If your window won’t stay open, slams shut, or becomes difficult to lift, the issue often comes down to a worn or broken balance system. Modern windows rely on internal counterbalance mechanisms to carry the sash weight smoothly and safely. Understanding window balance parts makes it easier to troubleshoot a problem, identify the correct replacement, and keep windows operating like new.

This guide breaks down the most common window balance systems—block & tackle, spiral, and constant force balances—and explains the different pieces that make each system work.

Why Window Balance Parts Matter

Window balances are engineered to counteract sash weight so the window can move up and down without drifting or dropping. When one component fails—even something small like a shoe or pivot—performance suffers.

Knowing the purpose of each part helps you:

• Diagnose why a window won’t open or stay open

• Identify the right replacement components

• Avoid incorrect part ordering

• Improve window safety and lifespan

Whether you’re a homeowner, installer, or repair tech, learning window balance parts gives you a major advantage.

Block & Tackle Window Balances: Parts & Functions

Block & tackle balances are extremely common in vinyl and aluminum double-hung windows. They use a pulley system to provide strong, smooth counterbalance support.

Core Block & Tackle Window Balance Parts

1. Balance Channel (Metal Housing)

This is the main metal body that holds the internal components. It typically runs vertically along the jamb liner.

Role: Protects the internal cord and pulleys while guiding movement.
Common problem: Channel bends or corrodes, causing friction and poor travel.

2. Tension Spring (Internal Coil Spring)

Inside the channel is a coil spring that stores and releases energy as the sash moves.

Role: Provides the lifting force that offsets sash weight.
Common problem: Spring fatigue causes sash drift or slamming.

3. Block (Pulley Assembly / “Block & Tackle” Unit)

The “block” contains pulleys that the cord loops through to multiply force and smooth travel.

Role: Converts spring tension into controlled sash support.
Common problem: Pulley cracks or seizes → uneven lifting.

4. Cord (Nylon or Composite Cord)

This cord loops through the pulley system, connecting the spring system to the bottom attachment point.

Role: Transfers force from spring to sash shoe/hook.
Common problem: Cord frays, stretches, or snaps.

5. Guides (Top and Bottom)

Often plastic end caps on the channel. They typically come in winged or non-winged styles.

Role: Retains internal system, protects edges, and allows movement in the window jamb.
Common problem: Plastic breaks, allowing the balance to shift or release.

6. Pivot Lock Shoe (Balance Shoe)

The shoe is the most important interface between the balance and the sash. It travels up and down and connects to the sash via a pivot bar.

Role: Engages the pivot, locks/unlocks tilt features, guides movement.
Common problem: Shoe cracks or locking cam fails → sash tilts incorrectly or won’t stay seated.

7. Pivot Bar 

A metal bar attached to the sash bottom corner that inserts into the shoe.

Role: Connects sash to shoe and enables tilt-in.
Common problem: Pivot bar bends or shears → sash won’t stay aligned or comes loose.

How to Identify Block & Tackle Balances Quickly

Look for:

• A metal channel on each side

• Tilt-in sash with pivot bars

• A shoe visible inside the jamb liner

If these are present, you’re likely dealing with a block & tackle system and will need the correct combination of window balance parts: channel length, shoe type, pivot bar style, and weight rating.

Spiral Window Balances: Parts & Functions

Spiral balances are often found in older vinyl, wood, and aluminum windows. They’re recognizable by the visible spiral rod and a tube or housing.

Core Spiral Window Balance Parts

1. Spiral Rod (Steel Spiral)

This is a metal rod with a spiral groove that stores tension. Depending on if the balance is for a tilt or non-tilt window, the end of the spiral rod will have a different shape. Taking note of this when ordering replacements is very important.

Role: Acts like a torsion spring—tension is wound into the rod.
Common problem: Rod bends or loses tension → sash won’t stay up.

2. Spiral Tube (Housing)

A plastic or metal tube that surrounds the rod.

Role: Keeps the rod aligned and protected.
Common problem: Tube cracks, causing drag or misalignment.

3. Coupling (End Fitting)

At the bottom end of the spiral rod is the coupling, sometimes also referred to as the tip, which hooks into a shoe or pivot area. The couplings come in different colors that indicate the weight range of the spiral balance, so choosing the correct color is crucial when ordering replacement balances.

Role: Transfers torsion tension to the shoe connection.
Common problem: Tip breaks → immediate loss of balance support.

4. Pivot Lock Shoe (Spiral Shoe)

Different from block & tackle shoes, spiral shoes engage the spiral rod tip and provide sash support.

