PCCB weight thresholds

[supermono]

So I have this set of 997 PCCB but I have no idea how worn they are. Can anyone tell me the sort of figures we're talking about? I'm assuming it's a few grams of loss not tenths since the weight is to 0dps.

SM

[Sandy59]

Is the wear not determined by their thickness, do they not have the max & minimum size stamped on them ??

[mm450exc]

I thought wear is down to weight of the disc. The weight/thickness is stamped onto the hub. Looking at the manual...

For perforated brake discs, the minimum thickness -x- must always be measured on the inner or outer
friction surface track -arrows- .
·
Wear limit: The brake disc minimum thickness is stamped on the brake disc chamber (example: Min.
Th. 33.7 mm).
·
– Measure the brake thickness -x- with a suitable micrometre screw or a brake disc gauge around the
inner or outer friction surface tracks -arrows- .


Evaluating surface roughness (Sr) (max. 80 micrometre permitted)

[supermono]

I honestly don't understand what you're saying steels have a wear in mm limit I understand that. But PCCB have a weight change. Can you elaborate your answer please I'm being a bit thick...

SM

[mm450exc]

supermono said:

I honestly don't understand what you're saying steels have a wear in mm limit I understand that. But PCCB have a weight change. Can you elaborate your answer please I'm being a bit thick...

SM

I thought PCCB go by weight. I'm sure this is a factor. But looking at the manual the thickness counts as well. Here is what they mention in the manual...

46 51 02 Checking front PCCB brake discs (wear
assessment) - as of MY 2005

- Checking information on PCCB brake discs
- Checking PCCB brake discs (wear assessment)
top of page
Checking information on PCCB brake discs
Basic information
Checking involves the following:
Associated surface fracture
1. Visual inspection for any surface changes to the brake disc friction surfaces Indication of wear:
Associated surface fracture > 1 cm2 -arrow- , but no accumulation of smaller fractures € Visual
inspection of the surfaces of the brake disc friction surfaces (indication of wear) .
Surface roughness of PCCB brake disc

2. Assess the surface roughness (Sr) of the brake discs (max. 80 μm permitted), since this affects smoothness
of braking (noise), braking performance/pedal pressure and brake pad idle time € Evaluating surface
roughness (Sr) (max. 80 micrometre permitted).
46 51 02 Checking front PCCB brake discs (wear assessment) - as of MY 2005 1300

Minimum thickness (x) of the PCCB brake disc
3. Check brake discs for minimum thickness -x- . The minimum thickness of the brake disc (example:
Min. Th. 33.7 mm) is stamped on the brake disc chamber € Checking brake discs for minimum
thickness.

Edge damage on PCCB brake disc
4. Check brake discs for edge damage -see illustration- (damage caused as a result of improper use)
€ Checking brake discs for edge damage.

[mrdemon]

The weight of each disk when new is printed on the hat part.

[supermono]

mrdemon said:

The weight of each disk when new is printed on the hat part.

Yes, well stamped actually but the question is how much lighter than that stamped figure can it become before it's a paperweight?

SM

[HokumPokum]

i dun know how mm450xc can be more clear.

the 4 criteria are listed in the porsche manual. If you satisfy all 4 conditions then you are good to go. otherwise, time to replace. If visually they look ok, then you measure the thickness all round and make sure it exceeds the minimum everywhere.

[mm450exc]

I believe the weight translates to about -100g+.

[Rockster]

supermono said:

Yes, well stamped actually but the question is how much lighter than that stamped figure can it become before it's a paperweight?

SM

My info is there is a new weight etched onto each rotor.

A front rotor is considered worn out if the actual weight is down by 100 grams from the weight on the rotor.

A rear rotor is considered worn out if the actual weight is down by 55 grams from the weight on the rotor.

You should confirm the above with your OPC for these numbers may have changed over time.

Also, weight alone is not sufficient to say a rotor is suitable for continued use.

The condition of the rotor most also be ascertained by a thorough inspection.

Total 911 in its 1st 50 issue DVD has a 3 part article (in issues 48, 49, and 50) that cover PCCBs quite thoroughly and cover what to look for. Highly recommended.

[supermono]

HokumPokum said:

i dun know how mm450xc can be more clear.

Well because he started with "I thought wear is down to weight of the disc..." Which agrees with my question about weight then wrote about thicknesses. I couldn't see any continuation of the weight discussion anywhere.

See Rockster's post for the magical weight into I was after.

Thanks Rockster, very useful.

SM

[supermono]

Rockster said:

My info is there is a new weight etched onto each rotor.

A front rotor is considered worn out if the actual weight is down by 100 grams from the weight on the rotor.

A rear rotor is considered worn out if the actual weight is down by 55 grams from the weight on the rotor.

You should confirm the above with your OPC for these numbers may have changed over time.

Also, weight alone is not sufficient to say a rotor is suitable for continued use.

The condition of the rotor most also be ascertained by a thorough inspection.

Total 911 in its 1st 50 issue DVD has a 3 part article (in issues 48, 49, and 50) that cover PCCBs quite thoroughly and cover what to look for. Highly recommended.

It's amazing really that given they start at about 6kg of which I estimate the vast bulk of the weight is in the SS hub. Leaving what? 1.5 kg or less actual disk? And that can reduce by 100g before it's done for. Anyhow I'll get mine weighed before sticking them in classifieds.

Thanks again.

SM

[HokumPokum]

the OPC manual does not use weight of PCCB disc and OPC does not check the weight of each disc. They only measure thickness.

Unless you remove the discs and weigh yourself, i don't think this is an avenue.

[supermono]

HokumPokum said:

the OPC manual does not use weight of PCCB disc and OPC does not check the weight of each disc. They only measure thickness.

Unless you remove the discs and weigh yourself, i don't think this is an avenue.

Understood it's easier to measure thickness when mounted but mine are out on my dining table so weighing is an easy option. I might as well mic them too.

Thanks everyone.

SM