DIY Brake rotor cryogenics?

[G-Man]

It sounds like something out of "Mythbusters," but I heard you can do your own brake rotor cryogenics at home with "fairly good" results.
I'm thinking - rotors on the outdoor gas grill (400-500F) for a while, cool them, then into a cooler with dry ice (-110F). Maybe two-three cycles?
This forum has wise engineer-types - is this the dumbest idea you ever heard? Just crazy enough to work? Likely to end in tears, divorce, and meeting the fire department?

[Greg Amy]

Have a video camera running.

First thought is that you're going to crack 'em when you quench 'em like that...

Personally, I'm a skeptic of "cryogenics"; knowing what I know of metallurgy (basic undergrad MechE info) you really need to get closer to the melting points of materials to significantly affect them. I think "frozen rotors" are nothing more than hoo-ey designed to part you from your cash. And, I suggest that as you run rotor temps to as high as 1000F due to surface friction from a high-metallic-content brake pad any value from "cryo'ing" them to -150F (or whatever) is immediately lost.

But that's just me; I've got absolutely nothing to back up that opinion.

If you do this, I do want video...

GA

[Matt93SE]

Well, the big issue is the controlled heating and cooling of the parts. It takes many hours to slowly cool and reheat the parts following a true cryo process. It does in fact change the microstructure of the steel, but the processes take many hours (days) to do properly. i.e. The cooling rate is something like 20 deg C per hour down to -200C, then it's held there for 48 hours and brought back up to room temp at a race of 15deg C/hour.

the numbers are probably way off, but it's a long, slow process, and the metals must be cooled well below the -110F of dry ice before the good stuff happens.

do some poking around on Google and you can find more information about the process. dig a bit deeper and you'll find sites that discuss the metallurgy changes that happen during the treatment. i.e. austentic structure converted to martensitic.

[Greg Amy]

...sites that discuss the metallurgy changes that happen during the treatment. i.e. austentic structure converted to martensitic.

See, that's where my skepticism comes in. Austentite exists in a very, very narrow range of temperature...above the eutectoid temperature of steel, damn near its melting point, something like 1350 degrees F. Martensite occurs by quenching the austentite.

No amount of "cryo" treating will affect that. Thus, I say: "hoo-ey."

I'm open-minded to relevant links.

GA

[chuck baader]

Greg, get a pair of cryo and a pair of stock fronts and try them back to back. You'll be surprised, trust me...CB

[Marcus Miller]

Greg, get a pair of cryo and a pair of stock fronts and try them back to back. You'll be surprised, trust me...CB

+1, at least on a severely underbraked car, like a 1st gen Rx7.

[Matt93SE]

I did that test a few years ago on my old track car. $100 in dryo treatment wasted because the rotors lasted exactly as long.

Greg, I agree with you.. there's lots of witches brew and snake oil out there about the process. even done right it's not something many people see a difference in. done at home you definitely won't see a difference.

[Z3_GoCar]

I happen to work with a guy who used to run our heat-treat facillity. Cryo-treating is real, but I can see how some might not do it properly. The parts have to be properly heated and held at the correct temperature, then slowly cool to ambient, once at ambient then the cryo-treat. This has to be repeated several times. So, I can see how a company can do somethng like this once and claim their parts are cryo-treated when they're not. Secondly, if it cost as much as a set of rotors to properly cryo-treat rotors and they don't last twice as long, you've just upped what you pay for a set of rotors.

[tom91ita]

i am interested but not to increase "apparent" rotor life but pad life. my preferred pads are nearly $200 per set.

the wear rate of the pads are related to the condition of the rotors. when the rotors get the small micro-cracks, they turn into sanding wheels and just eat up the pads.

the small glazed look of the rotors and the roughness is not as easy to detect.

Chuck, surprised in a good way or or a bad way? what is your experience?

[timo944]

Is it legal in IT? Per GCR, section 6 Brakes:

"Brake rotors and drums shall not be modified other than for truing within manufacturers specifications."

[tom91ita]

Is it legal in IT? Per GCR, section 6 Brakes:

"Brake rotors and drums shall not be modified other than for truing within manufacturers specifications."

i think this might be in the ITCTYDIYCDI category (if they can't tell you did it you can do it).

but if you define manufacturing as casting/pouring/machining and surface finishing then this is the "finishing" stage.

[Gary L]

Is it legal in IT? Per GCR, section 6 Brakes:

"Brake rotors and drums shall not be modified other than for truing within manufacturers specifications."

The allowance is found in "Cars and equipment", not the ITCS.

9.3.16. CRYOGENIC TREATMENT

Cryogenic treatment of components is allowed unless specifically prohibited in the category or class preparation rules.

[Greg Amy]

Cryogenic treatment of components is allowed unless specifically prohibited in the category or class preparation rules.

And it is specifically prohibited, via ITCS 9.1.3.B:

"Other than those specifically allowed by these rules, no component or part normally found on a stock example of a given vehicle may be disabled, altered, or removed."



