Following the 356 series, Porsche took a quantum leap forward in the design of their next rear engine sports car designated the 901. Peugeot objected to this branding on grounds of having rights in France to model names with three numbers with a zero in the middle. Rather than sell the new model with a different name in France, Porsche changed the zero to a one, and so the birth of the 911.
Porsche Brakes & Suspension / Handling
Sports car owners are typically obsessed with what? HP, acceleration, top speed. What about the BIG ONE---bringing it all to a successful stop! For anyone balanced in their driven-thought, stopping---braking performance---is an equal counterpart to top speed etc. That said, braking power is but one component within a Porsche's handling profile that can be controlled / adjusted / refined to suit your driving style. Suspension (encompassing shocks, struts, springs, torsion bars), stance (ride height & rake), corner balance, tire type, chassis rigidity, alignment, aerodynamics where high speed driving is concerned... all these areas play into how your Porsche handles... how it feels. Balancing each area to compliment the others is the science & art of handling refinement... also called ride tuning.
Pads & rotors wear the most. Grommets---that protect pistons from dust and moisture---wear from heat and age. A worn grommet exposes the brake caliper's piston allowing it to rust. A rusted piston's performance degrades over time with the end result in the worst case being the piston seizing to the caliper---a potentially desperate condition for any sports car that's driven aggressively. This begs a recommendation: when assuming driver authority for a Porsche you're unfamiliar with, assuming the brakes are in proper working form is ill advised. Best to always confirm for yourself that stopping power exists. This should be done with increasing levels of speed and braking loads applied for each tested level. You can never go wrong checking unfamiliar brakes before driving.
Will old brake fluid serve to stop your Porsche? It will. It's possible to go for years without replacing brake fluid---but that's not advised for anyone that cares about maintaining their car's optimal braking capacity. In a nutshell, brake fluid degrades from heat, age, and moisture-gain. In turn, this degrades the "stiffness" brake fluid has. And it's this stiffness that translates into braking clarity a driver feels when brakes are applied. In contrast, old brake fluid lacks braking clarity. Because braking clarity degrades slowly over time, this condition generally goes un-noticed by the same driver of the same car.
Best-practice? Flushing a brake system and replacing old hydraulic fluid with new should be accomplished every 15,000 - 25,000 miles as a best-practice procedure. The earlier target being for Porsches driven under high performance braking loads. The latter for casual performance braking loads. This servicing of your Porsche will maintain a clean brake system, optimal braking clarity, and prevent internal corrosion of the brake system as a whole. Let's face it, slowing down or stopping is more important to your health than how fast you can go. Among other things, I'm here to serve your good health.
The tighter your suspension is set up the less your Porsche's chassis rotates on it's axis---the less it has to lean into corners and then has to recover. By minimizing lean, the less mass there is moving about. This reduction of mass in motion translates into a Porsche handling with greater clarity and precision.
Newer cars have suspension systems that can be adjusted on the fly. This provides a refined ride under changing conditions as a Porsche's on board computer is capable of making automatic ride adjustments. Some degree of suspension adjustment is also available through a car's driver preference settings. Classic cars are locked into suspension settings given existing torsion and sway bar types, shock type & configuration, ride height, rake and corner balancing. All these aspects affect how your Porsche handles.
Above: Example of Porsche brakes that suffered from a combination of service-repair neglect and not being driven much. Performance of front right caliper (above) borders none existent due to frozen piston. Car pulls noticeably to left under braking---reason this owner's now attending brakes. Piston's grommet... disintegrating from age. Piston... rusting and seized to caliper. Pads removed from this brake assembly are at right above. Pad material is crumbling... one pad fell apart as you see it and did so without instigation. These are low quality / economy brake pads from Mintex. Not recommended.
Below: Replacement parts for brake system above. OEM calipers, vented/drilled rotors (upgrade), and low-dust brakes pads from EBC. While vented rotors were not absolutely necessary for this casually driven Porsche, the added cost is negligible compared to the improved braking power acquired. Customer was given non-vented rotor option and chose these. EBC Red Stuff were installed on basis of their low-dust performance and this car being a street driven Porsche. Is important for brake pads to be bedded properly when installed as I always do.
Vented / drilled Porsche brake rotors prevent hot gasses from building up between brake pad and rotor surfaces thus allowing improved contact between these surfaces. Holes also significantly increase rotor surface area resulting in improved rotor heat shedding. Both these factors translate into a vented / drilled brake rotor's ability to perform under much higher braking demands compared to a conventional, non-drilled rotor.
The most common of all handling related adjustments in any car is wheel alignment---the pointing of tires relative to each other and the center line of the car. There are three control aspects to alignment. Toe, camber and caster.
Toe front and rear is typically set slightly inwards meaning your tires do not run parrallel to the center line of your car---the front of the tire is closer to the center line of the car than is the rear of the same tire. This is a "toe in" setting. The reason for this setting is to compensate for the natural tendency tires have to turn outward when being driven.
Camber is the angle of the tire relative to a perpendicular line of your Porsche's chassis.
Caster is the angle between the vertical steering line and the center point of a tire's ground contact. Caster is typically set positive. This helps a car self-steer based on the front tires ground contact being behind the steering axis.
