98 TJ brakes - rotors & pads

All-cast rotors are a great upgrade to those lightweight composite rotors that Jeep stopped using in newer Wranglers. I did that upgrade to my '97 for several reasons with greatly reduced warping being one of them.

Jerry

wow, you even get cryogenically frozen ones now.

guess the science is good ( it gets done on high end knives ), but whetherit makes a practical difference I know not. Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Here's a rational quote from one of the sword sites:

"I really wish this would just go away, but obviously it is not going to anytime soon. The cryogenic (subjecting it to severe cold, as in LN2 or -290F) treatment of blades is not a new thing, and it is also not a magic thing.

"There are two potential changes that can occur. The first is dimensional stability can be improved. This is what happens to the rifle barrel. By being subjected to severe cold, the barrel now no longer changes dimension as much as it used to when it heats up from repeated firing. Gauge block standards have been cryogenically treated for years for this reason, it reduces the margin of error induced by changes in temperature.

"The second possible thing that can happen is the change to martensite if there was retained austenite in the microstructure of the material. This is applicable to blades, but only if retained austenite is present. If the heat treating is done well, then there is no retained austenite present, i.e. no benefit to the cryogenic treatment. Retained austenite can be a problem with high alloy steels (stainless steels with high carbon are particularly susceptible, but still only if the heat treatment was not optimal in the first place). Low alloy and simple steels (likely what your kukri is made from a 10xx steel) are extremely unlikely to benefit from a cryogenic treatment, as they are unlikely to have any retained austenite to convert to martensite in the first place."

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Whether or not you think anything is BS is unimportant Bill since you think most things you don't understand are BS. Cyrogenically treated parts do indeed change their metalurgy and do pick up tensile strength and hardness in the process.

Jerry

Jerry Bransford did pass the time by typing:

I dunno. Tend to agree with Bill on this. From my classes in material science a metal (liquid) only changes its properties based on how long it's kept at how high (not low) a temperature and how quickly you quench it.

When I first saw that site it rang my bullshit detector loud enough to wake the dead in five states.

Somewhere out there there is a study on cryogenics vs non and they show no difference in wear at all. If I find that link I'll post it.

All that fancy tempering and annealing stuff must not work either because the metal is never returned to the molten state. ;-) Think of it as a thermal stress relief and additional annealing cycle. Cryogenic treatment does work and in many applications provides a marked improvement in material durability. I would not pay twice as much for a rotor since I do not believe it will last twice as long as an untreated one, but this outfit:

to have a pretty good handle on the process and their prices are notoutrageous.

L.W. ("ßill") Hughes III did pass the time by typing:

Hmm. Interesting. Maby not as bs as I thought, but then again that's only one test with a few samples. I'd have more belief if they were in common use for critical apps like aircraft. Still it's interesting and I can get Liq N here. :) It's fun to play with.

Can't we just answer the original guy's post and tell him to buy some good quality after-market rotors, like those from Raybestos?

I put them on my 2000 JGC, and they give much better service and life that the OEM rotors.

--James--

Good question, all I know is several Jeepers have told me that Jeep went back to using cast rotors sometime in the not-too-distant past. It was a nice surprise to read that, that was for sure.

Jerry

Nope. The benefits of cryo treatment can be seen *easily* on something like a trombone slide. It depends on the stresses introduced during the heat treatment, metal forming and/or machining because it can have zero effect too.

Is it worthwhile? In most applications probably not.

-John

He probably meant REALLY squeeling, like metal-on-metal...

-jeff