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Have you ever heard that cross drilled brake rotors crack? Here's the story...

adznight

By adznight,
in Victoria

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adznight Newbie

adznight

Posted
Posted

Hi all, after speaking with DBA (as I need new rotors) I thought I'd ask why cross drilled rotors are only recommended for "street use" because I know a lot of people wonder why this is the case and what will suite them. The E-mail reply was as follows...

Question -

"Just one more question. I know that cross drilled are not recommend for track use, is this because of the weakening effect on the rotors or is it more a liability thing? I have heard of cracking of the discs but realistically what sort of braking are you going to have to be doing to cause this?"

Reply -

"Adam,

the reason why we don't recommend cross drilled rotors for racing or track work is due to the following:

The disc rotor face surface area is reduced due to the holes and as a result this face heats up faster under braking.

Once you release the brakes the rotors cool very quickly due to the holes.

Due to this rapid heating and cooling of the rotor face it is possible for the rotor face to sustain what is known as heat shock.

Because the rotor is unable to heat soak and dissipate heat evenly the face of the rotor can develop cracks around the holes.

The use of slotted rotors allows the disc to heat soak and cool more evenly so the rotor is less prone to suffering from heat shock.

Heat shock can be evident in cross drilled rotors even when used by an extremely energetic driver on the street. If the drivers driving style is fast with rapid jabbing of the brakes and exallerator pedals he/she will be more likely to have problems with cross drilled rotors. Due to this reason we recommend the fitting of cross drilled rotors for looks only and improved braking performance under normal driving conditions.

I hope this answers your question, but if you have any further queries please feel free to email me.

Kind Regards,

Aaron Franklin

Technical Sales Advisor

Disc Brakes Australia Pty Ltd"

Thought this might be some helpfull info!

inark Grand Master

inark

Posted
Posted

so is it safe to assume from that that cross drilled AND slotted discs will be less prone to this?

"The use of slotted rotors allows the disc to heat soak and cool more evenly so the rotor is less prone to suffering from heat shock"

R32Big_boy Veteran

R32Big_boy

Posted
Posted

The cracks would still form around the cross drilled holes inark beacuse the change in temp would still be significant. The only way to go on the track is slotted. Do they make 5000 series for the 34 yet adz?

RTFGTR Proficient

RTFGTR

Posted
Posted

I failed my RWC for the first time because I had drilled rotors with 1cm - 2cm cracks on each hole nearest the edge of the rotor... they looked sweet but the funny thing was I passed my Engineerring Cert. but not the RWC.

prae Rising Star

prae

Posted
Posted

From what I've heard the DBA rotors were drilled after they were fabricated? While the Porsche and other high-end rotors had the holes cast from factory?

Drilling post-fabrication gives less structural integrity doesn't it?

I could be wrong though..

inark Grand Master

inark

Posted
Posted
Because they aren't $200 rotors like DBA are...

HAHA good point.

so in other words his statement is only relative to DBA rotors... not in general

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