Initially it showed up as a clunk when I let off the throttle, then another clunk when getting back on the throttle. It drove me nuts! I had the wheel off, I had checked all the hardware on the rear suspension on both sides... nothing. The wheel didn't wobble at all.

I started driving the car less and less. but when I did, I noticed the car yawing more and more heavily when getting on and off the throttle. It got worse, down right difficult to control at higher speeds unless I just tossed it in neutral. I thought for sure that it would be suspension again. But everything seemed ok when checking it on the ground. I jacked up the wheel and found it to be all wobbly. An Ah-ha moment for me.

I removed the centercap and wiggled the wheel to see if the axle would wobble with it. And much to my suprise it did not. So I immediatley am like, "I'm an idiot. I've been driving around with loose lug nuts! Nope, they were tight as can be. Something had to have seriously failed. So I removed the axle nut, the wheel, the rotor and this is what I found...



Needless to say, that little piece of metal was all that was driving my car, and that nothing was really holding my wheel on. Just another failure to keep an eye out for.

Wow, thanks for posting. I've never seen anything like that before.

Does that crack go around the entire hub? If so, what was keeping the wheel on the car?

[EDIT] I suppose the brake caliper was. Yikes!

[This message has been edited by Patrick (edited 11-01-2012).]

Yes, the crack went all the way around! The flange was loose from the bearing!
I suppose the wheel being bolted to the flange kept it tighter to the hub. That gap probably opened up a bunch once the wheel was loosened from the flange. There is a little lip that kept it roughly in place.

The brakes were fine, but who knows, if I kept on diving it the wheel would have definitely worked its way off, taking out who knows what.

This hub was on the car for about 9 years. If I recall, it was a duralast. But after 9 years I could easily be wrong.

Wow... I've never seen that before. It is a wake up call for those modifying hubs though.

Though no one has suggested this, I doubt the crack initiated from the bolt hole centered in your picture. It more likely ended there and started somewhere else around the base of the centering ring where there may not have been an adequate radius to prevent cornering stresses from concentrating there. Or perhaps a machining fault along the radius. Do you autocross or otherwise place large side loads on the suspension (maybe bumped into a curb sideways?)

Nah, I was being a good boy. However, I will note that I am running corvette rotors, and there is an aluminum concentric ring contacting that fillet edge. I didn't check, but the concentric ring may have been square cut on the inside edge? Still, being aluminum, I can't see it being hard or sharp enough to cause the fillet to fatigue. I have to maintain that it is primarily a quality issue. I'll have to check the other side soon.

Ouch.

a guess? If concentric rings were sandwich between rotor and hub creating stress when you tighten the lugs then could be a/the problem.
likely starting point is 1 of side of that big cut to clear wrench to mount the unit.

Replace both since they come from whatever source.

Since you drove w/ that... likely replace the rotor and replace both rear pads. I'm surprise you didn't overheat the brakes.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

This is very timely for me. I have a similar clunk in the right rear and new ball joints and tie rod ends hasn't fixed it. After alignment, it still wants to wobble on roadway imperfections. Since the previous owner tried using the car for drifting, I may have the same problem. I'd guess that the only thing holding your wheel on was the caliper and brake pads. Thanks for this heads up.

Here is a pic of my 85 rotors that are low mileage but have been under the bench for over 20 years. What is the distinct ring in the surface finish? It looks like its made from two parts. The failure in the part above appears to follow the inner edge of this ring along the base of the machined radius.

Any thoughts?

[This message has been edited by Yarmouth Fiero (edited 11-01-2012).]

quote Originally posted by theogre: Ouch. a guess? If concentric rings were sandwich between rotor and hub creating stress when you tighten the lugs then could be a/the problem. likely starting point is 1 of side of that big cut to clear wrench to mount the unit. Replace both since they come from whatever source. Since you drove w/ that... likely replace the rotor and replace both rear pads. I'm surprise you didn't overheat the brakes.

The brakes survived unscathed, the caliper probably moved with the rotor fairly well. The wobble on the wheel wasn't enough to cause damage, except that the slider boots, which were new are completely shot. As for the concentric rings, the rotor slipped completely over them, it has a recess that contained the lip on the ring, so there should have been no extra stress. I put another used bearing in for the moment, and it drives much better, when I put my f40 trans in, I'll get some new wheel bearings. It's not my daily at the moment so I'm not too worried.

That's scary, a hard enough corner to that side might have been enough to pry the wheel up from the inside and overcome the caliper. Another cause of wobbly, or swaying rear end is a loose CV axle nut as I discovered a couple of days ago. 200 lb/ft is a lot of torque to apply even with a good size torque if you weigh a good bit less than 200 lbs.

