Power-slot rotor questions.

[AtomicDog]

All,

I had a rather scary experience the other day. Drove through some standing water immediately prior to being cut off at a tollbooth. Had the civic driver checked his rear view mirror, I'd have known I wasn't in New Jersey...

Long story condensed: applied brakes, nothing happened for the first three or four seconds. After what must have been an eternity, the car began to slow begrudgingly. I have read several posts regarding this quirk on the board, so I will begin with the disclaimers.

To my standards, the brakes are adequate - unless they are wet. When soaked, they are past useless and well into nonexistent. I have checked out the system, and know that I am due for some work in the near future. I have stock backing plates installed, and have flushed the system recently.

Finally, the question -

Has anyone used the power slot rotors? I am leaning toward the cryo-tempered version, since metals are sort of a hobby of mine, and I know how it improves the wear characteristics by reducing grain size, blah blah. Without a doubt, I will not buy cross-drilled rotors, so it comes down to plain Zimmerman or Power slot (cryo or standard).

If your mileage has varied, please share.

TIA,

Chris

[MattAlpha]

Why will you not go with cross-drilled rotors?

They should stop you better when they are wet better than plain ventilated or slotted rotors.

-Matt

[Bill Verburg]

That is one area where slotted and drilled rotors shine, since there are no good drilled options for your car slotted would be the way to go.

[AtomicDog]

Matt,

Every place there is a hole, water can leave. The downside, is that a brake pad can't grip there, either. In short, the same size rotor with holes is not really the same size rotor after all.

Bill might say that the drilled rotor has less thermal mass, which is bad. They are also lighter, reducing unsprung weight, which is good. They are prone to cracking.



Bill,

Am I glad you're here!

Carrera brakes - where to begin? Following your advice, and that of others who are wise in the ways of braking, I want to optimize the system, rather than replace it with the biggest thing I can fit.

Have you had any experience with the cryo-tempered rotors? They are twice the price, but should last at least twice as long with the proper pad selection, no?

I've been looking at Hawk HPS and Ferodo. The red box Mintex that Steve likes have a few significant dissenters, and the Pagid orange (4-2?) are just too much $$$. Metal-masters are a decent value too, I suppose.

I drive my car daily. I don't care about noise or dust, but I want the rotors to last for awhile. Assertive driving is really my thing, but I would like to try a DE soon.

I will probably add the backing plates and air deflectors for a ducted cooling system, but will save the scoops and hoses for that DE later. Your thoughts?

Chris

[Bill Verburg]

cryo-tempered rotors

Pseudo science/ B.S.

I have never used Ferodo, gotta take STeve W's word for them

I had good luck for agressive street w/ Repco Metalmasters, now sold as Axxis or PBR Metalmasters, and Pagid Blue for track use get something w/ a higher temp. range.

Get as much cooling as you can.

Use only fresh high temp brake fluid

[AtomicDog]

Bill,

Why throw the BS flag on cryo? On a cast part, it reduces the grain size. I will not bore everyone else with the basis, but the wear rate reduction on industrial tooling is fairly well documented.

Chris

[Bill Verburg]

It's your $, IMO BS. I wouldn't waste a penny on it.

[glenncof]

I have some Hawk HPS on the front of a '85 and really like them and they are not even ceramic.

I am using Zimmerman cross drilled with them.

[zipinitaly]

I put Ferodo's w/power slots on my SC and love them...don't drive my car in the rain, so wet performance is unknown.

[BertBeagle]

Originally posted by AtomicDog
Bill,

Why throw the BS flag on cryo? On a cast part, it reduces the grain size. I will not bore everyone else with the basis, but the wear rate reduction on industrial tooling is fairly well documented.

Chris

For my two cents worth I agree with Bill on cryo. I am in the brake testing business and did extensive work with cryo rotors some years ago. I have sent out rotors to many different companies doing the cryo work and have, for a short while, owned one of the machines (did not get it for brake components). I have tested them for Brembo (I am a Brembo dealer and have two brake dynamometers) and others. Brembo has tested them at their facility in Italy. In short, I believe I have done more qualified testing, both on dyno and at race tracks with professional teams than possibly anyone. I can say without question that the process does nothing, for a rotor used in racing, to extend life or improve stopping. Brembo came to the same conclusion from their testing.

Many of the companies that sell / promote the service swear by it for fleet vehicles. I have not tested in that area and do not have first had information. But I think, for cast iron, it is pretty much ineffective. Many of the people in the cryo business also recommend doing the pads as well - that is where the snake oil really starts to seep into the picture. People in the cryo business tend to find a way to show positive results on anything you want to throw in their tank - another sure sign of snake oil presence.

The process does enhance performance of cutting tools and inserts, drills, etc. and many plants have inhouse cryo treatment for that purpose.

Match shooters also like it. I know a guy who has been a national champion and says that the process will not improve the accuracy of a rifle barrel but will increase the life in match competition.

All cryo testing results that you get form the companies in the business seem to be subjective – and a little slippery.

[Craig 930 RS]

Cryo = crap.
2 pro race teams crew chiefs - friends - at Daytona think they are a crock.

Back to the original post - Do you still have the water shields up front?
Very bad for track use, but keeps thee water off......

[wastintime]

my .02 cents... cryo rotors are worth their weight in gold. I look at it as how many race track laps I can get out of a set of frozen rotors vs. oem rotors... it's usually about 3 times as many laps for cross-drilled, 5 times as many for slotted. I absoutely swear by frozen rotors.

having run slotted, drilled, stock rotors on race cars, I think slotted rotors are great, we run them on the WRX, you don't have to worry about the cracking associated with drilled, but get most of the performance gains of not trapping gasses or water.

