# Question about cross drilling brakes



## Grogthefrog (Jul 25, 2003)

I have a 2002 GTi 3337, it has stock vented disk brakes but i love the look of cross drilled. so my question is, is there places that would just cross drill my rotors? i'd rather not have to buy new rotors as of yet. If there are places that do that, will that weaken my rotors at all? would i actually see the benefits of crossdrilled rotors?


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (Grogthefrog)*

If you drill your disks, they will certainly crack from the heat when you brakes. The disks you buy are casted with holes. 


_Modified by ttcs at 3:19 PM 1-29-2004_


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## Grogthefrog (Jul 25, 2003)

*Re: Question about cross drilling brakes (ttcs)*

thanks, i'll just have to buy some it sounds like, they aren't too expensive anyways


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## MikeBlaze (Aug 9, 2001)

*Re: Question about cross drilling brakes (ttcs)*


_Quote, originally posted by *ttcs* »_The disks you buy are casted with holes. 

They should be, not all are. Check before you buy.


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## Grogthefrog (Jul 25, 2003)

*Re: Question about cross drilling brakes (MikeBlaze)*

what exactly do you mean by "casted"


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (Grogthefrog)*


_Quote, originally posted by *Grogthefrog* »_what exactly do you mean by "casted"

Sorry if my english is rosty...
What i mean is that the holes are made by the mold when they cast the disk.


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## Grogthefrog (Jul 25, 2003)

*Re: Question about cross drilling brakes (ttcs)*

ahh, so do some places actually get rotors and just drill them themselves and mark the price way up? but all in all, I can't do that, i'll have to buy cast crossdrilled rotors it sounds like


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## vento III (May 2, 2002)

*Re: Question about cross drilling brakes (ttcs)*

I believe the zimmerman brand has the holes casted into the rotor instead of drilled.I have done some searching and those are going to be the one's for me.


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## BikeBoy24 (Jun 10, 2001)

*Re: Question about cross drilling brakes (vento III)*

I'm pretty sure no MK4 front rotors are casted with holes. All of them have the holes drilled by CAD. Porsche rotors on the other hand, have holes casted in them. It's a very expensive process.


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## MikeBlaze (Aug 9, 2001)

*Re: Question about cross drilling brakes (ttcs)*


_Quote, originally posted by *ttcs* »_If you drill your disks, they will certainly crack from the heat when you brakes. The disks you buy are casted with holes. 


Interesting bit of info from Brembo's FAQ: http://brembo.com/hp_faq.htm#22
"_*Are discs with cast-in-place holes better than cross-drilled discs?* 
Brembo has extensively studied and tested cross-drilling versus casting the holes in place and found no significant effect on performance or durability_"


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## Grogthefrog (Jul 25, 2003)

*Re: Question about cross drilling brakes (MikeBlaze)*


_Quote, originally posted by *MikeBlaze* »_
Interesting bit of info from Brembo's FAQ: http://brembo.com/hp_faq.htm#22


interesting, so i guess it comes back to, can i possibly have my stock GTi rotors cross drilled? i can only assume it would be cheaper then buying new rotors and it's mostly for looks and a little performance. especially b/c i aslo want the steel braided brake lines.


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (MikeBlaze)*


_Quote, originally posted by *MikeBlaze* »_
Interesting bit of info from Brembo's FAQ: http://brembo.com/hp_faq.htm#22
"_*Are discs with cast-in-place holes better than cross-drilled discs?* 
Brembo has extensively studied and tested cross-drilling versus casting the holes in place and found no significant effect on performance or durability_"

Very interesting!! I will have to dig deeper into this....


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## MikeBlaze (Aug 9, 2001)

*Re: Question about cross drilling brakes (Grogthefrog)*


_Quote, originally posted by *Grogthefrog* »_
interesting, so i guess it comes back to, can i possibly have my stock GTi rotors cross drilled? .

It may be cheaper but holes that aren't, what's the word--chamferred maybe??, will eat up your pads quicker due to the edge of the hole. Take a look at a good drilled rotor and you'll see what I mean.


