Cross drilled and sloted

[Ricks15]

Brake rotors that r slotteD AND crossdrilled really crack right away????? Just want someone to clear this myth up.:confused:

[SochBAT]

not right away.

Depending on how you drive, and how you brake really has effects on the rotors.

Make sure they have quality slots/dimples. Don't get blankies and have BillyBob drill em at home.

[punxva]

also, they will wear your pads down faster, because of the grooves in the rotors.

[KA24DESOneThree]

Doing both is just for show. In reality you're reducing swept area, thus decreasing pad effectiveness.

Drilling rotors went out with organic pads. Slotted rotors is where it's at now; check out the ALMS cars.

Seriously though, this question could've easily been answered by looking on Google for 15 seconds. Or by searching on this very website.

[g6civcx]

Okay, I'll attempt to answer this for you. Please do realise it is late so if I make any mistakes, please forgive me and go ahead and correct me. I'll discuss each topic separately.

Please note that my sources come from my many discussions with the engineers at CarboTech.

Cross-drilling:

The purpose of cross-drilling is to create space between the pad and the disc. Traditionally, brake pads degas under use (they release gas particles). This layer of gas may cause the pad to actually separate from the disc momentarily, causing inefficient braking. It can also help the brakes cool.

Drilling holes into the disc allows these gas particles an escape path. As an added benefit, you get reduced unsprung weight reduction.

The main disadvantage to this is that unless the drills were done effectively, i.e. baked in a cryogenic chamber of some sort at the time of casting, it may cause cracking under prolonged use. In other words, if you take a drill press to a disc, chances are it will crack around the drill since the thermal coefficient of the disc is greatly reduced around the edge of the drill.

Also, some argue that by reducing the weight of the disc, you decrease its mass, and, hence, reducing its thermal adsorption. Something with less mass can't take as much heat as something heavier, and will overheat more quickly. So the benefit of unsprung mass reduction is juxtaposed with the reduced braking effectiveness.

So my main conclusion from this discussion was that yes, cross-drilling can be effective if done correctly! Reputable companies like Brembo drill as part of the manufacturing process, not after the fact. So chances are if you're buying Brembo cross-drilled discs, it was done by a drill press after the disc was solidified/cured in manufacturing. You're better off buying it directly from the manufacturer if you insist on cross-drilling.

Furthermore, modern pads do not degas as much. So the benefits of cross-drilling is greatly neutralised by advances in pad design. I concluded you don't really need cross-drilling with a good set of pads, but I'll leave this up to you.

Slotting:

The purpose of cutting slots into the disc is in effect to create numerous edges that grind away the surface of the pad, exposing a new surface with every turn. This allows a more consistent surface to mate up with the disc. So it should theoretically offer more consistent, reliable performance.

The disadvantage and benefits in terms of weight savings are the same as cross-drilling. They can also crack if not done properly.

My conclusion is that it is not beneficial, but ultimately the decision is yours. Just make sure you do your research before spending money. Brakes is a safety item, and you should take care so everybody is safe.


But take it with a grain of salt. It has been many years, and technology changes every day. Who knows? Maybe Jim Bob with his drill press has figured out something that Brembo never thought off :)

[Shawn_of_the_Dead]

Hope nobody minds that I link this from another forum, but here you go. This should clear it all up.

http://www.dallasimports.net/forums/index.php?showtopic=11487

[g6civcx]

Hope nobody minds that I link this from another forum, but here you go. This should clear it all up.

http://www.dallasimports.net/forums/index.php?showtopic=11487

That's a good link. I only have one small thing to nitpick. It's about the comment about looking at F1 cars to determine effective racing technology. F1 cars are no-compromise race cars with extremely large budgets (read $100+ million to buy in, much much more to actually be competitive). They have extremely large amount of R&D support on the factory level.

Looking at them to find out what is and isn't good racing technology and practises may not be the best idea for the budget racer. :yum:

[phreze]

Yes they can afford to replace rotors, calipers, and pads every race or even twice a race, and their brakes costs more then most peopls cars.

[Shawn_of_the_Dead]

True.

I dont argue that point at all. The information given within though, can easily dissolve any myths about cross drilled/slotted.

[g6civcx]

Informative link otherwise.