[SuperMacGuy]

I was at Summit Point yesterday for FATT. During my 2nd heat I had my left front hub fail. It let loose in turn 5-6 or so, and if you know Summit, that's about the slowest part of the track. Which is right after the part of the track with the highest pucker factor IMO (downhill at 80-100 depending, about a 30 degree turn a little off camber and max braking soon as you're through it). So I am OK and there is no body damage.
The hub flange sheared right off, and the wheel getting pushed back it must have bent up either the brake caliper or the slide pins, the caliper doesn't float any more. A guy with a TA next to me thankfully had a spare hub, so I got that on and drove carefully home. This was a Mike Minear hub so I'm contacting him to see if he wants to inspect it. I'll probably get a new one from him over the winter.
I'm thankful that was all relatively low drama. If that happened almost anywhere else on track, well all the other places are pretty high speed, and it would've been a real wreck, literally.

Chris

[PeteL]

I evaluated the broken parts for Mike. The main issue I had with the material of the failed parts is that they were a relatively porous casting. Unfortunately the corrosion on the fracture surface prevented me from determining if there was porosity at the origin of the fatigue crack, but the porosity I saw was significant and could have played a role.

Making the hub from bar stock or a forging instead of a casting would eliminate any porosity issues.

You can make castings work, in fact the Duralast hub that I also examined was a casting but a much better one. However, it can take several iterations of trial castings and destructive evaluations before you get a casting right.

The same is true for carburizing, nitriding and induction hardening. I wouldn't feel comfortable with any of these processes without some level of destructive evaluation to make sure they were done correctly.

One of the factors that Mike will have to weigh is how well he believes he can monitor the quality and consistency of any given process he uses Large automotive companies have specialists to do just that. Some processes are easier to do that with than others.