Wheel size question..excuse my ignorance, but..
 

I am looking to upgrade to 18 tires. I want to stay with OEM. In the manual it states I need 7.5 J x 18, offset 50 fronts, and 9 J x 18, offset 52 rears. I was looking at a set on ebay for 8 fronts and 10 rears. The guy selling these state they came off his Boxster S with no spacers needed. Would this size fit mine and is it the right size? Thanks.

docdyh

2002 Boxster with 16 factory wheels.

The wheels in the picture above are 8x18 and 10x18 with no spacers. No rubbing problems either, but I don't think they are factory wheels. The rears have about a 2" lip on the outside.
If the eBay wheels came off his car I would think they would fit yours.

Have you driven a Box with 18's? If not I suggest you do because the ride is VERY MUCH firmer than your 16's
I have just changed back to 6 & 7 x 16 from 7.5 & 9 x 18 because I now drive a lot on rougher sealed roads and found the 18's were trying to shake the car apart not to mention the degraded steering at higher speed.
The 16 dramatically improved everything and in fact unless you are driving " in extremis" I doubt you will detect much difference in roadhandling.
I will keep the 18's for when I sell the car.
Cheers,
Glenn

I think this all comes down to what you are going for in your Boxster. If you are going the best suspension then the 18 inch option is the way to go hands down. If handling isn't a concern for you then 16 inch wheels are the best for comfort. By the way 18 inch wheel look SUPER good on a Boxster and will give you a much more aggresive looking car.

Wheels are my next upgrade also. I'd be going from the 17" that came as part of the sport package to an 18". I was doing this to fill up the wheel well and was hoping the wheels would stick out wider and line up more with the fenders. If I didn't upgrade my wheels can I just get spacers to bring them out farther?

Well, as shallow as it may sound, I want to upgrade for looks. I understand that I will have a much firmer ride. Hey Ronzi, By "lip" I assume that you mean the rears extend laterally from the fender? Would anyone put on 17's as an compromise of aggressive looks yet, decent ride ? What do spacers actually do. I wish someone would post a "wheels 101 Lesson" here for those like myself. Thanks.

"Hey Ronzi, By "lip" I assume that you mean the rears extend laterally from the fender? Would anyone put on 17's as an compromise of aggressive looks yet, d
decent ride ? What do spacers actually do."

By "lip" I mean there is a 2" extension of the rim that extends out from the center spokes, thus moving the outer rim flange further from the spokes. Usually this is done to widen the wheel without putting all of the increased width on the inside of the wheel and risking interference with suspension commponents.
The 18" factory wheels that I have seen use a different method of accomplishing the same thing. They have a thicker center section with the mounting bolt holes recessed deeply, and the wheel spokes are pretty much flush with the outside wheel flange. I suspect this is a considerably more expensive solution to the problem, which is probably why Porsche uses it.

Certainly using 17" wheels is a justifiable compromise between the 16s and the 18s. They fill out the wheel wells a little better, and have the added advantage (over the 18s) that tires are about $50 apiece cheaper.
From the ride standpoint, I find the 18s a little choppier, but not grossly so.
I put the 18s on the car in the summer, and the factory 17s on in the winter.

thanks ronzi..that is helpful...

Ronzi, So these spacers I see for sale - from 5mm to 17mm or there abouts. Can I add a spacer to my 17" wheels to bring it out more in line with the fender?

"Can I add a spacer to my 17" wheels to bring it out more in line with the fender?"

I have personally not used spacers, but sure, that's what they're for. Some of them will require longer bolts, and other types have a set of bolts for attaching the spacer to the hub, and then you use your regular wheel bolts to attach to the spacer.