Hi all,

Wondering what all of you do to prevent rain failures for your lights. As a preface, I run dynamo lighting on my two 'main' bikes (randonneur // city commuter).

During a recent 600k, I got caught in a *torrential* downpour (read: almost white-out conditions) and had to ride about 10 minutes before finding adequate shelter from the deluge. My front light (a standing Edelux II, mounted on a rando-rack and slightly covered by a front handlebar bag) was totally fine and continued working.

My rear light, a B&M Toplight Line Brake Plus, failed and would not give any light output. It didn't work the rest of the ride (luckily we were only 13 miles from the finish, and I had back-up rear lighting), but after my bike dried out by the next day, my tail light was working again just fine.

I have ridden in steady rain and it has been totally fine in the past, and given the extreme conditions, I guess I shouldn't be surprised that it had failed. However, the potential weakness (water getting into the unit in *just* the right way) makes me nervous, and makes me want to come up with a solution to seal off the unit or cover it somehow so that it doesn't happen again.

Is there a way to either cover up the light pretty securely (i.e. not just a sandwich bag tightly-wrapped), or maybe use Shoe Goo or any sort of rubber cement on the seams of the unit? Or is all hope lost and it should just be expected when riding in rain?

I use a minute amount of silicone grease on the o-rings and seals. It improves the seal and its hydrophobicity helps prevent the entry of water.

I've got some Chinese CREE headlamps. So far the lamps have been fine. One battery pack got waterlogged. After a couple of days it dried out and I resumed using it. I now put the battery packs in a plastic bag (grocery vegetable bag). Not tightly sealed, but close, twist, fold back over, twist again... and it all gets stuffed into the pouch, and so far I've been problem-free.

I've designed electronics for a more demanding type of vehicle, and it is possible to make things completely waterproof. However, it's not easy and it's not inexpensive.

If the light housing has two halves and snaps together, you could try applying some sealant between the halves when they are separated, and then mating the halves together and letting the sealant cure. You may also want to apply sealant at the mounting bolts, any wires that enter the housing, and possibly around the switch (if there is one).

I've used silicone caulk as the sealant.. specifically, G.E. 280 . It's not very acidic, which reduces the chances of corroding any copper conductors. You can get it at most hardware stores for a few bucks.

good luck,

Steve in Peoria

Like was mentioned above, on my commuting bike,I run a cheep CREE light with a defuser lens. I have not had any water related problems. I use a voltage regulator and draw the power from the main e-bike battery. the regulator is quite water-tight.

My other light is an Light and Motion helmet light, and I have not had any water problems with it either.

in summary, I don't have water problems.

I also have a B&M Toplight Line Brake Plus and the connectors for the standlight supercap failed recently so I had to take apart the housing to fix it and I'll say, the physical construction of the light leaves a lot to be desired. Not sure if all of them are like this but my light was glued together and the plastic is quite brittle so, even going exceptionally carefully, it still chipped off several sharp plastic shards which left gaping holes in the seam. Not joking when I say you MUST wear safety goggles if you attempt to open this light because you can seriously injure your eyes from the high-velocity shards of plastic. In my opinion one is almost certainly not going to be able to open the light without breaking it so that leaves out e.g. adding a silicone gasket or encasing the electronics in epoxy or anything like that.

I too have considered some type of waterproofing for this light and have come to the conclusion that I'd probably have to either wrap the heck out of the light with clear plastic tape of fabricate some kind of external casing. Since my light is now partially broken anyway I went with the tape for now. We'll see how it does...

edit: on second thought water might be intruding in a few places: where the bare wires enter the housing, by the spade terminals, where the bolts exit the housing and the "off switch". It might be possible to dab a little silicone over these areas and around the seam for good measure.

Thanks for the super-useful information, both of you. I was thinking of external-casing like they make for cameras, if only it existed for this very-specific model of rack-mount tail light!

From what both of you have said, it sounds like some carefully-applied tape and silicone will be the best I can do.

I also sometimes have a Carradice on that Bagman support where the light is attached... however for the 600k I only had a small bag attached there which meant the light was more 'exposed' than if the Carradice were present.

Wondering aloud if I can make a U-shaped "guard" out of some acrylic and attach it to the Bagman to keep water from coming above, and from sloshing around near the fender going upwards into the bottom of the light. Won't be as good as a fully-enclosed and sealed case but couldn't hurt, of course.

Will keep updated with progress!

My Non Brake light Line + is working fine, for several years , PNW Coastal weather *

I read here of several failures of the brake light version, perhaps unrelated to moisture intrusion.

How about Clear Packing Tape? I have an old VistaLight blinky I taped on after it seemed the way people got spare red lenses was theft, so I made it Inconvenient.

* 1 on my Brompton, & 1 also mounted low , behind the rear of the seat post Bottle cage of my Bike Friday..