solid or two piece rotors

[Bob]

What are the merits of having two piece rotors?

[xsiveone]

You can replace the rotor braking surface without replacing the hats. Can get costly with big brake packages like Brembo, StopTech and AP.

X

[No Doubt]

Less unsprung weight and the aluminum hats permit the rotor itself to expand and contract uniformly as the temperature rises and falls during brake application. In addition, as X mentioned, you can replace the rotor surface separately.

[PowerPro01]

Depending on the rotor's architecture, a 2-piece MAY have better heat isolation and resistance, and slightly less unsprung weight, if you are tracking and/or endurance racing. If "regular" driving is your style, and SOME possible unsprung weight saving is NOT important, a 1-piece is generally less expensive and, overall street-wise, equally effective. Several sources for 1-piece allows for slotted and/or drilled rotors, just like the "big boys" and their 2-piece jobbies.

[MikeyB]

^ What he said. Stillen has great one piece rotors if you go that route. Thats what I am using.

[No Doubt]

These are my Brembo's. They utilize a two piece design. StopTech does as well. I used to have VB&P rotors that also used a two piece design.

Note: Neither Brembo or I advocate the use of drilled rotors for track use. The rotors pictured (Brembo Gran Tourismo) are in fact drilled and not cast holes as is commonly believed. The same rotors are also available in a slotted version for that purpose.





Here's a pic of the VB&P rotors I had.

[No Doubt]

Here's what Stoptech has to say about 2 piece rotors:

"The 2-piece racing rotor will cool more effectively due to less restrictive airflow and will be much less prone to distortion under even the severest driving conditions. Though more expensive initially, long term operating costs in an aggressive driving environment may actually be less as the rotors will typically outlast other designs and the aluminum hat may be reused."

I should add the fact the aluminum HAT allows the friction surface to expand and contract uniformly which helps prevent, or at least delay, the onset of heat checking and cracking. Like PowerPro01 said this is more of a factor during track use.

[PowerPro01]

BTW, using a "common" drilled/slotted 1-piece like the AC Delco DuraStop, and cryogenically AND heat-treating 'em saved us a fair amount of dough, and they wear like granite. Kinda just about WEIGH like granite, though...

[No Doubt]

Heat treating is sometimes part of the cryogenic process depending on who does it. They heat them up to about 400 degrees for a predetermined amount of time and then cryo them with liquid nitrogen for a calculated amount of time as well.

The cryogenic treatment itself consists of a slow cool-down rate (4.5 degrees F/min) from ambient temperature to the temperature of liquid nitrogen. When the material reaches approximately –315 degrees F, it's soaked for an appropriate time (generally 24 hours). Then the part is removed from the liquid nitrogen and allowed to warm at room temperature in ambient air. By conducting the cool-down cycle in gaseous nitrogen the temperature can be controlled accurately and thermal shock to the material is avoided. Single-cycle tempering is usually performed after cryogenic treatment to improve impact resistance, although double or triple tempering cycles are sometimes used.

This results is a slight increase in Rockwell hardness of a point or two, which is not much of a change, but still an improvement in the right direction. The big improvement is stress relief and stabilization.

[xsiveone]

With the price of the OE replacements, I wouldn't buy a set of cryo treated. You can get 4 replacement rotors for $92 shipped. Of course, those who are using big brake kits and not the OE calipers your replacement options aren't so cheap.

I'd rather replace a set of rotors than pay big bucks for cryo treated OE rotors and get a little more life out of them.

X

[PowerPro01]

Heat-treating SHOULD be a mandatory part of the cryogenic method, but not all people do it that way...
Like the rotors themselves, shop...
As to their wearability, after cryo, let's just say under even SEVERE usage, you'll be a looooong time worrying about replacements, and EVEN with the "dual treatment", are less expensive than 2-piece, at least in our case. But, 2-piece are lighter, and afford better heat dissipation, IF you can substantiate either or both AND the costs...
Proper cryo treatment, using heat-treat and nitrogen, can be had for as little as $50 a rotor...less if you find a "sympathetic" supplier. Added to the costs of DuraStops, and NOT requiring caliper changes beyond ti/stainless pistons, these will stop equally to many "big buck" aftermarket systems. Ask Heinricy or most any T-1/World Challenge racer, constrained by rules. And the slotted/drilled look is there, without the "bling"...

[No Doubt]

I agree. With OEM equivalent rotors available from places like NAPA and Rockauto for ~$20-$25 ea. cryo treating is not very cost effective. However, in a situation where you need a set of rotors to last as long as possible it can be beneficial.

Other parts can also be cryo treated such as transmission and differential components. To name a couple.

[xsiveone]

I agree, with OEM equievalent rotors available from places like NAPA and Rockauto for ~20 ea. cryo treating is not very cost effective. However, in a situation where you need a set of rotors to last as long as possible it can be beneficial.

For your big Brembo 14" rotors, I can see getting them cryo treated, but going with OE rotors that are cryo treated just isn't cost effective when you can get OE rotors so cheap.

X

[Bob]

Any suggestions where I can look at various rotor options?

[Cobra-R]

I had/have Brembo two piece rotors on my 95 Cobra R(my track car), the durability just was not there. They are sitting in my garage collecting dust now. I am using $62/ea Brembo one piece rotors now.

From personal experience (and experience of others around me) I wouldn't spend the extra money for the two piece rotors. I throw a new set of rotors on after I wear out my second set of pads and have had no problems at all.

Brian