Slotted/Drilled Rotors vs Solid (1 Viewer)

The topic of swapping out the OEM solid rotors for slotted and/or cross-drilled rotors has come up here a number of times. Often, one of the stated reasons for not going to drilled rotors is because of stones getting caught up in the holes. I came across this thread which discusses the topic in nauseating detail and in a nauseating way, but the info it good. Thought it might be of interest:

http://corner-carvers.com/altimathread.php.html

If you don't care to go thru an endless stream of rantings and arguing, the gist is that the slotted/cross drilled rotors are bling (you can leave high-end ceramic rotors and pads out since they're talking about cast rotors; besides, we can't get ceramic rotors for the 80). Cross-drilling (as well as slotting) in any way, weakens the rotor with the possibility of catastrophic failure increasing under heavy load/useage, though for DD use, it may not make much difference. The thread also serves to remind how civil this board is compared to many others...

Lots more discussion and accusation in the thread on the physics and engineering. Bottom line is that if we really want to improve the braking significantly on our 80's, we'd have to go to larger rotors/pads.

F* that is a long thread, did you read all of that? takes a long time just to schroll though.

Thanks for the readers digest version.

I too could only make it through a fraction of that post and agree with your overall assessment except for one thing... slotted rotors do serve a purpose as opposed to being just 'bling'. So why don't car mfr's put them on in general? Liability and long life. Agreed that if not done right, it can be the starting point of a stress fracture. Thats the same reason they can't be turned (broken bits/damage). The general population want reliability and long life which simply begs the mfr's for 'middle of the road' compromises.

So if larger diameter rotors and greater surface area pads are the answer to being able to stop on a dime, why not just make the rotor dia. just under the overall tire size?
Answer: Driver feel, ability, and PREDICTABILITY.
Can you imagine being able to stop your LC in less than (lets say) 60 feet from 60mph? If not for abs, everyone would be locking up the tires. What if you were driving in rain or snow? What if you panic stopped while an F350 was behind you (with or without a trailer). What if a Pinto was between you two? WHAT IF your toddler wasn't strapped in a seatbelt? btw - shame on you if thats ever true

Yes my friends, mankind does not deserve nor could handle the sheer, awesome braking power of that magnitude. We would end up killing ourselves leaving the monkeys and dinosaurs to inherit the earth once again.

WET

I do come from a bit of an auto-x background, and slotted, drilled rotors are great for braking performance, IF they are CAST that way. Taking a simple Brembo blank and drilling it will create weak spots. The only good cross-drilled rotor is cross-drilled from inception, not by someone later on down the road.

PS, I believe all DBA rotors are cast with the holes, as opposed to drilled later.

the other thing is.....

it's a one use rotor. they cannot be turned on a brake lathe. the holes in the rotor will break the lathe bit.

Curiosity only... do the high-end performance cars (Mercedes, Ferarri, Porsche, ... ) come from the factory in 2005 with slotted, or drilled, or solid rotors?

-B-

B, i just looked at a ferarri today at the local "way to expensive for me" car lot. They were drilled, but not slotted. But just to add, i know that the other day at the race shop, i noticed the toyota tundra craftsman truck rotors were slotted and not drilled. hmmmm....

I have all 4 drilled Brembo rotors, in terms of cooling down i dont see any difference between stock OEM VS Drilled but one thing pain in da as... when you need them to resurface it, because not many machine shop willingness to cut them.
im interested slee drilled rotors-http://www.sleeoffroad.com/products/products_drivetrain_main.htm

2badfjs said:

it's a one use rotor. they cannot be turned on a brake lathe. the holes in the rotor will break the lathe bit.

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NOT...Sorry 2badfjs someone has given you bad info. I recently turned my drilled and slotted rotors with no issues. Also DBA endorses turning of there drilled and slotted rotors.

high end vehicles use carbon fiber ceramic composite rotors (drilled) for weight reduction and high performance braking.

Porsche website has a movie clip of their brake system. kinda cool

http://www2.us.porsche.com/pccb/default.asp?market=PCNA

WET

concretejungle said:

B, i just looked at a ferarri today at the local "way to expensive for me" car lot. They were drilled, but not slotted. But just to add, i know that the other day at the race shop, i noticed the toyota tundra craftsman truck rotors were slotted and not drilled. hmmmm....

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Concrete below is a copy of a previous post of mine on the subject of slots and holes.



