Slotted, crossdrilled, and plain...

[Sarra]

I just bought a set of brake pads, front and rear, for my car. Now that I have them, I thought it might be a good idea to do the discs as well.

For a street car, is there any benefit with going with slotted, drilled, or slotted and drilled rotors over plain vented rotors?

I know already that slotted or drilled will increase brake dust and eat pads quickly, or at least that's what I've read on the internet. And drilled rotors are prone to breaking...

Second, if you do decide to get some drilled or slotted rotors, should you get 4 of the same thing, or just put slotted up front and plain in the rear?

Last, if you put a set of plain vented rotors up front and put a set of powerslotted rotors in the rear, will it change brake bias?

[shazapple]

I have slotted up front and stock in the rear. It probably does change the break bias, but I havent done any 'testing', not that it would be noticable on the street.

IMO, theres no need for slotted, and definitly no need for cross drilled. I only got these slotted rotors because they were cheap ($50) and Id like them to hold up for autoX

[Sarra]

Alrighty, plain front and rear. Thanks

[Perdue]

I have slotted front and rear. I've had them since I upgraded the brakes. Most say you won't see much of a difference, but the slotted rotors will help to keep the pads cleaned, while also wearing them down somewhat quicker.

[GT Wagon]

Alrighty, plain front and rear. Thanks

For plain old street driving stick with standards discs. Cross drilled discs come two ways. Pre-cast and aftermarket drilled. The pre-cast come on 911's, Ferrari's etc and are ungodly expensive. The aftermarket drilled are affordable HOWEVER, it really depends on who made the holes. A lot , and I mean a lot of shops are drilling their own rotors because for a few minutes of slapping them on a drill press they can charge twice as much for the same plain rotor.

Do this wrong (and most times it is wrong) and you weaken the rotor. The result is it cracks under heat/cool cycles and the rotor can actually come apart. Typically what you'll see is a short while after buying cross-drilled rotors they'll warp and drive you nuts with that pulsating feel.

Slotted rotors keep the pad surface clean like a cheese grater. Again, for street driving you'll probably not see any benefit however you will notice your pads get chewed up awfully quick.

Lastly keep in mind the way brakes work is the rotor slows the car down by absorbing energy (dissapating that energy as heat) using the solid mass of the rotor. By drilling holes/slotting the rotor mass is removed and the effectiveness of the rotor actually decreases.

[legacy92ej22t]

Slotted Rotors are good if you like to drive fast and stop late. In heavy braking applications having slotted rotors will help brake fade. If you just drive around like normal then no, slotted rotors aren't for you. If you like to drive fast and take cruises on the backroads then yes, slotted would be a nice upgrade.

What GT wagon says is true....kind of. While a slotted rotor won't absorb energy and heat as quickly as a non slotted rotor (and there isn't that big of a difference) it will absorb energy/heat much longer. That is why it helps to combat brake fade. The pad and rotor won't get overheated as quickly during heavy braking.

Also having slotted rotors will help from getting pulsing do to pad material build up on the rotors.

Most cross drilled are the suck.

Which ever you choose, cryo treating your rotors is a definite recommendation.

[sheepdog]

Cross drilled rotors have saved my life on more than one occasion. Get good, cryo treated ones though, and a hard compound pad designed for it.

[scottzg]

anyone ever put the rotors on the wrong sides? OMG does it make a difference.

[Legacy4Life]

I bought cross drilled rotors from Brembo because (like most people who changed their rotors) the old ones were done and I had to replace them.

I mostly just bought them for the look! And I really do like the look in the summer with the nice wheels. In the winter they don't show up through the steel rims.

I bought two sets, one for summer (which stay nice since they aren't exposed to the road salt) and a second set for winter, which are rusted terribly.

For whatever reason, one set warped quickly and I thought I had made a mistake, but the second set didn't at all. It was the winter set that warped (fortunately) and I think I might have done it by spraying them in a car wash bay one time while rinsing the salt off the car while they were hot and that cooled them too much too quick. I don't know if there's any truth to that, but it was the only thing I could think of since I hadn't been driving hard at all with them.

Whichever, I've had cross drilled for over a year now and haven't had any bad experiences with them. They stop me just as well if not better and they look really nice! Plus with the painted calipers, people look at the wheels and notice the cross drilled. It gives an increased performance look!

http://memimage.cardomain.net/member_images/8/web/584000-584999/584957_13_full.jpg

[sheepdog]

I leave my set on my accord year round. I didn't notice a difference in how well I stopped, I just wasnt replacing warped rotors every other time I changed my oil or every time I had to stand on them from 60mph (damned ECB meets)

[Sarra]

Hmmm... Sometimes when I head up in the hills, I do a lot of low speed driving (usually 35 or less), with lots of braking, usually from going down a long, STEEP hill. these roads frequently have snow or puddles of water, like potholes (now you know why I perfer 15" and 16" wheels :p), so warp resistance is a definate bonus! Right now I'm leaning more toward a vented brembo, and when I get new inner fenders, I'm going to make brake ducts to help even more (with a splash guard an a guard to prevent water from going up to my intake).

