DamonB

Some people use cadmium ("cad plated") rather than zinc for the same result. High temp paint has worked well for me

maxcooper

I had some stock-sized rotors cryo-treated. They seemed to hold up much better to the abuse I was giving them than the two sets I had destroyed in the year or two before that. I think I used them for 2 years or so before switching to a big brake kit (they were starting to crack, but had already lasted much longer than the previous two sets). All of the rotors were the same Brembo solid-faced jobs. I don't know how cryo works, but it did seem to make my rotors last longer (before heat-checking or becoming grooved). I have no idea if the temps were different (but I doubt it).

Good brakes feel better. Lots of cars have brakes that feel like crap (even when new). Replacing old lines with stainless, getting some new rotors and pads, flushing the fluid, and bleeding the air out all improve the condition of your brake system. If you've got lousy pads, decrepit lines, nasty fluid, and warped rotors, replacing all that junk is going to improve the feel of your brakes, even if it doesn't decrease your minimum stopping distance.

I bet my car can pull about the same skidpad numbers with loose tie-rods, but it sure isn't going to feel the same. Part of the driving experience doesn't show up on the magazine test numbers. Brake feel is one of those things, and it definitely worth your attention even if it wouldn't change your stopping distances. Don't kid yourself about having super-brakes, but if they feel better after you put a little work into them, that might be a reasonable reward for your money and efforts.

Slots and holes are mainly just for looks, IMO, but getting a bunch of new parts in there should make your brakes feel better. The brake lines aren't very visible, but I guess they might look good in someone's mod-list signature. SS lines do seem to improve the pedal feel, IMO, which means they have some real value to me.

My daily driver got a new master cylinder, decent touring pads, rear rotors, some ATE Super Blue, and a power bleed and its brakes never felt better. I might even throw some SS lines on there and try some more aggressive pads the next time. Good brakes are fun.

-Max

Dyre

Everything Damon has said about brakes is 100% correct. If you choose not to believe him it's your fault at this point.

Thank you for saving me the trouble of typing the exact same thing Damon-

EDIT: On edit, BREMBO DOES NOT OFFER DRILLED OR SLOTTED OEM REPLACEMENT ROTORS! Just warning those of you buying these off ebay and other vendors- They are machined by someone else who buys them from Brembo and re-sales them.

theloudroom

He's offered no proof about drilled rotors performance in wet conditions, other than saying "rotors are hot". That's hardly a definitive answer.

He could be right, but IMO he's just guessing. I've heard various unverifyable statements that Porsche claims cross-drilled rotors improve wet-braking. Why is Porsche using them if they are an absolute performance disadvantage?

If he can offer a more substantial response than "no" he might settle the question, but if "no" and a bunch of unrealted quotes about brake pads outgassing and durability are all he can muster, then the question still remains.

Every thread like this that I've ever seen is the same. A whole bunch of people quoting other people and putting forth a bunch of anedotal evidence. Everyone has a REALLY strong opinion on the subject without having an equally strong a grasp of the subject.

If you wanted to be able to authoritatively say "no" you should be able to provide an authoritative explanation to back it up.

I'm harldy claiming to be an authority on this subject, but I'd like to provide what knowledge I can towards a real, scientific exploration of this. I'd like to look at things like "How fast will a drop of water vaporize on a 500 deg F piece of metal? Is it fast enough?"

I'm not interested just in minimum stopping distance, I'm also interested in the performance of the rotors by themselves.

There are a lot of things to consider here. Sure the pad will scrape off most of a drop of water, but how much doesn't get scraped off? If the rotor and the pad were perfectly flat it would be zero, but they aren't. Anybody have some numbers?

Once you admit that there's a possibility of a certain amount of water getting inbetween the pad and the rotor, you should consider what effects that might have. At room temp. it would provide a lubricating effect. At higher temps, you're going to have water changing phase while it's in between the pad and the rotor. This would result in steam, this steam is going to be under pressure and the harder it is for this steam to escape the more trouble the steam is going to cause you.

rynberg

He said this:

quote:
--------------------------------------------------------------------------------
Originally posted by theloudroom
"Do crossdrilled rotors perform better in wet conditions?"
--------------------------------------------------------------------------------
No. Even if they did the point is entirely and completely moot. If the rotors are getting doused with that much water then the tires and road are also wet. The following bold italics added for emphasis: The grip of the tire in the wet will degrade much more rapidly than the "grip" between the pads and a wet brake rotor. This means that some how an improvement in rotor performance in the wet is useless as the tire has less grip in the wet. If you can come up with examples of the brakes being completely doused in water while the tire and road are dry, I'm all ears.


Damn Damon, a Gun's N Rose's lyric come to mind..."sometimes I feel like I'm beating a dead horse..."

maxcooper

Bigger rotors with holes might be fine for heavy use on the FD. But many of us have seen the effects of using cross-drilled, stock-sized rotors on the FD at the track. They crack up, quickly. That doesn't mean that a 14x1.25" rotor with holes would crack, but if we are talking about stock-sized rotors used for track events on the FD, I feel fairly confident is saying that they don't work well.

Porsche (reportedly) uses rotors with cast-in holes, and that combined with also using larger rotors may explain why Porsche cars have holes in their rotors without having lots of problems with cracking. They may have chosen to use holes for a number of reasons, including aesthetics, weight, and possibly some braking performance reason. But it isn't clear that braking performance was the motivation behind adding the holes.

Stock-sized, cross-drilled rotors are likely fine for street use on the FD, and I know lots of people that run them on the street with no problems.

