Front Brake Disc Drilled Holes Filling With Crud

[Gazoak]

Morning All,
My front brake disc drilled holes on my 981S are starting to fill with crud, particularly the ones close to the hub and on the outer edge. This was pointed out to me on my first service at OPC Chester a couple of weeks ago by the service advisor yet it is not part of the service to clear the holes. They have said they can be drilled out and I have poked around with a bradawl but it seems as hard as nails! They have said if left, the discs will overheat and crack. I have done just under 4000 miles in the car so a little disappointed with the dealer response. I read on the pistonheads forum that someone cleared the holes with a wooden skewer but I don't believe that for a second. Does anyone have experience of this. I notice that the GT3 Cup cars have grooved steel discs rather than drilled so was thinking of taking this option when they need replacing. Can anyone give me any tips or recommendations as to what route to take going forward and if they have any experience of this, costs, brands etc. None of the rears have filled with crud yet they are wearing quicker due to engine weight etc. None of the Macan's Turbo included seem to have drilled discs which is surprising considering it's weight and performance, likewise, neither does the Rolls Royce Wraith which is a 2 ton car with a 4.5 second 0-60 time! Are they really necessary of just for show?
Thanks, Gary

 

[ralphmusic]

There is nothing unusual about drilled disks, they are fine on a road car but need checking from time to time lest they become blocked with brake dust, as your seem to have been. Setting aside your OPC being unhelpful, the holes can normally be cleaned out easily, I have used a machine screw to clean them out after each track day.

I have just moved to slotted Girodiscs which are larger diameter and save me the drilled hole cleaning process. Check out my thread in the Modified section of the forum. The disc upgrade for front and rear costs c£2.3k plus fitting. I am not sure there are any slotted alternatives available in the stock 981 discs sizes.

As to your blocked discs, get an Indy to drill them out and just keep an eye out for any accumulation thereafter.

 

[Motorhead]

Gary,

Here's a bit of informatoin on grooved versus drilled discs:

https://www.apracing.com/products/race_car/formula_student/sae/brake_discs.aspx

Both types will disperse water more efficiently than a plain disc.

Although it's a bit tedious to do, just run an undersized drill through your disc holes to clear them out.

Jeff

 

[Ray]

Gary,

I am going to be very interested in the replies which you will get from this post. I have a couple of Porsche's and the 3.2S Boxster has had several sets of discs and this has not been down to wear this has been down to corrosion. The corrosion happens on the inside face of the disc where you cannot see it. The first indication I got from the brake pedal was a small judder when braking. After a few more weeks the judder was getting progressively worse. When the discs were removed the inside face was not flat due to rust building up on the face.

My garage did say that I may be better off using solid discs as they felt the corrosion was due to the material and drilled vented discs. One precaution I tried to take was to periodically jet the holes. A friend took the more labourious way out and used a wooden dowel, that's dedication.

Ray

 

[ralphmusic]

An observation, jet washing is a pretty ineffective way to clean the holes as it will turn any remaining dust into a solid and unless the brakes are used directly after the process will undoubtedly help rust the discs.

 

[ian harvey]

Gary,

I agree with the other replies. Probably nothing wrong with your discs and they'll last a long time so you should not have to consider changing them in the foreseeable unless you are going to subject them to particularly heavy use.

I clean mine out periodically with a drill, with hardly any force required. There are some 'dummy' concave holes near the centre and you may have tried drilling one of those.

If you have the opportunity/facility/inclination to remove your wheel and gain access to the disc, you'll soon get into a groove with the drill and it won't take too long. Almost therapeutic. By the way, I place some king of container underneath to catch the crud which can be messy and be careful not to breath the dust in.

Ian

 

[Ray]

Thats what I do. As soon as the car is cleaned etc The cars discs are dried off by running the vehicle. You can actually see the water go through the holes when you jet but if your way is better stick with it. For me there is no right or wrong way only the way you feel that you get the result you are happy with.

Ray

 

[Ray]

An observation, jet washing is a pretty ineffective way to clean the holes as it will turn any remaining dust into a solid and unless the brakes are used directly after the process will undoubtedly help rust the discs.

