Motorcycle Auxiliary Brake Lights Explained | What They Are & Why Riders Use Them
Rear-end visibility is one of the most important safety factors for riders—especially in stop-and-go traffic, on multi-lane highways, and during poor weather. A motorcycle auxiliary brake light adds an extra layer of protection by providing additional brake illumination beyond your factory tail light. Whether mounted to saddlebags, a tour trunk, the fender, or the license plate frame, auxiliary brake lights help drivers behind you notice braking sooner—and react faster.
This guide explains what auxiliary brake lights are, how they differ from tail lights and 3-in-1 signals, the most common formats and mounting locations, and how to install them on Harley-Davidson, Indian, and metric motorcycles using Eagle Lights LED rear lighting.
Definition: What Is an Auxiliary Brake Light?
An auxiliary brake light is any additional rear-facing red LED that illuminates when you apply the brakes, in addition to the factory brake/tail light. It doesn’t replace your primary tail light—it supplements it, often from a different height or angle to create a more obvious brake signal for following drivers.
- Primary purpose: Increase rear visibility and shorten driver reaction time
- Typical behavior: Lights up in sync with the main brake light; may include running-light dim mode
- Formats: Saddlebag light bars, tour trunk bars, fender-mounted light bars, plate-frame LEDs, under-fender strips
Related but different: A brake light modulator briefly flashes your existing brake light. An auxiliary brake light adds more illuminated surface area and a different location, which can be even more noticeable.
Auxiliary Brake Light vs. Tail Light vs. 3‑in‑1
| Component | What It Does | Best Use |
|---|---|---|
| Main Tail/Brake Light | Factory running + brake functions | Required for road use; base rear visibility |
| Auxiliary Brake Light | Additional brake illumination (often with running mode) | Add-on safety and style; higher or wider brake footprint |
| 3‑in‑1 LED Light | Combines running + brake + turn in one unit | Clean, minimalist rears and fender‑eliminator builds |
Why Add an Auxiliary Brake Light?
- ✅ Faster Recognition: Multiple brake points (center + sides or higher up) catch the eye more quickly.
- ✅ Wider Signal: Saddlebag and trunk light bars create a wider brake signature for drivers behind and diagonally behind you.
- ✅ Height Variation: A trunk or tour‑pak bar sits higher, improving visibility for taller vehicles like SUVs and trucks.
- ✅ Style + Safety: Clean, OEM‑like LED bars modernize the rear while adding meaningful function.
- ✅ Redundancy: Extra lighting can remain visible even if luggage, passengers, or accessories partially block the stock light.
Popular Auxiliary Brake Light Formats
1) Saddlebag Light Bars
- Low-profile LEDs mounted on or beside the saddlebag lids or rails
- Often include run + brake + turn functions
- Excellent for touring platforms (Street Glide, Road Glide, Road King, Chieftain, Challenger)
2) Tour Trunk / Tour‑Pak Bars
- High-mounted rear LED bar on or under the trunk lid
- Increases brake visibility for taller vehicles
- Great match for long-distance touring builds
3) Fender‑Mounted LED Bars
- Thin, bright LED bars mounted under or across the fender lip
- Provide a clean visual line and extra brake surface
- Work well on bobbers, Softails, Sportsters, Scouts
4) License Plate Frame LEDs
- Plate frames with integrated run + brake LEDs (sometimes turn signals)
- Ideal when fender real estate is limited (tail tidy builds)
- Pairs well with side‑mount plate brackets
5) Under‑Fender / Under‑Rack LED Strips
- Stealthy strips for subtle added illumination
- Useful when you want extra brake visibility without visible bars
Explore options in the Auxiliary Lighting collection and pair with integrated tail lights or 3‑in‑1 signals for a complete rear solution.
Legal Considerations (U.S. & Canada)
Auxiliary brake lights are legal in the U.S. and Canada when they follow common rules:
- Color: Rear brake lights must be red.
- Brightness/Visibility: Must be visible from appropriate distances (commonly 300+ feet).
- Flashing Behavior: Continuous flashing is not allowed for brake lights in many jurisdictions. If using a brake modulator, ensure the pattern is DOT‑compliant (brief initial flashes then steady‑on).
- Turn Signal Color: Red or amber (rear) depending on local laws—keep functions distinct if the auxiliary also includes turns.
Tip: Keep brake and turn functions clearly separated in color and behavior; avoid continuous flashing on the brake circuit. When in doubt, follow DOT guidelines for modulation (short pulse then steady‑on).
