AD or YH wheels.

[firstgenaddict]

JL8... is why they were changed.
There is a specification for a primed wheel with a part number sticker so they were available OTC.

[KurtS]

Any change notice that came thru had the part disposition noted.
Sometimes it's a coordinated change with another part(s) so all parts affected had to hit the line at the same time. Sometimes just exhaust the existing supply like this wheel change (a small dimensional change to clear the JL8 caliper). Sometimes it's replace immediately and scrap existing inventory or use for service.

[jdv69z]

I guess what I'd be curious about, and will probably never know, is whether or not when the last AD wheels were being used up, a Z/28 Camaro with a combination of both wheels AD and YH was assembled and came off the line.

[X33RS]

I believe that is what Kurt or someone here was trying to determine the last time this subject came up.  I submitted my info at that time to help with that question but I don't know if they ever came to any conclusions.  Might want to check with someone here that is keeping tabs on that stuff.  But like so many other things with these cars it's probably ongoing and ever changing with no definitive answer.

[X33RS]

Since JL8 triggered the wheel change, I guess the question could be...and I'm sure most know...when did JL8 become available on the option sheet?  That would at least tell you YH's were in full swing by then.  That's my thinking anyway.  Knowing that option started in Feb I believe really throws a monkey wrench in that line of thinking, with YH wheels on production cars at least in Dec 68 already.  That's a widespread time frame.

[william]

The earliest known JL8 car was final-assembled on or about February 24, 1969. By that time there were no AD wheels in production inventory.

[X33RS]

Thanks William that clears up my foggy memory.  James' comment about the reason for the wheel change just got me thinking out loud.   I was just wondering about the date spread, with the wheel change sometime in late 68, knowing my 12D Z has YH's.  I was guessing GM must have had JL8 on the drawing board early on to implement the wheel change 2 months prior.  Makes sense.

[william]

I have always suspected something came up in testing production JL8 parts that delayed availability. Early print ads for the '69 Z/28 mention it so it must have been assumed it would be ready. Chevy Engineering built a few '68s with JL8; one of them was tested in the July '68 Car & Driver. Engineering was done, parts were tooled up & available. Perhaps some "unintended consequence" came to light.

[X33RS]

Interesting William, thanks

[KurtS]

And that's why this would have been an 'exhaust existing parts' change - it was far enough before JL8 hit production.

[HOT3O2]

It would be interesting to know if any 12C or 12D cars got a mixture of the two. One AD left on the rack, Install it along with 3 YH's plus the spare. You never know.

[X33RS]

All mine including the spare are YH's on my 12D Z but that's an interesting thought.   William determined mine was a very late 4th week build based off the vin and data plate sequence.  Something around the 27th or so I believe is what he guessed at.   Nearly the end of the month really when you think about it.   So mine may not be the best example of the wheel change over.  The problem I'm told is that there aren't very many documents Z28's in this time frame to go by since it's a slow time of year for car sales.  So we may never know for certain.

[HOT3O2]

All mine including the spare are YH's on my 12D Z but that's an interesting thought.   William determined mine was a very late 4th week build based off the vin and data plate sequence.  Something around the 27th or so I believe is what he guessed at.   Nearly the end of the month really when you think about it.   So mine may not be the best example of the wheel change over.  The problem I'm told is that there aren't very many documents Z28's in this time frame to go by since it's a slow time of year for car sales.  So we may never know for certain.

That makes sense. Mine is a 12B. I'm sure the 5 AD's were some of the last ones installed.

[Shirlwtt]

I have talked to people who had '69 Z/28 cars that they bought new that had wheels with mixed dates and or YH and AD wheels on the same car during the transition. It is my understanding that GM exhausted stock as they made the change. Bill from Kansas.

[william]

Since you didn't personally experience this I'll chalk it up as an old wives tale. Mixed dates wouldn't matter but codes did. Wheels were coded on the BBC [box 133] for a reason. IF that occurred it was an assembly error and maybe involved a very few cars built late Dec.

Decades ago someone theorized that '68 DF wheels were used on early production '69 Z/28s. Not one '69 is known to have been built with them but it took years to get that out of everyone's brain.