Rotors, blank, slotted, drilled?
 

I just replaced my brake pads, and got my rotors turned, and found out my front rotors are warped. :(

As you all know (or don't) I Auto cross, Rally cross, and some occasional track days.

Should I stick with Blanks Or go to slotted, drilled, or drilled+Slotted? an explanation would be nice, but i trust the senior seccs members enough to blindly follow at this point. (lemming status has been achieved!)

I've had great luck with the DBA Slotted 1pc rotors. They're somewhat affordable and have held up quite well.

Also, Dean found some discount generic brand rotor that I would try, since they're so cheap, I'll look for the link later.

First off, your rotors do not "warp"- ask Caroll Smith, author of numerous awesome race car/driving information books.
http://www.stoptech.com/tech_info/wp...rakedisk.shtml

Second, I would say plain or slotted- definitely not drilled. Plains is best for autocross, slotted can help at the track, but honestly if you have the right pads it's far from necessary. I have no real argumetns against slots though. The traits I would shop rotors on are vein/venting design, material (good luck getting any har dinfo on their smelting process!) and then price if there are multiple rotors that satisfied me on the other criteria.

Awesome brake info:

http://www.teamscr.com/grmbrakes.htm
http://www.teamscr.com/rotors.htm
http://www.geocities.com/nosro/abs_faq/
http://corner-carvers.com/altimathread.php.html
http://www.scoobymods.com/forums/arc...hp/t-1122.html

And of course... Let's talk about brakes! Best tech thread on this board, hands down.

The turning should have unwarped them if there is such a thing as warped in the first place.

There are an infinite number of references on this.

The short answer is blank, or slotted unless you have a huge need for the additional cooling of drilled and can afford the cheese grater effect on pad life and the tendency for cracking on all but cast in holes.

Slotted will wipe moisture, and pad sluff which is good at minor cost to pad life.

Blank will be cheapest and best pad live.

For your frequent cold/wet use, I would suggest slotted.

Prices on STI rotors are down under $200 for a front set, and under $150 for rears, so it is no longer a super big deal if you don't like them.

*frantically clicks on provided links*

Thanks :)

I like sloted+drilled look nice on the car but I only auto-x no TT and it's still have many hair linecracks. I heard that do not use the e-brake after hot lap it might warp the rear rotors. I just park my car in gear after the hot lap.

I donot turn my rotors just changing the pads.

I think all Subarus use drum brakes (RE: different pads and friction surface) for the E-Brake. I actually bring my car to a stop only with the e-brake when I come off the track.

Some slotted rotors would sure look nice Alex. As long as they aren't much more expensive, I'd get some of those.

I'd suggest using the actual brakes when coming off track.

The "e-brake" is really a *parking brake*... I wouldn't use it while rolling for anything less than an actual emergency. Plus, replacing the shoes in those is a huge PITA.

Yeah, there's nothing wrong with using your discs coming off track. What do you think racecars use? Most have no parking brake system at all. Just try to avoid clamping down on the brakes when the wheels have come to a full stop.

It's just because the R4-S's get a real work out and I don't want them xfering material to the disk and causing pulsing. It's not going to wear out the e-brake pads if I use them to come to a stop from a slow role.

You made it sound like you're using the e-brake on your cool down lap instead of the discs. :lol:

If you say so. ;)

I do really like the look of Drilled & Slotted also.

sounds like some slotted will be great for me , esp with lots of snow driving (hopefully) in my near future :) hopefully i can find a good deal on some . Trying to work with a possible new connection, he was showing a slotted disc for 70$ which makes me think they found the RS or WRX size, as i've had a few car places do already.

Function > Form

+1

lol, I think to own a Subaru, you have to subscribe to that belief. :P

I got a full set of fronts and rears for < $300 shipped to Reno a month or so ago, so $70 / rotor is reasonable...

I try, but it's hard sometimes when I see nothing under my hoodscoop. :(

Try padding it with a rolled up pair of socks.

Did you ever read that thread about the guy that used socks in place of an oil cap in his M3?

Hey, don't get me wrong, MY Subaru is sexy as HELL, but only out of coincidence... :lol:

<wagon comment>

</wagon comment>

So I've got 96K on the car and am still on the original rotors. They don't pulse at all and have never been turned. They do have grooves from normal wear, but nothing crazy and judging by the lip where the pad doesn't contact the rotor, they seem like they have plenty of meat left on them. I wish I had a micrometer. Maybe I should pick one up.

But OEM blanks are only like $125 shipped and I'm about to do new R4-S pads on all 4 corners (well actually, I might go back to the stock pads for the Winter since they have over 50% left). Any reason to consider new rotors for the new pads? Anyone know the min. and OEM Thickness for front and rear rotors?

Min thickness should be stamped or cast into the rotor.

Pick up a cheap digital caliper at Harbor Freight.

If they are not down to minimum, it might be time to turn them to go with the new pads.

$125/pair or each? A pair it is a fair price, each it is a rip-off...

Pair. Okay, thanks. I'm not a big fan of turning rotors though. I can never find a place that does it on the weekends, you end up with less heat sync material, pulsing always comes back, etc, and it's just too much of a hassle when new ones are so inexpensive.