Several months ago I contacted DBA tech about some questions I had on my rotors. When Al Colebank of DBAUSA contacted me he understood my braking issues partly because he personally drive a very heavy turbocharged 1995 FZJ80. When I ask about turning the rotors he said no problem but use a fine cut. What about cracking – he said that it should not be a problem with DBA drilled rotors because they dissipate the heat. He also said that drilled rotors would not stop your vehicle faster and that all DBA drilled rotors offer is reduced mass, heat dissipation, gold color and a performance look (aka bling). The slots on the other hand will help you stop quicker. The slots deglaze your pads. I then asked about pads and he said PBR ceramic pads are what he is going with

concretejungle said:

B, i just looked at a ferarri today at the local "way to expensive for me" car lot. They were drilled, but not slotted. But just to add, i know that the other day at the race shop, i noticed the toyota tundra craftsman truck rotors were slotted and not drilled. hmmmm....

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I don't think you'll find any race team that will use "drilled rotors." As stated above, "drilled" rotors are actually cast not drilled into a solid rotor. As the above link states, "drilled rotors" are to provied cooling. However, sloted rotors are not entierly meant to just clean pad material when braking. There is a gas build up between pad and rotor under braking. The slots dissapate this gas as the rotor turns, keeping the pad in contact with the rotor. Now about cooling.....every race preped car will have a intake and vent system to cool the brakes. There is no need to use "drilled rotors."
"Drilled" rotors are good for performace street cars because of their improved cooling and street cars do not have an intake systme that directs cool air on the brakes. Both "drilled" and sloted rotors are not able to be turned and are intended to be replace after so many race hours, or miles....now that is hard to define in a stree driven car.
Bottom line, if you want good brakes use upgraded calipers (the more pistons the better) rotors can only do so much alone.

Now for my 2 cents....I have cracked brembo cross drilled rotors on my supra twice! I now use TRD japan sloted rotors and have had no problems. Between the two types I can't tell a difference, on a the street or track.

Here is a thread to reference. I aint gots no mo arguement left in me so I'll reference past arguements!

https://forum.ih8mud.com/showthread.php?t=16245&page=1&highlight=DBA

Some personal experiences since then...

Two weekends ago while i was out snow running with some fellow Toyota friends I got my ass stuck, really stuck, on an extremely loose sidehill made out of small loose granite gravel. As always its a long story but the short story is i yielded to someone and slipped sorta sideways off the trail and onto steeper and steeper sidehills. Picture a skinny and slightly flat section cut into the side of a steep loose hill, that was the 'trail'. Ohh I forgot, on top of the trail was 14" minimally of snow! At first I was parallel to the trail with the right wheels hanging onto the outermost edge and the left wheels well off the trail and digging deep down. But then as I progressed, the truck slipped more and more sideways and ass first further onto the steep loose sidehill. Basically after lots of angled advances of a few feet, I got myself perpendicular to the trail which was both the most safe and most stuck way to be!!!

Anyway, to my point, I got back to the trail after about 55 minutes of clawing and chewing up all the snow as well as the top ten inches or so of loose granite gravel. I absolutely could not back up so I had to advance, chew up crap, level it little between the front and rear wheels and then claw and chew some more. I was scared about the brakes cause the bottom half of the wheels on the inside were filled, absolutely filled with loose gravel granite. There was nothing practicle to do to scoop it all out before going further and even if i did within seconds the things would be full again so fawk it. I even mentioned to my friends that I'd likely be calling Slee for some new slotted only rotors the next day! Folks for 55 minutes of stop and level and go my entire bottom half of the wheels were absolutely full of crap, they sounded like gemstone tumblers, i could see gravel pouring out of the holes in the wheels, i could hear it flinging all inside the wheel wells. The insides of the rim were scoured clean and even the outside clear coat was ground down on the bead area! After all that, not one single little stone got stuck in any hole on any rotor! Now, maybe that's luck, maybe that's just the fact that to get a stone stuck in such a way that it would not just get glanced out by the pad is like one in a million or something. Who knows, its just another data point and nothing else. HTH.

one more thing I didn't add was having any type of rotor cryo treated will give you great results. This is not cheap though, you could buy sets and sets of rotors for one set of cryo treated rotors.

RavenTai said:

F* that is a long thread, did you read all of that? takes a long time just to schroll though.

Thanks for the readers digest version.

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Unfortunately...yes. It was painful, but I kept being drawn back to the drama of it all. It was ultimately unrewarding.

