Monday, November 17, 2014

Knog Blinder—How to Fix Broken Mounting Strap

The Knog Blinder 4 is a great rear blinky bike light—super bright, cool flashing modes, and USB rechargeable.  But the Achilles' heel of these bike lights is the attachment band, as confirmed by the repair needs around the internet. (Same issue with the Knog Frogs!) A few of these sites have hinted at fixes, and certainly the 3D-printed cover is a good go at it (I tried it and it works!), but when I had two of these lights' straps fail on me I had to find a simpler / smaller / cleaner solution.

Knog Blinder with broken strap on right side
Knog Blinder with broken strap on right side
It turns out all it takes is a few minutes with some snips, a zip tie, and two small o-rings.  The result is a mounting mechanism that works very similarly to the original but if it breaks it is easily fixed!

The Fix

First I zip-tied together the two dangling leads of the broken rubber band very tightly (using the smallest ties I had, 4"), then trimmed off the excess rubber.  Now there is a loop that something can attach to.

Tie together the two loose ends to make an attachment point - Knog Blinder
Tie together the two loose ends to make an attachment point
I put a small o-ring through (dimensions I used were 7/8"OD and 1/16" thickness which is size -018; those linked ones should work) and looped it around itself like a hand strap on a camera.  That ring can simply hook on the existing sturdy hook built into the light instead of the metal buckle.  I gave it a good tug which made it long enough to fit all the seat posts in my fleet (luckily only range 25.4-27.2mm).  But taking that thin rubber on and off the hook is no fun by itself -- this is why I attached a second o-ring the same way to the end of the first ring and simply use it as a handle.  Now taking it on and off the bike is incredibly easy.

Two o-rings make up the replacement strap with handle
Two o-rings make up the replacement strap with handle
This fix has lasted me many rides including 34 miles to go to and from work.  It does not budge and so far has no signs of breaking.  If it does, it's easy to replace the o-rings.  If the zip-tied rubber casing breaks I will have to come up with something new again (yup—see below).  This fix should work for the Knog Road and 4V light versions as well but I've never used them.

On bike from right
On bike from right
On bike from left
On bike from left
Knog has an otherwise great light, but the original Knog metal buckle may unwittingly be the cause of the strap failures.  I suspect that most people wrap the band around the seat post first loosely, and then simply cam over the buckle to tighten.  This would be fine except that the band is so sticky -- the portion of the band closest to the buckle does most of the stretching since the rest is relatively stuck in place to the post.  This portion over-stretches and eventually fails.  Perhaps the solution is a less grippy rubber on the band?  Or doing away with the buckle and making more of a pull-tab like in the fix I have created here.  Or a stretchy band with multiple attachment points like a belt.  Regardless, building in some sort of attachment loop so that the band can be replaced would likely save Knog a fortune in warranty cost.

Now enjoy your rejuvenated light and go for a ride!

-Mike

Update 5/20/2015:

After about 6 months of regular use, the original rubber that the o-ring gripped onto broke off (half expected), so a new solution was needed. Now I simply use three o-rings (one is still the handle) like so:
Knog Blinder 4 o-ring configuration
The o-rings simply wrap around the sturdy side of the original hook system, then go underneath and around the seatpost to attach to the bike. To prevent the o-rings from falling off when the light is in my pocket, I drilled two very small (1/16") holes to put a needle and thread through. Unobtrusive and plenty secure to hold the rings in place while off the bike.
Knog Blinder o-ring attachment


Time to shop for new bike lights? Please consider using my link to REI for all sorts of awesome cycling and outdoor gear. Definitely my favorite store.
 

-Mike



12 comments :

  1. Awesome Idea!
    Ordered Blinders after reading a site recommendation only to realise afterwards that the band is flimsly in most reviews
    Will stock up when the time comes

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  2. I have 3 of these broken lights. Now I have a stock of 3 working lights! Pity about the crappy strap because the lights themselves are great. Thanks for your idea

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  3. Thanks! I did exactly this three months ago and the light has held fast to my seat post ever sense. Great and fix. Thanks for posting it.

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    Replies
    1. I'm really glad this is working out for so many people! Thanks!

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  4. IMO it is criminal that the straps cannot be replaced by themselves. Mine broke within two months - it just snapped in the middle of the night. Being a sealed unit, the rubber strap by itself cannot be replaced. It should be, and the makers should be making a good supply of these things available at a reasonable cost. My reviews on this product (otherwise the best light I have ever had) is going to be a one-star. The case claims this lamp will save on the purchase of 600 AAA cells in its lifetime. It has not even got past the first two cells for me.

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    Replies
    1. Make sure to contact Knog for warranty replacement if that is what you prefer; they have very nice customer service!

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  5. Thanks very much for this. Great light but let down by the strap, so really helpful to see your two sets of advice. Kind regards, and happy cycling! Simon.

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    Replies
    1. Thanks! I'm glad it helped! I'm a big fan of fixing things rather than tossing in the trash.

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  6. Thanks. Just fixed a Knog Frog like this too!

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