Low speed steel rim center failure / separation (how / why?)

[SumGuy]

The owner of a '68 Chrysler convertible suffered a complete steel rim failure recently. It happened on a Tucson city street at low speed, minimal damage to the car (possibly only to the front drum).

Many of us old-timers have never seen one of these stamped steel wheels fail like that. Very eye-opening. Some speculate that putting radial tires on these rims (designed for bias tires) might play a role, but I can't see the physics for that.

Has anyone seen this before?

 

[Chief2025]

Gotta love the Canadian rust eh.........

 

[SumGuy]

Gotta love the Canadian rust eh.........

This happened in Arizona. I doubt the rims on that car have ever been to Canada.

 

[mk378]

Fatigue cracking? Were all the lug nuts on and tight?

 

[CapriRacer]

As someone who has done some failure forensics - albeit on tires - allow me to take a crack at this.

First thing I notice is that the failure is at a bend in the metal, not at the junction between the rim and the spider. That suggests a fatigue related crack at a stress concentration area.

The second thing I notice is that one of the stud holes is split.

I am struggling to understand how the split could take place, because if the wheel was mounted solidly to the hub, then the fatigue crack at the bend in the wheel would have separated, but the center section with the hole would have stayed intact and attached to the hub. I suspect that hole was damaged in the final stages of the failure and is not the source of the failure.

Bottomline: Fatigue crack due to age.

 

[Pablo]

As someone who has done some failure forensics - albeit on tires - allow me to take a crack at this.

First thing I notice is that the failure is at a bend in the metal, not at the junction between the rim and the spider. That suggests a fatigue related crack at a stress concentration area.

The second thing I notice is that one of the stud holes is split.

I am struggling to understand how the split could take place, because if the wheel was mounted solidly to the hub, then the fatigue crack at the bend in the wheel would have separated, but the center section with the hole would have stayed intact and attached to the hub. I suspect that hole was damaged in the final stages of the failure and is not the source of the failure.

Bottomline: Fatigue crack due to age.

This - aided by corrosion over the years. Yes even in AZ

 

[SumGuy]

The center might have first started to tear away, putting too much stress on a few remaining lug holes and that's why one of them tore. If this is ultimately caused by age, then a lot of these 50 - 60 year old wheels are still on cars today.

And sorry, I don't see much if any corrosion on that rim.

Some of my snow tires are still mounted to 15 - 20 year old steel rims that are horribly, horribly rusted.

 

[Pablo]

The center might have first started to tear away, putting too much stress on a few remaining lug holes and that's why one of them tore. If this is ultimately caused by age, then a lot of these 50 - 60 year old wheels are still on cars today.

And sorry, I don't see much if any corrosion on that rim.

Some of my snow tires are still mounted to 15 - 20 year old steel rims that are horribly, horribly rusted.

You are NOT going to always see stress micro corrosion with your nekid eye.

 

[SumGuy]

You are NOT going to always see stress micro corrosion with your nekid eye.

I did a google search on your term "stress micro corrosion". What I found is that it means a type of corrosion produced by the presence of a corrosive environment caused by micro-organisms. The presence of micro organisms was a common theme of every search result I see on page 1 of google search results.

I doubt there are many micro organisms causing a corrosive environment for steel car wheels in Arizona.

 

[Pablo]

I did a google search on your term "stress micro corrosion". What I found is that it means a type of corrosion produced by the presence of a corrosive environment caused by micro-organisms. The presence of micro organisms was a common theme of every search result I see on page 1 of google search results.

I doubt there are many micro organisms causing a corrosive environment for steel car wheels in Arizona.

Google fail.

https://duckduckgo.com/?t=ffab&q=stress+micro+corrosion&ia=web

https://duckduckgo.com/?t=ffab&q=stress+crack+corrosion&ia=web

Yeah there are no rusty hunks of steel in the desert.

 

[Astro14]

What strikes me about this is the damage around the bolt holes.

If the wheel just failed and broke off, why the split and distorted seats around the lug holes?

It looks to me like the car was run for a bit with the wheel a bit loose, and it banged around causing the fatigue, and damage around those lugs,which led to the crack.

 

[rijndael]

It's pretty hard to guess about the prior misuses/circumstances around a 57+ year old rim.

 

[BigCahuna]

It's pretty hard to guess about the prior misuses/circumstances around a 57+ year old rim.

It should still be under warranty eh.,,,,

 

[ecotourist]

Another way to stress the steel at that bend would be with heavy side loading. Examples would be repeated hard turns in a heavy car (check) with stickier that expected tires (check). Or as @Astro14 suggests having been run while loose at some point.

A quite likely mechanism is that the wheel may have had an original defect that simply propagated over time.

I think the term some of you have been looking for is stress corrosion cracking. I don't think it would take very much salt to keep that going in an existing crack. Ever run on a salted road? Quite possible.

 

[Fordiesel69]

It was going to fail from the day the center part was stamped. Aviation has these types that reminds me of the northwest 747 that the rudder servo fatigue failed. There was no real design flaw, was just old, so they shortened the intervals.

 

[Pablo]

Wow on my PC that steel looks thin!!

 

[JMJNet]

50+ years of heating and cooling?
Tucson probably have a lot of extremely hot days in the past 50+ years.

 

[mrsilv04]

50+ years of heating and cooling?
Tucson probably have a lot of extremely hot days in the past 50+ years.

How do we know that this car has been in Tucson all of its life?

 

[krzyss]

If this failure becomes more popular we will know it is just regular fatigue.
Was it helped by improper torquing? Very likely over +50 years of usage.

I guess "original" antique in running condition can only be "original" to a degree. All wear parts (that may be everything in +50 year old equipment) need to be replaced.

Krzyś

 

[JMJNet]

How do we know that this car has been in Tucson all of its life?

Well, you don't have to be in Tucson.
In Canada, like where OP, it is probably 50+ years of extreme cold.
This happened in the street of Tucson which I assume in AZ according to the OP.
Or may be Tucson, mexico ???

Be thankful it last that many years.
Most of us don't.