Understanding Delrin Bushings and Their Role in Suspension Upgrades

Motorcycle suspension systems rely on bushings to isolate moving parts, absorb vibrations, and allow controlled articulation. Factory-installed rubber bushings are designed for comfort and cost-effectiveness, but they introduce compliance that can dull handling and wear out over time. Replacing them with Delrin bushings—machined from acetal resin—delivers a direct, low-friction connection between suspension components such as swingarm pivots, linkage bearings, shock mounts, and triple clamps.

Delrin (polyoxymethylene, or POM) is a semi-crystalline thermoplastic known for high stiffness, low moisture absorption, excellent dimensional stability, and a coefficient of friction close to that of nylon but with much greater fatigue resistance. These characteristics make it a superior material for suspension bushings where precision and durability are paramount. Unlike bronze or brass bushings, Delrin does not require constant greasing and will not corrode. Unlike polyurethane, Delrin maintains its shape under high loads and temperature variation, preventing the “squish” that can introduce unwanted movement.

Incorporating Delrin bushings into a DIY suspension upgrade allows you to eliminate the play inherent in rubber, reduce stiction, and improve feedback from the tires. The result is a more predictable, stable ride—particularly beneficial for sport riding, track days, or adventure touring where suspension precision matters.

Tools and Materials Required for a Successful Installation

Before starting, gather the following items. Using the correct tools prevents damage to the bushings and ensures a safe, precise fit.

Essential tools

  • Metric socket set and combination wrenches (typically 10–19 mm)
  • Torque wrench (specifications vary; usually 30–90 Nm for suspension bolts)
  • Digital calipers (for measuring existing bushing I.D., O.D., and length)
  • Drill press or hand drill with step bits or reamers (for minor sizing adjustments)
  • Rubber mallet or dead-blow hammer
  • Bushing press or a C-clamp with appropriately sized sockets (for pressing)
  • Fine-grit sandpaper (400–600 grit) for deburring
  • Silicone-based lubricant (lithium grease can swell Delrin – avoid petroleum products)
  • Safety glasses and mechanic’s gloves

Materials

  • Delrin bushings – available in standard sizes (12 mm, 14 mm, 16 mm I.D., etc.) or custom-machined from bar stock. Reputable suppliers include McMaster-Carr, Grainger, and specialty manufacturers like All Balls Racing (for pre-sized kits).
  • Stainless steel or zinc-plated washers – to create thrust surfaces where needed.
  • Thread-locking compound (blue Loctite) for pivot bolts.

Step-by-Step Installation Process

Follow these steps carefully. Each model of motorcycle may have unique disassembly procedures; consult your service manual for torque values and removal sequences.

1. Remove Suspension Components

Stabilize the motorcycle on a center stand or paddock stand. Remove the rear wheel (if working on the swingarm) or front forks (if replacing triple-clamp bushings). Disassemble the linkage, shock, or swingarm according to the manual. Note the order of washers and spacers; photograph the assembly if needed. Clean all mating surfaces with brake cleaner to remove old grease and debris.

2. Measure and Source the Correct Bushings

Using calipers, measure the inner diameter of the suspension bore (where the bushing sits) and the outer diameter of the pivot bolt. The bushing O.D. should have a light press fit (0.001–0.003 inch interference) into the bore. The bushing I.D. must allow the bolt to slide freely with about 0.002–0.005 inch clearance. Length should match the original bushing or the width of the mounting eye.

If you cannot find pre-sized Delrin bushings, order oversized blanks and machine them down using a lathe or drill press with a reamer. Many DIYers turn their own on a mini-lathe for perfect fit.

3. Prepare the Bushings

Deburr the edges with sandpaper to remove machining marks. Ensure the bushing surfaces are smooth; any roughness will increase friction. Apply a thin coat of silicone lubricant to the outer surface before pressing – this eases insertion and prevents galling. Do not use oil-based greases, as they can degrade Delrin over time.

4. Install the Bushings into the Suspension Components

Align the bushing squarely with the bore. Use a bushing press or a C-clamp with sockets to press it in gradually. If using a rubber mallet, tap evenly around the circumference to avoid cocking the bushing. The bushing should sit flush with the component face (or slightly recessed if a thrust washer is used). Never hammer directly on Delrin – use a wooden or plastic drift.

For swingarm linkages, two bushings are often required per pivot point, one at each side. Ensure they are oriented identically.

5. Reassemble and Torque to Specification

Insert the pivot bolt with a light coat of silicone lubricant. Install washers and nuts, then tighten bolts to the manufacturer's torque spec. Delrin does not compress like rubber, so overtightening can crush it or bind the pivot. Use a torque wrench – typical swingarm pivot bolts range from 40–80 Nm. Apply thread locker to bolts that are not cotter-pinned.

After assembly, check for free movement by hand; the linkage should articulate without binding. If it feels tight, increase the bolt clearance slightly by polishing the bushing I.D. with sandpaper.

6. Test Ride and Adjust

Lower the motorcycle, pump the suspension several times to settle the bushings, then check all bolts for correct torque. Take a short test ride on familiar roads. Notice the difference in feel: you should experience less deflection, more direct feedback, and reduced rear-end squat under acceleration. If you detect harshness or vibration, double-check that the bushings are aligned and that you haven't increased stiction due to too-tight clearances. Some riders prefer to run a 0.003–0.005 inch clearance for street use, while track-only bikes can tolerate tighter fits.

