Introduction to installing brake lights
My Matchless G3LS left the factory back in 1951 without any brake lights, as was the norm in those days. However, on today’s busy roads this really isn’t such a sensible arrangement any more. Hand signals might have been sufficient 60 years ago, but I think the majority of modern car drivers would just think you’d gone mad if you started waving your arm up and down as per the “I’m slowing down or stopping” hand signals specified in the Highway Code! I’d much prefer to keep my hands firmly on the bars and therefore needed to fit some brake lights instead.
Back in India where I bought the bike, it seemed to be viewed as an unnecessary extravagance to have any working lights at all fitted to your vehicle, let alone going to the hassle of installing brake lights where the manufacturer had not seen fit too! But as the bike had to be rewired anyway, it seemed an ideal opportunity to get a brake light fitted. Simple rear brake lights switches were plentiful as they’re fitted to most of the Royal Enfield Bullets that plod about the place, and the modification to the rear lamp unit was straightforward. Fitting a front brake activated stop light was a little more difficult to retrofit, but as the rear brake was the only one with much stopping power on my old Matchless at the time, this wasn’t really an issue.
Here in Hong Kong though things are a little different as it’s compulsory to have brake lights which function when either the front or rear brake is applied. So another wiring modification was required to add a switch to the front brake lever before the bike could go for its pre-registration examination. In the end, like so many things, it’s easy when you know how and so that is what this guide is all about – how to upgrade your classic motorcycle to have brake lights that work when either brake is applied.
The article covers the following topics:
- Introduction to installing brake lights
- The law concerning rear lights in the UK
- Installing a rear brake light
- Rear brake switch
- Brake light bulbs
- The LED alternative
- Brake light wiring
- Installing a front brake light
- Front brake switch
- Bulb and wiring
- Conclusions and your comments
The law concerning rear lights in the UK
Before I get down to the practicalities of the switches and wiring, I thought it worth finding out what the law in the UK says regarding fitment of brake lights to classic bikes back in the UK. After a quick search on the web, this is what I found…
“Every stop lamp fitted to… a solo motor bicycle or a motor bicycle combination first used on or after 1st April 1986 shall be operated by the application of every service brake control provided for the use of the rider.”
“Exemptions: For this test if a stop lamp is fitted, it must meet the requirements of this inspection, but need not be fitted to a machine which:
a. cannot exceed 25mph, or
b. was first used before 1st January 1936, or
c. was first used before 1st April 1986 and which has an engine capacity of less than 50cc.
Machines first used before 1st April 1986 must have a stop lamp that operates from at least one brake control.”
So my conclusions from these two documents are as follows:
– Motorbikes first used before January 1936 don’t need to have any brake lights fitted at all.
– Bikes first used before April 1986 must have a brake light that works from at least one of the braking systems.
– Bikes first used after April 1986 must have a brake light that works with both of the braking systems.
Therefore my 1951 Matchless must have a brake light fitted even though it didn’t have one when it left the factory, but it only needs to operate from one or other of the brake controls (i.e. when either the front or rear brake is applied). It need not necessarily be connected to both braking systems. So my Indian setup (with only a rear brake light) would also be fine for the UK, but the Hong Kong requirements (for both front and rear brake lights) are more stringent.
So, how did I go about ‘upgrading’ my old bike to meet these requirements? Read on to Page 2 to find out…
Installing a rear brake light
Let’s start with the relatively simple task of fitting a brake light which operates upon application of the rear brake. This is quite straightforward and not at all expensive, and most importantly will be enough to get your bike through this section of a MOT in the UK.
Rear brake switch
First, you’ll need to buy a switch that can be fitted to the rear brake pedal and which will illuminate the bright rear light filament when the brake is activated.
These are readily available from lot’s of different sources such as Jampot Spares, Paul Goff’s website, or AMC Classic Spares to name but a few. I picked up a couple of Royal Enfield switches whilst I was living in India – they’re fairly crude but do the job (Hitchcock’s Motorcycles sell them back in the UK).
These switches have a built-in clamp arrangement which is easily fitted to the frame of your bike next to the rear brake lever, down by the side of the rear wheel. A picture says a thousand words so hopefully the photo on the left should give you the idea!
The switch connects to the brake lever using a long spring which means that exact positioning is not critical so long as the switch is off when the brake pedal is released and activates when the pedal is pressed. Experiment with a few positions and angles to see which works best.
