XYZ Racing Tarmac Rally Coilovers — Maserati BITURBO SI φ52 welding (PCD: 4X98) 1986-1991

The Biturbo SI’s twin-turbo V6 pours in boost mid-corner, and on the original dampers that surge arrives faster than the chassis can settle – the nose loads, the tail steps out, and the driver is left catching a car that was never given a platform to match its engine. The XYZ Racing Tarmac Rally coilover is built for exactly that fight: sealed-stage pace on closed tarmac roads, where a Biturbo needs its strut kept planted through compressions and crests rather than skipping across them.

For an eighties Italian GT with a genuinely quick powertrain and a chassis that’s had forty years to soften up, that’s the brief. This kit is set up to keep the Biturbo’s contact patches loaded when a mid-corner ripple or a patched surface arrives at speed, not to turn the car into a show piece.

What this coilover does for your 1986-1991 Maserati Biturbo SI Φ52 Welding (PCD: 4X98)

On a Biturbo running sealed-stage events, the surface changes lap to lap – patched tarmac, an expansion joint, a compression that wasn’t there on the recce. This coilover is calibrated to absorb that unevenness without transmitting the jolt straight through the chassis: harsh compressions are damped rather than bounced, so the tyre keeps its contact patch loaded and traction doesn’t disappear the instant the road gets rough. That matters most exiting a turbocharged corner, where the SI’s boost lands and any unweighted rear tyre turns power into wheelspin instead of drive. The welded strut construction is built to hold its damping character consistently through a stage rather than fading as the dampers heat up, and the added stability under load is what lets a Biturbo driver commit to a line on a road they’ve only seen once.

About the Tarmac Rally coilover

XYZ Racing’s Tarmac Rally coilover is the sealed-stage end of their range, tuned around closed-road pace notes rather than a circuit’s repeatable surface. The valving is set to soak up the impact of broken or patched tarmac and to shrug off the bigger hits – a mid-corner pothole, a badly repaired seam – without kicking the body off its intended line. XYZ built the settings from its own tarmac rally programme, so the compression and rebound curves reflect what actually happens on a stage: unpredictable surface changes taken at speed, not a smooth apex. For the Biturbo application the kit uses the φ52 welded strut construction specified for this chassis, keeping the damper body rigid under the loads a rally stage puts through a strut rather than a road car’s steadier inputs.

Fitment for the Maserati Biturbo SI Φ52 Welding (PCD: 4X98) (1986-1991)

This kit is specified for the Maserati Biturbo SI built between 1986 and 1991, matched to the φ52 welded strut fitment and the 4×98 PCD used on this chassis (MS03). Confirm your Biturbo runs the φ52 strut before ordering, since Maserati revised strut specification across the Biturbo’s long production run.

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This Tarmac Rally kit is built to the exact φ52, 4×98 spec your Biturbo needs – pick your spec below.