A Better Way to Mount Lights

A Better Way to Mount Lights

Small parts often get overlooked, but they can make a big difference in your cycling experience. Take light mounts, for example. Adjusting the angle of your headlight beam is useful: In town, you want to angle the headlight low so it doesn’t blind oncoming traffic. Out in the mountains, you need a higher beam. Otherwise, you ride into the dark when you descend at speed and go into a dip in the road.
Yet trying to adjust the headlight by hand usually results in one of two outcomes: Either the mounting bolt is really tight and doesn’t move at all. Or light moves to the desired position, but the bolt turns and loosens in the process, and soon the light rotates on its own.
Of course, your headlight should never come loose. In the real world, even if it’s tight to start with, vibrations tend to loosen many headlight mounts, no matter how much Loctite you use during assembly. And the faster you ride, the greater are the vibrations…
There had to be a better solution! Working as a team, Compass Cycles has developed new headlight mounts that finally meets our expectations.
It all started with my own bikes, where I’ve slotted the mounts of the Edelux headlights, so that the attachment of the rack goes in between. That way, the bolt clamps both sides of the light mount, and no matter how often I adjust the headlight’s angle, it won’t come loose. Unfortunately, slotting the headlight’s mount is difficult, especially on the latest headlights.
We figured out a way to use the same concept without modifying the light itself: Secure the light with a locknut. The bolt is tightened only so much that the light doesn’t rotate on its own. That way, you can adjust the light angle by hand. The locknut locks in this adjustment and prevents the bolt from coming loose. (It’s just like the adjustment of a cup-and-cone bearing in many hubs and classic bottom brackets.)
On one side, we use a Nylon washer that provides a little “give” and allows the adjustment. The washer between the light and the mount must be metal, otherwise, there is no good “ground” to the frame, which is a problem if you run a taillight or the “connector-less” SL system.
We now include this setup with all Compass racks that are equipped with a light mount. For those with older racks, we offer the bolts and washers as a retrofit. When you use B&M lights, the new Compass light mount has another advantage: The bolt isn’t so tight that it risks cracking the plastic mounting eyelet. Yet thanks to the locknut, it won’t come loose.
If your rack has only an eyelet for mounting lights, we designed a light mount that offers the same functionality. It incorporates Nitto’s proven stainless steel light mount, but with our own hardware. A toothed lockwasher prevents the mount from rotating (top bolt). The light itself attaches to the mount (bottom bolt) with a set of locknuts that allow the adjustment.
We also worked out a solution to another problem: With a light mount on the left side of the bike, the weight of the headlight tends to loosen the attachment bolt by turning it counter-clockwise.
Theo had the idea of mounting the light mount to the inside of the rack. That way, the weight of the headlight tightens, rather than loosens, the bolt. It’s a small detail, but it can make a big difference.
We also offer a version for racks that don’t have eyelets, but separate, adjustable struts (above). It incorporates all the neat details of the other mounts, making it a great solution for those racks.
We’ve tested all these mounts extensively before offering them to our customers. It’s not really rocket science, but once you have a headlight that you can adjust on the road, without tools, you won’t want to miss that feature. As to lights coming loose in mid-ride – that just shouldn’t happen. Because in the end, there was a better way – it just took commitment and teamwork to figure it out.
The new light mounts are one example of how at Compass, we design products that meet our own high expectations. When we are out on spirited, multi-day rides in the mountains, we want our bikes to fade into the background, so we can enjoy the amazing roads, the stunning scenery, and the wonderful company of our friends.
Click here for more information about the Compass lights and mounts.

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Comments (19)

  • 47hasbegun

    A little red threadlocker will keep that bolt from loosening. 😉
    How does the nylon washer compare to using a split steel washer? Wouldn’t the nylon compress more over time? I do like the jam nut against the threaded rack eyelet/regular nut.

    January 4, 2017 at 4:56 am
    • Jan Heine, Editor, Bicycle Quarterly

      Threadlocking compounds like Loctite can help keep bolts from loosening, but they shouldn’t be used as a substitute for good design. When the stresses on a bolt are not considered, they usually loosen even when Loctite is used.
      The split steel washers are intended to keep parts from rotating (even though they don’t do a good job at it), so they wouldn’t work well here. The nylon washer won’t compress much, since the bolt isn’t very tight (so the light can rotate).

      January 4, 2017 at 11:15 am
  • John Collier

    In the last photo the nylock nut pictured is too thick for the application. The thread needs to be through the nylock’s plastic retainer by at least two threads.

    January 4, 2017 at 7:37 am
    • Jan Heine, Editor, Bicycle Quarterly

      Good eye! The photo shows a prototype with an incorrect nut. The nuts supplied with the production version are thinner, so the bolt protrudes all the way and engages in the nylon part at the end.

      January 4, 2017 at 11:16 am
  • Kirt

    Looks like the mount Nitto makes.

    January 4, 2017 at 11:42 am
    • Jan Heine, Editor, Bicycle Quarterly

      As explained in the text, the Compass light mount uses the main part of the Nitto mount, but with our own hardware. You could recreate it on your own, by buying a stock Nitto mount and all the screws, nuts and washers. It would just be a bit more expensive, because we buy the hardware in bulk and pass the savings on to you.

      January 4, 2017 at 12:02 pm
  • Owen

    Given the choice, which side of the rack would you mount a light on for visibility/safety or does it not matter much?

