I need ROTORS: Slotted vs. Drilled vs. OEM ?????

textar is more common...all the dealerships i have checked at here in Toronto sell textar as the oem part

Originally Posted by Erick Sermon

textar is more common...all the dealerships i have checked at here in Toronto sell textar as the oem part

That's some interesting info. I wonder to what extent their is regional variation in what's stocked as "OEM". For example, I don't recall ever seeing the Textar brand sold or advertised in the states.

It might be a branding thing. Textar is part of TMD Friction which also markets the Pagid and Mintex brands. But I'm also not sure I've ever seen either of those two brands on a rotor, just on pads.

In the belief that if something is worth doing, it is worth doing obsessive-compulsively, I've been reading up on rotor design and metallurgy.

In regards to distinguishing a higher quality rotor from a lower quality one, here's some things I've learned:

* curved vanes and pillar vanes are about 20%+ more efficient at shedding heat than straight vanes

* a higher carbon content in the rotors is good since it heats it transfer heat faster and also inhibits crack propogation

* alloys are good, especially with the higher carbon content rotors. Some of the main interesting ones are
** molybdenum helps maintain strength, improves resistance to heat cracking and signifigantly increases thermal capacity
** copper increases strength, has marginal benefit on corrosion resistance, and moderately increases thermal capacity
** chromium also helps maintain strength and improves resistance to heat cracking, but can decrease thermal capacity
** nickel has similar properties to copper
** titanium - increases the coefficient of friction, but this can result in accelerated wear and lower overall performance

As a couple reference points, the main alloying elements in OEM BMW rotors are chromium and copper. The higher end rotors also tend to have a higher carbon content. In comparison, Porsche rotors tend to be high carbon with chromium, copper, and also molydenum.

Of course, when comparing your various rotor options, you'll likely have a hard time finding out too much about the metallurgy. But in the case that you do, you can now have a better idea of what it all means.

what a thoroughly enjoyable thread. i actually have a minor in metallurgy and took extensive coursework in casting and foundry technique's.

the concept of making perforated holes is possible however not functional with mass production casting methods. an example of what i'm refering to is rather basic and overly meticulous type of casting method. what we would do is make a sand casted object(for hypothetical sake lets say a perforated vented brake rotor) using a plastic(styrofoam) mold(so at this point we have a circle of swiss cheese looking plastic) obviously twice as this is a vented rotor . then we would make the actual "slats"(i believe this is the correct terminoligy) that would go inbetween (once again styrofoam) and glue or bond them inbetween so now we have a plastic perforated vented rotor( once again out of styrofoam but their are other mediums used such as wax) at this point you would place it in a casting block and pack in sand(technically on both ends surronding the mold) making a pouring font in the process (for me more specifics, please google sand casting). with the pouring mount completed and ready we pour the molten material (be it a metal or alloy metal) into the casting and let it solidify. we'd remove it by cutting or otherwise remove the pouring mount and tada we would now have us a metal perforated vented rotor (2 words: tongue twisted go ahead try it as many times as you can lol). i have kind of left out some nit pick details but this is the basics of it. obviously making this plastic doppleganger of the desired product is extremely time consuming and is probably not cost effective. hopefully this makes sense to some people maybe if you do google sand casting it will make more sense at that point.

some slight disclaimer
1)this is a very very basic method of casting and has several possible defects that could result and effect quality and identical repeatability. such defects as porosity poor grain microstructure or other misc. contaminents can be a result if not careful. not to mention if you make each hole out of place or one bigger then the other etc with the plastic mold.
2)there are several types of sand casting and this is simply one of them , that seems to make the most sense to me to make this particular product in a semi repeatable fashion.
3)ironically enough i do not actually do this for a living at all anymore so please dont send me any request to make this as i do not have the time or means to accomplish this physically or financially.
4)please don't flame me later on if i have missed any important steps in the process as i am trying to keep this as basic as possible for more people to understand their are many more steps to ensure quality when using any casting method.

I honestly really loved this thread. jpr's detail is incredible and is much more convincing. I also have to say, this is one of those few arguments that stay interesting and don't degrade to an annoying series of insults. I applaud(in my head ) both Rob of UUC and jpr for their maturity.

Also, concerning the Carbon ceramic brakes, I believe the might also be drilled. I think they have a two step process where first the some carbon disc is made at a pretty low temperature and is relatively soft (and I believe drilled at this point) and than the disc undergoes a second process where the disc are reheated to an extremely high temperature and infused with silica or something. Sorry, I don't have any backing or accuracy.

