Superalloy rotors

Willwood has rotors that are interesting and I was wondering if anyone had experience with them. The application would be a 17xxlb mid engine car that shall remain nameless ;)   I thought that being that the factory rotors on this application were already dainty and being that so much weight reduction has already occured that these would a. likely be well up to the task and b. Shave some more crucial unsprung rotational weight. I know the s1 elise has aluminum rotors so there's that. Anyone had experience with these? Thanks in advance.  

Also... I think they're beautiful and wouldn't rust presumably. So, yeah. 

"Our newest Super Alloy rotor in 11.75” diameter is targeted directly to Dirt Late Model and Modified racing. Wilwood’s proprietary Super Alloy material provides the lowest rotating and un-sprung weight, without degradation, shrinkage and warping like comparable Iron & Steel lightweight rotors. Super Alloy rotors provide a durable lightweight option in applications where sustained temperatures remain in the low to moderate range, and high heat spikes are only observed on an intermittent basis. Our special alloy and proprietary manufacturing processes give these rotors high resistance to thermal distortion with excellent friction and wear characteristics against the pads."

dirt late models are supposed to weigh 2300lbs iirc. So my application should be ok at 17xx I'd think. 

For......autocross? Street driving? Track? They're also absurdly thick and I think require their own hats and maybe a different caliper? I looked at them briefly but never came up with any answers. I'd call Wilwood.

For autox and street, maybe some hpde type stuff. They list thicknesses that would work for my application iirc. Wilwood sells hats in the proper configurations to work for my applications. Spendy but I need rotors anyway and although I'm not trying to go crazy money wise, it's a pretty radical build so I dont mind stretching a bit if they're viable. 

I think they’re for applications where you are required to run a rotor, but want as little rotor as possible. Pay attention to the note about heat - they have very little heat capacity. That wave design is another way to drop mass.  They’re thick because they’re a drop-in replacement for a real rotor.

Thing is, you want some heat sink capability in your rotors. Super-light means the heat has nowhere to go, so it transfers to your calipers, pads and fluid. It also means a lot of expansion and prone to cracking.

The early Elise ran MMC rotors. It wasn’t a success really. 

Isn't it not merely a factor of how much heat can be absorbed but also dissipated? If they could shed the thermal load quickly as to not heat soak then that would be just as effective as having alot of thermal mass, would it not? 
 

I was told that the reason that they stopped putting those rotors on elises was that the supplier went under. 

As far as the mmc/ aluminum rotors on s1 elises are concerned (not that they are very pertinent to this conversation, just interesting), this was on lotus talk (lotus forum)

"I am the process engineer who worked on the manufacturing of the original MMC brake disc's. As I recall, (From around 1995) the brake system was designed by AP racing and the Disc's were cast by Lanxide Corp. of Delaware and machined by Brake Parts Inc. in McHenry, Illinois 
These alloy disc's were made of high SiC aluminum with 30% silicon carbide added for the wear properties. Back then we were told the disc's should last approximately 100K miles. Only poly crystalline diamond or diamond coated tools could cut this material since the silicon carbide particulate made it like machining a grinding wheel."

Yes, you have to shed the heat as well, but you load it into the rotors far faster than you can possibly dissipate it. Think about how short a time you’re under maximum braking. That heat has to get stored somewhere - it’s why rotors are actually incandescent even with fan-assisted brake ducting.

I remember the MMC rotors from back in the day. They had some problems with noise and didn’t work well with water. Good thing it never rains in the UK :) I looked at putting them on a Miata but I didn’t know enough about how at the time. 

As for these rotors - if you really really want to use them, call Wilwood and talk to one of their application engineers. They’ll tell you if it’s a good idea. Keep in mind that you have to engineer your brake system for your hardest use. If you drive on the street 99% of the time and then go to one track day, you need the same brake capacity as if you do track days every weekend. 

More and more research that I'm doing says they're too light duty. Bummer, it woulda been cool if it was viable. Thanks Kieth. Guess I'll have to settle for floating irons. 

I remember the SCC FD getting aluminum brake rotors.  They needed special pads.

Oddly enough, after that first article gushing over them, they never spoke of them again.

I've got a set on the back of my 2325lb street/strip FB RX-7. I would not buy them again for this car, lots of pulsation in the pedal.

Grant

Carbon said:

dirt late models are supposed to weigh 2300lbs iirc. So my application should be ok at 17xx I'd think. 

Dirt oval cars also aren't also doing anything like the braking you see at an HPDE.

Look at midgets for example, they don't even have a brake rotor on the right front wheel. Only the left front. And it's used to set entry angle more than really slow down.

In reply to z31maniac :

I raced midgets for a decade, you're not wrong. The bias adjuster when set farther to the front acted as stability management to quell understeer on corner entry. 
 

I was hoping to find a relatively low rent way to shave unsprung rotational weight on the commute attack car. Carbon ceramics aren't in the budget unfortunately. 

Carbon said:
 

I was hoping to find a relatively low rent way to shave unsprung rotational weight on the commute attack car. Carbon ceramics aren't in the budget unfortunately. 

Strange-style drag rotors weigh practically nothing.  They are heavily drilled and milled STEEL rotors.  New they are expensive, keep your eyes open for used.  Have had customers who daily drove them no problem.

Yes, they are little 10" diameter 3/8" wide rotors with half of the friction surface milled away.  But unless your commute is on Mount Panorama, they're fine.

I would not track them.