996 C4S vibration under hard braking

[Roberty]

Any advice/suggestions greatly received. Have just this afternoon Arrived in Stuttgart after a 5.5 hour trek across from Paris and the car (996 C4S) seems to have developed a bad vibration during heavy braking from high speed 100kph+.

This wasn't noticed at all when driving from Calais to Paris on Sunday and the brakes appear to all be in great condition.

Admittedly you probably can't see, feel for warped discs but they look good and were all changed, discs and pads, front and back less than 8k miles ago.

Any ideas? And does anyone have any advice/experience on whether Porsche will be helpful/willing to look at the car (I don't have an appointment) tomorrow? Stopping by for the Museum and a pre booked factory tour.

Supposed to head straight onto Switzerland once done. Should I carry on or does this need sorting ASAP?

Edited by Roberty on Thursday 23 June 06:55

[Por911T]

Certainly sounds like warped discs. If the steering feels fine prior to braking - and the shudder only appears under braking id say its certainly discs. More so if you can feel it through the pedal . Given the distance your going to cover Id say a 2nd opinion wouldn't go amiss. Best pf luck & enjoy the trip.

[Magic919]

Probably pad transfer. I wouldn't worry too much. You won't do any harm leaving it until you return. Some people fit PF pads to sort it out.

[EGTE]

Could also be rust on the mounting bells that the disk mates up to; only needs to be a tiny amount to cause big problems.

[anonymous-user]

It is the discs, but why after long motorway drive is the question?

I had the exact same thing happen on our 997 after driving down to South of France. The discs were oldish anyway so I replaced them. Fine for 9 months, then another long drive to South of France and same issue.

Makes me wonder whether sticky caliper or something allows pads to leave deposits on discs - and only evident when lots of miles between braking (eg French autoroute).

[Roberty]

Thanks for all the responses. Dr Mark I think you are right, the car displayed similar issues not long after I got it 2.5 years ago which lead to me changing all the discs and pads, problem solved.

It has been fine ever since, no track days and circa 8k miles. Driving to Paris it was ok and the issue only showed itself on the longer stretch to Stuttgart. I think your right maybe a trailing brake has overheated a disc which has lead to warping.

The vibration is apparent but Not overly so through the steering so I think it's probably one of the rears.

Was at Porsche Stuttgart today so went in to the dealership first and asked to speak to a technician, was quickly told that they could schedule a short meeting with a technician in an hours time but that they could not do any work as they are booked up for 4 weeks! Gave up at that point and went and. Enjoyed the Museum, cafe. And factory tour instead. Now in Switzerland and I'm sure it is a warped disc but have decided it's safe enough to continue just bloody annoying!

Thanks all for your feedback, got all next week at family in France so may take some time to get the wheels off and investigate, Design911 will deliver to France right?

Cheers all, Roberty