Heatshrink Selection Guide for Motorsport Wiring

This motorsport heatshrink selection guide explains how to choose between Raychem DR25, Sumitomo W5DL and Raychem ATUM for motorsport wiring harnesses, EFI looms, ECU wiring, engine bay wiring and custom automotive harness builds.


Different heatshrink products do different jobs. DR25 is mainly used as outer harness sleeving. W5DL is used as an SCL-style adhesive-lined heatshrink for sealing and strain relief. ATUM is used for adhesive-lined sealing, repairs, transitions and moisture protection.


Quick Answer

Use Raychem DR25 for outer harness sleeving, Sumitomo W5DL where you need SCL-style adhesive-lined sealing and strain relief, and Raychem ATUM for adhesive-lined sealing, repairs, transitions and moisture protection. In a motorsport harness, these products are often used together rather than as direct replacements for each other.

DR25 vs W5DL vs ATUM

The table below gives a practical overview of where each product is normally used in motorsport and custom automotive wiring.

Product Type Main Purpose Common Motorsport Use
Raychem DR25 Flexible heatshrink tubing Outer harness sleeving and wire bundle protection Engine bay looms, ECU harnesses, main trunks, branches, chassis wiring
Sumitomo W5DL Semi-rigid dual-wall adhesive-lined heatshrink SCL-style sealing, strain relief and encapsulation Harness ends, branch transitions, splices, breakouts, connector backshell transitions
Raychem ATUM Adhesive-lined dual-wall heatshrink Environmental sealing, repairs and moisture protection Sealing joins, repairs, cable transitions, connector-to-cable sealing, strain relief

Raychem DR25

Raychem DR25 is used as outer sleeving over wire bundles. It protects the harness from abrasion, heat, fluids and general engine bay conditions. It is commonly used in professional motorsport wiring because it gives a clean, compact and durable finish.

Use DR25 for:

  • Main harness trunk sections
  • Engine bay wiring looms
  • ECU and EFI harnesses
  • Sensor and injector branch sections
  • PDM and power distribution wiring
  • Chassis loom protection
  • Race car and drag car wiring harnesses

When not to use DR25 by itself

DR25 is not adhesive-lined. It protects the wire bundle, but it does not seal the ends by itself. For sealed ends, transitions and strain relief, DR25 is often used with W5DL, ATUM, moulded boots or other adhesive-lined products.

Sumitomo W5DL

Sumitomo W5DL is a semi-rigid, dual-wall, adhesive-lined heatshrink. When heated, the inner liner melts and flows, helping encapsulate the part underneath. It is commonly used as an SCL-style alternative for harness sealing, strain relief and moisture protection.

Use W5DL for:

  • Harness end sealing
  • Branch transitions
  • Breakouts
  • Splice protection
  • Connector backshell-to-cable transitions
  • Strain relief on harness sections
  • Areas where void filling and encapsulation are useful

W5DL as an SCL-style alternative

W5DL is useful where you would normally reach for an SCL-style adhesive-lined heatshrink. It is not sold as Raychem SCL, but it fills the same general job in harness work: sealing, encapsulation, strain relief and protection at ends, joins and transitions.

Raychem ATUM

Raychem ATUM is an adhesive-lined heatshrink used for environmental sealing and protection. It is useful where you need the tubing to shrink down and the adhesive liner to seal around the part underneath.

Use ATUM for:

  • Moisture sealing
  • Cable repairs
  • Connector-to-cable transitions
  • Sealing wire joins
  • Protecting small harness sections
  • General adhesive-lined heatshrink work
  • Strain relief and environmental protection

ATUM vs W5DL

ATUM and W5DL are both adhesive-lined products, but they are normally chosen for slightly different jobs. W5DL is a good SCL-style choice for firm sealing, encapsulation and harness transitions. ATUM is a flexible adhesive-lined option for sealing, repair work and general environmental protection.

How to Choose the Right Product

Choose the heatshrink based on the job it needs to do. Do not use one product everywhere just because it is available.

Job Best Choice Why
Protecting a wire bundle Raychem DR25 Designed for harness sleeving and outer bundle protection
Sealing a harness end Sumitomo W5DL or ATUM Adhesive liner helps seal and support the transition
Branch transition or breakout W5DL, ATUM or moulded boot depending on design Provides strain relief and sealing around the transition
Repairing damaged insulation or sleeving ATUM Adhesive-lined heatshrink is useful for sealing and repair work
Professional motorsport harness finish DR25 with W5DL, ATUM or boots DR25 protects the loom, adhesive-lined products finish and seal the ends

Typical Motorsport Harness Stack

A professional motorsport harness often uses multiple products together. A common setup is:

  • Tefzel wire for the conductors
  • Raychem DR25 over the wire bundle
  • W5DL or ATUM at harness ends and transitions
  • Moulded boots or adhesive-lined heatshrink at breakouts
  • Labels and documentation for circuit identification

The goal is not just to make the harness look tidy. The goal is to protect the wiring, support the transitions, reduce movement, prevent moisture entry where required and make the harness serviceable.

Common Mistakes

  • Using normal cheap heatshrink as outer harness sleeving instead of DR25.
  • Using DR25 by itself and expecting it to seal the harness ends.
  • Oversizing heatshrink so it stays loose after shrinking.
  • Forcing heatshrink over a bundle that is too large and damaging the wire underneath.
  • Using adhesive-lined heatshrink where the harness needs to remain flexible and serviceable.
  • Not planning transitions before the harness is assembled.

Practical Selection Tips

  • Use DR25 for the main outer sleeve on motorsport harness sections.
  • Use W5DL where you want an SCL-style adhesive-lined finish for sealing, strain relief or encapsulation.
  • Use ATUM for adhesive-lined sealing, repairs and connector-to-cable transitions.
  • Measure the actual finished bundle size before choosing heatshrink.
  • Check the supplied size and recovered size before ordering.
  • Plan branch points, boots, labels and splices before shrinking anything.

Shop Heatshrink & Harness Protection

12Volt Motorsports supplies Raychem DR25, Sumitomo W5DL and Raychem ATUM for motorsport wiring harnesses, engine bay looms, ECU wiring and custom automotive harness builds.

Shop Raychem DR25 Shop Sumitomo W5DL Shop ATUM

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FAQ

What heatshrink should I use for a motorsport harness?

Use DR25 as the outer harness sleeving, then use adhesive-lined products such as W5DL or ATUM for sealing, strain relief, transitions and repairs.

Is DR25 adhesive-lined?

No, DR25 is not adhesive-lined. It is normally used as outer harness sleeving. Use W5DL, ATUM or another adhesive-lined product where sealing is required.

What is Sumitomo W5DL used for?

Sumitomo W5DL is used for SCL-style sealing, strain relief and encapsulation. It is useful on harness ends, branch transitions, splices, breakouts and connector backshell transitions.

Is W5DL the same as Raychem SCL?

W5DL is not Raychem-branded SCL, but it is used as an SCL-style adhesive-lined heatshrink alternative in harness work. It is commonly used where sealing, encapsulation and strain relief are required.

What is ATUM used for?

ATUM is adhesive-lined heatshrink used for environmental sealing, moisture protection, cable repair, connector-to-cable transitions and general strain relief.

Can I use normal heatshrink instead of DR25?

Normal heatshrink can be used for basic insulation and simple repairs, but DR25 is a better choice for outer harness sleeving in motorsport, engine bay and harsh-environment wiring.

Last updated: June 2026

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