But, as Tom noted, it can't be detected, so it's between you and your conscience.

For me, it's irrelevant: I can buy three sets of rotors for the cost of a pair of "frozen rotors".

GA

[Knestis]

i think this might be in the ITCTYDIYCDI category (if they can't tell you did it you can do it). ...

Tom gets the MKL (Made Kirk Laugh) award for the day. It's even better if you say the acronym out loud - "It city, die why city."

K

EDIT - On topic, I wouldn't be surprised to see back-to-back comparisons of untreated rotors yielding pretty substantial differences, lot-to-lot quality being what it is.

[Gary L]

And it is specifically prohibited, via ITCS 9.1.3.B:

"Other than those specifically allowed by these rules, no component or part normally found on a stock example of a given vehicle may be disabled, altered, or removed."



But, as Tom noted, it can't be detected, so it's between you and your conscience.

For me, it's irrelevant: I can buy three sets of rotors for the cost of a pair of "frozen rotors".

GA

Of course, this discussion could go on forever, but cryogenic treatment is specifically allowed by these rules. "Rules" in this case, being the GCRules, not the ITCSpecifications. Actually, the ITCS paragraph that Tom mentions is IMO probably closer to a prohibition... it doesn't have the "other than those specifically allowed" clause.

[Z3_GoCar]

The allowance is found in "Cars and equipment", not the ITCS.

And it is specifically prohibited, via ITCS 9.1.3.B:

"Other than those specifically allowed by these rules, no component or part normally found on a stock example of a given vehicle may be disabled, altered, or removed."



But, as Tom noted, it can't be detected, so it's between you and your conscience.

For me, it's irrelevant: I can buy three sets of rotors for the cost of a pair of "frozen rotors".

GA

But the IDSYCYC section only generally disallows cryo-treating, it doesn't specifically disallow cryo-treating as per the gereneral section of the GCR. So it should be legal. The ITACS also don't allow for installing a fire suppression system and yet those are legal per the general GCR.

[seckerich]

I'm with you Kirk, rolled out of the chair with that quote. Saved for future reference.

[Greg Amy]

But the IDSYCYC section only generally disallows cryo-treating, it doesn't specifically disallow cryo-treating as per the gereneral section of the GCR. So it should be legal.

GCR 1..2.3.C.1:

"The Category Rules take precedence over the General Technical Specifications."

Do you *really* want a rules nerd like me to be able to build a car doing everything the GCR allows but is not specifically disallowed in the ITCS?

The ITACS also don't allow for installing a fire suppression system and yet those are legal per the general GCR.

Interesting perspective, but some kind of fire suppression is required for all cars; we're only discussing that level of a system installed. Cryo treating, on the other hand is an allowance; the ITCS trumps all allowances.

As I said, if we use your logic, you might want to spend an evening reading the GCR again; more than a few light bulbs might go off...

GA

[Z3_GoCar]

GCR 1..2.3.C.1:

"The Category Rules take precedence over the General Technical Specifications."

Do you *really* want a rules nerd like me to be able to build a car doing everything the GCR allows but is not specifically disallowed in the ITCS?


Interesting perspective, but some kind of fire suppression is required for all cars; we're only discussing that level of a system installed. Cryo treating, on the other hand is an allowance; the ITCS trumps all allowances.

As I said, if we use your logic, you might want to spend an evening reading the GCR again; more than a few light bulbs might go off...

GA

Oh really??

I hope you follow the GCR's before you follow the ITCS. With IDSYCYC, where in the ITCS does it say we're allowed to install a cage? You'll want to check out the 2011 GCR, not a mention of installing a cage as per any part of the GCR in the ITCS. So if the ITCS takes presidence over the GCR, and with IDSYCYC we're not allowed to install a cage.

[Greg Amy]

So if the ITCS takes presidence over the GCR, and with IDSYCYC we're not allowed to install a cage.

The ITCS takes precedence over the GCR for anything it specs, it does not replace the GCR in its entirety. Thus, anything mandated in the GCR but not mentioned in the ITCS is also mandated for cars prepped to the ITCS And, when conflicts exist between the GCR and the ITCS the GCR defers to the ITCS.

For example, if the ITCS specifically said cages and handheld fire extinguishers are not required, then it would take precedence over the GCR requirement for cages and fire extinguishers. It's how IT racers get around the FIA certification requirement for fuel cells.

So, since:

- the ITCS takes precedence over the GCR for anything it calls out/conflicts, and
- the ITCS specifically states "[o]ther than those specifically allowed by these rules, no component or part normally found on a stock example of a given vehicle may be disabled, altered, or removed", and
- it is illegal to the ITCS to disable, alter, or remove any part not specifically called out in the ITCS, despite being allowed in the GCR, then
- the ITCS overrides the GCR allowance for cryo treating.


Ergo, cryo treating of brake rotors is illegal.

Like I said, in reality it's undetectable, and personally I think it's all hoo-ey and money wasted...but ...

GA