Re: question about brakes
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Thursday 6th May 2004
Porsche Brake Problems
orsche enthusiasts are embroiled in a building row over the longevity of the company's hi-tech and extremely costly Ceramic Composite Brake (PCCB) technology. The ceramic discs were claimed in Porsche's original literature to be 'the most effective braking system ever featured on a production Porsche'.
Launched on the 911 GT2, the company said the cross-drilled and ventilated discs were '50 per cent lighter than conventional alternatives' and combined with 'an innovative new composite brake pad... temperature is no longer a factor in brake performance'. Most amazingly, Porsche's own literature claimed that each disc would offer 'a service life of approximately 300,000km (186,000 miles)'.
However, many Porsche owners - who either bought GT2s or paid the Pounds6000 option price to have the PCCB system fitted to a GT3 - are finding that the discs and pads don't last anything like as long. Trackday drivers are finding that hard use can lead to extensive cracking of the discs and the need for replacement. Replacing four PCCB discs and pads costs over Pounds27,000. A figure that has shocked owners who have been affected. GT3 owners at least have the option of swapping back to conventional steel discs.
Owners and Porsche specialists are trying to pin down the reason for the problem, and most agree that excessive heat is the main cause, although some are also blaming gravel damage from trackside excursions.
The general consensus of opinion is that the nose design of the 996-series 911 does not draw enough cooling air onto the front brake discs. Porsche specialists are devising fixes for the problem, including altering the angle of the nose-mounted radiators to allow more air into the wheel wells. Special ducting is also being designed by specialists to channel more air to the discs.
For its part, Porsche has now changed the wording of its literature, warning brake components must be checked and, if necessary, replaced after track driving. Some dealers have replaced discs under warranty, but others are now not changing cracked discs until the fissures are relatively extensive.
The same problems have already been encountered in the US, according to Steve Wiener, of Porsche specialist Rennsport Systems, with some PCCB discs cracking badly enough to physically fall apart. However, he told evo that failures are not consistent and much depends on the individual driver.
'The problems are caused by heat, but each driver is different and some are harder on the brakes than others. Professional drivers are unlikely to cause a temperature 'spike' when driving hard.' Wiener ruled out gravel-trap damage as US circuits generally don't use it. 'We are switching back to iron Brembo or Alcon discs and advising owners of PCCB-equipped cars to take the discs off and store them for when the car is eventually sold.'
A Porsche UK spokesman said that while there had been PCCB failures, these were all attributable to 'significant overheating' of the brakes. 'While the ceramic discs can take much higher temperatures than steel, they are not indestructible. We are also quite happy with the amount of brake cooling that the 996 provides for its front brakes.'
A number of 911 drivers have also told evo that they no longer place high value on the braking abilities of PCCB. The hot word is that PCCB are not felt to brake better than steel discs using Pagid yellow sport pads, which are Porsche's factory standard. Other owners are now saying that PCCB are actually less effective on the track than steel discs with Pagid orange pads (designed for 24-hour endurance racing).
The truth is, with the composite discs so phenomenally expensive, few enthusiast drivers can currently risk this hi-tech option.
Comments: 0 Article from: evo