Brake light bulbs
Next, you’ll need to decide how to install the additional bulb (or change from a single to double filament bulb) in order to have both tail and stop lights. This is going to depend largely on what type of brake light unit your bike has as this will determine what bulb(s) you can fit inside. I’m working on the assumption that you won’t want to change how the bike looks by replacing the light unit itself.
Let’s look at swapping from a single to twin filament bulb to start with. Most rear light bulbs have a 15mm bayonet fitting (i.e. the metal base is 15mm in diameter and has two little pins that stick out to locate it in the holder). If they just have the one filament they’re probably a BA15s (“BA” means bayonet, “15” is the diameter and “s” means single filament). The diagram below shows all the different types of single and dual filament BA15 bulbs available.Pay particular attention to the position of the pins, both when the bulb is viewed from below and also from the side. The ‘standard’ layout is for the pins to be directly opposite each other when viewed from the bottom, but in some cases (type BAZ15d) one pin is offset slightly. Looking from the side of the bulb, the pins are normally both at the same height, but can also be offset so that one is higher up than the other (types BAY15d or BAZ15d). The other thing to check is the length of the pins as some bulb types have one which is longer than the other (type BAX15d).
It’s not easy to remember which type is which, hence why the above diagram is so useful – click here to download a copy of the full bulb diagram sheet which also shows various other common bulb types.
The reason for all of these slightly different pin configurations with bayonet-fit bulbs is to make sure that you install the bulb the right way around so that the correct filament is connected to the relevant circuit. Most twin filament bulbs have two different brightnesses – a low wattage (typically 5W) filament for the tail lamp and a higher wattage (typically 21W) filament for the brighter stop lamp. If you put it in the wrong way round you’d end up with very bright tail lights but stop lights that are barely noticeable. With non-symmetrical pin layouts, it makes it much more difficult (but not impossible!) to get it wrong.
Chances are that the original single filament tail light bulb will be a BA15s (the only other type of single filament bulb shown in the above diagram is a BAU15s used where a car has clear indicator lenses and so the bulb has to be orange coloured).
A BA15d bulb has exactly the same pin layout so should fit directly into your existing BA15s bulb holder. However, the contacts at the bottom are obviously different and so you’ll need to swap that part of the holder assembly for one with two contacts to accept a double filament bulb. With the bulb removed, these contacts should just push out from the rear as they are only usually held in place by the bulb itself pushing against the spring underneath.
Most of these contacts are fairly interchangeable as there is no precision fit, but you may need to be careful when inserting the replacement double contact part to make sure that it lines up correctly with the contacts on the bulb. This might take a bit of trial and error, but once it’s in place and the bulb is inserted it should stay where it is easy enough. Just make sure that the bulb is in the right way around as discussed above so that the brake light is the brighter of the two.
The LED alternative
An alternative to swapping to a twin filament bulb is to install an LED brake light unit, such as the ones sold on Paul Goff’s website. These completely replace the existing bulb and bulb-holder arrangement with an array of LED’s mounted on a separate circuit board. This option is a bit more expensive, but has the advantage of lowering the electrical power requirements thereby giving your old dynamo / alternator charging circuit a bit of a break.
LED’s use much less current than traditional bulbs – in this case a tiny 0.035 Amps (0.42 Watts) for the LED cluster versus 1.75 Amps (at 12v) for a traditional 21 Watt brake light bulb! For more on this subject, see my “installing LED lighting” article.
You’ll probably need to drill a couple of holes to mount the little circuit board within your existing light unit, but the direct wiring from the board to the bike should give a more reliable connection than a modified bulb holder arrangement as described above. Juts make sure you connect the LEDs the correct way round as, unlike a normal bulb, polarity is critical!
Brake light wiring
So now that the switch and new bulb are in place, it’s time to connect them up with some wiring. This is very straightforward as you only need two wires. I was about to draw a diagram, but then realised that it’s so simple that there wasn’t much point!
The first wire goes from the battery live terminal (i.e. the one that is NOT connected to the earth of the bike frame) to the switch. If you have a fuse fitted to your bike then connect to the protected (i.e. not the battery side) of this so you don’t accidentally fry the electrics in the event of a fault. On my Matchless, nearly all of the electrical connections are made inside the headlamp shell on either the back of the main switch or the ammeter. Running you new wire from the ammeter back to the new brake switch takes a bit more wire, but I think will give a neater end result as you can run the wire back under the petrol tank along with all the existing wires.
