ISO 18137:2015

Overview

ISO 18137:2015 - Leaf springs - Technical specifications defines the technical requirements and tolerances for leaf springs used mainly in road vehicles. The standard covers materials, dimensional and shape tolerances, characteristic requirements (spring rate, camber, fatigue), and manufacturing controls (hardness, decarburization, shot peening, presetting, lubrication, surface protection). It also includes illustrations of common spring types (multi‑leaf, parabolic, sliding ends, progressive designs) and refers to Annex A for test methods.

Key topics and technical requirements

• Scope and applicability: Applies to leaf springs for road vehicles; other vehicle types may refer to it.
• Materials: Preferably hot‑rolled spring flat bar in accordance with ISO 683‑14 unless otherwise agreed.
• Dimensional tolerances:
  • Straight span and fixed half straight span tolerances are specified by range and type (examples: ±3.0 mm to ±6.5 mm depending on span and Type 1/Type 2).
  • Assembled spring width and eye widths have defined tolerances (assembly width tolerance examples: +2.5/−0.8 mm up to specific widths).
  • Eye inner diameter tolerances (e.g., ±0.5 mm for d ≤ 25 mm; ±0.6 mm for 25 < d ≤ 40 mm).
  • Flank bending limits: ≤ 2.0 mm/1 m for leaves installed in the bracket; ≤ 3.0 mm/1 m for others.
  • Perpendicularity/parallelism of spring eye: not to exceed 1% of the spring end width (1% bA) when other tolerances apply.
• Characteristic requirements:
  • Spring rate tolerances (parabolic springs ±6% Type 1, ±10% Type 2; other leaf springs ±8% / ±10%).
  • Design camber tolerances (e.g., ±3.0 mm Type 1, ±7.0 mm Type 2).
  • Fatigue life: requirement to be agreed between purchaser and supplier; test methods referenced in Annex A.
• Manufacturing controls:
  • Hardness guidance tied to ISO 683‑14 / ISO 18265; hardness range when specified should be less than 82 HBW.
  • Decarburization: no harmful decarburization allowed on the tension side; depth to be minimized/agreed.
  • Shot peening: performed after heat treatment and before assembly/coating per ISO 26910‑1; intensity and coverage to be agreed.
  • Presetting, lubrication, surface protection: presetting is normally required; lubricant/surface coatings specified as needed.

Practical applications and users

ISO 18137:2015 is used by:

• Leaf spring manufacturers and OEMs for design, production acceptance, and quality control
• Suspension and vehicle chassis engineers specifying spring performance (rate, camber, fatigue)
• Procurement and contracts teams to define tolerances and manufacturing requirements
• Test laboratories performing dimensional and mechanical tests (see Annex A for methods)
• Regulatory and certification bodies assessing component conformity

Common applications include heavy‑duty truck and commercial vehicle suspension, trailer springs, and any road vehicle systems using multi‑leaf or parabolic leaf springs.

Related standards

• ISO 683‑14 (hot‑rolled steels for quenched and tempered springs)
• ISO 16249 (springs - symbols)
• ISO 26909 (springs - vocabulary)
• ISO 26910‑1 (shot peening procedures)
• ISO 3887, ISO 6506‑1, ISO 6508‑1, ISO 18265 (testing and hardness conversion)

For procurement or technical specification, reference ISO 18137:2015 when defining leaf spring material, dimensional tolerances, mechanical characteristics, manufacturing processes, and test requirements.