Wheel alignment basics — which parameter is adjusted by changing tie-rod length? Identify the alignment setting that is directly altered by modifying the effective tie-rod length on a steering linkage.

Introduction / Context:
Wheel alignment is defined by camber, caster, and toe. Service technicians commonly adjust tie-rod length during alignment. Recognising which parameter this affects is essential for accurate vehicle handling and tyre-wear control.

Given Data / Assumptions:

• Conventional rack-and-pinion or recirculating-ball steering with adjustable tie rods.
• MacPherson strut or double wishbone suspension (typical passenger vehicles).
• No adjustable upper mounts or special cam bolts unless noted.

Concept / Approach:
Tie rods connect the steering rack (or center link) to the steering knuckle arms. Changing the effective tie-rod length rotates the knuckles slightly inward or outward relative to the vehicle’s centerline, thus altering toe angle. Camber and caster are set primarily by suspension geometry, cam bolts, shims, or slotted mounts; steering gear ratio is fixed by the gear design.

Step-by-Step Solution:
Identify the linkage component adjusted in alignments: tie rod(s).Understand the effect: shorter/longer tie rod pulls/pushes the knuckle → changes toe-in or toe-out.Conclude that adjusting tie-rod length directly affects toe.

Verification / Alternative check:
Alignment procedures universally specify toe adjustment via inner/outer tie-rod threads while camber/caster require different hardware or shims. Post-adjustment steering wheel centring also involves equalising left and right tie-rod changes.

Why Other Options Are Wrong:

• Camber: typically altered using cam bolts, slotted strut towers, or shims, not tie-rod length.
• Caster: altered with shims, adjustable arms, or subframe position, not tie-rod length.
• Steering gear ratio: a design characteristic of the gearbox/rack; not field-adjustable.

Common Pitfalls:
Adjusting only one tie rod causes off-centre steering wheels and unequal toe. Always split adjustments symmetrically when possible.

Final Answer:
Toe