is this number somewhat fixed or will it depend on the model?

specifically model J042 17x7 +55 and J043 17x8.5 +65

I'm just wondering how much will the offset be reduced by and if it will fit fine without rolling the fenders

 

Quick google search shows it lowers it about 15mm but I am sure some people have done this and can give a more specific answer.

 

typically around 12mm to 15mm so around 7+40 ish and 8.5+50ish