Stock ride height and rake compared to the same car lowered and raked 2 degrees. All else being equal, the lowered & raked version of this 930 will handle noticeably better than its stock iteration due to a lower center of gravity, tighter suspension, improved aerodynamic ground effects, and 2 degree rake for braking.
Front wheel camber for racing is often seen clearly negative. This benefits corner handling as the outside tire---during a turn---goes perpendicular thereby providing maximum contact with the pavement (when it's needed most.)
Stance encompasses ride height, rake, and wheel spread.
Regarding ride height, the lower the center of gravity, the better a Porsche handles. In simple physics: lower means there's less vertical mass/weight above a car's bottom plane for inertia to grab when that car turns. The lower a Porsche is set, the tighter that car's suspension will be. This is because travel distance must been taken out from a suspension's travel allowance when a car is lowered. The result of lowering is therefore a harder/stiffer ride. This is optimal for competitive / high performance driving. For the street, it's a matter of preference. Some like a tight ride while others don't. Driving performance aside, the lower a Porsche is, the more aggressive the car's "look" is. Aesthetically this can be very appealing. And apart from a tighter ride, less below-car clearance translates into the need for driving with increased road surface awareness for the pavement ahead. This is a constant focus when driving unfamiliar roads.
Rake refers to the pitch of your Porsche front-to-back. Ideally, the setting is a 2 degree nose-down incline. The purpose in this setting is to improve front wheel breaking. Given a Porsche's heavy weighting on the rear wheels, the front wheels are at an immediate disadvantage in terms of frictional contact force against the pavement when brakes are applied. Rake improves frictional contact of the front tires through the pre-angulation of the chassis. In simple terms, rake partially eliminates the nose down travel the chassis of a car goes through when braking. While this is not a tremendous stopping advancement, any performance gain when braking should be considered beneficial.
If you have a professional 4-wheel alignment with proper air pressure in all 4 tires and your car pulls to one side, there's a very high probability your Porsche's not properly corner balanced. Not only does this condition adversely effect steering in a straight line but also when cornering and braking. In a nutshell, the more unbalanced a Porsche's corner weighting is, the more poorly that car will handle.
What is corner balance? It is the weight of a car as distributed to the pavement through each tire. In a perfect world, (with scales under each tire,) the front left & right side weight of your car would be equal with your weight in the driver's seat. Left & right rear weights would be equal too. Deviations from the perfect world are acceptable to a certain degree. The less deviation the better. Speak with any number of professionals concerning corner balancing tolerances and you'll get different deviation tolerance opinions. My preference for street driven Porsches is for a side-to-side difference of 15 lbs (or less) in the front and 25 lbs (or less) in the rear. For racing, I like 10 lbs (or less) front as well as rear for medium competition. Equal side-to-side for serious competition.
The weight of each corner is controlled by adjusting ride height at each corner. This might seem a simple matter but as one corner's weight is adjusted, the other corner's weights change. (The higher the chassis' corner is, the greater the weight being placed on that particular corner. Inversely, the lower the chassis' corner is, the less weight there is on that corner.)
Regardless of all other handling considerations, to truly handle as a Porsche is designed to, corner balancing is a must-have.
Driving style has a great deal to do with what type of tires are most appropriate for a car. Hard compound tires are for casual drivers. Soft compound are for the more aggressive.
Tire profile also affects handling. Generally speaking, the lower a tire's profile, the higher the performance. Small profile changes do not require wheel changes. Beyond a certain point, a higher or lower profile will not fit existing wheels correctly. Nor will extremes fit in the space a Porsche's wheel wells offer. Modifications to accommodate tire size preferences can be made to some degree. Flaring the wheel wells for instance.
Tire width contributes significantly to handling because more width means more contact with the pavement. Wheels, spacers, and fender flaring can come into play when modifying tire widths.
Racing is another dimension entirely. Tire selection can and is elevated to a science. Pavement type, weather including ambient temperature, altitude, a track composition including number and profile of corners, and driver preferences are all considerations. The goal being to out think your competition where your car's contact to the track is concerned---adding one more advantage to your racing edge.
The stiffer a chassis is the less twist there is in when cornering. Chassis twist makes a car feel rubbery in corners---unwanted. Among Porsches, coupes are more rigid than Targas and convertibles given the coupes roof structure.
To tighten a Porsche's chassis' rigidity, cross bars can be fitted to the cabin's interior behind the seats as well as in the frunk. Rigidity for racing purposes is accomplished with roll cages and more aggressive cross-bracing front and rear.
The difference between a braced 911 and non braced is immediately apparent when driving a braced Porsche.
Differences in car form can aide or hinder a desired aerodynamic effect. And quite often one effect comes with sacrificing another. The chart (at left on desktop website only) shows aerodynamic effects for various Porsche car configurations. Click chart to enlarge it.
With my experience in GT and GTP class racing, I'm very familiar with making Porsche handling refinements---great and small---to meet the desires of individual driving styles and preferences.
Porsche aerodynamic data. Speed is displayed in 7th column in kilometers per hour (V KPH.)
Click chart to enlarge.
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Happy Porsche driving! And remember to please buckle up because being glad you did is a wonderful thing ~~~
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