How to Mount Tail Lights on Bikes

Nearly every bicycle tail light sold seems to come with hardware to mount it to the seat post, and observation would show that is in fact the most common location for people to put them.  However, if you put a cargo rack on the back of your bike, this location can become impractical for a number of reasons.  The rack itself may block visibility of the light from the rear of your bike.  And if not, any cargo you may actually want to carry on the rack surely will.

For many mounting the light to the back of the rack makes the most sense.  But how best to do that?  Some racks don’t have any special locations for mounting lights.  If they do, they may not be compatible with your light.  How can we sort this out?

When it comes to permanent rear rack light mounts – where the light gets bolted onto the rack – there are three common “standards” you are likely to run into, and a couple of US manufactures that are popular enough to almost be standards:

  • Two horizontal holes, 50mm apart.  This is most common among European rack manufactures like Tubus
  • Two horizontal holes, 80mm apart (Topeak has adapters in this size.  See below)
  • Two holes, vertically oriented.  This is the most common bolt on options from American manufactures.
  • Topeak racks often have mounting points built into the rack that are only compatible with Topeak lights.
  • The slide-on / clip-on mount made popular by Planet Bike, among others

If you do not yet have a rack, light, or both and are reading this knowing that you will be purchasing soon, you’re in good shape.  Just being aware of the different mounting options will make you much more educated in your purchasing selection than most.

However, if you already have a rack and a light and you’re trying to figure out how to make them work together, you’re probably going to have to resort to either replacing the light, or finding an appropriate adapter.

As mentioned above, Topeak has an adapter that will allow you to affix an 80mm spaced light to a Topeak rack that has their integrated light mounting option.  It is interesting to note, however, that they do not seem to offer either a 50mm horizontal adapter, nor the vertical mount adapter.  If you’ve got a Topeak rack, getting  a Topeak light to go with it may just be your best bet.

Planet Bike, however, does sell a handy adapter that will allow you to mount pretty much any of their lights on a rack with a bolt on mount point.  This adapter bolts to the rack, and accepts the very common slide in clips.  Lights with these types are common not only on Planet Bike lights, but on may lights made by the other brands as well.  They are popular because they can be uncliped from the mount point, and clipped onto any piece of clothing (like a backpack or saddle bag) should you need to.  If you bought one of the smaller tail lights in the US market, there is a very strong chance it is compatible with this adapter.

Finally – what if your rack doesn’t have any light mount points?  This is unfortunately true for almost all of the low to mid priced, US made cargo racks.  Well – you’re not entirely out of luck.  Planet Bike also has a “universal” adapter that can perhaps help you out.

Knowledge of these different options can go a long way towards helping you make the proper tail light selection for your bike and rack.  While one would assume that a bike light will somehow just “work” for your bike, that is unfortunately not always the case.  And a light held in place with bolts will generally last you longer – and make you safer – than one hung in a haphazard way.

Also read: 5 Secrets To Cycling Success

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