Apart from having a power cable fall out once or twice from the front headlight (which has since been remedied with a pair of pliers), the only other challenge has been getting the system to work reliably in the rain.

After a few weeks of tinkering around with my bottle dynamo and on and off rain here in Melbourne, I thought I’d post my thoughts.

The biggest problem with riding in the rain with a bottle dynamo attached to your bike is maintaining friction between the dynamo roller and your bicycle tire. What works well in the dry can easily become a slipslide of ‘oh crap where did my lights go?’ in the rain.

My dynamo is a Busch and Mueller Dymotec 6 which comes with two rubber roller heads. Back when I was using a Gatorskin 700×28 on my rear the rubber roller heads were friction proof.

Whether it was raining, hailing or even cycling through swimming pool sized puddles the rubber rollers never stopped running along the tire.

These days I’m using Continental Travel Contact 700×37 tires and despite having a specific track along the sidewall of the tire for dynamos, they simply don’t perform in the wet. Infact I’m convinced this raised track is what’s causing the roller to slip in the rain.

It’s the same concept that explains why road tires are more grippy in the wet then their knobbly mountain bike counterparts.

With the Travel Contact tires you have a raised edge which prevents full contact of the roller along the tire sidewall. The Gatorskins on the other hand have no such track so the roller is able to make uninterrupted total contact with the tire sidewall.

So inefficient is the sidewall track on the Travel Contact tires that it doesn’t even need to be raining for you to lose lighting. If the roads are even slightly wet, after around ten minutes or so of cycling the tire is wet enough that constant friction is lost.

Not keen to go back to my recently retired Gatorskins (although I would in a flash if Continental ever put out a larger size then 700×28), I decided to stick with the Contact Travel tires and see if I could modify the roller in some way to work in the rain.

Luckily for me Busch and Mueller make a weatherproof roller for the Dymotec 6 specifically for riding in the rain. The downside?

Coming in at $15, the weatherproof roller is the most overpriced bicycle part I’ve ever bought.

The roller is essentially a stainless steel brush in the shape of a circle. Instead of the much more forgiving rubber wheel, the weather resistant wheel uses the harsh friction created by the ends of the steel bristles to maintain contact.

The end result is a dynamo with less drag and noise then the rubber wheel that works brilliantly in all weather conditions. Hell this setup works so well I reckon I could take the Long Haul Trucker underwater and still have lights.

Unfortunately though the weatherproof roller will decimate your sidewall.

When I left the bicycle store the guy told me not to use the weatherproof roller all the time, just in the wet. Figuring I only use the roller once or twice a week for a 10km commute and that replacing the rollers was quick but kinda annoying I’d just leave it on.

Surely 20km a week of dynamo damage wouldn’t be that noticeable would it? I mean I’d be using the roller rubber all through winter (4-5 nights a week) with no noticeable damage.

Oh my god was I wrong.

After just 2 weeks of using the weatherproof roller my sidewall looked battered. In the close up below you can clearly see the damage done by the weatherproof roller compared to the other side of the tire (note the near complete wear of the sidewall tread!).

Prior to using the weatherproof roller there was no noticeable wear on the sidewall tread.

Apart from the drastic increase in tread wear there’s also that worrying slice which runs the length of the sidewall. Oh and keep in mind this is with a sidewall tread, I’d hate to see what this roller does to normal sidewall tires!

I imagine a tire sidewall completely collapsing on you as you ride along isn’t a pleasant experience.

I have read some other stuff on the internet such as modifying a coke bottle cap into a roller that seems to work ok in the west but realistically that doesn’t seem to be a long term solution.

I’m convinced it’s the sidewall tread on the Contact Travel tires that’s causing the slipping in the wet with the rubber wheel so for now I’m just going to put up with it. I’ve found that if you ride slowly (15km/h or so) the rubber roller manages to maintain contact when it’s raining.

Winter is almost over here so I haven’t had to use the dynamo at all over the last week or so and on top of that Melbourne doesn’t tend to get much rain anyway. At this stage apart from trying a touring tire with a smoother treadless sidewall I’m happy with a dynamo that is functional most of the time.

Of course if I still can’t get the rubber wheel to work on a smooth sidewall (this should be do-able considering it worked brilliantly on the Gatorskins), there’s always the dynamo hub option but I kind of like the neatness of a bottle dynamo so I’d like to get the system working reliably in the wet first.

Something about having a removable dynamo that can be turned on and off appeals to me more then a non-removable hub dynamo. On the other hand safety is kinda important, no point dying trying to save money.

I’m proud to announce my Surly Long Haul Trucker has now joined the ranks of complete self sufficiency.

I had to do a bit of research on bottle dynamos as I literally knew nothing about them. I was aware of their more fancier cousins, the hub dynamo, but knew their cost was more of a long term investment then a simple add on to power your lights.

After a few hours and lots of reading I came to the conclusion that the best place to mount my Dymotec would be off the front fork facing forwards. That way if it ever came off it’d be more likely to fall to the ground rather then get sucked up into the fork from behind and start smashing up spokes.

Once I started to fit the dynamo however I soon realised the Dymotec 6 was strictly a rear wheel dynamo, there was no way I was getting this thing mounted onto the front fork.

Upon further investigation the bracket I learned that the bracket I had been supplied with was called a ‘Dynamohalter’ and was designed to be fitted to the seat stay (the rear triangle of the bicycle).

