| So the diameter of the spare wheel well is around 20.5”. Using crude measurements I figured I would need around 15” of clearance on the inside diameter of the wheel so the caliper has clearance. The inside diameter of the G37 wheel is 15.5” but unfortunately the offset was not enough for the spokes to clear the caliper and thus the need for a spacer. The original donut that comes on the G37 is a 145/80R17 which is 26.13” in diameter. I was running 275/35R18 on rear which is 25.58” diameter and 245/35R18 down from 245/40R18 on the front. I had decreased my aspect ratio slightly as I was getting some rub on the front. The larger aspect was 25.72” and the smaller was 24.75”. I now plan on running 255/35R18 on the front with the new larger 9” barrels which will be a 25.03” diameter and more suitable. I also plan on running a 145/70R17 as the donut which will bring the diameter to 24.99” and line up with my new front tire size.
All that rambling is for perspective on sizing. The original spare was a space saver and inflates to bring it to size. You’d have to run a 145/30R17 to be able to fit the wheel into the spare tire well. Once my wheels come in I’ll deflate my donut to see if it will squeeze into the well and report back. (My guess is no since the tire will need to fit into a 1.75” cross section on either side.) There is a 370Z spare that is 145/70R18 but those tend to run $200+ dollars and would only be beneficial if the spoke design extends farther than the G37 and eliminated the need for a spacer. From looking at images online it’s hard to tell but probably not worth the extra $100 for a temporary tire.
On a side note - I ended up ordering a four pack of the spacers on accident so if anyone would like a brand new one let me know. These are the forged version and around $15 plus shipping.
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