Brake Light FAQ (Final Draft)

compiled & edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.

Man, you must be burned out!
Steve #001

Does your taillight burn out prematurely? Hey, we're not getting personal, we're just asking. Many riders have had this problem. The taillight flexes when the bike is ridden; the entire assembly flops up and down. The tail light filament breaks, but the brake light continues to operate. So don't get burned out man.

VERY often it's just your contacts. See the Section below: My Brake Light Doesn't Work for more details on reasons why it may not be working.


What's the Replacement Bulb for the Brake Light ?

by Hombre Sin Nombre



Correct Bulb Type:


The Correct bulb is listed in the Owners Manual. The bulbs are #7528 or a #7225 available at any parts store.


Note that it has been said that the bike does not use #1157s: This is what was said. "While they are very similar apparently the 1157s don't quite fit or work. The correct bulb can be found in any auto parts store.  The stem will be silver-coloured instead of brass.  Sylvania bulbs come in black and green packages and the number is stamped in the stem. If you use an 1157 it will work for many years and when it goes out the base will be corroded into the socket, you will break the glass trying to get it out, and end up having to buy a new brake light instead of just a bulb."


However physical dimensions (but not electrical specs) of the #1157, #2057, and (BMW OEM) #7528 are IDENTICAL and INTERCHANGEABLE. Perhaps somebody bought a cheap generic discount bulb, had it corrode or break off. The stock taillight assembly is vented to the air, and the plain brass lamps are more subject to corrosion than the plated bulbs.


In the USA you can buy cheap generic bulbs with that do not meet ECE specs. ECE specs require bulbs to be rated at 12 volts DC, and to have plated bases and larger contacts.


US spec bulbs often have plain brass bases, and can be rated at operational voltages of 12.8-14 volts DC.


The #1157, #2057 and #2357 bulbs are common types often available in the USA as generic discount bulbs made to meet the lower US specs. The #7528 and #7225 are a newer Euro style bulb, made in Europe, not commonly used in the USA, and therefore only available made to higher ECE specs. (Most US industrial electronic supply catalogs do not even list the #7528 or #7225 bulbs.)


For a few cents more, higher quality #1157, #2057, and #2357 ECE spec bulbs are also available. Other than that, the main difference between the #1157/#2057 and the #7528/#7225 is that the latter bulbs have a brighter brakelight (35 MSCD/candlepower, as opposed to 32 for the #1157/#2057), but less longevity (150 hours as opposed to 1200 hours).


SO, FINALLY, lacking the OEM #7528, your best substitute for the OEM #7528 would be the #2357 built to ECE specs, but it's likely no brighter than the #7528, as the #2357 is spec'd at higher voltage, but it would have a much longer life expectancy than the #7528. Note that the #7225 has a much dimmer running light - just 1.2 candlepower.

ALL the bulbs below are Ba15d (dual contact/dual filament) INDEX BASE (axially offset pins, one direction only). External dimensions are identical. Physical differences vary only in terms of construction materials. The bulbs below differ only in terms of the lamp filaments/wattage/output/expected life, as noted:

BULB# # Voltage Amperage/Filament MSCD Hours/Watts ECE Ratings
1157 12.8/14 2.10/0.59 32/3 1200/5000  
2057 12.8/14 2.10/0.48 32/2 1200/5000  
2357 12.8/14 2.23/0.59 40/3 400/5000  
7528 12.0/12  1.75/0.42 35/3  150/1500  21/5W
7225 12.0/12  1.75/0.33 35/1.2 150/1500  21/4W

MSCD is "Mean Spherical Candela", or "candlepower".

(edited) chart source:

My Brake Light Doesn't Work (at ALL/Only with the Rear/Brake/Stays On all the time)


by Flash #412, Richard #230, Mark#403, Marc in CA, Francois, Jim Powell and Kristian #562



This isn't really one question, because there are a few different reasons why it doesn't work, so this FAQ separates them out according to symptoms. Here are the Questions again:


1. My Brake Light Doesn't Work at ALL

2. My Brake Light only works when I use the Rear (Foot Pedal) Brake

3. My Brake Light only works when I use the Front (Hand Lever) Brake

4. My Brake Light is always on.



1. My Brake Light Doesn't Work at ALL


As neither Brake works the Light it most likely to be the Bulb itself, or the Contacts. The Soft Copper Contact metal seems to be a very common problem, even more so than burnt-out bulbs, but first have a look at the bulb. If it is the Contacts, removing the lens cover and wiggling the bulb, pushing in slightly, should produce a working brake light in certain bulb positions.


To check the Contacts, try simply scraping the copper contacts with a sharp knife and then scraping a very small amount of lead off the end of the bulb, on a rough stone or with an emery board or piece of sandpaper, just to scrape off any oxidation. Then slightly bend out the copper contacts towards you (i.e. To rear of bike, closer to the bottom bulb contact), and reinsert the bulb. To bend the Contacts you will need a piece of bent wire or something you can hook the contact towards you with. Don't pull them too far, older copper gets brittle and they could break.

2. My Brake Light only works when I use the Rear (Foot) Brake.


The symptoms indicate the Front Brake Switch is out of order. There is a little microswitch acted upon by your front brake hand lever, just at the pivot of the lever.  It is attached with some tiny nuts and screws.  Loosen the screws ever so slightly and adjust the switch.  If that doesn't make your brake light come on when you squeeze the lever, it could be the switch is either stuck or bad.  You could give it a squirt of WD40 to free it up. If you remove the switch be very VERY careful not to lose the little piece called the "druckstuck" (literally push piece, very precise these Germans) that goes between the tit on the switch and the lever itself.

