Here’s a breakdown of the steering rack for the Suzuki Swift ZC21S (and closely related models) — what it is, how it works, what to check, and specifics you’ll want to know if you’re sourcing or replacing one.

What is the Steering Rack?

The steering rack (or ''rack & pinion'' assembly) is a key part of the steering system. In general:

• It converts the rotational motion of the steering wheel into lateral (left-right) movement of the wheels.  
• For cars with power steering (hydraulic or electric assist), the rack also integrates the assistance mechanism (hydraulic fluid or motor) that reduces driver effort.  
• The rack is connected to tie-rods/ends which then connect to the steering knuckles / wheels.

Specifics for the Suzuki Swift ZC21S

Here are details specific to the ZC21S model (and associated engine/variant) you should know:

• The ZC21S is part of the second-generation of the Swift (in many markets) with 1.3L / 1.5L engine options.  
• A listing for a steering rack for this model shows the OEM reference part number as 48580-63J51 | 48580-63J51 (or similar) for the 1.5 variant.  
• Some listings mention ''Fits Suzuki Swift 1.5 / 1.6 ZC21 / ZC31 / 1.4 RS414 steering rack'' for the ZC21/ZC31 body codes.  
• In the Malaysian market there are adverts for a ''Power Steering Rack'' for the Swift 1.5 ZC21S model (year roughly 2011-2016 in one listing) indicating the part is available locally.  
• Some listings also emphasise ''Right Hand Drive'' (RHD) fitment (Malaysia/UK etc).  

What to Look Out for / What the Description Should Include

When sourcing or replacing the rack for the ZC21S, make sure the description or the unit meets the following:

• Compatibility: Confirm body code (ZC21S), engine size (1.5L etc), steering side (right or left).
• Part number: Compare the OEM reference (eg 48580-63J51) with what you’re buying. The listing at B-Parts warns that small deviations in index letters can affect fitment.  
• Condition: New vs. reconditioned vs. used. Some listings for the Swift show ''re-cond'' racks.  
• How complete the assembly is: Does it include inner tie-rods / ends / boots / seals? Some racks may require reuse of other components. For example, one parts site states ''Comes complete with new inner rack ends'' for a Swift rack.  
• Seals / boots: The rack boots and seals are critical to prevent fluid leaks (for hydraulic racks) or to keep dirt out (for electric/power assist racks).
• Mounting points: Ensure the mounting brackets and bushings align with your car.
• Type of assist: If your car is power steering, ensure it’s a ''power rack'' and matches the assist type (hydraulic vs electric).
• Warranty / return: Especially with re-cond or used racks, check for warranty or size of allowable return.
• Installation note: Replacing a rack often requires alignment afterwards, and some setups may need bleeding if hydraulic. Also note: one listing suggests ''installation will apply additional charge'' and that the part may be overhauled/reconditioned.  

Basic Description of the Product (for listing)

Here is a sample description you might see if listing or buying the rack:

Product: Steering Rack & Pinion Assembly (Power Steering)

Fitment: Suzuki Swift ZC21S (1.5L) – Right Hand Drive

Part Number: 48580-63J51 (and equivalents)

Condition: New / Genuine / Aftermarket / Re-conditioned (specify)

Includes: Main rack body, inner tie-rod ends, boots, seals (confirm included)

Features: Made in Japan / OEM quality / tested for play/leaks

Notes: Please confirm chassis number and compatibility before purchase. Professional installation recommended; alignment required after installation.

Visual Reference