What is the perfect offset?
 

I'm sure JD is tired of answering all of my stupid "will this set of wheels fit with this offset?" questions! So I think if I can get some opinions on what is the best all around offset for a set of 18" wheels (7.5"-8" front and 9"-10" rear) on a 986 Boxster, you won't have to read all my redundant wheel questions :D. Also, would the same offsets be appropriate for 19" wheels?

One other question about offsets. If I have a rear 10" wheel with an offset of 58, and I put a 15mm spacer, it would change the offset to 43. Is this correct?

I'm currently looking at a set of 18" Carrera III wheels with front 8"/57 offset and rear 10"/58 offset. I know they would need spacers for proper fit but I just want to finally get it straight in my head how to figure the offset/spacer formula :D.

Thanks in advance for all of your input on this guys! :cheers:

Perfect offset?

Wheels that don't require spacers. Less unsprung weight. Less stress.

JD won't mind... he's a life force, remember! - not just a man!
Anyway's if he cuts up rough - just get him banned! :D

MH.
Perfect kind of depends on the eye of the beholder?
Some like their wheels tucked in, less road rash etc etc, whilst others like them to run pretty flush with the fender?

So the perfect offset is not easily defined.

If you want to run flush, and without spacers as suggested by flavour - dig out a thread between JD and Porsche Pete. He ender up with 19" Victor Khans and the fit was sooooo good with no spacers.

You also need to consider if you intend to lower your car as this too can have a bearing on how wide you can run without rubbing - unless you run PSS9 dialled to rock solid!

Its not a clear cut formula.

I have no real plans to lower my car. As far as the stance, I would like the wheels pushed out just a little more than stock to give it a more aggressive look. I don't want the car to look overly modified (that is why I've been looking at Carrera and Cayman wheels).

There are too many variables when it comes to wheel fitment to suggest a "best" offset recommendation. However, in the past I've provided the following information:

Here are some guidelines to follow when choosing wheel fitments:

Fronts : 8 to 8.5 inches wide with offsets ranging from +35 to +45 depending on how aggressive you want to go.

Rears: 9 to 10 inches wide with offsets ranging from +35 to +45 depending on how aggressive you want to go .


* These are general guidelines, and specifications can vary depending on the vehicle's suspension set-up and application .

In the case of the carrera lights that you're referring to., I would recommend lowering the offset on both the rears and the fronts by at least 10mm's to start. Also, to answer your question regarding how offset is effected by wheel size, the short answer is that it is not. While larger wheels and tires may ultimately create clearance problems of their own, offset itself pertains to the distance or measurement from the centerline of the wheel to the back pad (the part of the wheel that interfaces with the vehicle's hub). Generally speaking, the offset plays the same role with regard to wheel fitment regardless of circumference. That is to say, provided two sets wheels have the correct fitment, the same offset that say an 18 inch wheelset had, the same would apply to a larger 19 inch set.

Thanks JD, you are the wheel guru!

One other question about offsets. If I have a rear wheel with an offset of 58, and I put a 10mm spacer, it would change the offset to 48. Is this correct?

You are correct.