Brake Pad Build Up

[RichS1963]

For the second time whilst owning my 997.1 CS Tip I appear to have pad build up which shows it self by low speed pulsing when coming to a halt.

The first time it happened, I explored swapping the pads to an aggressive 'race' style pad for a short period to clean up the discs. However, the cost of doing this exceeded replacing the discs (Sebro) and standard (Textar) pads, so that's what I ended up doing.

Less than 2000 miles in, it's happened again. Whilst I recognise it might be because I'm not bedding them in properly, I'm after suggestions as to how to remove the build up.

So, first option - economically priced race pads. Any ideas?

Second option - get the discs skimmed. I've actually kept the previous set of discs which had less than 2000 miles of use. I could experiment with these. Anyone know who might do this in Kent?

I'm open to other suggestions...

[Porsche911R]

doing 5 x 100 mph stops might clear it, don't let ABS cut in while driving esp when doing the big speed bedding in stops.

[RichS1963]

I'll find a private road and see if it works...

[Orangecurry]

..reading between the lines, you've had two sets of replacement discs, and both have started to show vibration after n-miles, where n is a low number?

Classic reason for this is that the discs have not been fitted carefully - not seated exactly straight, due to careless installation, or dirt/contamination between hub and disc-mating surface.

This tiny 'wobble' in the disc will cause the pad-material build-up at the high points... and make them higher - and so on.

If someone else is doing the fitting, get someone who knows what they are doing to check for runout whilst the discs are on the car.

ps Sebro IME are excellent quality.

[AvonM]

I *believe* this can also be caused by pad material build-up from heavy braking and then leaving the pads hard against the discs (i.e. foot still on the pedal) when stopped - typically would be triggered by stopping at a set of traffic lights at the end of a motorway offramp. And then the situation tends to get worse as the built-up area on the disc tends to be where the brake pads 'catch' the disc on stopping.


I'm not a mechanic but it has happened to me on heavy vehicles (i.e. S-max) and that was the explanation I was given.

[RichS1963]

That's my opinion as the first 1500 miles or so were problem free.
It doesn't help being Tiptronic.
Want to try the aggressive pad option to clean them up but need suggestions.

[Orangecurry]

AvonM said:

I *believe* this can also be caused by pad material build-up from heavy braking and then leaving the pads hard against the discs (i.e. foot still on the pedal) when stopped - typically would be triggered by stopping at a set of traffic lights at the end of a motorway offramp. And then the situation tends to get worse as the built-up area on the disc tends to be where the brake pads 'catch' the disc on stopping.


I'm not a mechanic but it has happened to me on heavy vehicles (i.e. S-max) and that was the explanation I was given.

All correct - but for the OP why would this happen twice and only on the replacement sets of discs?

[Orangecurry]

RichS1963 said:

That's my opinion as the first 1500 miles or so were problem free.
It doesn't help being Tiptronic.
Want to try the aggressive pad option to clean them up but need suggestions.

If the discs are not seated true, this will not help.

New discs will take a variable amount of miles to show vibration, as the pad-material build-up on the disc high-points takes time.

Get the new (or skimmed) discs checked for runout whilst fitted on the car - there may be an issue with one of the hubs.

[AvonM]

Orangecurry said:

All correct - but for the OP why would this happen twice and only on the replacement sets of discs?

Driving style causing it to re-occur? I no longer have this problem after learning to roll the the car forward 1/2 a wheel turn a few seconds after coming to a stop to put the pads against the (relatively) cool side of the disc. Or taking foot off the brakes and using the handbrake to hold the car (also can affect brakes)

(I'm not saying this is the only reason, just personal experience)

[boxsey]

In my experience pad build up is felt through the brake pedal at all speeds. As it's at low speed only I'd be looking for other reasons for the vibration.

[Orangecurry]

Orangecurry said:

get someone who knows what they are doing to check for runout whilst the discs are on the car.

Orangecurry said:

Get the new (or skimmed) discs checked for runout whilst fitted on the car - there may be an issue with one of the hubs.

OP - find out what the problem is, as you don't know yet.

If the discs are being cooked by your driving style, then there is no 'repairing' you can do to that disc that will last - the actual material/area of the disc becomes physically changed by the fusing of the hot pad material, and even if you get it skimmed, the slightly changed properties of that area of the disc will cause problems from now on.

[RichS1963]

Thanks for all the input.
Driving style - I certainly don't drive it hard and other than the occasional blast, treat it very carefully.
The last time it occurred, was on the way to Le Mans. Had to stop very quickly on cold brakes and then pulled over to get directions. In gear, foot on brake. Immediately noticed pulsing from then on.

I'll get the discs checked for run out and report back.

I've started to use the hand brake just as I'm bringing the car to a halt to see if I can minimise the current build up.

[Nobby Diesel]

Orangecurry said:

..reading between the lines, you've had two sets of replacement discs, and both have started to show vibration after n-miles, where n is a low number?

Classic reason for this is that the discs have not been fitted carefully - not seated exactly straight, due to careless installation, or dirt/contamination between hub and disc-mating surface.

This tiny 'wobble' in the disc will cause the pad-material build-up at the high points... and make them higher - and so on.

If someone else is doing the fitting, get someone who knows what they are doing to check for runout whilst the discs are on the car.

ps Sebro IME are excellent quality.

Exactly this.
I had an OPC fit new wheel bearings (under warranty) many years ago. They didn't do it correctly and the effect was the discs lasted around 1200-1500 miles, before starting to vibrate under braking.
Funnily enough, it was the last time I used an OPC.

[RichS1963]

Just emailed my Indie to see if they've got the appropriate gauges to check for run out.

[Orangecurry]

Are they the garage that fitted the last two rounds of brake discs?

[RichS1963]

Haha... Nope

[RichS1963]

Visited my Indie today.
Whilst neither I nor they have tested for run out, on the basis of their knowledge and experience, it sounds like one or both hubs are not flat.

Now the interesting part...
Porsche quoted £305 per hub plus vat.
Rose Passion in France, £166 inc vat

Also 20% saving on the wheel bearings.

Called our continental colleagues and they assure me that the hubs are genuine Porsche.

Anyone purchased parts from these guys?

[Fl0pp3r]

...Googles 'rose passion'...gets some interesting results!

[Orangecurry]

I have heard good things about Rose - I nearly ordered a Sachs clutch from them, as they are the cheapest, but GSF or ECP had one of their stupid-35% off weekends, and it was just cheaper.

But every other day of the year, Rose don't take the p155 like most UK-based companies do.

I'm still slightly worried that you are ordering 400 GBPs worth of kit, and you still don't *know* what the problem is....

How is your Indie going to diagnose?

[RichS1963]

Thanks for the feedback on Rose Passion.

When I visited the Indie today, I spent some time chatting to the mechanics. I explained in great detail the experience I had had from the time of initial ownership. I also took with me the previous set of discs that had been replaced.

Whilst looking at these, it was pointed out to me the area of corrosion on the face which meets the hub. It was evident that rather than there being a crisp line of rust along the line of exposed metal versus where it would be mated to the hub face, there was significant 'blending' which is indicative of there not being a flat surface. Does that make sense?

So here's some man maths... Do I take the car in and get them to explore if and where the run out is - a couple of hours labour. Or do I just buy new hubs and for virtually the same labour cost, eliminate a potential (and by the look of it, the most likely) cause?

Interested in your view.