Best Bikes for Auxiliary Brake Lights
Harley‑Davidson
- Touring (Street Glide, Road Glide, Road King): Saddlebag bars + trunk bars create a wide, high brake signature.
- Softail / Dyna / Sportster: Fender bars and plate‑frame LEDs add safety without clutter.
Indian Motorcycle
- Chieftain, Challenger, Pursuit: Saddlebag and trunk bars shine for height and width.
- Scout, Chief: Fender bars and plate‑frame LEDs keep builds minimalist yet visible.
Metric & Modern Classics
- Honda Rebel/Shadow: Fender bars or plate‑frame LEDs for compact rears.
- Yamaha Bolt/XSR, Kawasaki Vulcan, Suzuki Boulevard: Mix fender bars, 3‑in‑1 signals, and auxiliary strips for clean rears.
- Triumph Bonneville/Thruxton/Scrambler: Discreet under‑rack strips maintain classic lines.
Wiring Basics & CANBUS Notes
Many modern bikes monitor lighting circuits via CANBUS/BCM. The easiest path is to choose plug‑and‑play harnesses designed for your platform—these avoid fault codes and ensure proper brightness for run/brake functions.
- Power Sources: Tie the running lead into the tail/running circuit, and the brake lead into the brake circuit.
- Ground: Use a solid frame or harness ground.
- Modulators: If adding a brake flasher, insert it inline on the brake lead feeding both your primary and auxiliary brake lights.
- CANBUS Bikes: Use platform‑ready harnesses or CANBUS/anti‑flicker modules to prevent errors.
Good to know: Auxiliary brake lights typically do not require load resistors. Those are used to correct turn signal hyperflash, not brake circuits.
Installation Overview
Time: 20–60 minutes depending on kit and mounting location
Tools You May Need:
- Screwdrivers, Torx/hex keys (for mounts/trim)
- Wire stripper/crimper or Posi‑Taps (if not plug‑and‑play)
- Zip ties and loom for wire management
- Adhesion promoter (for certain peel‑and‑stick light bars)
Steps (Typical):
- Mock‑up the bar for alignment; clean the mounting surface.
- Route wires along OEM harness paths; avoid moving parts and hot surfaces.
- Connect running lead to tail circuit, brake lead to brake circuit, and ground to a solid ground.
- Secure the bar (hardware or adhesive) and dress the wiring.
- Test run + brake function; if applicable, confirm turn signals operate distinctly.
Shop plug‑and‑play options in Auxiliary Lighting and platform‑specific rear lighting under Integrated Tail Lights and 3‑in‑1 Lights.
Placement & Visibility Tips
- Height Stacking: Combine a trunk bar (high) with saddlebag bars (low) for maximum visibility.
- Width Matters: The wider the brake signature, the sooner drivers recognize you’re slowing.
- Angle: Aim bars square to following traffic; avoid shining up into the sky or down onto the fender.
- Contrast: Smoked lenses are stylish; ensure the LEDs are bright enough for daylight.
Troubleshooting
- Aux light doesn’t turn on: Recheck ground and tap points; verify polarity (some LEDs are polarity‑specific).
- Running but no brake: Brake lead is not on the correct circuit; test with a multimeter at the brake line.
- Dim output: Poor ground or shared circuit drop—use a dedicated ground and ensure solid connections.
- CANBUS fault: Move to a platform‑specific harness or add an anti‑flicker/decoder module.
- Adhesive bar lifting: Clean with alcohol, use adhesion promoter, and apply with firm pressure at room temperature.
FAQs
Q: Do auxiliary brake lights replace my stock tail light?
No, they supplement it. Your factory tail/brake light stays in place; the auxiliary adds surface area and visibility.
Q: Are they legal?
Yes—use red output for brake, maintain steady‑on after any brief modulation, and ensure visibility at legal distances.
Q: Can I combine an auxiliary brake light with a modulator?
Yes—wire the modulator on the brake lead feeding both the main and auxiliary lights. Use DOT‑compliant patterns.
Q: Will they cause hyperflash?
No. Hyperflash is a turn signal issue. If you’re adding auxiliary turn functions, use proper LED relays or resistors.
Q: Smoked lens or clear?
Smoked looks stealthy; clear maximizes perceived brightness. Eagle Lights LEDs are bright enough for smoked in most conditions.