I did get Akebono ceramic pads, but I'm not sure if they'd hold up to slotted rotors, and drilled are out. I wouldn't do it for the looks, because with my Outback wheels on, well, you really can't see the rotors anyway. :p Maybe when I get the 16" Legacy wheels...

I wonder if I could put a porsche engine/transmission/brake/wheel swap onto that RX-7 I'm gonna buy... Oops, wrong forum :p

[Huffer]

Umm, rotors from reputable companies will be fine - provided you bed them in right.

That means, not installing them and going out to romp on them straightaway.

There are specific ways to bed in rotors, which take some time, and care.

Sarra - in your case, with the hills you drive on, and the fact that you do like to thrash the brake a bit, you will want to be ESPECIALLY careful bedding both the rotors and pads in.

I don't want to hear you come back 3 weeks from now saying your new gear is warped because you made them glow again.

[Sarra]

Umm, rotors from reputable companies will be fine - provided you bed them in right.

That means, not installing them and going out to romp on them straightaway.

There are specific ways to bed in rotors, which take some time, and care.

Sarra - in your case, with the hills you drive on, and the fact that you do like to thrash the brake a bit, you will want to be ESPECIALLY careful bedding both the rotors and pads in.

I don't want to hear you come back 3 weeks from now saying your new gear is warped because you made them glow again.

:p I don't think that's going to happen, I'm intentionally NOT going any faster than my snow tires speed rating, nor am I beating on them too much. The only time I ever do hard braking is when something unexpected happens, say, a cat jumps infront of me. I intentionally do early braking during normal driving so I can go easy on the clutch, engine, and brakes.

Driving in the hills isn't so much stressful as prolonged. When you're at 5,000 feet descending a steep hill, engine braking only helps so much, so you end up using the brakes to slow you down, and that friction builds up over a 3 or 4 mile period... Going only 35 mph for the duration of that time, at a 45degree angle or steeper, your brakes get hot. not necessarily hot enough to glow, but hot enough that the amount of water vapor that results from hitting a little puddle is a little scary. I know most of it comes from the exhaust, but there's always a second little puff from both sides if you step on the brake a moment later...

Right now, I'm leaning towards brembos for front and rear. Unless someone has a better suggestion?

[Jonathan]

I have been running KVR Cross-drilled rotors on my '99 Legacy GT Ltd for the past 3 years. Normal street driving only. No problems.

For serious track time or even some Auto-X use, I wouldn't recommend them.

[strat81]

slotted rotors will also stop a bit better in the rain (at least in my experience) because the pads get through the film of water that is on the rotors and grab sooner.

[B's Legacy Wagon]

Glad i read this thread before i purchased. i to was looking at getting the brembo cross drilled rotars and calipers to show them off. threw the new rims iam getting. i totally thought i had to get these for better preformance. i dont race at all just daily driver so you guys just saved me some money. Ill stick with the regular rotors maybe still do the upgrade on the calipers and steel braided hoses. question i am thinking about is during spring summer ill run the 17"-18" rims and tires but paln on running my stock subaru rims with snow tires from probably november threw february. we get lots of rain up here in portland and some snow here and there maybe a week at the most.

[Grafton]

I am extremely pleased with my ATE slotted rotors

[Lone_legacy]

Typically what you'll see is a short while after buying cross-drilled rotors they'll warp and drive you nuts with that pulsating feel.

I had cross-drilled rotors (f&r) installed with PBR ceramic pads back in June 09 and for the past couple months I get that pulsation through the brake pedal anytime I apply the brakes over 100km/h. I thought there wasn't a chance that they could have warped so fast, yet now I am not so sure. I got them locally for a good deal, so I'm certain they are not Brembo quality. What do you guys think?

[rougeben83]

some pads need a thin layer of beded-in material on the rotor and pad surface to work properly (both stopping, noise, and uneven material buildup - ie "warping"). You use slotted or cross-drilled rotors and you're effectively preventing the pad from building up that needed layer and you'll get some of the issues described here.

For example, my R4 pads were extremely noisy when I had them new, even after bedding them in 5 different occasions. Now that I have a couple of thousands of miles of pad buildup on the rotor and pad, they aren't that noisy, even when its below freezing.

[prodriver1]

i have oe replacement brembo fronts that are crossdrilled and zinc coated (whatever that means) and vented rotors from a 93' leg turbo in the rear with hawk ceramic pads and new (last year) 03' wrx calipers and braided lines and NO ABS. it hurts my face if i stop full bore:) the setup is cheap and all subaru:) i want to upgrade to an STi break master cylinder to get a little more feel the stock one feels maxed out. just keep the holes in the rotors clean!

