Replacing brake discs/pads
Discussion
I was at a track night last night at knockhill - fantastic night and was mixing it with a few race prepared ferarris, 996-gt3rs, 996-gt3, 996-turbo, 993s and many others. Possibly the best line-up of cars I've seen at a track day.
Anyway, the question - I seem to have warped front discs as I experience vibration under braking when the brakes are hot (not at all when cold, or in normal road use). Can I upgrade the front discs/pads and leave the stock brakes on the rear?
I was thinking of some pagid orange pads and zimmerman cross-drilled discs for the front...is this a bad idea if the matching equipment isn't on the rear?
Anyway, the question - I seem to have warped front discs as I experience vibration under braking when the brakes are hot (not at all when cold, or in normal road use). Can I upgrade the front discs/pads and leave the stock brakes on the rear?
I was thinking of some pagid orange pads and zimmerman cross-drilled discs for the front...is this a bad idea if the matching equipment isn't on the rear?
Greg, I used to own a Boxster S so I know what you mean about the brakes. I've never been impressed by Zimmerman discs. I bought some many years ago when I used to run a 968 Club Sport (and when I was register secretary in PCGB) and they were worse than the standard Porsche items - too soft and very prone to wear. I ended up comissioning a set of front 4-pot brakes from AP Racing using Performance Friction Carbon Metallic pads which were superb. I can highly recommend such a set up on your Boxster.
As for whether upgrading the Front is enough, I've usually done so and left the rear set-up intact because most of the additional braking performance is needed at the front. Depending on the brake bias system on the car, and most modern cars are pretty sophisticated I don't usually find it a problem. Worst case if you need to restore some braking to the rear, you can fit a pad with a higher friction level although this might adversely affect the performance of your handbrake when stationary (which works on the rear brake).
As for whether upgrading the Front is enough, I've usually done so and left the rear set-up intact because most of the additional braking performance is needed at the front. Depending on the brake bias system on the car, and most modern cars are pretty sophisticated I don't usually find it a problem. Worst case if you need to restore some braking to the rear, you can fit a pad with a higher friction level although this might adversely affect the performance of your handbrake when stationary (which works on the rear brake).
Thanks DoctorD - this is exactly what I was hoping for, and I can always upgrade the rear brakes at a later date. I'm going to start by changing the front pads to a set of Pagid Orange, and see if this cures the problem - as I have had it suggested that the extreme heat in the pads may be causing the pad to lift from the disc under heavy braking, therefore giving the vibration when hot - and noticeably no vibration when cold, which doesn't make sense if the disc is warped!?
Greg, it's not pad lift. What happens with virtually all pads is that when hot they deposit their material on the disc face, some more than others. Depending on the type of pad material and disc surface most road pads when they overheat will leave material (only several microns thick) and when your pads make contact with the disc they vibrate because they are not in complete contact with the disc. This makes it 'feel' like your disc is warped, but rarely is that the case. What you need is first of all a pad with a higher operating temperature than standard, then enquire as to the behaviour of the pad when it overheats.
There are many different parameters to sucessful pad performance. Most of us just tend to think of friction/retardation but there is the effective temperature, the bite, fade, pad wear, plot shape, comfort and noise, disc life and other things that most of us wouldn't wish to know about. And all of these are influenced by the disc material, cooling, type of brake fluid etc.
I'm rambling on, but I don't know how Pagid Orange work in the Boxster's system. Many people I know prefer the Pagid Yellow (RS19) which are just as stable, but operate over a slightly higher temperature range with greater friction levels. The RS4-4 Pagid Orange is more likely to fade and the wear level is quite poor also. Either should be better than the standard Porsche item.
>> Edited by DoctorD on Thursday 15th April 15:13
There are many different parameters to sucessful pad performance. Most of us just tend to think of friction/retardation but there is the effective temperature, the bite, fade, pad wear, plot shape, comfort and noise, disc life and other things that most of us wouldn't wish to know about. And all of these are influenced by the disc material, cooling, type of brake fluid etc.
I'm rambling on, but I don't know how Pagid Orange work in the Boxster's system. Many people I know prefer the Pagid Yellow (RS19) which are just as stable, but operate over a slightly higher temperature range with greater friction levels. The RS4-4 Pagid Orange is more likely to fade and the wear level is quite poor also. Either should be better than the standard Porsche item.
>> Edited by DoctorD on Thursday 15th April 15:13
Greg, the discs will usually recover depending on how badly built up the deposits are. Fitting a more abrasive pad will help, but worst case you could have your discs removed and sent to a local machine shop for re-finishing. Should be OK though with just a fresh set of abrasive pads.
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