Forester STI SG9 Enkei RS05RR Fitment: 18x8.5 vs 18x9 vs 18x9.5

Choosing Enkei RS05RR wheels for a 2004–2007 Subaru Forester STI SG9 is not just a matter of finding 18-inch wheels in 5x100. The STI has a relatively high-offset factory wheel and a performance brake package, so a wider RS05RR may gain a pronounced outer position while approaching the inner suspension. This guide compares the 18x8.5 +42, 18x9 +40 and 18x9.5 +43 Enkei specifications using the factory SG9 STI wheel as a reference, then explains what is—and is not—known about brake clearance.

The comparison is based on published Japanese-market Subaru vehicle specifications, Enkei's own size chart and real HausofWheels product listings. It is not a certificate of physical fitment for any particular customer's car.

2005 Forester STI SG9 factory wheel reference

Japanese-market specifications list the Forester STI Version TA-SG9 with 18x7.5 +48 wheels, 5x100 PCD and an approximately 56.1 mm hub centre (often rounded to 56 mm in Japanese databases). A 225/45R18 factory tyre reference appears in SG9 fitment records. This is a useful starting point, not proof of the equipment on a modified or imported vehicle.

Sources: 2005 Forester variant-specific Japanese wheel table and 2005 Forester SG9 hub and tyre reference.

Enkei RS05RR 5x100: 18x8.5 +42 versus 18x9 +40 versus 18x9.5 +43

All three dimensions are listed in Enkei's official RS05RR manufacturer specification table. The 18x8.5 +42 and 18x9 +40 versions use the listed F face, while the 18x9.5 +43 uses the M face. That face difference is another reason to check specific caliper clearance rather than comparing offset alone.

Calculation method: the added rim width is divided equally on both sides of the centreline (25.4 mm per inch), then adjusted for the offset change. For example, moving from 18x7.5 +48 to 18x9 +40 adds 19.05 mm to each half-width and 8 mm from the reduction in offset, placing the outer rim 27.05 mm farther outward and the inner rim 11.05 mm closer to the suspension. These are nominal bare-rim changes, not tyre or measured fender clearances.

Compared directly with 18x8.5 +42, the 18x9.5 +43 extends about 11.7 mm farther outward and reduces the inner clearance by about 13.7 mm. Although +43 sounds more conservative than +42, the full extra inch of width matters far more.

What can you actually buy from HausofWheels?

Use the live product page for price, condition, accessories and availability; stock states may change. These examples were checked against the HausofWheels catalogue rather than inferred from a generic manufacturer size table:

• New RS05RR 18x8.5 +42, 5x100 — genuine Matte Dark Gunmetallic square set, listed under Sydney Stock at the time this guide was prepared.
• New RS05RR 18x9.5 +43, 5x100 — Enquire for Stock listing; its representative photograph shows an 18x8.5 +42 wheel, so the displayed spoke/face depth should not be taken as the exact 9.5-inch configuration.
• Used RS05RR 18x9.5 +43, 5x100 — a separate Sydney-stock set with tyre and condition details that must be checked individually.
• New staggered 18x8.5 +42 front / 18x9.5 +43 rear, 5x100 — an enquiry listing illustrating a staggered option. Verify tyre rolling circumference very carefully on an AWD Subaru.

The 18x9 +40 5x100 is a documented Enkei manufacturer specification, but an active HausofWheels product listing was not identified when this guide was prepared. Treat it as an enquiry or special-order possibility, not an advertised available set; confirm lead time and current Australian supply before ordering. Compare all RS05RR listings or all 5x100 wheels rather than relying on a snapshot of inventory.

Do RS05RR 18-inch wheels clear factory Forester STI Brembo brakes?

PCD, wheel diameter and offset do not establish Brembo clearance. The SG9 STI can have a substantial factory performance-brake package, and a wheel's spoke profile, centre disc and inner barrel must clear the actual caliper and rotor. Enkei's F and M face codes are design information, not a promise of clearance for your exact Subaru. Modifications, replacement rotors, spacers or previous brake swaps may change the answer.

Ask for the exact wheel size, offset, model code and current brake hardware, ideally with a wheel-specific brake template or measurements from a documented matching setup. Check inner suspension and outer guards separately. The RS05RR 18x9.5 +43 wheel sits 20.4 mm closer to the inner suspension than the reference factory wheel, regardless of its Brembo clearance.

Read our brake-caliper clearance guide and the broader RS05RR buyer's guide for additional considerations.

Centre bore and hub-centric rings

Enkei's RS05RR manufacturer table lists a 75 mm wheel centre bore for the three 5x100 specifications above, whereas the standard SG9 reference hub is approximately 56.1 mm. Where the exact wheels have that 75 mm bore, they require an appropriately sized and fitted 75.0-to-56.1 mm hub-centric ring solution for hub centring. Verify wheel-specific bore, ring seating, material suitability and correct wheel-nut seat/thread before installation. A hub ring does not change PCD or solve caliper interference.

See hub-centric rings explained and wheel-nut thread pitch explained.

AWD warning: the tyres supplied with used or staggered RS05RR wheels

One separate used RS05RR 18x9.5 +43 square wheel set in the HausofWheels catalogue currently describes 245/40R18 tyres on the front and 255/35R18 on the rear. Based on nominal tyre-size arithmetic, those sizes have approximate diameters of 653.2 mm and 635.7 mm—a difference of 17.5 mm, or about 2.7% relative to the larger size. Actual measured rolling circumferences depend on the individual tyres and their wear.

Do not assume the included mixed tyre sizes are suitable for a full-time AWD Forester STI. Confirm the exact vehicle manufacturer's AWD tyre requirements and consult a qualified tyre specialist about a matched, appropriate tyre set before installation or use. This is a reason to verify tyres separately from the wheels, even when all four rims share the same dimensions. HausofWheels supplies genuine wheels and does not provide tyre fitting or testing.

Does the SG9 use the same PCD as every Forester or WRX?

No. A factory SG9 STI is a 5x100 Subaru, whereas some later Subaru generations and performance trims use 5x114.3. Never use the model name alone to determine stud pattern. Confirm the exact model year, version and actual hubs before comparing a newer WRX STI or Forester wheel.

For wider model comparisons, see Subaru 5x100 versus 5x114.3, 5x100 Subaru WRX wheels and the wheel offset calculation guide.

What information should you send before ordering?

1. Your Forester STI year and SG9 chassis confirmation; specify whether hubs or brakes have been converted.
2. The exact Enkei RS05RR diameter, width, offset, PCD and desired finish.
3. The factory or aftermarket front and rear calipers and rotor sizes.
4. The current suspension type, ride height, camber and existing wheel/tyre dimensions.
5. Your intended tyre manufacturer, size and use, with an AWD-compatible rolling circumference plan.
6. Whether you need a new or used wheel set and your preferred pickup/shipping option.

Send a Forester STI wheel-fitment enquiry with those details, or browse genuine Enkei RS05RR wheels. Hurstville pickup is by confirmed appointment once an order is ready. We supply wheels only, without on-vehicle test fitting.

Sources and editorial method

Data in this article comes from Enkei's official RS05RR technical size and bore chart, Japanese-market 2005 Forester STi wheel records, and our current genuine wheel product records. The wheel-position and nominal tyre-diameter calculations are original arithmetic based on the stated dimensions, not physical fitment tests. No manufacturer or supplier has certified these RS05RR configurations as clearing every SG9 STI brake and suspension setup; measure and verify before purchase.