[Lone_legacy]

some pads need a thin layer of beded-in material on the rotor and pad surface to work properly (both stopping, noise, and uneven material buildup - ie "warping"). You use slotted or cross-drilled rotors and you're effectively preventing the pad from building up that needed layer and you'll get some of the issues described here.

For example, my R4 pads were extremely noisy when I had them new, even after bedding them in 5 different occasions. Now that I have a couple of thousands of miles of pad buildup on the rotor and pad, they aren't that noisy, even when its below freezing.

So you think bedding mine in again will alleviate the pulsation? Also, I thought a good brake service would help if there is uneven build up.

[rougeben83]

Try bedding them in again. I can't make any guarantees that it will stop the pulsation, but there's a chance it could. It may have gone on long enough that there's just too much uneven pad deposition and you'd have to resurface the rotors...that is if you can find a place that will resurface crossdrilled or slotted rotors (most won't as it may dull the lathe)...

[Lone_legacy]

ok thanks. I'll try that then. Otherwise resurfacing I guess.

[dodik]

i've been using drilled and slotted for the past 30k miles on current car and had just drilled for about 50k on the old one. both sets i bought cheaply on ebay from canada. steel is not that great and they are basically stock rotor only with slots or drill holes. but they stop much better than plain do especially when wet or hot. i do a lot of breaking everyday commuting 15 miles in about an hour :smt021 . its a stop and go here in the morning. if you are not doing anything crazy where you NEED competition stoping power than getting el cheapo ebay knockoffs isnt bad but if you live in the middle of nowhere and put you car in gear and dont brake till you get wherever you are going than just get plain. i noticed that i have more problems with slider pins and accelerated pad wear more than anything else.

[slaytalera]

unless you live up in the mountains with roads with higher speed limits like i do, you dont need slotted/drilled. i had a standard set of rotors that i warped a couple times in the front, swapped them out with DBA 4000 rotors and i havent had a problem since.

[warrior]

This is upsetting that no one has talked or even touched on resurfacing the hub that the rotor presses up against.

Overtime, there's rust build up between the two said metal bits and a smallest spec of rust can prevent the back side of the rotor pressing firmly and flush on the wheel hub.

Take a wire brush, some sand paper and polish the wheel hub surface to a shine! This will make your new rotor completely flush against the hub and prevent warp.

A lot of brake rotors warp because people are too lazy or uneducated on a simple 5 min task.

Since I've started resurfacing the hub, I've had no rotors warp on me.. even the crappiest made in china ones have survived under extreme braking conditions :grin:

[prodriver1]

This is upsetting that no one has talked or even touched on resurfacing the hub that the rotor presses up against.

Overtime, there's rust build up between the two said metal bits and a smallest spec of rust can prevent the back side of the rotor pressing firmly and flush on the wheel hub.

Take a wire brush, some sand paper and polish the wheel hub surface to a shine! This will make your new rotor completely flush against the hub and prevent warp.

A lot of brake rotors warp because people are too lazy or uneducated on a simple 5 min task.

Since I've started resurfacing the hub, I've had no rotors warp on me.. even the crappiest made in china ones have survived under extreme braking conditions :grin:
i didnt mention because its just what you do when you change them over. i think most everyone knows that:)

[warrior]

i didnt mention because its just what you do when you change them over. i think most everyone knows that:)

You'd be surprised how many people don't know this ;)

[Sarra]

I always bust out the cordless drill and prota-wire-wheel when I do brake jobs.

You should hear the brakes I've got on the WRX. No anti-squeal, and I'm running my old BK's front rotors and brackets. Very loud brakes when they squeal.

Still haven't upgraded my brakes... Mostly due to the engine being on it's way out, I'm not gonna be able to AutoX. :(

[ScaryFatKidGT]

What does cryo treating do exactly? (Like for performance I know what cryo treating is)

So for street it doesn't madder but what about for track? Rotors take most of the heat from braking how can you upgrade them beside just making them larger? Do expensive cross drilled and/or two piece rotors help with fade? It seems like there would be significantly less area to absorb heat.

Also Is there a good sweet spot for rotor size between stopping and unsprung weight? Porsches and Corvettes manage to stop great and have good handling/steering. I remember reading that someone put 05 LGT brakes an a BD/BE and it increased high speed turning force significantly.

[Sarra]

Cryo treating involves cooling the rotors down to ridiculous temperatures, then heating them. It is a form of tempering, changing the molecular structure of the metal, making the bonds stronger between atoms. Basically, it helps them last longer.

Brake fade is typically caused by outgassing brake pads, bad brake fluid, or brake fluid with a boiling point that is too low.

To combat brake fade, you would want to run ceramic pads, composite pads, or metallic pads, and get the highest quality DOT3 brake fluid and bleed your brakes. Water boils at 100 degrees C, but you can get brake fluid that boils much hotter. Over time, moisture gets pulled into the brake fluid, lowering the boiling point of brake fluid.