3. My Brake Light only works when I use the Front (Hand Lever) Brake.


You will need to check inside this Rubber Cap, as it houses the electrical Switch Contacts for the Rear Brake Pedal. Often it can get dirty in the Cap, so pull the cap off and give the wires a good clean, remove the wires and clean the contacts, reinsert the wires. Clean inside the Cap before reinsertion.


Alternatively you could have a problem with the "pinbolt" between the brake pedal and the brake cylinder. Just loosened the nut and extend the pinbolt a couple of turns.


4. My Brake Light is always On.


  1. Check the Blade Switch at the Rear Brake Pedal. There is a small blade spring which is used to push the tit in the switch back into the switch. The blade spring is supposed to sit on top of a bar that is on the right hand side of the brake pedal and as you depress the pedal it pushes the spring up and then activates the light through the switch. If the blade spring gets under the pedal (which it can easily do) the brake light stays on. Easy to check before starting to pull micro switches apart. Ratso.



To check this condition first you have to know what is ON, i.e. is that the Brake Light or just the taillight. To do this,

  1. Find the microswitch at the Front Brake Lever and note how its tiny "nipple" gets pressed in when the brake lever is disengaged, and is released so that it protrudes when the brake lever is engaged or pulled.

  2. When you press the microswitch nipple (using e.g. a fine jeweller’s screwdriver), if it has NOT previously been pressing in properly, your brake light should dim down to the normal taillight mode.

  3. The solution is to loosen the two tiny screws ever so slightly and adjust the switch. If that doesn't make your brake light come on when you squeeze the lever, it could be the switch is either stuck or bad.  You could give it a squirt of WD40 to free it up. If you do undo the screws completely to clean it or replace it, be very VERY careful not to lose the little piece called the "Druckstuck" (literally push piece, very precise these Germans) that goes between the tit on the switch and the lever itself.

  4. Now, when the brake lever is disengaged, the nipple remains sufficiently pressed in so that the brake light doesn't stay "always on."


  1. Check the Bolt holding the Brake pedal is not loose or bent. Remove, grease and replace if necessary. Note that this bolt ALSO holds the Chain Roller (See the Chain Roller FAQ).

5. Brake Lights Intermittent


  1. If you've just installed new lights lights (especially flashers) check the Bulb Wattage is correct!  Don't forget to check the bulbs. A driving light bulb on my ST took six months to finally burn out, and when it did it, took the fuse with it. The filament was broken but showed continuity with a VOM check. Sometimes it came on by itself, other times it would light up if I tapped it, and it always came on and stayed on if it was hot from operating and then was turned off and then back on again. teddco. Refer the Aftermarket Lights FAQ.

  2. If your battery discharged some over the winter, your alternator and VR system may be trying to charge the battery while running your (flashing hyperlights) and brake lights. Some electromechanical flasher systems draw a lot of current and could hang up with open contacts in a low voltage condition. In that case, your brake lights may be on (switch contacts closed), but the voltage may be too low to actually brightly light up the bulb and run the flasher. If not, it could be an intermittent open circuit or a high-resistance short to ground. Time to drag out the Voltmeter and check voltages and resistances.

  3. I had intermittent brake lights on my ST because of the floppy tail light assembly. I removed the lens and the bulb and gently pried the contact for the bulb out a little bit. No problems since. Paul #1289.



If none of the above solutions work, check the under seat wiring/connectors to the back light. Take off the seat. Look at the bunch of connectors in the area of the seat lock mechanism. The wire for the brake light goes through one of those. You might want to break the connection and check it for corrosion. A little bit of Vaseline (petroleum jelly) on those connectors is not a bad idea. You might want to change out the bulb, too, just on general principles. Sometimes one end of the filament becomes "unhooked" but can spot-weld itself if it is in just the right place when the bulb is turned on. That sort of intermittent action will give you fits, too. It might just be your bulb contacts and for some reason you forgot to turn on the ignition key before checking if the light was working. Flash



It is possible BMW have replaced the Front Brake Switch:

Replacing the Entire Brake Light Assembly

December '01

Loose Tail Light Assembly Fix

Solution 1

November '01

I have a temporary fix for mine.

Solution 2
by Tom#981


Solution 3
by John #549
Apr '02

I got tired of the cheesy and cheap rear light housing and the contacts never staying in contact -- no brake light or no running light. After putting in a halogen light for the winter (from Dennis Kirk) the additional heat from the bulb melted the thermoplastic housing and made the situation worse. Rats. Here's a solution:

Taillight assembly modification of a metal light receptacle. From the back of the assembly. Note trimmed plastic area (click photo to enlarge). Wires are terminated with male spade connectors that attach directly to the BMW wiring.
Taillight assembly modification from lens side of the assembly. Socket does not protrude all the way through to prevent the bulb from contacting the lens.


Solution 4


Solution 5

Paul #1289, Red '99 F650ST, Quebec.

Hydraulic Brake Light Switch? (Rear)


Yes it is Possible:


Rear Brake Switch

See the Front Brake Switch FAQ for Switch Alternatives