Cryogenic Rotors: Good or Snake Oil?

[jpachard]

All, Has anyone got any experience with cryogenic rotors? I am thinking of going this route but would like to hear from the group if they are worth it. This would be for a track car.

Thanks in advance!

James

[LouZ]

I have them.

Went thru a set of Zimmerman fronts in no time - cracks galore!

IMHO, the cryo's are holding up much, much better with over 20 track days on them. I use PF97's all around, and am quite agressive on the brakes.

[Resident Sicko]

I have used cryo rotors on my S2000 and a few other Honda track cars and have held up quite well. If there is a group buy for new rotors that are cryo treated and cad plated, count me in!

[vincer77]

Cryogenic treatment is scientifically sound.

[bart1]

They should work, but my club president has some hanging on his wall that cracked sooner than stock ones on his GT3RS.

[Lil bastard]

Cryogenic treatment is scientifically sound, but there's a catch... Not all Cryogenic Treatment is the same.

Cryogenic processing changes the crystal structure of the material which can enhance fatigue and abrasion resistance of the material. This change consists of Atoms literally moving and realigning within the Rotor material itself and this process takes a long time.

It involves subjecting the material into extreme cold up to minus 300 deg F. Properly done, this process takes many hours (up to 60 hours) and involves numerous steps to drop down to the desired temperature and bring it back to room temperature. Without this careful process, the rotors may actually underperform non-cryo rotors.

The company/person doing the treatment must be thoroughly versed in the procedure and follow it to the letter!

Maybe the two best Cryo Treatment companies out there are: Controlled Thermal Processing
in Antioch, IL, and Diversified Cryogenics, sold under the name Frozen Rotors. In fact, these would be the only two companies I personally would consider. This is because of their length of service - 25+ years. And the fact that their main markets are Racing and Police/Emergency vehicle applications.

There have been several startup companies over the past few years which do little more than dip them in liquid Nitrogen once and have them shipped within a few hours. These are the greatest Snake Oil scammers since Andy Granatelli and STP.

But realize that the only way to benefit from cryo treating is use the brakes hard. For a daily driver, going 15 miles to the office daily and cooling down for 8 hrs., there is no benefit whatever over standard rotors.

Cheers!

[Matt Monson]

Well put.

[jpachard]

Yes, This will be for a Club Racing application so I might give it a try. Thank you for all the valuable input.

Cheers, James

[Lil bastard]

Originally Posted by jpachard

Yes, This will be for a Club Racing application so I might give it a try. Thank you for all the valuable input.

Cheers, James

That would be a perfect environment to realize the benefit.

But, realize it is no Magic Pill, just an improvement. But, in Racing, every improvement you can get is an advantage.

You'll have greater heat transfer, delaying, but by no means eliminating, Fade.

And you'll get greater wear resistance, possibly offset by greater wear to the pads (depending on the compound you use) - something's gotta give.

Be sure to use a high heat brake fluid that is fresh and that the calipers and Master are in top shape.

Cheers!

[jpachard]

Originally Posted by Lil bastard

That would be a perfect environment to realize the benefit.

But, realize it is no Magic Pill, just an improvement. But, in Racing, every improvement you can get is an advantage.

You'll have greater heat transfer, delaying, but by no means eliminating, Fade.

And you'll get greater wear resistance, possibly offset by greater wear to the pads (depending on the compound you use) - something's gotta give.

Be sure to use a high heat brake fluid that is fresh and that the calipers and Master are in top shape.

Cheers!

Yes, I actually Club Raced for 3 years in an '87 911 so am all up to speed on the fluid maintenance. My 964 is getting converted to a US spec Cup Car so I have the larger brakes on the front. I was at the Glen in October with the stock brakes turning 2:12.8's and just eating through the stock rotors so the brake upgrade will be a welcome change, if for nothing else than to save me some $$ on rotors and pads.

Cheers, James

[Frozenrotors]

For those of you out here, that are questioning as to whether or not you can use Cryo-Treated rotors on the street? The answer, is hands down YES. A vast majority of people purchasing these rotors and pads, drive their vehicles every day. They all benefit from a MUCH LONGER LASTING ROTOR. They are also much more resistant to 'warping'. If you'd like more information, or need a quote, Just give us a call.

Keith
Frozen Rotors - High Performance Brake Pads, Brake Rotors

[chris_seven]

Deep cryogenic processing permanently refines the grain structure of metals at the atomic level. Carbon particles precipitate as carbides into a lattice structure and fill in the microscopic voids. This creates metallurgically improved and stabilized rotors that have a denser, smoother surface. As a result, you reduce heat and wear on brake rotors and pads.

I just don't like this explanation and unlike some of the other posts state I think the science is very dodgy.