[Craig 930 RS]

Chances are the rotors are different - different mfgr, something different. But........if it happens to work for *you*, stick with it.

Slotted are by far the best. Big reds on drilled with track use = grooving from the differentiation of friction from gasses escaped, vs. non. BIG grooves.

My 930:


Daytona 24 hr guys? Slotted.
Pics I took in Daytona:

[911pcars]

TransAm Jag front brake @ LBGP. Point and squirt course. Slotted.



Sherwood

[BertBeagle]

Originally posted by 911pcars
TransAm Jag front brake @ LBGP. Point and squirt course. Slotted.



Sherwood

The "golve" duct over the rotor on the jag works very well. The placement of the fan is fairly good however better would be to shorten the hose and take out as much bend as possible. The fan, a boat bilge fan, is not very good. Could also be used with a larger duct hose.

Here are some pictures that might interest some.

This is an excellent cooling fan. Available with a brushless motor and two variations of inlet cones. With the right ducting will move over 3 time the air as the rig on the jag.



Here are rotors and pads form the Nextel Cup race at Martinsville - happy hour plus 500 race laps and over 1000 sever brake applications. The rotor finish and pad wear is excellent - good brake ducting. This is one of the hardest brake applications in racing.



Here is what a Martinsville stop looks like with Raybestos 15A pads. Hawk DTC 70 or Mintex F2R are a better choice.

Here are some of the latest calipers used in NASCAR. They share design features with calipers used in other series. NASCAR experience, because of its severity, is used to improve the calipers in other forms of racing.

One has a diagonal bridge to reduce caliper flex under braking. Another has a duct to move air between the pads and caliper body. The rotors shown are the latest groove design, and I think the best, from Brembo. The rotors are pre-bedded before going to customers and are ready for use. Money spent on dyno bedding rotors is worth more, in my opinion, that cryo. The Martinsville rotors were pre-bedded.

The little two piece intermediate rear, with 30mm and 34mm pistons would make a nice rear for a Porsche with a 304x25mm or 278x24mm rotor.

The last two pictures show a gimmick caliper made by Alcon with thru piston cooling. The piston has a cooling duct through the center with air fed thru form the outside. Each piston has an inner and outer seal. It was also used some in F1. It was not well received for various reasons.

[Craig 930 RS]

Does that Jag fan "blow" or "suck"?

The principle behind the vanes would say that air enters through the center of the rotor and exits out the vanes. (?)

[911pcars]

"Does that Jag fan "blow" or "suck"?"

Craig,
Haven't been on the receiving end, but since the inlet is at the front of a 170mph max. track car, I'd say it blows. Which is to say fast cars also need cooling air when they can only go 40 mph.

The large duct feeds most of the cooling air to the eye of the rotor. The smaller ductwork leading to the clamshell housing is to force cooling air on both sides of the rotor and to avoid warpage.

An add'l cooling trick (or necessary addition) are these misting nozzles in the air inlet of the large duct, seen here in a later model sister Jag.



Sherwood

[hcoles]

+1 on if the shields are off the rotors get wet during street driving...
I'm thinking of putting mine back on for the remainder of the rainy season.
-Henry
89 911

[DEAN911]

You guys are all getting away from the original question and suggesting all this great hardware but all of this is not necessary. I made the same mistake you did on my Audi. I put power slot rotors and mintex pads on the car and on a cold and wet winter drive on the highway I almost rear ended an suv. Applied the brakes and traveled 50 to 100 feet before anything happened. Did research on Audiworld.com and found all sorts of advice but the bottom line is ..."put it back the way it was". For a daily driver with little or no track time all this fancy hardware is just to make you feel good. I you don't drive the car 10-10's you will never know the difference. The factory OEM parts work very well and do not have any wet braking issues. When I put the Audi back to OEM rotors and pads the wet braking issue went away. Be careful of the MOD'S SICKNESS. It is a real disease.

[BertBeagle]

Originally posted by DEAN911
You guys are all getting away from the original question and suggesting all this great hardware but all of this is not necessary. I made the same mistake you did on my Audi. I put power slot rotors and mintex pads on the car and on a cold and wet winter drive on the highway I almost rear ended an suv. Applied the brakes and traveled 50 to 100 feet before anything happened. Did research on Audiworld.com and found all sorts of advice but the bottom line is ..."put it back the way it was". For a daily driver with little or no track time all this fancy hardware is just to make you feel good. I you don't drive the car 10-10's you will never know the difference. The factory OEM parts work very well and do not have any wet braking issues. When I put the Audi back to OEM rotors and pads the wet braking issue went away. Be careful of the MOD'S SICKNESS. It is a real disease.

I think this is very true. I put oe replacement rotors on my car and used good aftermarket pads (under $20 from Pelican) and I love the performance. I used them at the Pelican at the Dragon event and had no issues running up and down Tail of The Dragon. They are great for even very aggressive street driving - and I have easy access to the best brake hardware available on the planet.

If you are doing some track day driving or upgrading you brake system there is very good advise as well as very bad on Pelican. I thought some might enjoy looking at current hardware. There is frequent discussion on grooved vs drilled and occasionally on cryo and other gimmicks. Grooved rotors will help some in the rain and give better bite in general (at the cost of faster pad wear) however a lot of the stuff discussed is not worth much of anything. There is a tendency that if you buy something outside of your particular field of expertise, you tend to tout your purchase (if only to yourself) as the right part and a good decision. Doesn't matter if it is a brake part, refrigerator, garden tractor etc. Most of the "sport" rotors you see for sale are nothing more than a cheep rotor with drilled holes , zinc plated and put in a colorful box - none of which adds value (accept to the seller) or performance.