I haven't addressed the topic of whether cross-drilling has performance benefits or not, assuming the rotor is big enough to have holes and not crack. I don't really know the answer. But most buyers are considering drilled rotors in the stock size. Anyone seeking maximum braking performance from the stock system should get solid-faced rotors. In the wet, you will be able to go into ABS lock-up easily no matter what rotors are on there, so I don't view that as a significant issue.

I am interested in the theory side of why or why not drilling would have some performance benefits, but for stock-sized rotors the answer is already clear -- they aren't big enough to survive heavy usage with holes, so they shouldn't have holes. If you just use the car on the street and know that you won't ever want to go to the track, get whichever rotors best match your budget and/or aesthetic sensibilities.

-Max

DamonB

If the rotors are getting doused with that much water then the tires and road are also wet. The following bold italics added for emphasis: The grip of the tire in the wet will degrade much more rapidly than the "grip" between the pads and a wet brake rotor. This means that some how an improvement in rotor performance in the wet is useless as the tire has less grip in the wet.


If you can come up with examples of the brakes being completely doused in water while the tire and road are dry, I'm all ears.


I'm claiming that it does not apply to the problem at hand. Please give the explanation of how a siphon spray gun and the drilling of holes through a rotor are relative examples of the same phenomena.

Please answer the above question if you are going to try and make me change my mind. I'm not against changing my mind but you'll have to convince me.


If the rotors are getting doused with that much water then the tires and road are also wet. The following bold italics added for emphasis: The grip of the tire in the wet will degrade much more rapidly than the "grip" between the pads and a wet brake rotor. This means that some how an improvement in rotor performance in the wet is useless as the tire has less grip in the wet.

If you can come up with examples of the brakes being completely doused in water while the tire and road are dry, I'm all ears.


And you think what I'm presenting is imaginitive?

And finally as to the idea of proof please read some of the links I have taken the time to add to our link list. I can assure you that they are not all conspiracy theorists

RX-7 Club Suspension Link List

As for all the websites I quoted above, I didn't bother to copy the URL's. Just take some text from each one, insert it into Google and I'm sure you can find them. As I said earlier don't believe everything you read but do qualify your sources. There's a tremendous amount of "scientific" information here that "proves" we never landed on the moon. Sometimes you have to have some facts under your belt in order to make a good decision.


I'm perfectly fine with you thinking I'm a nut. It's a free country and a free board here. As long as you don't break any forum rules (you have not) you're welcome to share your opinions. None of us will always agree with everyone else. Have a nice day.

theloudroom

I'll agree the tire performance is an issue here, but I'm not really asking about that. I'm interesed in an "all other things being equal" comparison of drilled vs. stock.



Picture a stock brake rotor, with cooling vanes. Imagine it rotating, moving air through the vanes. You'll have these channels, with air flowing through them between each set of vanes.

Enter Bernoulli, who discoved that fluid flowing past a hole creates a vacuum in it. In this case the fluid is air flowing between two cooling vanes, and the hole is one drilled in the faces of the rotor, between those two vanes.



http://www.dynamicscience.com.au/tes...of%20Bernoulli's%20law%20spray%20gun.htm



I don't think you're a nut, and I actually respect your opinion, but you're just not backing it up adequately for me. I'm not suggesting everyone go out and buy crossdrilled rotors for their car, I'm interested in this in a more theoretical sense. The real-world durability issues with an actually drilled rotor seem to outweigh the benefits. I'm not so sure that there can never be any benefit though, when done right. I have yet to see a FWD Porsche, so I'm not quite ready to believe that they've lost their minds.

Then again, they are building an SUV.....

DamonB

The air inside the vanes will be under some pressure due to the ram air effect of the ducting and/or pumping effect provided by the vanes. Given that the holes are so "short" through the rotor I don't think you're going to get a vacuum there that will suck more air into the vanes. If anything the air inside the vanes would leak out before it got to the outer circumference of the rotor.

Porsche needs the money. Selling trucks gets them that.

theloudroom

Good point. Then the air flows the other way

Or at least air flows through the hole in some direction.
There may be a "ram air" effect where air is entering the vanes, but there may also be a Bernoulli-type effect where air is exiting (the edge of the rotor is moving pretty quickly). Since flow requires a pressure gradient, I suppose it might matter where you drill the hole.

My line of thinking is that, cross-drilled rotors may or may-not cool faster than non-drilled, but drilling is going affect the airflow and therefore the cooling of the rotor.

(I don't have the background to figure the airflow for both cases, but I'm not willing to believe that there will be no airflow through the holes.)

Someone mentioned difficulty attaching a thermocouple to a brake rotor, what you'd want would be something like this:
http://www.testequity.com/products/1080/
You could put the car up on jackstands, set the cruise, heat up the brakes to a certain temp and see how fast they cool with both types of rotors.
It wouldn't be a perfect test, but if there's a significant difference, you'd probably see it.

Anybody wanna spend a few hundred to shut me up ?

I suppose it's better than John DeLorean's idea. (We need a coke smiley here) I'm not sure how much better though

David Beale

Years ago when "Cycle" magazine was worth reading, they noted that non-drilled rotors didn't start slowing a bike in the wet until the bike had travelled "one wheel circumference". Drilled rotors started slowing the bike immediately. The inference was that the water on the rotor reduced braking to zero until it was swept off. At that time disk brakes were new to bikes (yes, I'm that old). I suppose you could test this with your car as well. I have never noticed this, but I suppose I'm not that brave with the brakes in the wet on my bikes.

Devilish

to answer the original question - YES!!!

Just go out and get some SS brake lines, HP Plus pads for the front, HPS for the rear, and have a shop flush the whole system and put in good fluid that you provide.

I don't think rotors make a big difference.

ditto

Thank you so much needed that