GM drum hub failure

[Randy67]

Well, it looks like 43 year old parts don't like autocrossing. I had a right hub fail right at the end of my first (and only) run. Took quite a bit to get the car on the trailer, will be getting a winch for sure now. Luckily the disc brakes held the wheel in place enough. The caliper pins bent for sure and possibly the abutment as well. Rotor was chewed up some from contact with the abutment. I will know more once I get them off and the drivers side off so I can compare them.

Here are a couple picts of the carnage
Hub
https://static1.pt-content.com/images/noimg.gif

Hub now a 2-piece design
https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/noimg.gif

[David Sloan]

yep i would call that a failure! LOL!

They were good parts wile they lasted,(40 years)
Good luck if you need any parts i have a couple sets laying around.
Thanks for sharing

PS Make sure an check the spindle too.

[John Wright]

Yikes!.....:eek:

[Randy67]

Spindle will be checked as well. It looks like the flange just clean broke off. The bearings looked great and no marks on the spindle. Luckily I wasn't going fast when it happened, literally on the last turn of the run.

[JEFFTATE]

What kind of brakes , and wheels and tires were you running ???

[Charley Lillard]

You just need a little JB Weld..

[John Wright]

tires were you running ???Less than 200 TW? Might need to go after a billet set and get away from the cast.

[Randy67]

JB Weld cures all.

I am running C5 brakes (Kore3 kit) with 17x9 Soft 8 wheels and 275/40/17 Kumho V710 with a TW rating of 30, car weights 3360 lbs approx. I haven't weighted it since the LT1 swap.

I may use another cast hub for the short term, but would like to upgrade to Kore3's billet hubs (or similar) when finances permit. No more autocrosses with cast hubs though, not willing to temp fate twice.

[MrQuick]

Randy, was that a drum hub or an old roto that was cut down?

Another reason to run billet or modify for C6 hubs.
glad no one was hurt.
Vince

[Randy67]

It was one of my original drum hubs that was turned down on the outside for the rotor to fit and 1/2" studs installed.

[68sixspeed]

Wow, luckily it wasn't worse and you and the car are ok. Randy (proBell) had this happen at the XV challenge down at pocano a few years back, split one of those hubs but length wise through the bearings not around in a ring like that. The aluminum ones are good for most purposes but the bearings in those are still too small for serious road course work. I've made up a few sets of aluminum ones with larger bearings for higher load rating, or for a real heavy set custom spindles with grand national hubs on them. There really isn't a perfect fix that I've seen, even the vette sealed bearing hubs like int he ATS spindles will fail in road course applications. Tracking vettes we have to change bearings every couple years.

[John Wright]

I must lean on my truck too hard too...been through several front hub bearings in that since I bought it new in 2004.

[Apogee]

Impressive. Randy, did you by an chance magnaflux your hubs prior to modifying and rebuilding them when you did your brake swap? We've seen cracks in a few different places on a few different occasions, but never like yours. Glad the damage was limited to just a few brake parts and that both you and car live to auto-x another day.

Tobin
KORE3

[silver69camaro]

Holy crap! Glad things ended up OK.

[6'9"Witha69]

Never good to hear of a failure, but good when they happen at low speeds and nothing is really damaged. My friend had a '67 Chevelle he and his dad rebuilt in High School. On different occasions the LBJ pockets in the LCAs failed. Once was pulling into his girlfriend's driveway and the other time was pulling out of his own. Lessonj we learned? When something fails on one side, check the other.

[Randy67]

Impressive. Randy, did you by an chance magnaflux your hubs prior to modifying and rebuilding them when you did your brake swap? We've seen cracks in a few different places on a few different occasions, but never like yours. Glad the damage was limited to just a few brake parts and that both you and car live to auto-x another day.

Tobin
KORE3

No magnaflux was done, just inspected best we could. They did make 2.5 years of autocrossing. Makes me wonder if this was part of the reason for pedal kickback on lefthanders?

Tobin, do you happen to have the caliper abutments in stock? The only other thing I can see is the caliper pins are bent, I will know more tonight if there is anything else. The bracket looks okay but I will check it out once off to verify it is still straight.

In true Murphys law fashion, I have someone who wants to come look at the car tomorrow. Since I can't fix it before then, I will see if he still wants to come or wait until it is moving again.

[CarlC]

Yikes! My pucker factor just pegged the meter.

[John Wright]

I'll be running the ole MT machine over my cast hubs before it sees the highway. Just in case I accidentally over stressed the castings when I pressed in my 1/2" studs.

[DynoDon]

I am really curious about this failure. Not familiar with the brake setup. Does it offset the rotor like it would in a standard Corvette , thus loading the hub in a manner differently then it was engineered for? Stock style cast hubs have been road raced for years so I have to think that there is a load that is different than they were intended for.
What do you guys think?