Most rotors are manufactured from a Pearlitic Grey Cast Iron and this means that the normal benefits of deep cryopgenic treatment - which is the removal of residual austenite just aren't appropriate.

To say that lower temperatures fills in voids is a bit of a stretch.

One of the most significant dislocations present in the crystal lattice of most metals is a 'vacancy' dislocation and these are mobile and will diffuse in the structure depending on tempertaure. It is possible for the number of mobile vacancies to reduce but the vacancies would need to migrate to regions of high energy within the lattice such as a grain boundary and this action is very unlikely at low temperatures.

Diffusion of atoms in a lattice are usually governed by an Arrhenius Equation which is exponential with respect to temperature.

The creation of a mobile vacancy is generally related to atoms not being correctly positioned within a lattice. The atomic vibrations caused by temperature will mean those unfavourably positioned will move out of the lattice and cause a vacancy.

A metal melts when approximately 7% of its structure is made up of mobile vacancies - this is true for virtually all metals and unless they are superheated they do exhibit significant crystal order just above their melting points.

This simply means that when a metal is cooled down to cryo tempertaures the number of vacancies reduces. When it warms back up again they reappear.

I do not believe that a cryo treatment can 'freeze' the number of vacancies present in a lattice and maintain them as temperature rises and no electron microscopy has ever been presented to prove this point.

"There is also a theory which states that the atom to atom spacing in a crystal structure has an ideal distance where the bond energy is at a minimum. Reducing the temperature allow this spacing to become more even and closer to ideal, creating a better crystal structure."


This is also a problem if we look at the basic physics:

G=H-TS So if the crystal structure is more ideal, there must be a reduction in G.

But there will be no change in H, since there are no reactions occuring at this low temperature, and no change in S (since its still pearlitic iron).

This means that there is no permanent change from lowering T to a small value, then after X time raising it to 293K again.

The statement is made that cryo treatment increases density so that means the rotor must shrink. So how much does the density increase and therefore how much does it shrink? The industry never seems to quantify these remarks or do they all think we won't understand?

Finally carbide precipitation is also bit of a leap of faith. It has been shown that in tool steels Eta carbides can be preciptated following cryo treatment.

The theory is that the solubility of certain solute atoms reduces at low temperatures. Carbides can't form at these temperatures as diffusion is too slow but they do form as temperature rises.

There is good X Ray diffraction evidence that Eta carbides are present it tool steels but these type of carbides are generally not present in cast iron other than as primary carbides which are entirely stable and form during cooling.

There is no X Ray diffraction evidence presented to show that this mechanism exists in grey pearltic cast irons.

To say that carbon particles precipitate as carbides is interesting. For carbon to become a carbide it must combine with another element - usually metallic.
There is never any statement of which carbide is formed. To form a carbide would also mean in general terms that the activation energy needed to form the carbide would have to be supplied and this is not readily available at -300 degF

There are carbides present in Cast irons but they are normally primary carbides and are are formed in the melt and during the early stages of solidification.

My conclusion is that there must be a benefit in cryo treatment of rotors as too many people say they have gained an improvement but the Science is flakey (no pun intended) and like most of these type of processes is a bit over sold.


It is aso a pity that there is little or no published data in terms of wear rate, heat transfer rates etc. The evidence offered is mostly apochryphal and consists of statements such as 'life is three times better etc.

[Flieger]

Chris, can you recommend any good metallurgy texts for me? I am a Mechanical Engineering major but I do not know if I get credit for metallurgy classes, if they exist here at Cal Poly SLO. I may not be able to take them as elective classes due to chemistry pre-requisits (sp?). I am still very interested in the subject. I always found metallurgy and even minerology to be the interesting parts of chemistry, and very relevent to mechanical design.

[chris_seven]

Max,

I hope these two may keep you occupied for a short while.

Physical Metallurgy and Advanced Materials R.E. Smallman and A.H.W. Nagan ISBN-13 978 0 7506 6906 1

Mechanical Metallurgy G.E. Dieter ISBN-13 978 0 0701 6893 0

Regards

Chris

[jpachard]

Chris, thank you for the thoughtful response. I too am a bit surprised at the lack of data supporting the claims. I would think that a company like Diversified Cryogenics would have a few brake dynos and set up testing back to back. It would be easy to get some telemetry from a race team and set up an experiment where you run two identical sized rotors against one another, one with cryo treatment and one without.

Cheers, James

[Resident Sicko]

Either way, I am interested. I drove on cryo rotors (very well could have been factory Brembo rotors that were cryo treated after production, but noticed less surface rust on the rotors when subjected to water-rain or wash as well as a very nice mirror finish at the contact area.

Yeah, I am only speaking of looks, and not function. However it was enough to sell me on the idea and would like a set for this car. Count me in.