But like I said, it was interesting from an engineering perspective. I'm not taking any sides here other than drawing my own conclusions, but thought the board would enjoy another stab at this topic. Previous threads I've seen have dealt with the whole thing from only one or two angles.


Tubo: not disagreeing with you. I personally think it's unlikely that you'll "find" the right stone to get into those holes. I think it's more of a theoretical problem. The slotting is a potential winner, but I'd want to know more about how much quicker the pads would wear with those rotors.

My own view is that: a) given that our rotors have an inherent tendency to warp, we are possibly running rotors of a minimal size (i.e., they tend to get very hot under certain circumstances (e.g., hard braking or towing); little reserve capacity); b) running the 100 series pads may help braking, but will likely be a tad harder on rotors due to generation of more heat--I'd be curious to know if those running 100 pad have seen "more" warpage? Probably too few data points to know.

hmm these two shots are enough for me to stay with solid rotors.




it is pretty obvios that these cracks are coming from from the stress risers caused by the slots and holes,

Raven, what type of rotors are those? I have nothing even near to that on my rotors. I cannot imagine that those are DBA's?

I don’t know what brand they are, both pics are from that long thread linked at the top of this one,

For the most part (in least in automotive) a hole in a piece of metal is a hole in a piece of metal. And will induce stress no matter how much you paid for it, at work I see a lot of similar looking stress cracks in much more expensive parts then you would ever pay for a rotor, they almost always start at a odd shape in the edge of a part or at a hole, the third place you will see them is where a part bend's repeatedly

RavenTai said:

I dont know what brand they are, both pics are from that long thread linked at the top of this one,

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Ahh s***, I thought they were on two of your vehicles! Phew!!! Those rotors looked terrible but think about them as abused, or accidental or defective or whatever. IOW unless these things happen to the DBA rotors (which I think is the only other rotor of choice aside from OEM) then its not an apples to apples comparison.

As mentioned above, the DBA's are awesome rotors, the holes are cast in place, the slots (i think) are machined into place, they are turnable although I probably would not turn em, some of the recent revisions even have temp sensitive paint that instantly tells the highest temp the rotor ever got to.

All I'm saying is that I tried comparing my 80's braking in many situations against my father's stock, highly maintained 80 and time after time the DBA setup is superior. Even he agrees so its not an argument at least from him.

I think some of the conclusions from the other thread were that rotors are crossdrilled for two reasons - less rotational weight=less energy to stop and - crossdrilling assists with venting and dissipation of heat in the rotor. I think its safe to say the first reason is almost meaningless with our 80's; when your tire weighs 50plus pounds, it does not matter much if you shave a few grams off the rotors by having it drilled. I also think its safe to say that the second reason does make a major difference in an 80; that's alot of mass to stop, it takes a lot of frictional energy to do that, friction energy morphs to heat, and any amount of extra heat dissipation is sure to help total performance as well as total reliability of brake components.

The slots are to softly scuff the pads clean and assist venting of brake dust, brake gas, from what I was able to understand. Also from what I understand the slots, more than the holes help the braking performance on rotors of regular operating temps - the holes help get rid of the heat but not so much help the braking power, other than what braking power is lost with overheated rotors. Who the hell knows maybe I got it all back asswards?

Anyway my first message here was simply that in the worst of conditions that might cause a stone to stick in a hole, I did not experience that problem. Maybe luck, maybe not. Also, although I have not compared a DBA slotted only setup, I can promise anyone here that the DBA s&d rotors add an extra amount of performance over the OEM setup. Next time that I purchase replacement rotors I think I'll get the slotted only DBA's just for comparison again.

I'd like to ask if anyone here has actually had a problem with a stone getting stuck and causing damage? I read one post about mud getting in the hole and drying but has anyone here had a DBA go bad for any reason other than long term wear and tear? Just curiosity but it would be good data to have. Thanks.

Nope not mine, I am sitting on new OEM rears and PO installed Midas fronts that that I just noticed a few days ago are mildly warped I have had a few panic stops lately, the worst being a deer I was sure I was going to hit but missed it by inches ~70->5 MPH stop. already have 2 dead deer under my belt dont need any more, they are expensive.

looks like I will be shopping for new rotors by summertime? Put 100 series pads on last summer about 15K ago, will probably wait until those go and get rotors pads and caliper rebuild kits do it all at once.