[John Wright]

Don,
They use a portion of the old rotor or in this case drum to use as the hub, and then you can use the slip on style C5 rotors. Here is what a 3rd gen Camaro rotor turned down to make a hub looks like, this is what I used on my 2 gen Camaro....

https://static1.pt-content.com/images/pt/2010/04/C5hub-1.jpg

https://static1.pt-content.com/images/pt/2009/10/C5hub11-1.jpg

[DynoDon]

Don,
They use a portion of the old rotor or in this case drum to use as the hub, and then you can use the slip on style C5 rotors. Here is what a 3rd gen Camaro rotor turned down to make a hub looks like, this is what I used on my 2 gen Camaro....

https://static1.pt-content.com/images/pt/2010/04/C5hub-1.jpg

https://static1.pt-content.com/images/pt/2009/10/C5hub11-1.jpg
Thanks John. So the wheel ends up being a standard offset, not a "front drive" style like the Corvette? Shouldn't add any extra load to the hub then. Just higher cornering loads with bigger and better tires.

[Randy67]

Just to clarify, my hubs are the stock drum hubs, not cut down rotors. The cut down rotors are used on the later cars that didn't have drum front brakes, like 70-up F-bodies, 73-up A-bodies and such. The only change in offset was the thickness of the rotors.

[John Wright]

Just to clarify, my hubs are the stock drum hubs, .
I added a bold font to my previous post to help with clarity also...:cheers:

[Apogee]

No magnaflux was done, just inspected best we could. They did make 2.5 years of autocrossing. Makes me wonder if this was part of the reason for pedal kickback on lefthanders?

Tobin, do you happen to have the caliper abutments in stock? The only other thing I can see is the caliper pins are bent, I will know more tonight if there is anything else. The bracket looks okay but I will check it out once off to verify it is still straight.

In true Murphys law fashion, I have someone who wants to come look at the car tomorrow. Since I can't fix it before then, I will see if he still wants to come or wait until it is moving again.

Without closer pictures of the fracture, it's a little tough to tell how rapidly the failure ocurred, however it wouldn't surprise me at all if it was contributing to your knock-back issues. Do you see any corrosion/rust anywhere on the fracture line, indicating that a crack has been propagating for a while or does it all look "fresh"?

Abutments, pins, etc are all in stock, so please let us know if there's anything you would like us to help out with.

Tobin
KORE3

[Randy67]

Thanks, Tobin, I contact you as soon as I figure out what all needs replacing, should know tonight.

The crack looks very clean, no signs of rust that I could see. I will check it again tonight to verify though. The next hub and the my other one will be magnafluxed just to be sure.

John, thanks for the clarification. I was sure you knew what you were talking about, just didn't want anyone else to be confused.

[Randy67]

I took the rest of brake stuff apart tonight. The caliper abutment took most of the stress and is bent a bit, it will need to be replaced. The caliper bracket was bent very slightly where the abutment bolts up, you can barely tell without a straight edge. My machinist wants to see if to check if it can be straightened. Pretty tough bracket. Caliper escaped harm, only the fins on the backside touched the inside of the rim. I measured the caliper vs the other side and no spreading or twisting. That's good news for me.

[David Pozzi]

Coleman makes a steel hub for second gen Camaros, pretty heavy looking though. The cast 2nd gen hubs break often in circle track use.
It would be good to post up 1st gen Camaro hub sources if you guys have any.
I know Baer makes them for use with their brake kit, but I don't know if they sell them separately, or if the wheel flange is in the proper location.
Speed Tech
Kore3?
David

[Randy67]

Good idea on the hub info, I know Kore3 does have one. I will look into the Coleman hub for my 81, don't want to have a failure with that car. Edit: Here is the Coleman hub
https://www.lefthanderchassis.com/viewproduct.asp?groupflag=1&idgroup=2512781
Rotor size is small but maybe a larger rotor can be bolted to it. Unfortunately it won't fit the spindle on my Camaro which has the larger outer bearing (pin diameter is larger) but would work on the 70-79 spindle.
Edit again, here is one for the later ones:
https://www.lefthanderchassis.com/viewproduct.asp?groupflag=1&idgroup=2512782

I now have justified to myself why I trailer the car to events, even though it is streetable, just for problems like this.

[Skip Fix]

There is a conversion outer bearing for second gens that I believe allows you to run early rotors on later spindles-want to think an A34?

My 78 Pontiac shop manual says 77 was the last year for the smaller bearing- as they list for that rotor.

[Randy67]

You may be right with the years, I think I confused it with the control arm bushing change that happened in 80.

Well, went to the machine shop and the replacement hub is ready. We did find out that the broken hub had a void/flaw in the casting, right along the crack. It is the dark area (circled) on the hub and where the toothpick is on the flange in these picts. Sorry my camera couldn't take better pictures.
https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/noimg.gif