Count your blessings because you sure escaped a doozy of a potential disaster. I wouldn't doubt the drifting you mentioned caused that, think about it, how many competition drift cars have the added stress of the drivetrain sitting over the drift wheels and further more the abuse likely to be hashed out by a novice on stock equipment as he tries to swing a tail heavy car side ways. He or someone may have gone side ways into a curb with it also leading to that failure.

[This message has been edited by Joseph Upson (edited 11-02-2012).]

a few years ago.. advanced fired a vender/surplier because that type stuff was happening to brake rotors.. the rottor face was coming apart from the "hub" or hat..
failing just like what you see there.. only it was a brake rotor..
3 guesses the first 2 don't count ,on what country they where made in?
autozone/pepboys/us/oril/checker all used or still used that surplier.. at one time..

glad you caught it before anyone got hurt/killed..
everyone that try's to buy the cheaper bearings/hubs I try to talk into the national/moog part..
the house brand surplier we have isn't bad at all now.. but I just see to many come back for warranty/defective..
think you'lll find that flange part was cast not forged.. and make in china..

That looks familiar................
We had a similar failure on our secondary race car this season at Pocono.
It was a replacement hub from NAPA only 6 months old.
It appears the newer replacement units are machined thinner at the flange/sleeve area.
The original units were thicker there and not prone to failure.
Maybe Rodney has or will get us something better.

Joseph, the drifting car was is mine, not Fierobsessed. Easy to get all us Fiero........ username people mixed up

When machining parts, transitions from a vertical plane to a horizontal plane should be radiused. If a sharp transition is made by failure to use the correct tooling, you are prone to failure if high load forces are placed on the part. If that was an aftermarket hub, that may be the cause, irregardless of the quality of the material.

Yes, make from two pieces. Likely to save cost and time to make the parts at the time. Two pieces may not be made from same type of steel, IE Hardness etc....


Flange can break for several reasons... Examples:
Too big cutout to clear the wrench = too thin metal left.
Wrong Type/Grade/Hardness of metal.
Machining left stress risers to start.
Stress from something sandwich between hub/rotor and/or rotor/wheel, including poorly made concentric rings. Rings can "Dish" loading the flange.
Heat maybe too...
Yes, racing can to it too...

Yikes! Glad you caught it. I've seen a lot of worn/broken hubs through the years but that one takes the cake. Leave it to you!!

Fierochic, nice to see you back !!

BTW, regarding that rear hub bearing...that not really what you want to see.

For those that may not understand, the fiero is not full-breed race car. Also driving techniques like drifting is not a bright
idea. The car wasn't designed to do that. Anyone that is doing that is simply reducing the life of suspension components.

Remember, the design of the fiero is from the early 80s. Its was built for recreation and day to day driving.

You can rece the car, and do what you want, but don't expect suspension parts & bearings to last long.

If you intend to be driving the car hard, don't buy chinese parts as replacements. Get GM or US made parts for durability.
Just be careful what you are purchasing.

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fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. All original.

Ok, so I got bored and disassembled the bearing, spread it at the break and removed the flange...





I found that the split was internally V shaped. It was actually quite difficult to seperate the two!

It wasn't a clean break either, it was clearly jagged. Fortunately, the wheel wasn't just going to come off, and I had plenty of warning that something had gone wrong. Im just glad it was something that is pretty easy to fix.

Looks like it was that way for a while.

quote Originally posted by fierogt28: If you intend to be driving the car hard, don't buy chinese parts as replacements. Get GM or US made parts for durability. Just be careful what you are purchasing.

Yep, they are getting harder to find. But still the best.

quote Originally posted by Joseph Upson: That's scary, a hard enough corner to that side might have been enough to pry the wheel up from the inside and overcome the caliper. Another cause of wobbly, or swaying rear end is a loose CV axle nut as I discovered a couple of days ago. 200 lb/ft is a lot of torque to apply even with a good size torque if you weigh a good bit less than 200 lbs. Count your blessings because you sure escaped a doozy of a potential disaster. I wouldn't doubt the drifting you mentioned caused that, think about it, how many competition drift cars have the added stress of the drivetrain sitting over the drift wheels and further more the abuse likely to be hashed out by a novice on stock equipment as he tries to swing a tail heavy car side ways. He or someone may have gone side ways into a curb with it also leading to that failure.

Amen to that about the torque on the axle nuts. You won't get to 200 psi with an impact unless its a 3/4" truck unit. You need to tighten with the impact and then use a 30" breaker bar and a 30mm socket to do the work while the wheel in held firm on the ground. Also be sure to use only the interference axle nuts and not the ones anchored by bending the top with a hammer and punch.

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Fierobsessed, thanks for update.

Torque etc... See my Cave, Axle