Load Management
Progressive Rate
Leaf Springs
Manufactured from SUP9 and SUP9A spring steel with multi-stage heat treatment and precision shot peening — Tough Dog Armoured leaf springs are the primary load-carrying component for rear-axle armoured platforms handling B4–B7 ballistic protection packages.
Progressive rate geometry ensures a compliant ride under standard operating conditions, then stiffens progressively as armour weight engages — delivering both mission capability and vehicle control.
Engineering
Manufacturing Excellence
Progressive Rate Design
Each leaf is set slightly higher than the one below, ensuring contact along the entire spring length. Delivers a compliant ride under light load while progressively stiffening as armour weight is applied — the critical balance for mission vehicles.
SUP9 & SUP9A Spring Steel
Japanese-specification high-silicon manganese spring steels chosen for their superior fatigue resistance, yield strength, and resistance to permanent set — essential for vehicles carrying 1,500–3,000 kg of ballistic protection.
Multi-Stage Heat Treatment
Oil quenching followed by precision tempering creates a fine, stable grain structure throughout each leaf, maximising strength-to-weight ratio and fatigue life under sustained extreme loading.
Precision Shot Peening
Controlled steel ball bombardment induces compressive residual stress at the leaf surface — dramatically increasing fatigue resistance and allowing springs to operate at higher stresses without crack initiation or failure.
Performance
Tough Dog vs. Standard Leaf Springs
Technical Detail
Understanding Progressive Rate Load Management
A standard linear leaf spring applies the same rate per millimetre of compression across its full travel. For armoured vehicles, this creates a binary problem: a spring stiff enough to carry armour loads will be brutally rigid when lightly loaded, while a spring comfortable under light load will bottom out and lose control under armour weight.
Tough Dog progressive rate leaf springs solve this by engineering each leaf to engage the primary leaf at a different point in the compression stroke. Under light load, only the primary leaf is active — providing a compliant, controlled ride. As armour weight compresses the spring, additional leaves engage progressively, with each engagement providing a calibrated stiffness increase that matches the load curve of the ballistic protection package.
The result: a vehicle that rides normally when unloaded, and responds correctly under full armour load — without the ride degradation that makes fixed-rate springs unsuitable for dual-use armoured platforms.
FAQ
Frequently Asked Questions
Learn More
Resources & Technical Guides
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Experience Superior Load Management
Contact our engineers for load calculations and custom spring configurations for your armoured vehicle application.