If my rotors are in really good shape with no pulsing and no significant wear, how necessary is it to turn them when replacing street pads? I always have thought it was necessary to at least "break the glaze" but my rotors are in such good shape.

I've gone through a zillion different pad sets, and less than half a zillion rotors. Never turned even one. No issues even going from street to track/autocross pads.

I only turn rotors when they are heavily grained/grooved have uneven pad build up, glazed or surface cracked.

I have gone from full thickness to well below minimum without turning on some vehicles and I'm older than Kevin... :)

Only turn as needed. Having them ground is even better, but I don't think we have a shop with a rotor grinder in Reno, much less most of CA. At one point, my grandfather's shop had the only disc grinder in N. CA and I have no idea where it ended up when he shut down his shop many years ago.

Grinding leaves them with that buttery smooth surface with swirls like they come from the factory.

I love advice that corresponds with what I wanted to hear.

Thanks.

Um, buttery smooth? :lol:

Back to the topic...I had to replace my rotors and pads at 40K and I got Stoptech Slotted Rotors and Hawk pads from JSC Speed and I have abused them like craxy and they have been awesome, no wear at all. Even though you do not cahnge your calipers, the braking power, I would say, is increased by about 50-60% over stock. I would go with that.

Dude, I wouldn't exactly trust calipers from a cheap chinese factory. Granted accuracy isn't that critical with a rotor, but still..

i know napa in carson does it on the weekends, i dunno about the napa up here tho. i would assume that they would.

Yeah, always go for a quality name brand like Mitutoyo...

That'd be rad if NAPA off Panther Valley did it. I need a new tire gauge and possibly some cheap calipers anyway.

None of the Napas in town will turn rotors, they don't have a brake lathe at any of the locations.

Holy crap. +/- .005? That's awful.

Seriously... why bother with .1mm resolution if the instrument is only .2mm accurate. :lol:

An instrument can be repeatable within 0.1mm but only accurate to 0.2mm (or worse). When comparing 2 parts that have the same nominal dimension an instrument is more accurate/useful then if it has to measure something to an absolute accuracy of the same magnitude. In other words that caliper prolly can tell the difference between a part that is 25.0mm and one that is 25.1mm, but you cannot rely on it measuring something 150.0mm accurately within less than 0.2mm. Does that make sense?

No, I get the difference between accuracy and repeatability.

But for a set of calipers, where accuracy is usually the desired trait, why does the display have a .1mm resolution if the instrument is only accurate to .2mm? Shouldn't the last digit always be a multiple of .2mm to give the most accurate measurements?

It's even more pronounced on the inch side - resolution to .001" with accuracy only to .005".

Kinda like I tried to explain, the electro-mechanical system in the instrument can accurately distinguish a movement as small as .001" so that is what they set the resolution to. But the overall accuracy of the instrument, probably due to it's length and maybe it's user-zeroing method and user-thumb-pressure-dependent measurement method, is only good for +/-.005". For some instruments the accuracy is spec'd as a per-length spec - like .001"/inch.

WTF???

There are some EBC dimpled and slotted on eBay right now, also for sale by a Nasioc member. Ill see if i can find you the link, I may be wrong, but I dont think the dimpled ones have an issue with cracking.

They might not crack, but they're the most godawful annoying "WHIRRRRRRRRRRRRRRRR" you've ever heard in your life. Stay away from dimples on a dd.

Apparently a couple of the Kragen's in town will, but meh.

What do you guys think about these? http://www.tirerack.com/brakes/brake...r=&perfCode=A# (Hope the link works, LMK if not)

They're only $5 more than the Brembo blanks but they're supposedly "cryo treated". I also like that they've got a nice black coating.

Would spending twice as much on rotors that have a Left and a Right side be worthwhile? I imagine the veins in the middle can then be made to be directional or something?

Directional rotors cool better, but unless you are going to the track regularly, you won't notice. Spend the extra on the RCE brake ducts instead.

Those look OK. Most any coating will come off once really heat cycled, but nothing wrong with Cryo and probably worth $5.

I just wish I knew if that brand was good or not. I hate to steer away from OEM when I've been so impressed with the stockers. But I'm going to be ordering some rotors and pads for my GF's Civic so I thought I'd just get it all from Tire Rack.

Cast steel is mostly cast steel... All rotors come out of one of about 5 factories in China, Italy, Japan or I can't remember where. Company X buys those blanks, does the finishing and sells them.

There really is no magic in the OEM replacement rotors market. Subaru OEM rotors are as likely to come out of the same batch as these or any other OEM size.

Ground rotors are about as good and flat as you can get because if properly done, they are equally loaded while being "turned", so the material is not stressed or bent while being machined.

Cryo has shown a minor improvement in wear, but only if done slowly. Flash Cryo has not been shown to have significant benefit that I am aware of.

As I said, there is basically no low cost coating that can handle brake temperatures, so they will only look nice until you use them hard and then they will rust like every other steel rotor in the universe.

Since for the most part, "warping" doesn't actually exist, it is pad build up, so just be sure to bed your rotors properly.

So.... BUY THE CHEAPEST DAMN ROTORS YOU CAN FIND and don't pay more than $5-10/rotor for cryo if you really feel like it.

Thanks Dean. That makes me feel better about trying them.

They're on the way: