Wire Rope Core Types

Wire Rope Core Types

Fiber core, wire strand core and IWRC - what the core changes, with same-diameter data.

Three Core Types

Every wire rope is built around a core, and the core sets a rope's character as much as the outer strands do. Three types cover our range:

  • Fiber core (FC) - natural or synthetic fiber at the centre. Flexible and economical, and it holds lubricant well; the standard choice for general engineering and guying.
  • Wire strand core (WSC) - a single wire strand at the centre, as in the 7x7 construction. A middle option between fiber and a full steel core.
  • Independent wire rope core (IWRC) - a small wire rope inside the outer strands. It adds steel to the cross-section, giving higher breaking strength and much better crush resistance.

The core choice sits alongside the strand pattern: the construction guide explains how the outer strands behave, and this page covers what changes inside.

FC vs IWRC

Fiber core (FC) Independent wire rope core (IWRC)
What it is Fiber (natural or synthetic) at the centre A small wire rope at the centre
Breaking strength Baseline for the construction About 8% higher at the same diameter
Flexibility Slightly more flexible Slightly stiffer - the usual trade-off
Crush resistance Lower; the core can deform under heavy pressure High; handles multilayer spooling and hard service
Cost Lower Higher
Typical use General engineering, guying, flexible duty Lifting, winches, drums with multilayer spooling, hard service

Same Construction, Same Diameter

The clearest way to see what the core does is to hold everything else equal. These are published breaking strengths from our product tables, at 1770 MPa grade:

Construction Diameter FC (kN) IWRC (kN) Difference
6x36 10 mm 58.4 63 +7.9%
6x36 40 mm 935 1008 +7.8%
6x19 filler 14 mm 114 124 +8.8%
6x19 filler 48 mm 1346 1452 +7.9%
6x37 12 mm 75.2 81.3 +8.1%
6x37 48 mm 1203 1301 +8.1%

Compare a pair directly in the shop: 6x36 FC against 6x36 IWRC.

Which Core to Choose

  • Strength or crush resistance lead: IWRC.
  • Flexibility and cost lead: FC.
  • Multilayer spooling on a drum: IWRC - the steel core resists the pressure of the overlying wraps.
  • Small-diameter constructions such as 7x7 use a strand core.

The 6x19 family shows both routes: 6x19 filler IWRC and the sealed FC variant.

See the construction guide for how cores combine with strand patterns, and the breaking strength guide for working capacities.

Browse the full wire rope range, or tell us the duty and we will quote both cores at admin@greenlogy.cn.

Frequently Asked Questions

What is the difference between fiber core and IWRC wire rope?

The core is what the outer strands are laid around. A fiber core (FC) is natural or synthetic fiber, giving a flexible, economical rope.

An independent wire rope core (IWRC) is a small wire rope inside, adding steel to the cross-section: stronger, more crush resistant, slightly stiffer and higher in cost.

Which is stronger, FC or IWRC?

At the same construction, diameter and grade, IWRC is about 8% stronger in published breaking strength. For example 6x36 at 10 mm is rated 58.4 kN with fiber core and 63 kN with IWRC; at 48 mm the 6x19 filler rope is 1346 kN fiber core against 1452 kN IWRC.

What is a WSC core?

Wire strand core: a single wire strand at the centre, used in constructions such as 7x7. It sits between the two families - more strength than a fiber core in small diameters, without the full crush resistance of an independent wire rope core.

When should I choose IWRC?

Choose IWRC for lifting duty, winches and drums with multilayer spooling, hard service, and anywhere crush resistance matters. Fiber core suits general engineering, guying and jobs where flexibility and cost lead.

Are both core types available bright or galvanized?

Yes. Both fiber core and steel core ropes are supplied bright or galvanized across our standard constructions.