Break Discs!

[Hasan Shaikh]

So what's the secret behind it Shak!

[Shak]

Ok the reason why cross drilled disc's must not be machined!

Normal Solid disc's can be machined to the minimum thickness without having to face any probs or cracks.
Cross drilled disc's on the other hand will behave in a different manner!
So when Cross drilled disc's start to pulsate when braking softly usually means that the disc's have been cooked! (Hot Spots)
So by machining the disc's you are reducing the length of the cross drilled holes therefore maximising the chance of a fracture or a crack across the drilled venting holes under heavy braking.

So I would not recommend any Cross drilled Disc's to be machined!
Slotted disc's can be machined.
Mr Hasan hope this explains.
Lets hope we get a few more opinons on this subject!

[Hasan Shaikh]

Thanks Shak!

Really appreciate your advice and information.

[Ayham]

I believe that drilled discs can be skimmed, from an applied mathematical point, IF devised procedures are followed in terms of skimming bit feeding rate, how much as a maximum is to be shaved off the rotor, and maintaining a uniform temperature gradient throughout the rotor radius (in English, not stopping at one point more than another one along the rotor's radius, hence avoiding localized stress points).

If the shaving is in the range of that achievable with hand polishing, then I'd say the procedure is safe. Has been done before.

[Shak]

Thanks Shak!

Really appreciate your advice and information.

Any time bro! I have only passed on what BMW (Sytner) UK have taught me.

Its better to be safe than sory! when dealing with brakes on a monster of a car!:bmwbest:
Oh and by the way if crossed drilled disc's are Skimmed you will be changing your pads like you change your underpants every week!
Skimmng X drilled disc's is like sharpening a knife,