Big Brake Kit
XYZ Racing Hollow Front Brake Kit — Audi S4 (UFO) φ-φ (95-100) (HUB M12) (1991-1994)
SKU: XYZ-BRK-BKF-AU-21-D-FRONT
- IncludesFront axle pair (2 discs + 2 calipers)
- PositionFront
- Disc Ø380–444 mm
- Caliper pots8 / 12-pot
- Lead time10–15 working days
Fits Audi S4 (UFO) φ-φ (95-100) (HUB M12) (1991-1994)
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Caliper render for this kit:
The C4 Audi S4 arrived with an unusual inheritance. Audi’s UFO brake system, the large-diameter inner-clamped discs whose distinctive geometry earned them their nickname, was already being phased from the model range when the five-cylinder turbo S4 launched in 1991, and the platform has carried that complication for more than thirty years. The geometry that made UFO discs unconventional also made them susceptible to heat-induced warping under sustained deceleration, and finding replacement hardware that respects the M12 hub specification and original Φ-φ (95-100) diameter interface has grown steadily harder as these quattros age.
The XYZ Racing front big brake kit is built for exactly this fitment. It fits as a matched pair of front calipers and two-piece floating discs across the front axle, sized to the M12 hub specification and Φ-φ (95-100) diameter interface so it bolts to the C4’s existing front-axle hardware without modifying the hub, an important distinction for owners who want improved front-end braking without disturbing a chassis whose quattro drivetrain geometry is already established and expensive to alter.
What this brake kit does for your 1991-1994 Audi S4 (UFO)
The hollow-vane disc directly addresses the core failing of the original UFO setup. Better airflow through the disc keeps operating temperatures in check during the sustained braking load that a 230bhp all-wheel-drive car generates on a twisty road or circuit, particularly relevant on the C4 whose nose-heavy layout means the front axle absorbs a disproportionate share of deceleration forces. The two-piece floating construction lets the disc expand without warping the bell, where the original UFO geometry struggled, and trims rotating and unsprung mass off the front corners. Braided lines come as part of the kit to firm up the pedal.
Three pad compounds match friction to use without committing to a single trade-off between cold bite and peak-temperature longevity. Street is the quiet, low-dust default for everyday road use. Sport adds bite and heat range for harder road and mixed road-and-track work. Racing handles committed circuit sessions. Included painted caliper colours are Red, Yellow, Gold, Black and Anodized Black at no extra cost.
About the front brake kit
The kit uses a hollow-vane disc to improve heat evacuation relative to the solid-cast geometry of the original UFO discs. It is sized to the Φ-φ (95-100) diameter interface and M12 hub bolt pattern of the 1991-1994 Audi S4, fitting the existing front-axle hardware without additional hub parts or full-conversion machining. The calipers are hollow-bodied as standard for strength without excess weight, with an optional Hollow Racing upgrade for track-day use that drops the dust cover, is rated to 1000C and carries a two-year warranty.
The three-compound pad system spans road use through to track-day applications, so the same kit serves a car that does occasional circuits without a pad swap for the drive home. Beyond the included painted finishes, a Custom Color in any Pantone is available, along with premium polished-forged Titanium, Polished Gold and Polished Silver and candy Teal, Blue, Red and Orange. Discs come drilled or slotted at the same price, and centre-bell upgrades, two-tone in five anodized colours or in titanium, are selectable at checkout.
Fitment for the Audi S4 (UFO) (1991-1994)
Specified for the 1991-1994 Audi S4 built with the UFO brake architecture, using the M12 hub bolt specification and the Φ-φ (95-100) diameter interface. The direct-fit design avoids hub modification, relevant on a C4 platform where altering front suspension geometry carries implications for the quattro drivetrain’s alignment tolerances.
What buyers also search for
- Audi S4 C4 front brake upgrade for cars with the original UFO hub geometry and M12 bolt pattern
- 1991-1994 Audi S4 UFO hollow-vane disc big brake kit with road and track compound options
- First-generation S4 front brake kit for the Φ-φ (95-100) diameter interface
- C4 Audi S4 UFO brake replacement with multiple caliper finish options
Choose your pad compound and caliper finish from the options above, and we build it to your spec.
What’s in the kit
Front axle kit — supplied as a complete bolt-on assembly.
- 2×Two-piece floating discs — 380–444 mm: you pick the exact diameter with the "Disc size" option
- 2×Lightweight aluminium centre bells
- 2×Forged aluminium calipers — 8 / 12-pot
- 2×High-stiffness mounting brackets
- 2×Braided stainless steel brake lines
- 4×High-performance brake pads (1 set)
- 1×Fitting hardware & tools pack
Choosing your spec
Every kit is built to order around the choices you make above. Here is what each option actually changes, so you can spec yours with confidence.
Brake pads — Street, Sport or Racing
Every kit ships with a full set of high-performance pads; the compound is your call.
Street is the right default for fast-road driving — a strong, progressive cold bite with low noise, low dust and long disc life. Sport raises the working temperature and adds bite and fade resistance for hard road use and the occasional track day, while still behaving on a cold morning. Racing is a track compound built for sustained abuse: huge fade resistance and bite once heat is in it, at the cost of more noise and dust when cold. Match the pad to how hard you actually use the brakes — there is no benefit to a race pad that never gets up to temperature.
Caliper grade — Hollow vs Hollow Racing
Hollow is the standard caliper on every kit: a hollow-body forged caliper, lighter than a solid one, fitted with a dust cover and backed by a 5-year oil-leak warranty. For most fast-road and spirited track use it is all the caliper you need.
Hollow Racing is the track-grade upgrade. It runs the same hollow body but without a dust cover (so there is nothing to melt at sustained high temperature), uses a twin-metal piston that isolates heat travelling from the disc to the oil seal, and is rated to 1000°C. Available 286–380mm (front). Warranty is 2 years on oil leaks and 10 years on appearance. Built for professional racing and repeated track days.
Caliper colour & finish
Painted colours (Red, Yellow, Gold, Black, Anodized Black) are included at no cost. Want an exact match to your car? Custom Color (+£150) paints the calipers to any Pantone code you supply (15–20 day lead time).
Polished Forged finishes are the flagship: a forged caliper given a mirror-polished surface treatment that shifts colour with the viewing angle. Beyond the looks, the polished surface dissipates heat better, resists rust and stands up to the weather. Choose Titanium (neochrome, +£350), Polished Gold (+£300) or Polished Silver (+£250). They look their best paired with a titanium centre bell. Care: clean only with a dilute neutral cleaner or water.
Candy colours (+£200) use a deep candy-paint and polishing process for a mirror-reflection, boutique finish — pick Teal, Blue, Red or Orange (shown below right).
Centre bells
The centre bell is the CNC-machined aluminium hat that joins the disc to the hub. The standard anodized centre bell is included. The Two-tone bell (+£200) adds an anodized accent ring — choose Red, Yellow, Orange, Purple or Silver right here at checkout. The Titanium centre bell (+£500) is a forged titanium bell (bolts not included) that finishes off the polished-forged look.
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More XYZ products for the Audi S4 (UFO) φ-φ (95-100) (HUB M12) appear here as the rest of the range publishes.