Fitting an extra terminal on the back of the ammeter is probably the easiest way to tap into the power circuit. Just make sure that you connect to the output side of the ammeter (i.e. not the side connected back to the battery) if you want the current used by the brake light bulb to show up on the meter reading).
The second wire goes from the other terminal of the new brake light switch to the bright filament of the brake light bulb. It doesn’t matter which way round the two wires go on the switch as it is only a simple make-and-break connection that will operate the same either way. The other (dimmer) filament of the brake light bulb connects to the existing tail light wiring so that it comes of when you turn the headlight or sidelights on.
And that’s it – you should now have a working rear brake light which is enough to get your bike through a UK MOT and keep you a bit safer on the road! If you’d also like to fit a front brake light, then please read on to the next section of this article on Page 3…
Installing a front brake light
Ok, so you have a rear brake light fitted to your bike which is enough to pass the UK MOT test for pre-1986 motorcycles, but modern bikes have brake lights that work with both braking systems, so how do we achieve that? Here’s how…
Front brake switch
Fitting a front brake light switch is just as straight forward as for the rear brake as long as you have the correct switch, but this is just a bit harder to find. Modern bikes have the brake light micro-switch built into the brake lever assembly on the handlebars, but unless you’re going to change the levers, retro-fitting a switch is unlikely to be that satisfactory. It’s also not easy to fit the same sort of switch as used on the rear brake lever as there’s no suitable tube at the front of the bike on which to fit the switch so that it is pulled “on” when the front brake is applied.
But there is a special type of switch available that I only found out about recently when I arrived in Hong Kong. Here, both front and rear brake lights are compulsory and so some of the other classic biker’s I spoke to had already had to solve the same problem to get their motorcycles through the government test. Thankfully someone was able to give me one of these little switches to fit to my bike too!
The type of switch I’m talking about actually fits in-line with the front brake cable. It’s a small black cylinder (about 1″ diameter and a couple on inches long) with two spade terminals at one end and a hole for the cable to go through the middle. A photo is shown on the right.
To fit the switch, you disconnect the brake cable and then cut the outer cable at a suitable location. One section of the cut outer cable is then shortened by the same length as the switch so that the switch in effect becomes part of the outer brake cable. The two halves of outer cable plus the switch should be the same length as the original (un-cut) outer cable. The inner cable passes through the middle of the switch unaffected.
It may be necessary to cut the nipple off the wheel-end of the inner cable in order to remove the outer cable for cutting and then pass it through the switch. This can be replaced with a solder-free nipple (make sure it’s secure as your braking will be relying on it!) or better still, correctly install a new nipple on the end.
It took me a while to find a supplier of these switches on the web, but then I came across Carrot Cycles. They sell an ‘inline brake switch’ for £20 on their website here. It’s probably also a good idea to order the rubber boot for the switch (see here) for extra weather-proofing and protection. A similar switch can also be purchased from Venhill Engineering on their website here, although they are a little more expensive at £22.70. Other suppliers are no doubt available, but these are just the ones I have come across so far.
The switch is very simple – when you apply the front brake, the tension in the inner cable compresses the outer cable which in turn squashes the switch unit. This bring contacts together inside the switch completing the brake light circuit and giving continuity between the two contacts at the end of the switch unit. A slight downside to this arrangement is that it will introduce a little extra ‘sponginess’ into the feel of the brake as the switch compresses under braking, but my front brake was relatively ‘spongy’ anyway and so the difference was not that noticeable.
Bulb and wiring
Even with two brake lights for the front and rear systems you still of course only need the one brake light bulb. So assuming that you already have a rear brake light fitted, that part of the installation is already completed. Otherwise, please refer to the bulb section on the previous page.
The wiring is also exactly the same as for the rear brake light discussed previously. Again only two wires are needed, one between the battery and the switch, and the second between the switch and the bright filament connection on the rear bulb. The switched power supply from both switches goes to the same bulb so that the same brake light illuminates whether you have one or both of the brakes pressed.
When I wired in my front brake light switch, I connected the output from the switch to the output terminal on the rear brake switch. This was purely for ease and convenience as the rear brake light switch terminals were exposed and easy to access, whereas running another wire under the back mudguard to the rear light cluster would have been a bit more hassle. I’ll probably neaten this up when I get round to rewiring the bike, but it works just fine for now.
So that’s about it! Nothing too difficult was it? I hope you’ve found this guide useful to help with installing front and/or rear brake lights to your bike. If you have any comments or feedback on this article, I’d love to hear from you – you can leave your comments at the bottom of this page.