Discussion
Hi all, I've noticed tiny cracks starting to appear from the cross drilled holes on my brake discs, is this normal or should I worry and have them replaced? I was considering replacing them with Carbon Ceramic type discs has anyone looked into this or know the best way to do it? will the stradale discs fit, as this might be a sensible approach if they do?
Just spoke to one of the mechanics at the dealer who said that it's fairly standard for small hairline cracks to appear, due to high temperatures, they have a lot on their race cars, but they also said that when they join up I should start worrying!!! Have also asked them to investigate ceramic or carbon type discs............. so I guess we'll see what scary quote they come back with!
If it's a road car, might be worth checking what your insurance company think about that sort of advice.
How often are you meant to check if they join? What if they suddenly join from a big stopping moment?
Maybe I'm being overly conservative (having never had cross drilled discs). But I can imagine what sort of mess might ensue from disc failure...
Thinking completely illogically perhaps, but where in the hole are the cracks eminating from? Isn't stress meant to come from specific points/"risers"? Is it happening on all holes or just some? Could this be inidicative of a weakness in certain areas of the drilling?
From what I gather, cross drilling mostly has benefits for weight saving (forget "cooling"), so I often wonder about why it's applied to a 1350kg+ road car anyway...but that's just me.
How often are you meant to check if they join? What if they suddenly join from a big stopping moment?
Maybe I'm being overly conservative (having never had cross drilled discs). But I can imagine what sort of mess might ensue from disc failure...
Thinking completely illogically perhaps, but where in the hole are the cracks eminating from? Isn't stress meant to come from specific points/"risers"? Is it happening on all holes or just some? Could this be inidicative of a weakness in certain areas of the drilling?
From what I gather, cross drilling mostly has benefits for weight saving (forget "cooling"), so I often wonder about why it's applied to a 1350kg+ road car anyway...but that's just me.
The cracking is perfectly normal, and my rule of thumb is to replace when the crack meets another hole or turn around the edge and visibly goes into the ventlation channels between surfaces.
The 360 challenge and GT car discs are not cross drilled as the cracks would simply come too often, but cracks still appear.
I have found a company in Oz that uses a cryogenic heat and freeze process that dramatically reduce cracking and also improve performance and durability...and it's quite cheap if you do a big batch.
You can use this process on any material and gains are found in many areas. Brake suppiliers hate it for sales reasons though so don't expect any advise from them to recommend it!!
Apparently the process re-aligns carbon molecules giving a better structural integrity....whatever...it works and I'd never start an endurance race without this being done.
For example, in 2001 a Subaru WRX did a 24 hr race and changed discs and pads 3 times, the following year he used the process and the brakes did the whole race. I'm still collecting Ferrari data on it but it looks really good so far.
The best option for 360 road car brakes is to fit some cooling ducts as they have none!! The backing plate can be removed from the upright on the front and use either challenge or GT hub ducts etc.
My team make the GT ducts in shiny carbon fibre and a full set for front and rear (10 parts) can be bought for a measly AU$3000. It takes about 2 days to fit it all up, and some flexible tubing is required to connect the inlet ducts to the hub ducts. The front brake pipes need some re-jiggery to relocate in a style a la challenge.
The 360 challenge and GT car discs are not cross drilled as the cracks would simply come too often, but cracks still appear.
I have found a company in Oz that uses a cryogenic heat and freeze process that dramatically reduce cracking and also improve performance and durability...and it's quite cheap if you do a big batch.
You can use this process on any material and gains are found in many areas. Brake suppiliers hate it for sales reasons though so don't expect any advise from them to recommend it!!
Apparently the process re-aligns carbon molecules giving a better structural integrity....whatever...it works and I'd never start an endurance race without this being done.
For example, in 2001 a Subaru WRX did a 24 hr race and changed discs and pads 3 times, the following year he used the process and the brakes did the whole race. I'm still collecting Ferrari data on it but it looks really good so far.
The best option for 360 road car brakes is to fit some cooling ducts as they have none!! The backing plate can be removed from the upright on the front and use either challenge or GT hub ducts etc.
My team make the GT ducts in shiny carbon fibre and a full set for front and rear (10 parts) can be bought for a measly AU$3000. It takes about 2 days to fit it all up, and some flexible tubing is required to connect the inlet ducts to the hub ducts. The front brake pipes need some re-jiggery to relocate in a style a la challenge.
Hmmmmm - get them to replace them with stronger discs, somethi8ng like the Brembo disc which is slotted but not drilled.
Drilled is the operative word -- the holes are drilled in. And this sets up lots of local tension in the metal.
Porsche discs dont suffer from this because, as I understand it, the holes are cast in as part of the casting, and so they dont have all the stress issues of drilled holes.
Drilled holes may well look pretty, but they are demonstrably not strong enough if they are cracking.
Drilled is the operative word -- the holes are drilled in. And this sets up lots of local tension in the metal.
Porsche discs dont suffer from this because, as I understand it, the holes are cast in as part of the casting, and so they dont have all the stress issues of drilled holes.
Drilled holes may well look pretty, but they are demonstrably not strong enough if they are cracking.
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