Handling IssuesPosted on: 26, August, 2012
Porsche has always built cars with incredible performance, handling and braking. From the early days of the 356 to the modern Turbo S and everything in between, all provide balance and handling that makes every automobile manufacturer envious. Drive your Porsche into a corner fast and a completely different personality emerges – a magical personality that the engineers at Weissach make sure is within every Porsche, whether destined for your garage or a checkered flag at Le Mans. Of course, over time, and a lot of corners, suspension components wear and can even break. If you happen to notice an abrupt change in your Porsche’s handling characteristics, be sure to have the problem diagnosed immediately.
Whenever a handling issue is experienced, the first thing to check is the tire air pressures. If a tire is deflating, it can cause the car’s handling to become very unresponsive, unstable and potentially create a dangerous situation. A tire with very low air pressure driven at freeway speeds (or higher) can become very hot, potentially damaging its internal structure and sidewall. If this problem is not discovered in a timely manner, not only will the tire be ruined and require replacement, it could create a possible situation where the tire will blowout and even perhaps literally come apart. This is why it is very important to check the tire pressures on your car regularly — once a month if your car is not equipped with tire pressure monitoring. That said, a handling issue may not be related to a loss in tire pressure in any way.
Beginning in 2001, Porsche Stability Management (PSM) became available as an option on most models but was standard on the C4 and Turbo Models, with the exception of the GT2. PSM aids in correcting handling instability and loss of traction by obtaining data from multiple sensor systems to determine the car’s direction, speed, yaw and lateral acceleration. If PSM determines that a tire is losing traction, it can apply the brakes at individual or multiple wheels in an effort to assist in maintaining the directional control of the car. However, Porsche has some specific recommendations for tire wear to insure that PSM operates properly.
Porsche states that the tires tread depth must not differ by more than 30% for tires mounted on the same axle (front or rear) or any location on an all wheel drive model. Also, a newly replaced tire and the existing tires must match exactly in manufacturer, model and all ratings. If the tires do not match, there could be noticeable to serious differences in the handling characteristics between the tires, especially during high speed driving or abrupt maneuvers, like accident avoidance. If any of the tires have recently been replaced as a result of an accident or another issue, the tread wear differential between the existing worn and newly replacement tire(s) must be determined. If a 30% or greater difference in tread depth exists when compared to the new tire, the PSM system might conclude that a tire(s) is losing traction. This is because the smaller rolling circumference of the worn tire would be turning faster than the new tire(s) at any given vehicle speed. If you were to enter a turn fast with these conditions existing, PSM may take action and apply a single or multiple brake(s) that could really catch you off guard. The bottom line with PSM is that if you have mismatched tires or a 30% or greater tread depth differential as described, you will have to replace the older existing tires.
Porsches are intended to have a firm ride characteristic; there should be no excessive bounce in the suspension when encountering sudden dips or rises in the road surface. Additionally, you should not hear any noises from the suspension when it is working, such as a metal to metal clank or rattle. If you do, then something is worn, damaged or faulty. As the suspension components age, handling will of course degrade. Worn control arm bushings, leaking shocks or struts, broken sway bar brackets, etc., will take place over time. You and your Porsche technician should continually monitor the performance and wear of the suspension components, ensuring that as they age, repairs and replacements are performed so that the incredible Porsche handling will last indefinitely.
Tony Callas & Tom Prine