Perforated Disc Brakes......

[SWirth86]

Are there any cars that have perforated Disc Brakes? I don't think I've ever seen any cars that have them, yet motorcycles and bikes both use them.....
What's the advantage of having them perforated as opposed to regular disc brakes on cars? I'm guessing that they dissipate heat more, but then why don't cars use them?

 

[Howard]

Many sports cars have them. In fact, most all high-end sports cars have them.

And they're described as cross-drilled, not perforated (although that is just as descriptive). And in the link you label as "regular", those aren't "regular" discs. They're slotted discs. And slotting/cross-drilling both serve the same purpose - under high temps/pressure, the brake pads will start gassing (emitting gas, duh) and the slots/holes will help exhume the stuff.

 

[Stallion]

Baer sells slotted/drilled rotors. Nice units if you have the cash.

 

[SWirth86]

Thanks

I didn't realize that cars had them.....I guess I've never really noticed 'em

Heh, when I posted the 'regular' disc brake pic I didn't even realize that they had slots...

 

[Imported]

I've heard Brembo blanks stop better than their cross-drilled/slotted rotors since their is more surface area.. not sure on it's accuracy though. I'm guessing it's better for short use.

Theres another company that makes dimpled rotors too.. Powerstop or Powerslot I believe..

 

[Howard]

Noot very observant, eh?

Dimpled < drilled, in terms of cooling. If only slightly. Drilled rotors have just a tad bit more surface area to work with.

 

[Evadman]

I have a question on something... If you just drill your own rotors, will it still help with the outgassing? I would assume you would have to upgrate the pads as well to recieve full benifit?

For the record, advanced pads and rotors do not drasticly shorten stopping distances. But they will help you stop in the same distance repeatedly without fade.

 

[KokomoGST]

Originally posted by: Evadman
I have a question on something... If you just drill your own rotors, will it still help with the outgassing? I would assume you would have to upgrate the pads as well to recieve full benifit?

Drill your own rotors? Well, unless you're a skilled machinist and you know how to properly cross-drill rotors, you'll probably crack and/or warp your rotors very quickly. Especially if they're vented rotors. Most cross-drilled rotor manufacturers "build" cross-drilled rotors now instead of drilling normal blanks because that way they can build stronger rotors.

For the record, advanced pads and rotors do not drasticly shorten stopping distances. But they will help you stop in the same distance repeatedly without fade.

I'm sorry, but that statement is just WRONG... race compounds and aggressive street compounds and your lifetime Pepboys pads will all stop differently. Drastic? Even 5ft is drastic enough to prevent an accident... Once race compound pads are up to temperature, they will stop you significantly faster than your OEM pads. More friction = shorter stopping distances, and aggressive pads will create a whole lot more friction. In fact, that's why some race pads will dust like crazy and/or eat at rotors.

Cross-drilled is the proper term. On top of releasing trapped gas generated from the extreme heat of your brake pads, cross-drilling rotors obviously lightens them. Another reason why many race cars use cross-drilled & slotted rotors. Slotted rotors are also called water-slotted or gas-slotted rotors. The slots supposedly help with wet braking and channeling away water on the rotors, but I'm not so sure about that one since your pads can get hot enough to vaporize water on your rotors. Most cars don't have either because they're an additional cost to the manufacturer and cross-drilling, especially on the vented disc rotors (not solid like on motorcycles) of modern cars again will reduce the operational lifetime of the rotor and make it more likely to crack. Dimpled rotors don't do squat... unlike slots or complete holes, they can't channel those hot gasses anywhere...

 

[Finality]

I doubt you will see rotors x-drilled like that any time soon in a car mainly because of the extra weight a car has. However most high end cars have x-drilled and slotted rotors. Quite common these days....


In fact as someone mentioned you could get Brembo blanks from some companies that will x-drill and slot em for about $300 for the fronts and rears (a nice GD can get it to you for about $200). I'd recommend SS lines as well as new brake pads if you go that route though.

 

[Evadman]

KokomoGST

That statement was baised on an article I read in motortrend whenre they tested aftermarket rotors and pads (same tires) and found brake stopping distances were not drasticly changed, but repeatability was.

<edit>
Oh, and I am not talking about carbon fiber brakes, or race only brakes. Those are a whole different ballgame. I am speaking in general terms for street brakes.

 

[TechnoKid]

F1 cars and CART race cars use thick (about 3/4-1" thick) solid vented rotors.

