Bought very nice 996 wheels, what spacers do I need?
 

I was just at Woody's place today over at Bastrop, TX. I picked up a bunch of random parts, and he had these beautiful (to me) wheels off of a 996 he's got in his yard. He gave me what I felt was a very good price and I bought them. Both Woody and I have seen threads saying that 10" wheels will fit on the back of a Boxster. My car is a 2002 Boxster S 986. These new to me wheels are 10" wide, 18" diameter. The tires on them are 265/35/18. The problem here is that I'm coming from a mostly American car background, and am used to a simple measurement of "backspace". The way these wheels are measured confuses the heck out of me. So, I am hoping that since I'm told this is a fairly common wheel swap, someone can lead me to what spacer thickness(es) I need.

Starting with the back wheels, they are 10" wide, and are stamped on the back with "10Jx18-ET65". Tires, as I said above, are 265/35/18. Given my car is a stock 2002 Boxster S, what size spacers do I need to use to clear on the back side of the wheel, and where does that place the front side? Does that move the front side of the wheel out further in the wheelwell? I certainly don't want any rubbing issues at all.

The front wheels are stamped "7 1/2Jx18-ET50". The front tire size is 225/40/18. I am told that these don't need spacers. Is that true? No rubbing issues on bumps or turns at all? If I use no spacers on the front and spacers on the back, are the faces of the wheels set outboard in the wells the same amount? If not, how thick are the spacers needed on the front to equal the back? Do those spacers, if needed, present any rubbing problems?

Thanks for any and all information.

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You will need 15mm on the rear to bring them out to stock. Fronts are fine. Any thing that you add on to that is a matter of taste/purpose, for instance 25mm rear and 10mm front, etc.

Does “bring them out to stock” mean the stock track (ie outside edge), or the stock offset. As these wheels are so much wider than stock, the two can’t both be true.

For clarification....
 

It's necessary to use spacers to provide clearance in the rear of the wheel/tire so it doesn't interfere with the strut, etc. However all things being equal, I would like to move the face of the wheels further outboard for appearance purposes, to sort of fill the wheelwell better. So I guess the question is, what spacers are needed to provide clearance on the back side of the wider wheels. Also, disregarding the bigger wheels, on a stock car, how much do guys typically move their wheel out for appearance reasons? Once I know what spacers give me clearance, I can then determine how much more I need to go to actually move the wheels outboard for appearance reasons as well. Of course there comes a point that the spacers are just too wide to be structurally sound or practical. In the end, it has to handle and run good. Appearance comes next. What spacers do guys put on a stock 986 to make the wheels look better in the wells?

Lets say the answer to the above stock vehicle appearance question is 10mm, for example. If I need 15mm for clearance and 10mm for appearance, that would mean a 25mm spacer. I don't see many of them, and I imagine there's a good reason for that. I'm trying to sort all this out, and I appreciate all the help.

Priority number one is to provide the necessary clearance. Is 15mm the thickness for that? How big a spacer is just too big?

15mm spacer w longer bolts front
23mm spacer w longer bolts rear

Sounds good to me!
Here's a wheel size calculator to help you decide: https://www.wheel-size.com/calc/

I have the exact same set of wheels on mine from a 996. I did not use spacers on the front. For the rears, I have 20mm spacers from Wheel Dynamics. Talk to Eli. The spacers are very high quality and I have not had any issues in the 5 years that I have had them. http://wheeldynamics.com/porsche-cars.html

Thanks, guys!
 

Thanks so much to all of you for the great input. Bruce, I sent you a PM given that you have actually done this exact combo. If you could read it and get back to me I'd really appreciate it.

Thanks again to all.

I have a pair of 25mm spacers from when I ran the same size wheels on the rear of my Box for sale, they are hubcentric & I also have polished alloy lugs for them.

I second the recommendation for Wheel Dynamics. They know these cars very well. I have the first Gen RPK's. Love them!

Thanks guys!