The BMW R1100S has many strengths. Rear-light conspicuity is not really one of them.
The original tail light is compact and period-correct, but it is not especially convincing in bright daytime traffic. The brake light is better, but still concentrated in a small central area directly beneath the seat. On a modern road, surrounded by SUVs, bright daylight and distracted drivers, making the rear of the bike easier to read is a sensible upgrade.
The key is doing it without ruining the motorcycle.
This is not an argument for fitting tiny generic LED indicators on short stalks. They rarely suit the R1100S, often look cheap, may not be especially visible in daylight and usually make the rear of the bike look less original rather than more purposeful.
A better solution is to retain the original BMW indicator housings and upgrade what sits inside them.
The Weiser Legacy 2 EVO Triple Function Rear Kit replaces the original bulb and reflector assembly with LED panels that turn each rear indicator into three lights in one:
- Amber turn signal
- Red running light
- Red brake light
Each panel uses separate amber and red LED arrays. When riding normally, both rear indicators can act as additional red running lights. When braking, both illuminate brighter red. When indicating, the relevant side switches to amber and flashes as a proper turn signal.
The result is simple: instead of one relatively small rear light, the R1100S gains two additional red running lights and two additional brake lights, positioned wider apart and closer to the line of sight of following traffic.
That makes the bike easier to see without changing its character.
Why This Upgrade Works So Well on an R1100S
The original BMW stalk indicators are part of the bike’s design. They are properly proportioned, sit in the right place and give the rear end a clean, finished appearance.
The Weiser solution keeps all of that.
The original housings remain. The original stalks remain. The bike still looks like an R1100S.
The difference only becomes obvious when the ignition is on.
With clear lenses fitted, the housings can look cleaner and more modern when switched off, while the LED panels still provide amber indication and red running/brake-light functions when active. The visual effect is subtle rather than customised for the sake of it.
That is exactly the right approach for this motorcycle.
Weiser’s Legacy 2 range is intended for earlier BMW R and K motorcycles and is designed to fit inside the original BMW indicator housings rather than replacing them with aftermarket units.
The Kit
For the R1100S rear indicators, use the Legacy 2 EVO Triple Function Rear Kit.
The rear panels provide:
- 12 amber LEDs for indication
- 12 red LEDs for running and brake-light functions
- Original indicator-housing fitment
- A selectable running-light function via a small jumper on each rear panel
The running-light jumper gives two choices:
- Running light enabled: rear indicators glow red with ignition on and brighten under braking
- Running light disabled: rear indicators remain off until braking or indicating
For an R1100S, the running-light setting is the whole point of the conversion. Leave it enabled unless there is a specific local legal reason not to.
No Relay Is Needed on the R1100S
This is important.
The R1100S is a pre-CAN-bus BMW. The Weiser Legacy II no-relay installation guide is specifically intended for non-CAN-bus BMW motorcycles from this period and states that the LED modules are designed to mimic the 21-watt bulbs they replace. No additional relay, load resistor or inline fuse is required for this installation.
That also means this upgrade works well alongside the separate LED flasher-relay modification.
Link this sentence directly to your existing relay article:
For the correct flash rate with LED indicators, see our guide to the BMW R1100S LED flasher-relay modification.
The relay modification deals with flash behaviour. This Weiser installation adds the extra red running-light and brake-light functions. They are related upgrades, but they solve different problems.
Rear-Only Installation
Weiser also offers front dual-function panels, but this guide is deliberately about the rear only.
The rear conversion is where the R1100S gains the most practical benefit. The front indicators are already relatively visible and sit high in the rider’s visual field. At the rear, however, the bike benefits greatly from a wider, brighter brake-light signature.
The supplied installation guide assumes that the new running-light and brake-light feeds are tapped into the motorcycle wiring and then routed to each rear indicator. The original indicator wiring remains in use:
- Brown: earth / ground
- Blue: turn-signal feed
The two additional functions need two new feeds:
- Black: switched 12V for running lights
- Grey: brake-light feed
The Weiser instructions show these connections using Posi-Twist and Posi-Tap connectors, normally taking switched running-light power and brake-light power from wiring near the rear light assembly.
