Hawk Performance Ceramics - Group Buy

[peadya100]

I see.. id imagine the quality of the rotors on performance cars would be better than the dba rotors too.

Ive also heard that machining rotors is bad too as they can take up to 3mm off making them less capable with dealing with heat and more likely to warp.... please comment

[Rickchampion]

I'm in for a set of es pads if this goes ahead

[dr20t]

Alexei have a look at a few cross drilled discs next time you see one

Inevitably they all develop hairline cracks around the holes

It's the on/ off type nature of most street driven cars where they are constantly hear cycling in my opinion that causes the stress fractures

Mick

[Manaz]

I see.. id imagine the quality of the rotors on performance cars would be better than the dba rotors too.

Ive also heard that machining rotors is bad too as they can take up to 3mm off making them less capable with dealing with heat and more likely to warp.... please comment

All rotors have a "minimum safe thickness". As long as you don't go below that, you should generally be fine.

It's interesting - having just moved back over to the Subie scene, the way brake components are considered is very difference in the Euro car scene. BMWs, Audis, VWs, Mercs, etc, all treat the rotors as disposable - you get rid of them at the same time you change your pads. In the Jap and local car scenes, rotors are expected to outlast a few sets of pads. Euro cars seem to run softer rotors and harder pads, Jap/local cars seem to run harder rotors and softer pads. It would be interesting to have this confirmed/denied by someone in the know (who works for or who has contact with OEM manufacturers across both areas).

[alexeiwoody]

Ive seen a few cracked drilled disks from track days. Fully sick cracked.

That just points to incorrect use, insufficient strength in the disk vs the power. Eg shit disk on a 400kw evo. What do those guys expect?

When designing a disk - it's not enough to just grab a slab of steel because steel is strong enough on paper, the disk's structure also needs to be countered into the final application strength. That's probably why you hear about about boys cracking them on their toyotas and evos but Ferrari's not so much. Well that and the fact that there are way less Ferrari's out there

Overshaving the disk definitely causes all sorts of problems, and cracks are more likely to appear.

Holes are circles - they distribute the force equally through the material, they don't encourage cracks. Think about this - cracks are very fine almost invisible lines, while the drilled holes are v large in comparison. If we punctured the disk with fine needles - then we'd be promoting cracks big time.

As such I'd say prolonged use of old disks, crap material to start with, running too much power and overheating th disks is to blame. The holes play a very minor part compared to those.

Ps. When the cracks do appear - obviously they'll appear around the weakest point - which would always be the holes. This might be getting confused with the holes being to blame for the cracks.

[Manaz]

When the cracks do appear - obviously they'll appear around the weakest point - which would always be the holes. This might be getting confused with the holes being to blame for the cracks.

Rotors with drilled holes get the cracks. Rotors without them don't tend to get the cracks.

That's pretty conclusive.

[owen]

Do F1 cars have drilled rotors?

[Manaz]

Do F1 cars have drilled rotors?

Do F1 cars run carbon steel rotors?

Do they last for more than one race? Is the individual per-rotor cost more than you'd put into all your brakes combined even if you were absolutely insane?

Do F1 cars weigh less than half what your road car weighs?

Might as well ask if 747s run drilled rotors.

[peadya100]

Do F1 cars have drilled rotors?

Do F1 cars run carbon steel rotors?

Do they last for more than one race? Is the individual per-rotor cost more than you'd put into all your brakes combined even if you were absolutely insane?

Do F1 cars weigh less than half what your road car weighs?

Might as well ask if 747s run drilled rotors.

Hahahaha... classic!!!

[alexeiwoody]

Conclusive would be to say all drilled rotors crack. Since they don't - nothing is concluded.

Please, re read the part about designing a brake rotor for the application, holes need to be countered into calculation so as not to overstress the disk. If you run too much power - and crack the disk, that's your own fault for picking the wrong material for your power. If you want to have the cooling benefits of the holes, then use drilled.

If you don't want to afford brakes that have been proven to exceed your car's potential, then don't complain when cheap stuff breaks. Overused solid disks warp and can crack. So we shouldn't use solids? Overused drilled crack. Used correctly both have their advantages.

Group hug time?

Lol at F1 cars. Edit: scratch that 'lol'. Epic post!
I don't imagine F1 cars need the holes to help cooling, if they can afford the greatest materials out there - they'd just go for straight out structural strength.

[dr20t]

Alexei can you explain what you mean by too much power hurting brakes?

[alexeiwoody]

Big calipers clamping on rotor + constantly accelerating + decelerating. The more power your car has, the more potential to overheat/overuse the brakes on the track. It's not directly related, but assuming an aggressive driving style, more power means the more punishment the brakes take.......

I kind of abbreviated car weight, caliper size etc into 'power' sorry for the smartassedness/confusion? Im sure you know what I meant. Sleep time.

[Manaz]

Conclusive would be to say all drilled rotors crack. Since they don't - nothing is concluded.

Please, re read the part about designing a brake rotor for the application, holes need to be countered into calculation so as not to overstress the disk. If you run too much power - and crack the disk, that's your own fault for picking the wrong material for your power. If you want to have the cooling benefits of the holes, then use drilled.

If you don't want to afford brakes that have been proven to exceed your car's potential, then don't complain when cheap stuff breaks. Overused solid disks warp and can crack. So we shouldn't use solids? Overused drilled crack. Used correctly both have their advantages.

Group hug time?

Lol at F1 cars. Edit: scratch that 'lol'. Epic post!
I don't imagine F1 cars need the holes to help cooling, if they can afford the greatest materials out there - they'd just go for straight out structural strength.

My understanding is that drilled rotors aren't for better cooling (given all air flow is radial on a car's brakes), but rather to help with removal of gas buildup as pads are vapourised. Slotted rotors do this too, but without some of the issues inherent in drilling holes in the rotors.

Undrilled rotors do not develop the surface cracks that drilled rotors develop. I stand by that statement.

Yes, you can absolutely crack solid rotors. But that's not the surface cracking I spoke of in my post.

[alexeiwoody]

The holes catch the dust and this helps protect the rotor surface. ...drilled rotors are also known to dissipate heat faster, hence cooling benefits.

I still stand by that a correctly chosen/used drilled rotor will hold it's own and last. How long would it take to wear one of these out compared to a solid rotor under the same circumstances? I don't know, and have no way of testing....so maybe someone else can comment

Supposedly the holes keeping the rotor surface clean make it wear slower than solids...

Structurally it's pretty straight forward - Im inclined to believe incorrect use/setup of these has earned them the red mark next to their name, rather than the actual weakness of the design.

How did this all start. I just thought they looked cool.

[<GB>]

Other reasons they drill them is for less un sprung weight, weight reduction and rotational inertia resistance