Metro & Urban Rail Springs: Bogie, Axle-Box & Suspension Coil Springs

Metro and urban rail springs are the coil springs that carry a subway or light-rail car body, absorb track input and keep the ride comfortable for passengers standing and seated on a crowded train. CHENJI supplies metro suspension springs to rolling stock manufacturers, system integrators and maintenance teams serving urban rail networks. Subway cars run in stop-and-go conditions that put a high number of load cycles on every suspension spring, so a metro spring has to hold a stable rate for a long service interval and stay dimensionally stable in heat, cold and moisture — not simply match a wire diameter.

How a metro suspension spring is specified

Three dimensions are most often controlled on a spring drawing: free length, solid height, and load at the installed height. The spring rate follows the standard relationship k = G d⁴ / (8 D³ n), where d is the wire or bar diameter, D the mean coil diameter, G the shear modulus of the material and n the number of active coils. Coil spring design for this class of spring follows EN 13906-1, which covers the design calculation of cylindrical helical compression springs made from round wire and bar.

Metro & urban rail spring specification table

Values above are typical for metro and urban rail work and are confirmed per customer drawing before production.

Materials and manufacturing process

Metro and urban rail springs are hot-coiled from alloy spring steels such as 60Si2Mn and 51CrV4, then quenched and tempered to a typical 40–50 HRC working hardness. To raise fatigue strength the springs are shot peened, and dimensional control is exercised on free length, solid height and load at the installed height. The wire itself can be checked with the simple torsion test to GB/T 239.1. Surfaces are inspected for decarburisation and, on safety-critical parts, for cracks using magnetic particle inspection. Protective coatings such as zinc-nickel, zinc flake or epoxy powder are applied where the service environment demands corrosion resistance, verified if needed by salt spray testing to ASTM B117.

CHENJI has produced springs since 2014, runs 35 machines and 26–50 employees, and works from customer drawings to deliver springs that match the design intent. Our CRCC railway product certification CRCC10219P11758R2M is valid to 25 November 2027 and ISO 9001 certificate 626024QH073R1 covers the quality system.

Applications

Our metro and urban rail coil springs are used on metro and light-rail vehicles, commuter and suburban trains, and tram and people-mover systems, in both primary (axle-box) and secondary (bogie-to-body) positions. For volume programs we can arrange staged deliveries aligned with your build or maintenance schedule, and for overhaul programs we supply replacement springs matched to the original specification.

Frequently asked questions

Where are metro and urban rail springs used in a bogie?

A metro bogie springs the vehicle in two places. The primary, axle-box suspension sits closest to the wheelset and cushions the high-frequency track input, while the secondary suspension sits between the bogie frame and the car body and controls ride quality and body roll. CHENJI supplies coil springs for both positions, made to the customer drawing so dimensions, load and rate match the design intent.

What bar size and material are used for metro suspension springs?

Hot-coiled railway and metro suspension springs are commonly made from bar diameters of about 20–45 mm from alloy spring steels such as 60Si2Mn and 51CrV4, heat treated to the typical 40–50 HRC range. Our plant covers a wire and bar diameter range of 0.1–80 mm with heat treatment up to 1500 °C.

Why does a metro spring need shot peening?

Metro cars run in dense stop-and-go service and accumulate a very high number of load cycles. Shot peening raises the fatigue strength of the spring and is widely applied to suspension springs for exactly this reason, so the spring holds its rate for a long service interval.

Is your factory certified for railway supply?

Yes. CHENJI holds CRCC railway product certification CRCC10219P11758R2M, valid to 25 November 2027, based on TB/T 2211-2016, and ISO 9001 certificate 626024QH073R1. The company has also been audited by Bureau Veritas (MIC-ASR2451820).

Can you supply replacement springs for fleet maintenance?

Yes. As well as OEM production we supply replacement springs for fleet overhaul and maintenance programs, matched to the original specification. We work from drawings or samples and can arrange staged deliveries to suit a maintenance schedule.

Related pages

• Railway Suspension Springs
• Primary Suspension Springs
• Secondary Suspension Springs
• Railway Transit Springs

Request a quotation

Send us your drawing, sample or specification — our engineering team will confirm feasibility and reply with a quotation. Email liu@chenjisprings.com or call / WhatsApp +86 158 5311 1612.