EDIT: Question about lug knurl size.

[565bbchevy]

I'm finally getting around to ordering parts. I'm looking for 12mm / 1.5 pitch studs, but I'm very confused as to what would be the correct knurl size. The more I look the more I see numbers from .501 up to around .580, and it's different every time I find a new thread. Does anyone know the correct knurl size for a metric ('83 and up) rotor?

I don't know what the factory knurl is but I would go the next size larger knurl when you find out that way you can drill the original holes out and have a fresh hole for the knurl to grab onto but for me I would just get something bigger in an ARP stud and drill it that size especially for something driven on a road coarse I would want the added size and strength.
Auto stores usually sell the replacement studs you could mic them at the store to see the knurl size if can't find the info online.
Most wheels can handle up to 1/2" studs without modification.

 

[403Olds]

ARP has recommended hole sizes on their website. When I installed my 3" rears, I didn't use a press on mine, but a ball joint press (C-clamp style). They really do press in. I don't think that using an impact and a flat nut to run them in would work with the proper press fit.

 

[UNGN]

12.73mm Knurl.(.501") is stock. Stock length is 41.5 (1.63") (Dorman 610254)

For 1/2" longer studs, you can use Dorman 61323 which is 54mm lont (2.12") and has a 12.8mm Knurl (.504")

You don't want a knurl bigger than .505"

 

[307 Regal]

Thank you very much!

 

[Kenwash01]

12.73mm Knurl.(.501") is stock. Stock length is 41.5 (1.63") (Dorman 610254)

For 1/2" longer studs, you can use Dorman 61323 which is 54mm lont (2.12") and has a 12.8mm Knurl (.504")

You don't want a knurl bigger than .505"

Thank you kind sir for a concise answer, I’ve been reading different answers for this question for 2 days.

 

[KCP]

The reason for the wheels coming loose might really be strechted threads on the lugs. I see the very same on our drivers training cars (Toyota GT86, Porsche Cayman etc.) where we have to change tires nearly daily. Those cars get kicked around very hard every day. Every 50-60 wheel changes we have to change lugs / bolts due to stretched threads.