Its quick Ralph and I feel happy with doing it that way. I have found that there is no right or wrong way only the way which you choose to adopt. I dont have the time to drill every single hole out on 4 discs to me thats a little like stuffing a mushroom. But you choose what you like to do in life.

Ray

 

[Steve Brookes]

Morning All,

My front brake disc drilled holes on my 981S are starting to fill with crud, particularly the ones close to the hub and on the outer edge. This was pointed out to me on my first service at OPC Chester a couple of weeks ago by the service advisor yet it is not part of the service to clear the holes. They have said they can be drilled out and I have poked around with a bradawl but it seems as hard as nails! They have said if left, the discs will overheat and crack. I have done just under 4000 miles in the car so a little disappointed with the dealer response. I read on the pistonheads forum that someone cleared the holes with a wooden skewer but I don't believe that for a second. Does anyone have experience of this. I notice that the GT3 Cup cars have grooved steel discs rather than drilled so was thinking of taking this option when they need replacing. Can anyone give me any tips or recommendations as to what route to take going forward and if they have any experience of this, costs, brands etc. None of the rears have filled with crud yet they are wearing quicker due to engine weight etc. None of the Macan's Turbo included seem to have drilled discs which is surprising considering it's weight and performance, likewise, neither does the Rolls Royce Wraith which is a 2 ton car with a 4.5 second 0-60 time! Are they really necessary of just for show?

Thanks, Gary

From what you say it sounds like Chester will drill them out for you but it will come at an extra cost, so maybe ask them what they would charge. I guess it will be at least one hour labour so won't be cheap. Like Ian mentions above I do them myself with a cordless drill. Probably takes about an hour including taking wheels off (as long as you have a trolley jack to speed things up).

By the way if your rears are wearing faster that is more likely down to the PSM operating the rear brakes rather than due to the engine weight. The PSM does a lot more work than most think....just because you don't see the dash light flashing it doesn't mean that it's not doing anything.

 

[Gazoak]

As Ian says, maybe I've poked a dummy hole (no pun intended) close to the centre of the hub. Like I say they are as hard as nails. I'll try the ones on the outer edge. Yes Steve, I hadn't thought about the PSM's influence on the rears and thanks for the opinions on the benefits of drilled discs. I don't think I can afford £2.3k on a brake upgrade though!

 

[Tony]

All good info, drilled discs have been around for a long time, checking periodically is a good idea, I don't think it causes the cracking but does exacerbate it as the discs wear. Grooved discs are an alternative if thick enough not to warp.

Rusting of the inner surface is another issue entirely, one of the biggest culprits is washing cars and not fully drying the discs afterwards (water stays between pad and disc.

I presume the Macan solid discs is a throwback to the idea af offloading as per the Cayenne. The reason was to avoid mud being forced onto the holes - and cracking the discs!

Tony

 

[ChrisW]

I have carbon discs and I always jet-wash the discs after each track day ...

1. The discs work much better clean

2. Most of the brake dust is cleared out of the holes

3. Corrosion is not an issue

4. I would beed to be very careful to avoid disc damage if "drilling" ....

 

[Buddy]

Just one point to note if concerned that brakes are wearing at different rates, some manufacturers make the front and rear pads different thicknesses, in the case of Textar which was one of the OEM suppliers on the 987/2 the rear pads are 1,5mm thinner than the front, so it may be just that your pads started out thinner. Of course the best way to be certain is to measure new then once bedded in and afterwards periodically.

 

[richardjjs1]

What an interesting topic Thanks for all your input

 

[carnaby35]

I would have thought that the Psm would have to be really working frequently and hard to offset the effect of weight transfer and associated higher front brake wear, or am I wrong?

 

[Motorhead]

Chris,

After quite a few track day outings I can confirm that high rear pad brake wear does seem to occur, presumably due to the action of the PSM system. However, I can't recall having seen the PSM warning light flashing at any time while on track.

I must say that I was rather surprised when I discovered that the rear pads appeared to be worn more than the fronts when I checked, although if - as Kevan has pointed out - the rear pads are thinner than the fronts then perhaps the wear rates are very similar.

