Suspension Springs

Suspension springs carry the weight of a vehicle, absorb bumps and keep the tyres pressed onto the road. On leaf sprung vehicles, the spring is only as good as the parts that hold it in place: the U-bolts that clamp it to the axle, the saddles it sits on, and the pins and shackles that let it flex. Nolathane?s suspension spring range focuses on that leaf spring hardware, so the springs you have, or the new ones you fit, can do their job properly.

Worn, corroded or loose spring hardware lets the spring and axle move where they shouldn?t, causing noise, wander and uneven load carrying. Renewing it restores firm spring location on 4WDs, utes, commercial vehicles and classic cars.

How Suspension Springs Work

A suspension spring stores energy when the wheel hits a bump and releases it as the wheel returns, letting the body ride smoothly over the road. Shock absorbers then control how quickly that energy is released so the vehicle doesn?t keep bouncing. Together, springs and shocks keep the tyres in contact with the road for steering, braking and traction.

Spring rate describes how stiff a spring is: how much force it takes to compress it by a given distance. A higher rate supports more load and reduces body roll but gives a firmer ride. A lower rate rides more softly but sags more under load.

Types of Suspension Springs

• Coil springs are the most common type on modern passenger cars, SUVs and many 4WDs. They?re compact and work with separate links or arms to locate the axle or wheel.
• Leaf springs are stacks of curved steel leaves clamped together. They both support the vehicle and locate the axle, which is why they?re used on most utes, many 4WDs, vans, trucks and older passenger cars. Multi-leaf, mono-leaf and parabolic designs are all common.
• Torsion bars twist rather than compress, and are used on some independent front suspensions.
• Air springs use pressurised air bags, often with automatic ride height control.

Coil and leaf springs can be linear, with a constant rate, or progressive and dual-rate, getting stiffer as they compress for a softer ride when empty and more support when loaded.

Leaf Spring Hardware and Why It Matters

On a leaf sprung vehicle, the spring is attached to the axle and chassis by several hardware parts, each with a specific job:

• U-bolts clamp the spring pack to the axle. If they loosen or stretch, the axle can shift on the spring, which changes alignment and can shear the spring?s centre bolt.
• Spring saddles and insulators sit between the spring and the axle or chassis, locating the spring and reducing noise and vibration.
• Fixed pins hold the front eye of the spring to the chassis hanger.
• Shackles let the rear of the spring swing as it flexes, so it can lengthen and shorten without binding.
• Bushes at each pivot allow movement while absorbing vibration.

When any of these wear or corrode, the spring can?t locate the axle accurately, no matter how good the spring itself is.

Signs of Worn Spring Hardware

• Squeaks, creaks or clunks from the rear over bumps
• The rear of the vehicle wandering or steering itself, especially when loaded
• Instability under heavy braking or when towing
• Rust, cracking or visible movement at U-bolts, saddles, pins or shackles
• Seized pins that won?t turn in their bushes
• The axle visibly offset on the spring, or uneven rear tyre wear

Leaf Spring U-Bolts

Leaf spring U-bolts are one of the most important, and most overlooked, parts of a leaf spring suspension. They?re stretched when tightened, which is why they generally shouldn?t be reused once removed. Rust, damaged threads or a previous over-tightening can all weaken them.

Fit new U-bolts whenever the spring is removed from the axle, when fitting new springs or spring blocks, or when existing U-bolts are corroded. Tighten them evenly in a crossing pattern to the vehicle manufacturer?s specification, and re-check torque after the first few hundred kilometres as the spring pack settles. Each listing shows the dimensions of the U-bolt so it can be matched to the axle and spring.

Lowered and Raised Springs

Changing spring height changes more than the stance. Lowered springs reduce suspension travel and can make the shock absorbers work outside their designed range, often calling for matching shocks. Raised springs increase ride height and can change shackle angles, pinion angles and steering geometry. Either way, check that U-bolts are the correct length, that shackles and pins suit the new ride height, and that the change meets vehicle standards where the vehicle is registered. Rules vary between Australian states and in the UK and Europe, including MOT or periodic inspections, so check before modifying and tell your insurer.

Kits or Individual Parts

Spring hardware can be replaced as individual parts or as complete kits. Individual parts suit targeted repairs, such as replacing a corroded U-bolt or a single worn saddle. Complete kits suit full rear leaf spring services, where renewing pins, shackles, bushes and U-bolts together means no worn part is left to undermine the new ones. Always replace hardware in pairs across an axle so both sides behave the same.

Upgrading to Polyurethane and Greasable Hardware

Factory spring pins usually can?t be greased, so dirt and water wear the bushes and seize the pins. Greasable pins and shackles let fresh grease push out grit, which extends bush life and keeps the spring flexing smoothly.

Nolathane has been making polyurethane suspension bushings since 1974, originally developed to replace brass bushes in hillclimb competition. The signature red bushings are made in a range of durometers (hardness grades) for each position, and offer outstanding abrasion resistance, high load-bearing capability and resistance to oil, grease, ozone and weathering, which suits utes and 4WDs that tow and carry heavy loads.

After Fitting

Once spring hardware is replaced, tighten all pivots and U-bolts with the vehicle at ride height, check that the axle sits square, and have a wheel alignment (tracking) checked. Re-check U-bolt and shackle torque after the first few hundred kilometres, and grease any greasable fittings at every service. Our fitment guarantee means the parts you order for your vehicle are confirmed to suit it.

Shop Suspension Springs

Springs are part of our suspension parts range, and spring saddles restore the seat between the spring and axle.

Find the suspension spring hardware for your vehicle, then order online with fast shipping or have it fitted by a Nolathane reseller. Every product is backed by Nolathane?s warranty, 60-day returns give you time if a part isn?t right, and our local support team can help whether you?re repairing a noisy rear end, servicing a working ute or restoring a classic.