Role: Holds the spiral and supports pivot engagement.
Common problem: Shoe cracks, jams, or wears.

5. Pivot Bar (or Corner Pivot)

Same concept: connects sash to the shoe.

Role: Allows sash movement and optional tilt functions.
Common problem: Pivot wears, loosens, or bends.

6. Tension Tool (Specialty Tool)

This isn’t installed permanently but is necessary for adjustment.

Role: Used to wind/unwind tension safely.
Common problem: Without correct adjustment, the sash will drift or be hard to move.

How to Identify Spiral Balances Quickly

Look for:

• A visible spiral metal rod

• A tube along the side jamb

• Often seen in windows that are older or non-tilt

Spiral systems are serviceable, but correct tensioning is critical. 

Constant Force Window Balances: Parts & Functions

Constant force balances use a coiled steel spring that applies consistent tension across the sash travel. These are common in lightweight to medium-weight windows and are often used in non-tilt and tilt applications.

Core Constant Force Window Balance Parts

1. Stainless Steel Coil Spring (The “Constant Force” Coil)

This is a flat, coiled strip of spring steel. These coils are typically stamped with a number to indicate its weight range capacity.

Role: Provides consistent lifting tension as the sash moves.
Common problem: Coil snaps, rusts, or loses recoil ability.

2. Coil Housing (Carrier)

A plastic or metal housing holds the coil and controls release.

Role: Prevents coil unraveling or shifting.
Common problem: Housing cracks → coil slips or jams.

3. Coil Pivot Lock Shoe

This shoe connects to the sash pivot bar and attaches to the coil. Pivot lock shoes for constant force balances look different from traditional pivot lock shoes and are usually easy to identify.

Role: Transfers coil force to sash and enables tilt.
Common problem: Cam wear causes tilt issues or uneven travel.

4. Coil Anchor / Bracket (Top Mount)

At the top, a bracket anchors the coil system to the frame. Brackets are not always required for installation, it depends on which constant force balance you have.

Role: Secures the coil and maintains correct alignment.
Common problem: Anchor pulls out or bends → coil misfeeds.

5. Pivot Bar

Again, this attaches the sash to the shoe.

Role: Structural connection for movement and tilt.
Common problem: Pivot bar wear creates wobble and uneven closure.

How to Identify Constant Force Balances Quickly

Look for:

• A visible flat steel coil inside the jamb track

• A compact housing rather than a long metal channel

• Often used in windows with a simple track system

When ordering window balance parts for constant force systems, coil strength, shoe type, and mounting style must match precisely.

Common Window Balance Parts That Fail the Most

Across all three systems, these are the most common failure points:

1. Shoes – crack, jam, or lose tilt-lock function

2. Pivot bars – bend, shear, or corrode

3. Cords and pulleys (block & tackle) – fray or seize

4. Spiral tips and rods – bend or lose tension

5. Constant force coils – snap or lose recoil

Replacing the correct part restores function quickly without replacing an entire window.

How to Choose the Correct Window Balance Parts

When identifying replacement parts, gather these details:

• Sash weight (or approximate)

• Balance type (block & tackle / spiral / constant force)

• Channel length or coil size

• Shoe style and pivot type

• Tilt vs non-tilt features

Getting the right match prevents repeat repairs and improves the longevity of the window.

Frequently Asked Questions (FAQ)

What are window balance parts?

Window balance parts are the internal components that counterbalance sash weight so windows open smoothly and stay in position. These parts include shoes, springs, cords, coils, pivot bars, and mounting hardware.

Can you replace just one window balance part?

Yes—but not if any of the internal parts of a block & tackle balance or spiral balance are damaged. The only failed components that are replaceable are the pivot lock shoe, pivot bar, or coil (in a constant force balance). If a system is severely worn, replacing the full balance assembly may be best.

Which balance type is most common?

Block & tackle systems are common in modern vinyl tilt windows, while spiral balances are typical in older designs and constant force coils appear in lightweight or compact systems.

Conclusion

Whether you’re repairing a stuck window or sourcing replacement components, understanding window balance parts is one of the fastest ways to solve common window problems.

• Block & tackle balances use pulleys, cords, springs, and shoes

• Spiral balances rely on a rod, tube, and coupling tip

• Constant force balances use a steel coil, housing, bracket, and shoe

With the right parts and correct identification, you can restore safe, smooth window operation without costly replacement. For more information or assistance ordering the correct replacements, Contact Us Today! The WHD Team will be happy to speak with you.