So, with this in mind I then proceeded to go about installing the bracket correctly. Having a look at the rear of the cycle and holding up the bracket and dynamo I quickly realised I wouldn’t be able to mount the dynamo in front of the rear stay.

The reason for this was purely functional. When I’m out and about I always have my right side pannier with me and when I park the bike I almost always use the left side of the bicycle to to lean against something so that I can lock it.

Due to the positioning of the dynamo in the ‘off’ position (it rotates out when not in use), I found that the dynamo would more often then not be likely to get in the way of me locking up the Trucker and could become a resting point between the frame and whatever I was securing the Trucker to.

The thought of the entire bike leaning against a dynamo on a bracket didn’t appeal to me so I settled on going for the less safe but insanely more practical right side mount before the rear seat stay.

Bottle dynamos come in left and right hand versions, depending on your bike set up. Obviously had I of bought the dynamo for myself I’d have bought the right hand version to overcome this functional requirement, but given it was a present I had to make do with what I had.

The Dynamohalter seemed pretty chunky and sturdy so I really wasn’t worried about it coming apart or jiggling loose.

With the theory of how I wanted it to work all settled, I set about fitting the dynamo to the Long Haul Trucker frame.

First I wrapped some old tyre tube around the seat stay where I wished to fit the dynamo. This was for two reasons, one to protect the paint and secondly to provide some cushioning. The Dymotec 6 does weigh a bit and generally metal doesn’t clamp to well onto metal without a cushioner I’ve found. I also didn’t want the thing audibly rattling around just in case it was prone to making noise.

Given I’d never fit a bottle dynamo before I chose a ballpark area to fit the old tube and guessed on where the bracket would sit by holding up the dynamo to the sidewall. The tyre tube was then wrapped in a layer of duct tape before I began to clamp the Dynamohalter on.

One thing to note with the Dynamohalter is that upon first look it appears to be clamped onto the seat stay with just two bolts, not true. There is a third hole on the actual circle bit of the clamp which is where a little included screw thing winds into. The red arrow on the image above points to this hole.

I think the idea behind this is that you screw this in a bit so it’s just poking out and then it focuses the clamp onto a specific point as you tighten it, rather then all around and potentially crushing the small seat stay.

Once this little screw thing is in place you can begin to tighten the two outer bolts until the bracket it firmly in place. Then begin to attach the arm of the Dymotec to the end of the bracket (all the bolts for this are included in the kit).

When everything is done up semi tight you can position things around. The idea here is to get the rubber wheel flush with the sidewall of the tyre when the dynamo is in the ON position. Also you don’t want the dynamo to be digging into the tyre for obvious wear reasons.

This is how the dynamo wheel should sit on the sidewall


When fitting mine I found micro adjustments until the dynamo was such that the slightest pulling away resulted in the rubber wheel losing contact with the sidewall was best and would cause the least amount of drag. I also adjusted the ‘pressure’ setting on the dynamo to minimum as I wasn’t keen on too much drag (that scene where Bart Simpson decides to flick on his dynamo on his way to helping Principal Skinner look at stars comes to mind).

Once it was all adjusted properly I began to tighten everything and that was pretty much it. The units are designed to be maintenance free so apart from checking it every now and then to make sure the Dynamohalter bracket isn’t coming loose, there’s not much else to do but to enjoy the freedom of not having to rely on rechargeable batteries.

All done!


Some notes on the running of the Dymotec 6:


Noise – If you like riding in complete silence through the night a bottle dynamo might not be for you as they all generate some level of noise. Thankfully the Dymotec 6 from what I’ve read is on the quieter side and I’ve found the light hum it makes is more then tolerable; I can barely hear it when I’ve got my ear warmers on.


Drag – This is usually a big concern of people thinking about using a bottle dynamo. Whilst I’m not sure about the cheaper models, I’ve found the drag to be minimal from the Dymotec 6. It is however noticeable and I can feel the rubber wheel whizzing along the sidewall through my Brooks saddle.

Considering the light output I get from the dynamo though I find the drag is pretty good. Once you get going you can barely notice it, you only really feel it when you realise your bike stops prematurely as you approach traffic lights and stop pedaling.


Slipping in the wet – This seemed to be a major downfall of the bottle dynamo system vs. a hub dynamo. The first time I rode in the rain with the unit I was dreading that I might have to adjust the contact pressure which would result in a dramatic increase in drag but I’m happy to say that despite riding in some pretty heavy Melbourne rain the Dymotec 6 has not slipped on me once.

This is with the contact pressure set to minimal and the factory rubber wheel fitted so I am absolutely delighted with this result. There is an optional steel brush wheel available for greater protection in wet weather slipping but I’ve yet to see a need for it.


If you’re considering a bottle setup I’d seriously recommend you go for it. However I would advise to do it properly and purchase a quality unit that will last you years and not make a mess of your sidewall. You can get ridiculously cheap units on Ebay but I imagine they are nowhere near as efficient as the Dymotec 6 (40% efficiency) and are probably quite loud when in operation.

The feeling of having a completely self contained lighting system is amazing. It’s so nice to be able to just push a red button and have instant bright lights. I used to hate it when my battery flashers would start to lose their brightness and I knew it was time for a recharge – thankfully that’s now a thing of the past.