The Least-Intrusive Way to Wire It
The standard instructions recommend tapping into suitable switched and brake-light wires. That works, but there is a cleaner way to do it on the R1100S.
Rather than cutting into the main loom near the indicators, take both new feeds directly from the rear-light area:
- One switched 12V supply from the tail/running-light circuit
- One switched 12V supply from the brake-light circuit
From there, run two new wires neatly toward the rear indicators.
Use heat-shrink sleeving around the added wiring so that the new black and grey feeds sit cleanly beside the original brown earth and blue indicator wires. At each rear indicator, the four wires can then be terminated properly for the LED panel:
- Brown to E-
- Blue to TURN / +
- Black to V+
- Grey to B+
This leaves the original BMW loom substantially intact.
The only new wiring is the additional running-light and brake-light supply. It can be removed later without leaving a hacked-up harness behind.
That matters on a motorcycle which is increasingly valued for originality.
Installation Overview
1. Remove the rear indicator lenses
Remove the screws holding each lens in place. Remove the original bulb and reflector assembly.
Keep the original parts. They are worth retaining with the bike.
2. Identify the original wires
The original rear indicator wiring provides:
- Brown earth
- Blue turn-signal feed
These will be reused.
3. Add the two new feeds
At the rear-light assembly, identify:
- A switched running-light feed
- A brake-light feed that becomes live only when either brake is applied
Confirm both with a multimeter before connecting anything.
Run one new wire for running lights and one for brake lights toward each rear indicator. Protect the new wiring with heat-shrink sleeving or proper loom tape.
4. Connect the LED panels
Connect the original and new wiring to the Weiser rear panels:
| Function | Wire | Weiser terminal |
|---|---|---|
| Earth | Brown | E- |
| Indicator | Blue | TURN / + |
| Running light | Black | V+ |
| Brake light | Grey | B+ |
Do not assume wire colours on a modified motorcycle. Test the functions before making permanent connections.
5. Set the running-light jumper
Set each rear panel to the running-light-enabled position.
With the jumper in this position, both rear indicators operate as dim red running lights and become brighter red under braking.
6. Test everything before refitting the lenses
Check:
- Ignition on: both rear indicators glow red
- Left indicator: left side flashes amber
- Right indicator: right side flashes amber
- Hazard lights: both flash amber
- Front brake applied: both rear indicators brighten red
- Rear brake applied: both rear indicators brighten red
- Brake light in the centre tail lamp still works normally
Only refit the lenses once every function is correct.
What the Bike Looks Like Afterwards
With the ignition off, the R1100S still looks original.
With the ignition on, the rear of the bike becomes far more visible. The additional red lights make the rear profile wider and more obvious, while the brake-light function gives following traffic a clearer signal that the bike is slowing.
Independent reviews of Weiser’s later LED systems report noticeably brighter amber indicators and substantially greater rear-light output under braking. Owners also repeatedly describe the upgrade as a meaningful improvement over stock lighting rather than a cosmetic modification.
The same principle applies here.
The point is not to make an old BMW look modern. The point is to make an old BMW easier to see.
A Note on Originality
This is one of the rare upgrades that improves safety without compromising the motorcycle’s identity.
Nothing is visibly added to the rear of the bike.
There are no cheap aftermarket stalks. No tiny indicators. No awkward brackets. No extra brake-light pod hanging below the number plate.
The original BMW indicator housings remain exactly where BMW put them. They simply become much more useful.
For an R1100S used regularly on modern roads, this is one of the most worthwhile electrical upgrades available.
What You Need
- Weiser Legacy 2 EVO Triple Function Rear Kit
- Clear or original amber rear indicator lenses
- Two lengths of suitable automotive wire
- Heat-shrink sleeving or quality loom protection
- Proper crimp connectors, Posi-Taps or solder-and-heat-shrink joints
- Multimeter
- Phillips screwdriver
- Cable ties
- Electrical tape for final insulation where needed
Final Thoughts
The original R1100S rear light is adequate. The upgraded system is better.
It gives the bike more presence in traffic, makes braking easier to read and keeps the rear end looking exactly as it should.
That is the right kind of upgrade: practical, reversible, discreet and entirely in keeping with the motorcycle.