Join Date: Jan 2015
Location: Injun Territory, 'Merica!
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American oem steel wheels and steel wheels from the 60's-80's will have the size 13x5, 14x5, 15x6, 15x7, etc, followed by JJ or JK stamped inside on the spine of the wheel. The two letters JJ or JK are a reference to the standardized outer wheel lip design by the ASAE, American Society of Automotive Engineers. Those two letter codes right after the the size, typically, are NOT used to identify the wheel.
On Pontiac factory usage rally II wheels the two letter code stamped to the right hand of the valve stem identifies the original use of the wheel. (Some early JC coded rallyII's were stamped on the lh side of the valvestem). There are 34 of these specific 2 letter rally II ID codes. Wallace Racing site has a link with pics of various styles of date coding of original rally II wheels and how to decode the date the wheel was produced. Need to identify a specific 2 letter wheel code APPLiCATION, feel free & drop me a PM.
In the case of the oem 15x7 4 3/4" bolt pattern Rally II's, the most common are the HM and the HW. HM's could be ordered on '73-75 GrandPrixs, LeMans, '73 GTO's, Formula's and T/A's. The HW coded 15x7 followed in aprox '76 and was avail after '76 on TransAms & Formulas through the '81 model year. Both the HM and HW wheel will interchange. Typically, only hardcore '73 and '74 T/A restorers are interested in buying or piecing together date code matching sets of HM's.
Hope this helps shed light on these wheels and how to properly ID them.