Why? Well, their brakes are carbon based, so weight is not really an issue, although carbon brakes must heat up to operating temps for peak operation.
Also, they [solid rotors] provide for more surface area for the brake pads to contact, thus more brake 'grip'.
I believe that the brake rotor size is regulated in both F1 and CART to around 11.2", though this is only a small hinderance as the arodynamics of the car allow it to stop real quick, because they literally 'stick' to the road.

 

[TechnoKid]

Oh, BTW, the new BMW 745 series has 13.7" front, 13.6" rear solid vented rotors. Thats huge for any car. And they [the rotors] are both nearly an inch thick each. This car doesn't have 'crossdrilled' or 'slotted rotors'.

 

[KokomoGST]

Motor Trend? Wow, I couldn't trust them less... they didn't bed the pads to the each rotor most likely. There are also instances when the caliper pressure & swept area are so tiny that different pads won't change the fact that your brakes suck. However, with a properly braked car it will make a difference. I recall a lot of people including folks at Grassroots/SCC(?) criticized Motor Trend for being a bunch of biased idiots.

A lot of enthusiasts go out and buy composite brake pads these days which yes, do reduce fade but also stop significantly better than most OEM pads. Some OEM pads (like those on Porsches) are composite metallics already so there may be less to gain. How come EVERYONE in motorsports agrees that upgrading from production pads is a good upgrade? Mebbe because they have years and years of empirical data to back it up? It does really depend on the street pad you are using as different brands are definitely better than others.

EDIT: race compound brake pads on your street discs will stop you faster when up to temp... but it takes pretty severe temperatures to get most race compound brake pads to grip

 

[bizmark]

just to add my off-topic two cents....

the main benefit from bigger brakes (e.g. 13 inch discs instead of 12 inch discs) is NOT the swept area helping cooling. Rather it is the torque benefit of having the same braking power farther out from the axle -- a longer lever arm.

Also most high-end sports cars in recent memory have had cross-drilled rotors. Porsche 911, Maserati, AMG Mercedes, Ferrari, Lamborghini..

 

[TechnoKid]

Originally posted by: bizmark
just to add my off-topic two cents....

the main benefit from bigger brakes (e.g. 13 inch discs instead of 12 inch discs) is NOT the swept area helping cooling. Rather it is the torque benefit of having the same braking power farther out from the axle -- a longer lever arm.

Also most high-end sports cars in recent memory have had cross-drilled rotors. Porsche 911, Maserati, AMG Mercedes, Ferrari, Lamborghini..

Thanks for pointing out the bigger brake thing. Cross drilled imo, just help to cool the brakes, where as solid rotors have more actual braking surface. Many of the LeMans cars, be it prototype or GTS etc, have brake-ducted cooling, and I believe some use drilled and some use solid rotors. The advantage obvious here is that with solid rotors, and the aid of cooled-ducting (which may net the same cooling bennifit of or as drilled), more brake grip is achived, rather than expensing surface-area-to-pad on these 'holes'.

 

[Pooteh]

to fit these bigger brakes u gotta get rims right? how much do these cost? i'm not much for modding, but practical modding seems ok

 

[notfred]

The rotors and pads aren't the limiting factor on most street cars, the tires are. You put a set of 13 inch brakes with giant calipers behind a 175 width tire, and you're just going to lock the brakes up.

 

[HiTek21]

No need for cross drilled rotors on a honda civic, better off putting those hub caps with the fake cross drilled rotors on them =P

 

[Pooteh]

Originally posted by: HiTek21
No need for cross drilled rotors on a honda civic, better off putting those hub caps with the fake cross drilled rotors on them =P

heh oh well no new brakes for me then, i'll just spend it on a video card or somethin u should see my hubcaps, i've abused the sh*t out of em rubbing up against curbs. my poor poor civic

 

[brtspears2]

Originally posted by: HiTek21
No need for cross drilled rotors on a honda civic, better off putting those hub caps with the fake cross drilled rotors on them =P

Dont forget the red fake caliper

 

[tcsenter]

How come EVERYONE in motorsports agrees that upgrading from production pads is a good upgrade? Mebbe because they have years and years of empirical data to back it up? It does really depend on the street pad you are using as different brands are definitely better than others.

I would guess the same reason everyone in motorsports agrees that upgrading from production tires is a good upgrade? Or that upgrading from production engines is a good upgrade? Mass-produced OEM "stuff" just isn't developed nor intended to endure competition. Rare is it when even high-end sports cars come in competition ready form out-of-the-box (in a manner of speaking).