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What is Cryogenic treatment of rotors and why do it?

What is it?  Deep cryogenic treatment of brake rotors involves a slow freezing of the rotors (to about -300F), in order to eliminate the internal stresses due to the casting and machining processes.  It affects the whole rotor and is not simply a surface treatment.  It changes the grain structure of the metal permanently and transforms soft austinite (bad) into a harder martensite (good). 

What does it do?  Eliminating the above defined stresses improves rotor warping, wear, and heat cracking in heavy uses such as racing.  It also increases the strength without increasing the hardness.

I have been asked a few times if its worth it to either pay for new rotors with the cryogenic treated rotors or have the service performed separately on new rotors that do not come with the treatment.  So I checked with some industry experts at a 3-day brake engineering conference I just attended.  Because the conversation was off the record over a few adult beverages (exciting bar talk…I know), I’m not going to involve names and companies.  I will leave it at this:  If my other writings in the Brakes 101 section are not to be believed in your opinion, than this shouldn’t either.  If you find them useful, this should be useful too.

“Is the cryogenic treatment for street rotors worth it?”

In his response, he stated that in one an only one case in his life was the answer yes. It was providing rotors to a factory sponsored race team to solve an initial difference in feel/fade during break-in. That’s it.  We then had a discussion about how to get similar results from a proper break-in procedure.

Breaking in your BRAKES:   Conditioning your pads and rotors can be done just as effectively by a proper break-in of BOTH the rotor and pad pair. Yes - a rotor needs break-in too. His recommendation is to do a 10-stop series of brake applies of high decel (0.8g) back to back until you get to 10 from a speed of 60 to 5-10mph. Allow for cooling then do the 10-stop fade one more time. Racers may want to kick up the speed to 80mph for the applies.

You will likely get some green fade during the first ten stops somewhere in the 5-7 stop area - this is good. The next series fade will almost surely be later in the ten stops if at all. A third time is not necessary.

NOTE: it is very important that you do not come to a stop, even for a moment. The pads will be sticky enough to leave an imprint of the pad shape on the rotor and an uneven transfer layer.

This does mainly two things: prepare the pads by de-gassing the phenolics out of the pad material (the fade effect by the gas actually pushing back on the pad as it escapes beteen the pad and rotor), and preparing the rotors with a transfer layer.

In this guy’s mind, this is by far the best thing you can do for your new pads and rotors…including saving your cash by not paying for your premium priced cryogenic rotors or the aftermarket treatment.

If you put new pads on current rotors (very common), you can lightly/evenly sand the rotor surfaces with fine grit sand-paper to remove the old transfer layer. Then proceed with the break-in above. This would apply to carbon-mets, ceramics, and any organic pads that rely on a transfer layer.

The result should be a dramatic reduction in fade and the likelihood for heat cracks.