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Torsion Bar Set – Jaguar XK 120, XK 140, XK 150 – 51.09" x 1.057" Diameter (Pair)

Torsion Bar Set – Jaguar XK 120, XK 140, XK 150 – 51.09" x 1.057" Diameter (Pair)

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SKU 4722

Category: Jaguar XK120 / XK140 / XK150 Performance Torsion Bars 

The 4722 is a premium, heavy-duty front torsion bar upgrade engineered specifically for the legendary post-war Jaguar XK series (XK120, XK140, and XK150). These iconic sports cars rely on a longitudinal front torsion bar suspension layout to control track geometry and support front-end weight. Increasing the diameter to a robust 1.057", this solid 4340 alloy steel set delivers a significantly higher spring rate than standard factory bars. This transforms the classic driving experience—drastically reducing body roll, preventing nose-dive under heavy braking, and stabilizing the chassis during vintage racing, high-speed rallies, or spirited touring.

Performance & Fitment

  • Application: Jaguar XK120, XK140, and XK150 models.

  • Diameter: 1.057". A calibrated high-performance profile designed to sharpen turn-in and modernize cornering control without making the suspension overly harsh.

  • Length: 51.09" (Exact factory longitudinal layout dimensional fitment).

  • Spline Configuration: 25-Tooth Front / 24-Tooth Rear. Engineered to index perfectly into the factory lower control arm and rear chassis anchorage.

Premium Construction

  • Material: Solid 4340 Heat-Treated Alloy Steel. Forged from premium racing-grade steel designed to handle continuous structural twisting without sagging or losing its spring memory over time.

  • Manufacturing Process: Centerless Ground. The outer body of the shaft is ground to a mirror finish, maintaining absolute diameter consistency. This precision removes all microscopic surface imperfections, eliminating potential "stress risers" where fractures typically form under high-load conditions.

  • Coating: Heavy-Duty Powder Coating. Seals the raw steel against road moisture, engine oil leaks, and road salt, ensuring long-term protection against corrosive pitting.

🇬🇧 Classic Jaguar XK Suspension Tech & Installation Notes

Upgrading the longitudinal torsion bars on an XK-series Jaguar requires strict adherence to factory positioning and mechanical tuning:

  • ⚠️ Caution: High-Tension Energy: Torsion bars store an immense amount of mechanical energy. Before loosening or attempting to remove the factory bars, you must safely support the front suspension and completely relieve the tension using the rear chassis adjustment mechanism. Attempting to force a loaded bar out can cause catastrophic personal injury and permanently distort the chassis anchorage points.

  • ❌ Mastering the 25/24 Vernier Indexing: Jaguar brilliant engineered these bars with an unequal spline count (25 teeth on the front, 24 teeth on the rear). This serves as a mechanical vernier adjustment system for ride height. By rotating the bar slightly in one direction at the front lower wishbone and in the opposite direction at the rear chassis bracket, you can raise or lower the vehicle's front trim height in minuscule fractions of an inch, allowing for perfect chassis leveling and corner-balancing.

  • ❌ Spline Sockets Cleanout: Over decades, the splined sockets inside the front lower control arms and the rear chassis crossmember gather road grime, hardened grease, and surface rust. Before sliding the new 1.057" bars into place, thoroughly clean out these internal receivers with a wire brush and a premium penetrating solvent. Forcing a new bar into a clogged socket can easily strip the splines.

  • ❌ Anti-Seize and Lubrication: Always apply a generous coat of heavy-duty, waterproof anti-seize or a moly-based grease to both splined ends before installation. Because these splines must allow for slight movement as the lower control arm moves through its suspension arc, running them dry will cause severe squeaking, internal corrosion, and eventual seizure.

  • ❌ Maintain Left & Right Orientation: This product is sold as a matched Left & Right set because torsion bars are directional. They are structurally pre-stressed in a specific direction during manufacturing or take a permanent "set" based on the rotational torque of supporting the car. Ensure you inspect the bar ends for Left (Passenger side on LHD) and Right (Driver side on LHD) stamps. Swapping their sides will force the metal grain to untwist against its set, causing rapid ride height sag or premature bar failure.


What’s Included

  • (1) Pair of solid torsion bars

Warranty

Backed by a 1-year warranty for peace of mind.


4 in stock (can be backordered)

$ 702.36 702.36 USD $ 702.36

$ 702.36

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Torsion bars Jaguar Torsion Bars
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