Help please for wheel selection
 

I like the stock set up but need wheels for winter. I wan t a lighter rim, so if stock wheel is 17/7 ET48 mm and back space 6.1. What range of offset values will work? the same question for back spacing. Tire rack suggests wheels for BRZ that vary widely f rom the stock measures.

Ultimately the range of offset and back spacing values can only be determined by extensive experimentation. The largest published and trustable source of such experimentation in my opinion is Tire Rack.
So you know that any offset/backspace within Tire Rack's range will work. Are there any outside the range that could work? Start by looking at the wheel database DarrenDriven has put together, selecting any wheel that falls outside of Tire Rack's range. This will help you expand the range of tested offsets/back spacing.

So far I've determined the Kosei K4R to be the best value for a wheel much lighter than stock and with similar dimensions.

we have done 17x8 +42mm, and that fits perfectly fine.

this set, WEDSSPORT TC105N weight around 15.9 lbs.

http://farm9.staticflickr.com/8283/7...fbf49ef4_b.jpg

http://d5otzd52uv6zz.cloudfront.net/...47b7b2-800.jpg

And how much are they?

detail here

http://www.ft86club.com/forums/showthread.php?t=6364

Um, Enkei RPF1 in 17x8 with 42mm offset is lighter and over $700 cheaper. To each their own.

Regardless, I don't think I'd use either of them for a set of winter tires. If you really want light, wait for the Kosei K4R at the tire rack. For a real winter tire? I'd be looking at 16" wheels, they are cheaper, you will have a taller sidewall to deal with potholes better, and probably have a better and cheaper selection of snow/mud and snow tires.

Alternatively, get a nice set of wheels for summer and keep the stockers for winter (or pick up a second set of used stockers for winter).

my 2 cents.

If you are lookiing for stock type sizing for snow usage, a 17x7-7.5 or even 16" are better as wider width for winter tires wont necessarily get you more traction... A 16x7 would yield even better priced snow tires.