2015 Subaru STI Coilover Setup Advice for No Rubbing Issues

Summary

For a 2015 STI that’s stock now but going to coilovers later, the safer no-rub choice is the 255/35R18 on 18x9.5 +35. The 265/35R18 +38 can work, but it’s more likely to need camber and maybe fender work once you’re low.

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Best upgrade path

1. 18x9.5 +35 with 255/35R18 — Easiest to live with, good grip, minimal rubbing risk on stock and mild coilover drop.
2. 18x9.5 +38 with 265/35R18 — More tire, but tighter inside and outside; needs more careful alignment and ride height on coils.

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The parts to do it right

• 18x9.5 5x114.3 wheels (around +35 offset) — Proper width for 255–265 tires, good inner clearance to strut.
• 255/35R18 max-performance tires — Slight stretch on 9.5, clears fenders better when lowered.
• Quality coilovers (height + damping adjustable) — Later on; pick something with decent stroke so you’re not slammed on bumpstops.
• Front/rear camber adjustment (bolts or plates) — Lets you pull in the top of the tire to clear fenders with wider rubber.
• Hub-centric rings (to 56.1 mm) — Keep the wheel centered, reduce vibration.
• Proper lug nuts (12x1.25, correct seat) — Needed for most aftermarket wheels.
• Performance alignment — Set camber/toe after wheels and again after coilovers.

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Things to consider

• On stock suspension, both setups can work; 265s are closer to the strut and fender, especially at full lock and big bumps.
• Once on coilovers and lowered, 265/35 on 9.5 +38 usually needs at least -2° front camber and possibly rear fender rolling to stay rub-free.
• 255/35 on 9.5 +35 is a common STI fit and usually clears with a mild drop and reasonable camber.
• Tire brand matters: some 265s run very wide; those are the ones that rub first.
• Any significant drop plus passengers/cargo will make the 265 setup touch sooner.

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Realistic expectations & tradeoffs

• 255 setup: Slightly less ultimate grip vs 265, but better steering feel, less tramlining, and fewer headaches with rubbing.
• 265 setup: More grip, but you’re buying yourself alignment tuning and maybe fender work once you go low.
• Wider tires will follow ruts more and can feel heavier on turn-in.
• Either setup will need a proper alignment to avoid chewing the tires.

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Questions

1. How low are you planning to go on coilovers (inches of drop or “just a mild drop / pretty low”)?
2. Are you willing to roll/pull fenders if the 265s rub, or is “absolutely no body work” a hard line?