver must react properly to oversteer to prevent a complete loss of control. Many performance drivers/autocrossers prefer a car that tends to oversteer. The ability to rotate a car slightly while turning can be very beneficial in competitive situations. It is possible to reduce oversteer with suspension and tire modifications. the opposite condition is known as Understeer.

Normal/Natural Aspiration: This term refers to cars that do not use forced induction (turbo/super chargers) to draw air into the engine's combustion chambers. Normally aspirated engines simply rely on the pumping action of the pistons to suck air in through the intake and air filter. Opposite of "Forced Induction."

Performance Driving: This term refers to driving which pushes a car as close as possible to the limit of its tires' traction when turning. Most often practiced on high speed tracks or autocross courses, performance driving is both demanding on the car and driver. A driver skilled in performance driving is able to reach the absolute maximum speeds possible in any turning situation without losing control. A properly equipped car will offer greater traction, and therefore higher speeds while turning. It is very dangerous to practice performance driving techniques on public roadways.

Race Car: A purpose-built vehicle designed and constructed solely for competitive use. Sometimes beginning as a street car, sometimes built from scratch, race cars have two true functions - to go fast and to protect the driver from high speed impacts and roll overs.

Rotor: Also referred to as the ‘disc’ (as in ‘disc brakes’), this component is squeezed by the brake pads while rotating, slowing and stopping the car. Rotors are considered wear-items, which require replacement at varying intervals. Replacement rotors are available in various styles, including slotted, drilled, and vented.

Selector Rod: This part connects the shifter (stick shift) to the transmission. While this component is typically not considered a wear-item, its connecting parts can deteriorate over time. Furthermore, in most BMWs (and other cars that use the same transmission), the selector rod is thin and its connections are generally loose fitting. This can result in excess ‘play’ or wiggle that can be felt in the shifter, even when in gear. Upgrading to a more substantial selector rod with better connections nearly eliminates the excess play. It is a common modification when upgrading to a short shifter.

Consider this modification if:
1. You want to eliminate play or wiggle in your car’s shifter and produce a more accurate feeling shift.
2. You are installing a short shifter (best time to do this installation).

Shock Absorber: Commonly called ‘shocks’, these parts do what they say; absorb shock from bumps and variations in the road. Their main benefit is providing a comfortable ride by damping bumps that would otherwise shake the car with jarring vibrations. There are many types of shocks available. The main variations involve how stiff or soft they are. The stiffer the shock, the harsher the ride – but the better the car will handle turns. Conversely, a soft shock will yield a more comfortable ride, but will decrease handling ability. It is common for performance drivers to upgrade to a stiffer shock, typically in combination with stiffer springs.

Short Shifter: Also known as a Short Shift Kit or SSK, this part alters the length of ‘throw’ or travel distance that a stick shift has. Most factory-installed shifters have a very long throw when shifting (i.e. first gear to second gear). A short shifter can significantly reduce this distance. The result is a quicker, more precise feeling shift that can be appreciated every time you drive. The only common side effect is that some people notice a slight increase in effort when the shifter is pushed into gear. This negligible effect is a direct result of the short shifter’s altered leverage. Aftermarket manufacturers like UUC Motorwerks have engineered balanced short shifters that yield the shortest throw with the lowest possible increase in effort.

Consider this modification if:
1. You drive a car with a manual transmission - this is something we can recommend for every type of driving.
2. You use your car for track or autocross - where any time spent shifting is time you are not accelerating.

Springs: These parts act in tandem with the shock absorbers to keep the car stable over bumps and through turns. Unlike shock absorbers, however, the springs actually support the weight of the car. A spring’s stiffness will affect how much a car will lean while turning. Furthermore, a spring’s height affects how far the bottom of the car is from the ground. Cars that are “lowered” use shorter springs to create that low ride height. Upgrading to stiffer and/or lower springs is a common modification for those looking to improve handling capabilities.

Stainless Steel Brake Lines: These pieces replace the factory-installed rubber hoses that carry brake fluid to the calipers. Because they cannot stretch or expand like a rubber hose might, slightly less pressure on the brake pedal will push the same volume of brake fluid to the caliper. This can result in a firmer, more accurate pedal feel. These lines are typically included in all Big Brake Kits.

Consider this modification if:
1. You would like to improve your braking input, feel, and accuracy.
2. You are modifying any major brake components (best time to change install).

Strut Bar/Strut Brace: This part creates a solid connection between the tops of the front shock ‘towers’. At the front of the car, there is – very basically speaking – a ‘U’ shaped frame. The engine sits within that ‘U’, and the shock towers are the sides of the ‘U’. By connecting the tops of those towers, the strut bar essentially changes the ‘U’ shape to a closed rectangle. This solid connection results in a reduction of body flex, which can improve a car’s handling.

Consider this modification if:
1. You want to reduce your car’s body flex and improve handling.
2. You use your car for track or autocross.

Supercharger/turbocharger: A supercharger (also known as a blower) is an air compressor used to force more air (and hence more oxygen) into the combustion chamber(s) of an internal combustion engine. This additional mass of oxygen that is forced into the engine improves on its volumetric efficiency which allows it to burn more fuel in a given cycle - which in turn makes it produce more power. A supercharger can be powered mechanically by belt, gear, or chain-drive from the engine's crankshaft. It can also be driven by a gas turbine powered by the exhaust gases from the engine. Turbine-driven superchargers are correctly referred to as turbo-superchargers - or more commonly as turbochargers.

Sway Bars: More accurately called ‘anti-sway bars’; these parts are solid or tubular bars that help to reduce the body roll – or ‘sway’ – of the car when turning. Connected to the underside of the car’s frame and to the bottoms of the front and rear suspension components, they are forced to twist as the car leans. The bars’ stiffness affects how much force is required to twist them, thereby affecting the car’s handling ability. Upgrading to stiffer sway bars will reduce body roll and improve handling.

Consider this modification is:
1. You want to improve your car’s handling and reduce body roll.
2. You use your car for track or autocross.

Track Car: A vehicle dedicated to use on high speed race tracks, typically for Driver's Ed events, solo time trials, or autocross. The track car may or may not be street legal, and is not necessarily considered a 'race car'. The general purpose for owning a track car is to avoid using a 'nicer', daily driven vehicle for competition or high speed events that are inherently risky.

Underdrive Pullies: These parts replace the belt pullies that drive the water and power steering pumps with larger diameter pullies. This reduces (slightly) the amount of power taken from the engine to drive these accessory pumps. This ‘underdrive’ essentially diverts some of power that is lost rotating these accessories and restores it to the drivetrain. While it doesn’t create a more powerful engine, it allows more of the existing power to reach the wheels. There is no negative effect on the accessories being underdriven. That said, there is often a minute difference that can be felt in the power steering – it can feel more precise and less ‘soft’. This can really be considered an additional benefit to the performance driver.

Consider this modification if:
1. You would like to take advantage of more of your car’s existing horsepower.
2. You would like to improve the feel of your power steering.

Understeer: This term refers to a car's tendency to plow or push when turning, instead of smoothly completing the maneuver. As the car is turned sharply at speed, the front wheels partially lose traction. While this prevents a proper turn, it also will generally prevent a loss of control in a panic situation. Due to this safety factor, many manufacturers build in a good deal of understeer into their cars. It is possible to reduce understeer with suspension and tire modifications. This, however, may also increase oversteer - the opposite condition.