Benefits of Delrin Bushings Over OEM Rubber or Polyurethane

  • Reduced compliance: Rubber deflects under load, introducing unwanted geometry changes. Delrin's stiffness keeps suspension links in their designed position.
  • Lower friction: Delrin's natural lubricity minimizes stiction, allowing the suspension to react to small bumps and road irregularities. This improves both comfort and traction.
  • Wear resistance: Delrin outlasts rubber, which cracks and degrades from ozone and UV. Polyurethane can soften or swell with age; Delrin remains dimensionally stable.
  • No corrosion: Unlike metal bushings, Delrin does not rust or require periodic greasing in most applications. (Some bearings still need grease for longevity, but Delrin pivots can be run dry with minimal wear.)
  • Consistency: Delrin's mechanical properties vary little with temperature from -40°F to +180°F, whereas rubber hardens in cold and softens in heat.

Potential Drawbacks and How to Mitigate Them

Delrin bushings are not a universal upgrade. Here are common concerns and their solutions:

  • Increased vibration transmission: Rubber isolates high-frequency vibrations; Delrin transmits them. This can lead to a harsher ride on rough pavement. Solution: Pair Delrin bushings with properly tuned suspension damping and grip-friendly handlebar grips. Many riders find the trade-off worthwhile for improved control.
  • Noise: Delrin-on-steel pivots can produce creaking or squeaking sounds, especially when dry. Solution: Apply a very thin film of silicone grease to the bushing bore during assembly, or install a thin PTFE liner between bushing and bolt.
  • Incorrect fit: Too tight causes binding; too loose introduces play. Solution: Measure thrice, cut once. Use a reamer to incrementally open the bore if needed.
  • Over-tightening damage: Bolts can compress Delrin if the shoulder of the bolt is not properly contacting the outer race or washer. Solution: Use hardened washers between the bolt head/nut and the Delrin bushing to distribute load, and always torque to spec.

Where to Use Delrin Bushings on a Motorcycle

While Delrin can replace bushing in many locations, the most impactful upgrades are:

  • Swingarm pivot: Replacing rubber or composite swingarm bushings with Delrin eliminates lateral flex and improves rear-wheel tracking under power.
  • Rear suspension linkage: The dogbone and rocker arm bushings see high loads and frequent motion. Delrin here improves shock response and reduces stiction that causes harsh initial movement.
  • Shock mount bushings: Top and bottom eyelets benefit from reduced friction, allowing the shock to compress more freely.
  • Triple clamps: Some riders replace the rubber dampers in fork clamps with Delrin to sharpen steering feedback, though this is more common on track-only bikes.

Avoid using Delrin in places that require significant compliance or angular misalignment, such as steering head bearings (use tapered roller bearings) or footpeg mounts (where vibration isolation is needed).

Maintenance and Longevity

One of Delrin's advantages is its low maintenance. After installation, inspect the bushings annually during routine service. Check for:

  • Visible wear or elongation of the inner bore
  • Signs of cracking or stress whitening (indicates overload)
  • Free play at the pivot (excessive clearance)
  • Corrosion on the bolt (if the bushing was run dry, moisture can still rust the steel bolt)

If disassembly is needed, remove old bushings by pressing or tapping them out from the opposite side. Delrin can be reused if undamaged, but many riders replace them during major suspension overhauls simply due to cost-effectiveness. A set of four bushings for a typical linkage costs $10–$30.

Common Mistakes DIYers Should Avoid

  • Installing bushings without measuring the bolt: Bolts can vary in diameter by 0.1 mm between manufacturers. Always measure the actual bolt you will use.
  • Using petroleum-based lubricants: They can cause Delrin to swell or degrade over months. Stick to silicone or PTFE-based lubricants.
  • Forgetting to deburr: Sharp edges can act as stress risers and cause cracks. Lightly chamfer the bushing edges with sandpaper.
  • Over-tightening the pivot bolt: Because Delrin does not compress like rubber, torquing the bolt without proper spacer dimensions can load the bushing unevenly. Ensure that the bolt's shoulder (or a sleeve spacer) contacts the inner race of the linkage, not the bushing face directly.
  • Mixing materials without verifying compatibility: Some motorcycle specifications call for rubber to allow limited misalignment. Delrin is stiff; ensure that the suspension geometry can tolerate zero compliance. In some cases, a spherical bearing or heim joint is a better choice.

Advanced Tips: Machining Your Own Delrin Bushings

If you have access to a lathe, you can produce custom bushings to exact specifications. Start with 1-inch diameter Delrin rod (available from online plastics suppliers). Cut to length, drill and ream the inner hole, then turn the outer diameter to a light press fit. Use a sharp carbide tool to prevent melting the plastic. Finish with a fine file and sandpaper. This approach is especially useful for older or rare motorcycles where off-the-shelf sizes are unavailable. A step-by-step video guide by The Moto Builder demonstrates the process clearly for a Suzuki DR650 linkage.

Final Considerations: Is This Upgrade Right for You?

Delrin bushings are a proven, inexpensive way to tighten up a motorcycle's suspension feel. They are ideal for riders who prioritize feedback and precision over plushness. However, they are not a substitute for worn-out bearings or damaged linkages; always replace any fretted or pitted components before installing new bushings.

If you frequently ride on poorly maintained roads or do long-distance touring, consider a compromise: use Delrin only in the most highly loaded pivots (swingarm and linkage), and leave rubber at the shock mounts to retain some isolation. Alternatively, some manufacturers offer Delrin with a thin PTFE inner layer for reduced friction.

For a deeper dive into suspension tuning, refer to Race Tech's Motorcycle Suspension Bible or the technical articles on Motorcyclist Online. With careful measurement, proper installation, and a test ride, you'll quickly appreciate the transformation that Delrin bushings bring to your motorcycle's handling and confidence.