My final statement is that cast-hole iron rotors are useless. The gains are zero to none compared to a properly drilled rotor. The issues of hairline cracks in rotors isn't usually of much concern in a high quality rotor because the rotor will probably wear out before the cracks become a safety risk. It's also worth noting that almost any hard material that gets heated to high temperatures exhibits micro fractures. Even the lens of the hubble space telescope had micro fractures in its lens. This really scared the makers of the lens cause they discovered this after spending a few months polishing the lens, haha! Simply put, if want the looks you sacrifice performance, and if you ever use your brakes for more than daily driving, don't get drilled iron rotors.

Thanks for your input and feedback mcr_driver and mkodama!

Here's some links to additional material you might enjoy -

Introduction to Gray Cast Iron Brake Rotor Metallurgy - http://www.sae.org/events/bce/tutorial-ihm.pdf

Development of Disc Brake Rotors for Heavy- and Medium-Duty Trucks with High Thermal Fatigue Strength - http://www.mitsubishi-motors.com/cor...003/15E_06.pdf (among other things, has a nice discussion of surface cracking)

DISA group website - they manufacture many of the core and molding machines used for making rotors and there's some interesting in-process pictures - http://www.disagroup.com/eng/product...9/article.aspx

The Effect of Rotor Crossdrilling on Brake Performance - http://forum.e46fanatics.com/showthread.php?t=500950

There's no such thing as warped rotors - http://forum.e46fanatics.com/showthread.php?t=402902

Awesome thread everyone, thanks for the great info

omg that first link was a flash back to my classes lol i can't believe i actually still remember the iron carbide diagram. someone should find a multi alloy phase diagram.

on a side note as i was reading the link on "warped rotors" i had a thought pop into my head. is there anyway to de-bed a rotor? like say i'm using on kind of pad and change to a different one would i have to re-bed that pad of is there some other process besides changing the rotor as well?? or this is just a dumb question lol

I have a full stoptech II package with slotted and axxis ultimates. I love it, esspecially with the SS brake lines. Buy that.

OMG I just read this entire thread. doing research and got sucked in!!!

drilled....no slotted

Originally Posted by vids_blk323Ci

OMG I just read this entire thread. doing research and got sucked in!!!

haha, me too... I just kept reading and reading and getting sucked in! I was thinking of what I wanted to put on the M3 next and I think I'll go with slotted instead of drilled since I want the pads (and wear sensors) to last longer. What's the difference in performance between SS brake lines and the ones that came with the car? Do brake lines really need to be replaced or significantly alter performance? I've never thought of replacing them.

How ofter should calipers be replaced? I would probably replace those before the brake lines, or maybe both at the same time. Calipers are expensive to replace though.

All the info in this thread was so helpful!! I think I'll go with rotors from UUC next time... not sure if I want the SS lines or Hawk pads too, we'll see. How do Hawk and Pagid pads compare?

So basically, in a nutshell.
Slotted- Better for track use.
Drilled-Good for daily driving, not recommended for track?

Anyone have a pic of worn down slotted rotors? I can't imagine what they would look like if they indicate wear?

Well Said .. Thanks for your post ... I was Up in the Air about what to get with my E46 ..In the Past with my E39 i Always went with Blank ATE Or Zimmerman Rotors -- and Wagner Thermoquiet Pads and Never Ever had Problems ... So With My e46 I was Thinking of getting The Pretty Cross drilled rotors ...Since I Drive The Car Like a old man most of the time I rarely heat up the brakes .. i always thought the OEM setup was great to begin with ... Thanks again For your insight.
Willie

what you guys think of this?

http://www.ecstuning.com/BMW-E46-325...ors/ES2190216/

Depending on what car you have the slotted will most likely just be for show. I found a nice set of slotted and drilled that I put on the car. It doesn't go nearly as fast so the rotors are for bragging rights lol.

It will be mostly for daily driving. Depending on slotted and drilled, aren't they supposed to be as good as for breaking than the plain ones?

Mine currently are slotted StopTechs. Had them for two years now with axxis pads. Couldn't be happier with my brake setup now. They still look good and have a smooth surface. Car stops perfectly. Good for daily or track.

Previous vehicle, I had crossdrilled Brembos with kevlar greenstuff pads, the pads lasted me 4 months and the rotors had grooves and micro cracks all over it. They were good for track, but to noisy for street.

ouch. Thanks for the quick update.

Originally Posted by Wickedly

what you guys think of this?

http://www.ecstuning.com/BMW-E46-325...ors/ES2190216/

Absolutley no point to cross drilled/slotted rotors on the E46, aside from looks.

You will actually brake worse, and have less pad to disc contact.