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## BikeBoy24 (Jun 10, 2001)

*Re: Question about cross drilling brakes (MikeBlaze)*


_Quote, originally posted by *MikeBlaze* »_
It may be cheaper but holes that aren't, what's the word--chamferred maybe??, will eat up your pads quicker due to the edge of the hole. Take a look at a good drilled rotor and you'll see what I mean.

If that's the case, you can imagine the effect from slotted rotors.


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (BikeBoy24)*

I have ask around amongst my racing friends and they say that all disks with holes will crack more or less. There's no big differens between casted and drilled holes. Hardcore-racingdisks are nerly exclusive slotted.
One of my friend races a rearwheel(!) driven Golf mkIV: http://rejsa.nu/vwracing


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## spdrace11 (Oct 27, 2003)

*Re: Question about cross drilling brakes (ttcs)*

I had drilled rotors on my Formula Ford Race car. That car sees more braking in a weekend than most cars do in a life time. They never crack, however they do tend to eat brake pads more. If you do drill the stock rotors make sure you counter sink the holes so it doesnt act too much like a cheese grater on ur brake pads.


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (spdrace11)*


_Quote, originally posted by *spdrace11* »_I had drilled rotors on my Formula Ford Race car. That car sees more braking in a weekend than most cars do in a life time. They never crack, however they do tend to eat brake pads more. If you do drill the stock rotors make sure you counter sink the holes so it doesnt act too much like a cheese grater on ur brake pads.

There's a BIG differens in weight between a Formula Ford and a standard car, and the amount of heat they will generate.


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## DesuL (Feb 25, 2003)

*Re: Question about cross drilling brakes (ttcs)*


_Quote, originally posted by *ttcs* »_
There's a BIG differens in weight between a Formula Ford and a standard car, and the amount of heat they will generate. 

True but thats where size of brakes comes into play. I think the real issue still is still if cross drilleds will crack under heavy braking. I don't see the size of the car the issue but just the amount of braking on a specific pad or disk.
Couldn't read the website but your friends rear drive GTI looks awsome. Anywhere for more pics or stuff in english on the car? Or no such luck. Do you know what drivetrain is powering it? How the RWD is set
Im shopping for brakes right now and I am thinking twice about putting back on cross drilled 10.1 fronts on my scirocco. I am thinking that maybe I should stick with solid vented for my daily thrashing and weekend mountain runs. hmm


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (Nw81rocco)*


_Quote, originally posted by *Nw81rocco* »_
Couldn't read the website but your friends rear drive GTI looks awsome. Anywhere for more pics or stuff in english on the car? Or no such luck. Do you know what drivetrain is powering it? How the RWD is set

It's a length mounted 1.8T with a engine mangagement from a Mitsubishi EVO VII. It has 300+ hp. It has a 5-speed Getrag gearbox and a Ford rearaxel. Ohlins racing dampers. ø378mm front disks with watercooled eight piston calipers, ø305mm with four piston caliper at the rear.


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## genxguy (May 26, 2002)

*Re: Question about cross drilling brakes (Grogthefrog)*


_Quote, originally posted by *Grogthefrog* »_so my question is, is there places that would just cross drill my rotors?

Probably. I'd check the regional forums.

_Quote, originally posted by *Grogthefrog* »_will that weaken my rotors at all?

Yes, definitely. Matter of fact, you will lessen the life of the rotor because you won't be able to keep it til it wears down to minimum thickness.

_Quote, originally posted by *Grogthefrog* »_would i actually see the benefits of crossdrilled rotors?

No. Cross-drilled rotors were invented to vent the gas created by hard braking. With the current pads out these days, this is no longer an issue. Solid brake rotors have the added mass and surface area to cool down faster than slotted or cross-drilled rotors.


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## jib.ninja (Oct 27, 2003)

*Re: Question about cross drilling brakes (Grogthefrog)*

The deciding question when choosing new rotors is: "are you going for looks or simply performance?". 
Crossdrilled are the ****, and an obvious choice for looks. Many racing cars use slotted and vented rotors because they have just as good braking power as drilled, disipate heat just as well, but are stronger (no holes, slots). I don't think you will have a rotor grenade on you in everyday driving. If your comparing price, slotted may be a bit cheaper.
my .02 http://****************.com/smile/emthup.gif 
food for thought


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## BikeBoy24 (Jun 10, 2001)

*Re: Question about cross drilling brakes (genxguy)*


_Quote, originally posted by *genxguy* »_
No. Cross-drilled rotors were invented to vent the gas created by hard braking. With the current pads out these days, this is no longer an issue. Solid brake rotors have the added mass and surface area to cool down faster than slotted or cross-drilled rotors.

