more than skin deep
With a quarter of a million kilometres under the wheels, the chassis had certainly taken a bit of a hammering. The wear and tear of daily use, plus countless ski-seasons up and down mountain roads, frequent road trips and summer beach hops had resulted in a lot of dirt, grime and general crud that needed to be cleaned up and straightened out if any awards were to be had. Not only was appearance important, so too was longevity. It was mainly for this reason that most main undercarriage components were powder-coated and, where possible, zinc-plated prior as well. All hardware and brackets were either zinc-plated also, or chrome-plated where extra toughness and a superior aesthetic were required.
Rear uprights from an MY04 Impreza STi were chanced upon, with the same bearing diameter and 5x100mm wheel PCD as the fronts, so this will create a truly symmetrical 4WD system and allow a greater torque-split to the rear which, together with the 20mm rear swaybar, will give a more oversteer-ey handling characteristic. All 4 uprights were completely stripped, zinc-plated and rebuilt with new bearings, seals and ball joints. Nolathane suspension bushes were installed all round and a Whiteline anti-lift kit fitted up the front together with a Whiteline 22mm swaybar and later-model aluminium lower control arms, which were smoothed, media-blasted and then clear-coated for protection.
Eventually, the entire running gear will be upgraded to STi or better components, including a built 6MT with DCCD and matching rear differential, Chromoly axles and a custom one-piece, carbon-fibre driveshaft. In the meantime, the original LSD was kept and the 4.44 F.D. gearset installed to match the later-model WRX 5MT currently fitted. The original axles were painted and rebuilt, with the only other change here being a mix-n-match rear outer CV joint to interface between the Legacy axle and the STi drive flange.
Every high-horsepower drivetrain should have a “fuse”, an intentional weak point that, although designed to work perfectly under normal conditions, will fail controllably when a limit is reached and can be quite easily replaced at minimal cost. Most builders opt for this fuse to be the clutch since it is a consumable item anyway and meets the criteria outlined above. Many builders will install a twin-plate item believing it will handle x amount of horsepower their engine is producing and then wonder why they broke an axle or transmission when launching off the line!! The clutch option chosen here is a straightforward Stage 3 single-plate item capable of holding up to around 500lb-ft of torque; adequate for the task and when grouped together with stronger axles and a built transmission it will still be the weakest link in the chain.
Moving on to the driveline installation, this is all fairly standard, albeit with a few minor upgrades as deemed necessary and easy to do at this stage. The rear differential mounting bushes were replaced with genuine new items, whilst the transmission cross-member was fitted with K4RT30Y insulation pads (located at both ends of the central member, sandwiched between it and each end piece). These are manufactured from a urethane material so should hold up better than the original rubber items. Another popular upgrade is to replace the shifter bushings at the transmission end with urethane, so again Whiteline was selected since they offer a kit with the corresponding rear support block also, so this seemed a good choice. Finally, securing the gearbox to the firewall is a Perrin aluminium pitch-stopper, a simple but essential component even for a stock vehicle.
The suspension chosen for this build was initially a Koni adjustable insert designed to fit inside the original strut body, however the cost and limited availability made this an unwise option. Instead, a factory-replacement KYB gas strut with lowered springs from Cobra (NZ) were selected based on their price point and fit-and-forget nature. These items are still an upgrade over the original units and required no modifications to install, the only change being a repaint in the striking yellow colour you see here; far better looking than the boring old black and gives a hint to the Koni branding that was first envisioned.
Moving over into the braking department we have some rather interesting things going on here. Factory Subaru 4-pot calipers from a MY04 STi were sourced, restored and repainted Daytona Yellow, complementing the yellow strut bodies, gold hubs and also keeping with the Ferrari colour scheme. These calipers, although a direct bolt-on replacement with the 295mm front brake rotors, do not fit under every type of factory wheel option like the 2-pot sliders do, since there is that much more width to the caliper and wheel clearance depends on many things like offset and spoke design (I’ll be doing a write up on that topic a little later on, so stay tuned…)
So unfortunately the MY07 Legacy spec B wheels I always wanted to fit in fact do not fit, at least not without wheel spacers or having to grind about 5mm off the caliper. Not wanting to do either, I opted to try out an idea I’d been mulling over for some time; to relocate the caliper in a semi-underslung position. You will see many supercar manufacturers do this, such as on the Ferrari F430, Audi R8 and McLaren Senna, and many racecars such as the V8 Supercars, to lower the centre of gravity (CoG) of the unsprung mass. It also helps to move more of the vehicles’ total mass towards the centre of the chassis. This is why drivers cars usually have the caliper mounted on the trailing side of the rotor, behind the axle line.
It is useful to think of the “chassis” not only strictly in terms of the performance underpinnings, but also as that which supports everything else, especially in the case of a monocoque (or unibody) construction as most cars these days are, so the term refers also to everything else that gets bolted to the body.