RacingBrake.com Rotor failure

[M3kiwi]

Hi all, just thought I'd post some photos of my left front RacingBrake Rotor failure.
As I have/had recommended RacingBrake on here before.
This happened 2/3 of the way through session 3. Session are 15mins long every hr. I had just set my best time the pervious lap.
Rotors had a total 26,750km of use (over 4yrs), approx 745km of track use, which is 7 Driver training days over the same period.
The hats didn't fail, but 3 bobbins were shred. Rotor thickness is 27.48 (28mm new) Hat temp approx 143c, Racetech temp strips were put in placed at start of session 3. So I had just had an up close look at the rotors.
BS RB Rotor outside (Small).jpgRB Rotor mounting (Small).jpgRB_hat 3 lower nut heads gone (Small).jpgBS Closeup (Small).jpg20180811_131714 (Small).jpg

[TostitoBandito]

Ouch, that must have hurt when it went. Hopefully it didn't put you into a wall?

[M3kiwi]

Luckily I had just about finished my braking and was about to turn into the corner.
Checked my data, started braking at 139km/h rotor blow at 65km/h, distance under brakes 60mtrs.

[TostitoBandito]

Well that's good.

I don't have a BBK but I do have the two-piece PFC V3 rotors and I have to say I really like their bolt-less design (retained by spring). Seems like these sorts of failures would be much less likely, since you'd need entire chunks of cast aluminum/iron (which don't have bolt holes to weaken them) to fail rather than bolt heads shearing off and causing a cascade failure.

[Def]

Those lugs do look a little "light duty" on width compared to say an HD Wilwood rotor. Unfortunately for a material like that, once one starts letting go, the others are probably right behind due to it being a brittle material.

[M3kiwi]

Def
"Light duty" when compared maybe, add the fact the lugs extend approx an 1" below the rotor face means the forces on the lugs and fixings would be immense.
"Brittle" maybe the key word, a member on M3Cutters pointed out that the rotors had been through 35 heat cycles.
But as you can see from the photos there was no sign of fatigue eg. spider web cracking..

Up till this failure I would and have sung the praises of RB for being both innovative in design and function.
"The only weight reduction I have done on my car is replace the OEM exhaust system, removed my vaders and replaced them with Recaro CS Sportsters
My goal over the years has been to see how quick I could get around the track with the car basically setup as a DD."

So I sent RB an email, with as much info and photos as I could and offered to send higher resolution photos if required
This is an excerpt from Racingbrakes response
"To assure driving safety, track racing should not be rely on "track miles" or number of events, rather it's the driver's responsibility to have the brake inspected "prior" and "after" each event, and periodic replacement on pad and disc is recommended before a potential brake failure can occur"
I replied with
The info I provided, total miles, total track time etc
The photos are (worth a thousand words) of, Ring condition and thickness, pad condition, Hat temperature and failure areas etc
The links to my build threads was to show you how anal, I am with my cars maintenance and performance .
All the above was provided to you to help analyze what went wrong. With the idea that I would receive a logical explanation as to why this happened and some reassurance going forward that it was safe to use your produce again.
This reply wasn't addressed to me or signed by the sender.
I'm now in the process of finding a Rotor and Hat combination that works with my calipers,brackets and wheels.
And it's not as easy as I thought it would be..........

[LAWLence]

Sorry you had to go through that. I've posted about RB on here before over the years. Bad designs made with shoddy Taiwanese pot metal. Their engineering department consists of one super old dude whose only claim to success (at least that's what they told me) was anti squeal pads on the back of brake backing plates back in the 60s. I doubt the guy has ever heard of CAD or FEA.. stay away.

[TostitoBandito]

Yeah if there were no visible cracks prior to failure, then it's simply a product which isn't suited to track use. The part which broke had nothing to do with wear/usage at all, so your mileage/thickness shouldn't even be relevant (though it further indicates that the rings had lots of life left). The mounting mechanism/hardware and hat shouldn't "wear" at all. If they do, it's a bad design. The only explanation I can think of that might be your fault is if the fasteners holding the ring on were improperly torqued, either too tight or too loose. Sounds like that wasn't the case though.

A lot of people who buy BBK's don't track their cars and just want fancy looking brakes on the street. There's only a handful of manufactures like Brembo, PFC, Stoptech, AP Racing, or Wilwood who I'd trust to make BBK's which will stand up to HPDE or endurance racing use cases. There's not really any excuse for a rotor failing like that due to materials/design failure.

[Def]

You likely won't see cracking on a structural failure of a brittle material (which isn't an opinionated term, it specifically means a material that has less than ~3% elongation to break, a ductile material like 350 MPa yield structural steel will have a minimum elongation to break of ~20-25% and experience a structural failure completely differently).

The design looks like crap all the way around, and you don't need FEA to do a basic hand calculation that will show the shear/bending combination was too much for narrow lugs with that much offset from the rotor ring. The support to either side of the ring also causes problems in that small out of plane loads on the lugs cause large amounts of bending at the root of each lug.

It's hard to tell what went first, but I'd probably learn towards a bending induced failure at the root of a lug due to the small radius and narrow lug width used there. Then once one lug went, the rest had no chance to hold the load as it was already marginal with all lugs installed.