Wheel Stamping codes refesher

Help refersh my memory because I can't find my reference book that has the wheel codes listed in it. Specifically, the wheel codes for 15X7 ralley wheels for 1970-1973ish and on.

I recall that the 1970 code is "WG" and has a 1.25" backspacing IIRC. The 1971 is code "WM" and has a 1.00" backspacing. 1972,1973 had a different code but teh same spacing as 1971. Then from 1974 on the all have the code "WP" and are all 1.00" backspacing.

Is my memory failing me or... And let me know if you find my book.
Thanks!

 

You have the codes almost right but the backspacing is wrong. All the 15" wheels you mentioned have a 4 3/8" backspacing and the codes go like this,

70 (7.0 or WG, depends on when they were built)
71-72 (WM)
73-77 (WP)
I wrote an article for the 15" wheel options and another for the 14" wheel options for the BPG newsletter. If you are a member you can go to their website and look at/print off copies of the articles. The articles list all the application codes, rim codes, show how to decode the date codes, and list all the differences so you can easily figure out what wheels you have.

Maybe my articles are the "book" you are talking about.
Duane

 

I think he may be talking about the inner chrome lip when he is refering to backspacing. Where the 70 wheels are noticably wider at the point.

 

Sorry I was writing backspacing and thinking offset. At the point where the hoop meets the disc. IIRC, on of the easy ways to tell if a car has "WG" or "WM-WP" wheels was to set a quarter on the lip.

If the lip was 1" is was a WM or WP, etc. If it was 1.25" it was a WG.

Anyway, Thanks for the answer about the 73-77 wheels all being "WP" code.

And the book I am thinking of used to be carried by Year One in the literature section. I haven't checked the catalog yet to see if they still carry it.

 

It appears that the book I am wanting is out of stock with Year One. I posted a thread on the "papertrail" section. Thinking that that is a better place for it than here.