    January 4, 2017 at 12:05 pm
    • Jan Heine, Editor, Bicycle Quarterly

      It really doesn’t matter much. What you need to see and from where you need to be seen is in front of the bike.
      I have a slight preference for the light mounted on the left. On long night-time trips, I often ride just to the inside (left side) of the white “fog line” that shows the edge of the traffic lane. The paint is reflective, and if my light is on the right, it’s right above the white line, and thus I get a lot of reflection that makes it difficult to see much else. With the light offset a bit to the left, the reflection is much reduced.

      January 4, 2017 at 4:24 pm
  • james

    I’m happy to have my B&M IQTec Premium headlight in a fixed position, but for night time descents on winding roads I’d prefer a second or integrated high beam that has more flood to the sides and higher aim. Most dynamos are more than capable of supplying a second LED while you’re rolling at speed.

    January 4, 2017 at 1:06 pm
  • Paavo Nurminen

    I prefer my Schmidt Maschinenbau Edelux II head light on handle bar. B&M has now made available a versatile bracket for this kind of mounting: 470LHPB. It even comes with several thicknesses of rubber padding for different diameters of handle bar. For preventing vibration loosening I use two nuts tightened against each other. Of course a longer bolt than original is then needed.
    Also I use a rear light from B&M, 40 mm by 90 mm. It has double prism system and red reflector combination. With Topeak rack it becomes a system where parts fit together. Unfortunately I have seen it only in stand-by state. Even then it is really effective.

    January 6, 2017 at 1:51 pm
    • Jan Heine, Editor, Bicycle Quarterly

      Mounting the light underneath the handlebars is a great option:
      R&M light mount (Compass)
      Unfortunately, mounting the light on the handlebars prevents carrying a handlebar bag.

      January 6, 2017 at 5:02 pm
      • Paavo Nurminen

        I do not use handlebar bag. And mounting to the side as you seem to prefer casts a shadow from the front wheel. That shadow annoys me. Anyway, for reaching something from the bag needs stopping, at least for me.
        I have used a bracket you show in the picture above, but in my current racing bike the diameter of the handlebar is too big for using it (It is designed for about 25 mm diameter).
        Designers of bicycle lights think that they are clever, e.g. hexagonal indentation for the nut. In my case I bought a bolt and four nuts. From two of them I drilled off the threads to get a 10 mm high spacer.

        January 6, 2017 at 11:49 pm
        • Jan Heine, Editor, Bicycle Quarterly

          The key to a light mount underneath the front rack is positioning the light so the shadow of the front wheel is not obstructing your view as you turn. It’s very disconcerting if you descend a mountain road at night, and suddenly turn into the wheel’s shadow. This is especially a problem when mounting the light on or near the front axle.
          The light mounts on Compass racks are specifically designed to avoid that problem. We went through a number of prototypes before we found a location that is far enough forward not to cast an annoying shadow, but not so far forward to make the light vulnerable (and look ungainly).

          January 8, 2017 at 9:37 pm
      • Harald

        I don’t like handlebar mounted lights. Their beam hits the road at too steep an angle to produce good 3D feedback for road irregularities such as potholes and bumps. The lower a light is mounted, the better this gets, with fork-crown mounting being about the highest acceptable position in my experience. I was recently reminded of this after buying a fat bike with handlebar mounted battery lights. Fortunately on the fat bike it’s less crucial to see potholes…

        January 9, 2017 at 10:05 am
        • Jan Heine, Editor, Bicycle Quarterly

          That is why I prefer to put handlebar mounts underneath the bars, not on top. That, and the ability to get into the aero tuck, which requires resting your chin almost on top of the stem…

          January 9, 2017 at 10:15 am
  • Richard

    I was surprised at your comment, “When the stresses on a bolt are not considered, they usually loosen even when Loctite is used.” I’m guessing you mean that clamping force decreases, not that the Loctite fails to do its job(?) Your slotted light mount reminded me of racing car engineer Carroll Smith’s excellent books (including one primarily on fasteners) and his advice to use bolts in double shear, not single shear – even if you have to fabricate the other half of the bracket. Another useful reference is the Bolt Science website. There’s a surprising article on use of locknuts (why the thin one should be installed first) at the bottom of the page at Applicability to a headlight mount is uncertain, but the science may be worth knowing about. An approach that I’ve used successfully is to first securely fasten a bolt to the bracket, then clamp the light mount to the protruding threaded portion using two nyloc nuts in opposition (requires one bolt and three nuts). The trick is to install the inner opposing nyloc nut nylon-end first (after first running the nut onto the bolt the normal way to create some “threads” in the nylon).

    January 7, 2017 at 12:35 pm
    • Jan Heine, Editor, Bicycle Quarterly

      I was surprised at your comment, “When the stresses on a bolt are not considered, they usually loosen even when Loctite is used.”

      Loctite will only hold so much. A poorly designed connection – for example, a vibrating, cantilevered arm (like a light mount) tends to loosen the bolt – usually fails even if Loctite is used. In extreme cases of poor design, the mount itself breaks. A good example are decaleurs that are brazed onto the rack.

      January 8, 2017 at 9:24 pm
  • Richard

    The link for the above post seems not to have appeared. It is www [dot] boltscience [dot] com [slash] pages [slash] vibloose [dot] htm Or, just google “boltscience vibloose.”

    January 7, 2017 at 12:41 pm

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