Jeff

 

[Ray]

PSM = Porsche stability Management

(Button Marked “PSM OFF”)

PSM, which comes as standard, is an automatic control system that stabilises the vehicle at the limits of dynamic driving performance. Sensors continuously monitor driving direction, speed, yaw velocity and lateral acceleration. Using this information, PSM computes the actual direction of motion. If this direction deviates from the desired course, PSM initiates braking interventions targeted at individual wheels in order to stabilise the vehicle.

Under acceleration on wet or low-grip road surfaces, PSM improves traction using the ABD (automatic brake differential) and ASR (anti-slip regulation) functions, giving an agile response. When ‘Sport’ mode is selected on the optional Sport Chrono Packages, the PSM intervention threshold is raised to enable greater driver involvement – particularly at speeds of up to approximately 70 km/h (45 mph). The integrated ABS can further reduce the braking distance. For an even sportier drive, PSM can be deactivated. However, it is automatically reactivated for your safety if either of the front wheels (in ‘Sport’ mode, both of the front wheels) requires ABS assistance. ABD remains permanently active. PSM has been enhanced and now includes two additional functions: precharging of the brake system, and brake assist. If you suddenly release the accelerator pedal, PSM automatically readies the braking system. With the braking system having been precharged, the brake pads are already in light contact with the brake discs. Maximum braking power is therefore achieved much sooner. When sudden braking is detected, the brake assist function applies maximum brake pressure to all four wheels.

PASM = Porsche Active Suspension Management

(The button with the shock absorber image )

Optional PASM, the electronic damping control system, suits the new Boxster models down to the ground. PASM actively and continuously regulates the damping force for each wheel according to the road conditions and driving style. In addition, the suspension is lowered by 10 mm.

Forward thrust | Chassis The driver can select between two different modes: ‘Normal’ which is a blend of performance and comfort, and ‘Sport’ where the setup is much firmer. Depending on the mode selected, therefore, PASM can be both sportier and more comfortable than the standard chassis. The PASM control unit evaluates the driving conditions and modifies the damping force on each of the wheels in accordance with the selected mode.

Sensors record the body movements that accompany powerful acceleration, braking or uneven road surfaces. This enables intelligent adaptation of damper stiffness for the selected mode, optimising contact between each individual tyre and the road and reducing pitch.

I understand little of what is laid out in this article above. I much prefer word of mouth rather than going word blind and understanding little.

Just the way I am.

Ray

 

[ralphmusic]

Chris,

After quite a few track day outings I can confirm that high rear pad brake wear does seem to occur, presumably due to the action of the PSM system. However, I can't recall having seen the PSM warning light flashing at any time while on track.

I must say that I was rather surprised when I discovered that the rear pads appeared to be worn more than the fronts when I checked, although if - as Kevan has pointed out - the rear pads are thinner than the fronts then perhaps the wear rates are very similar.

Jeff

Jeff,

I checked my new Ferodo brake pads before they were fitted recently and albeit 991.1 fronts and 981 rears, they measured as follows:

Front 17.30mm Total 6.30mm Plate 11.00mm Pad material

Rear 15.50mm Total 4.90mm Plate 10.60mm Pad material

Interestingly the 981 fronts are listed at 18.50mm total, but I can't find the plate thickness anywhere.

 

[MrDemon]

if you have a 981 of any sort bar GT cars PTV will eats your rears,

PSM on 987's not so much as it's not a live system to help the car tuck in like PTV, PSM is more traction on the way out the bend if you have to much lock on and the rears spin a bit PSM will hold it back a bit, hence on track drive PSM off and sports mode on.

981 you cannot turn PTV off so it will just eat disks.

 

[Steve Lyle]

One slightly sideways thought to throw in the pot - from my experience on a variety of road based competition cars it appears drilled discs are more prone to developing wear ribs than grooved discs. I guess this is because the drillings do not exactly overlap each other as they rotate past the pad thus leaving a thin strip of undrilled disc which wears less. Alternatively, the drillings keep wiping the surface of the pad clean resulting in more pad wear on those strips. Whatever the reason I think the best option must be drilled and grooved discs to give the best of both worlds. They do exist but I have not been able to find any for my 981S to work with the standard callipers - does anyone else have any ideas?