If this were the case, why does Porsche still use x drilled rotors? Also, some big heavy porkers like the Benz S class also come with x drilled rotors. It's obviously more functional.


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## vdubjb (Feb 18, 2000)

every little bit helps.


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## MikeBlaze (Aug 9, 2001)

*Re: Question about cross drilling brakes (BikeBoy24)*


_Quote, originally posted by *BikeBoy24* »_
If this were the case, why does Porsche still use x drilled rotors? Also, some big heavy porkers like the Benz S class also come with x drilled rotors. It's obviously more functional.

How is it obvious? If you keep looking around you'll notice that Ferrari doesn't use cross drilled rotors, neither do Formula 1 cars.


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## vdubjb (Feb 18, 2000)

*Re: Question about cross drilling brakes (MikeBlaze)*


_Quote, originally posted by *MikeBlaze* »_How is it obvious? If you keep looking around you'll notice that Ferrari doesn't use cross drilled rotors, neither do Formula 1 cars.

f1 is a matter of regulations, you are wrong about Ferrari, I think..


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## MikeBlaze (Aug 9, 2001)

*Re: Question about cross drilling brakes (vdubjb)*

Ah, it didn't look like there were hole sin the composite rotors.
This is from the 456M though.








M3










_Modified by MikeBlaze at 4:51 PM 2-4-2004_


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## vdubjb (Feb 18, 2000)

*Re: Question about cross drilling brakes (Grogthefrog)*

575 brakes, all ferrari street cars have x-drilled rotors.


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## MikeBlaze (Aug 9, 2001)

*Re: Question about cross drilling brakes (vdubjb)*


_Quote, originally posted by *vdubjb* »_ all ferrari street cars have x-drilled rotors. 

Except the 456M, weird.


_Modified by MikeBlaze at 5:19 PM 2-4-2004_


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## ttcs (Feb 2, 2002)

*Re: Question about cross drilling brakes (MikeBlaze)*


_Quote, originally posted by *MikeBlaze* »_Ah, it didn't look like there were hole sin the composite rotors.
M3


In Europe the M3:s have cross drilled disks....


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## ZinK (Aug 6, 2001)

*Re: Question about cross drilling brakes (ttcs)*

Cross drillig a formula 1 carbon fiber rotor would be a little tough and cause weak spots, as carbon is not ductile at all. Microfractures in carbon fiber will degrade the rotors strengths where as the same microfractures in metal can aneal under heat.
My thoughts.


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## Grogthefrog (Jul 25, 2003)

*Re: Question about cross drilling brakes (jib.ninja)*

it is mostly for looks, i think have seen those stupid disks you can slide over the rotor to make it "look" cross drilled, but that is cheesy.


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## genxguy (May 26, 2002)

*Re: Question about cross drilling brakes (genxguy)*

Check out this FAQ. Lots of info, some related to questions here, some not.
http://www.stoptech.com/faq/
Also, check this page out. Very good read.
http://www.stoptech.com/whitep...h.htm


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## billzcat1 (Sep 10, 2001)

*Re: Question about cross drilling brakes (genxguy)*

Personally, I would never cross-drill a rotor myself. A couple friends of mine work at a CNC machine shop and the program they wrote to avoid the vanes and only drill through the vents of the rotor was quite complex. Also after doing so, rotors should be balanced.
Has anyone seen the carnage from the Audi TT with home-made cross-drilled rotors? A rotor exploded at a track event, basically destroying the entire corner of the car.
I'd leave it to the pros. 
As for Porsche rotors - they are definetly not cast with holes, but the vane castings are dimpled internally to accomodate the holes. Maybe this picture helps illustrate that. The holes are definetly machined, and you can see some of the dimpling in the internal casting.








PS: yes the rotor weighs 17 lbs!!


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