Cycling UK Forum

In the last year, I've been getting into brevet riding. Up till now, I've been using cheap LED lights and have decided it is time to invest in some proper lighting. I'm drawn towards the B&M 6v Bottle Dynamo (Dymotec is the model name) and combining it with perhaps the LED version of the IQ Fly. Buying from people like SJS Cycles or Dotbike, I can put together such a system for somewhere in the hundred quid range (no pound sign on my NA computer) or less if I go halogen. Considering that I like to tour as well, a battery free system is attractive. My question concerns whether the 6v B&M dynamo would do the job and what would be the best light to combine it with.

I'm not too worried about drag from the dynamo as nighttime rides tend to slow me down, but would also like to hear any opinions based on experience with this system.

Thank you.

In the past I have used a couple of different bottle dynamo systems including the one you are referring to. I wouldn't recommend it.

The B&M Dymotec comes with a rubber dynamo roller which slips horribly in the wet and this basically renders the dynamo non-functional. To counter this problem B&M also do a stainless-steel brush roller which certainly solves the problem - it works terrifically well in the wet - but unfortunately it chews up the sidewall of your tyre leading to early tyre replacement. The brush roller itself also wears out quite quickly and is expensive. (Shame about the dynamo because the Lumotec light that went with it was a lovely piece of kit.)

Due to the "wet-weather issue" I abandoned bottle dynamos in favour of a rechargeable LED system (L&M Vega) which I've been using for the last 2 years for commuting.

I've recently heard good things about the B&M IQ Fly light so I would consider moving to a hub dynamo in future, but I certainly wouldn't go back to a tyre-driven dynamo.

I've never done much overnight (long-distance) riding, but if I were you I'd be thinking in terms of a hub dynamo + IQ Fly, or maybe Ayup rechargeables, or if you want a cheaper solution how about one of the Fenix torches which take AA rechargeable batteries - 40 quid gets you a very powerful light and you can carry spare AAs (charged up) with you.

Hope this helps.

For a sidewall dynamo, you might like to look at the Axa HR (Spa Cycles) as well as the B+M.
Sidewall dynamos aren't quite as bad as Tony makes out, but they do have to be accurately aligned, and run on a rubber part of the tyre rather than the fabric sidewall of lightweight tyres. If they are properly set up, they work perfectly well - after all, people used them for audax events for years before the Schmidt dynohub came along. They can slip sometimes, have more drag than a hub dynamo, and are noisier, but on the other hand there's very little disadvantage when you aren't using them. The drag is noticeable, but not all that significant - maybe 1kph at normal riding speed.

For a light, you really want a recent LED like the IQ Fly. You should probably get one with a switch so you can upgrade to a dynohub later.

I've used bottle dynamos for commuting for twenty years. Hardly ever slip. The slippage problems only come when the drive wheel is worn out, so you replace it.

I mostly use Nordlicht 2000s, although they do occasionally get bearing failure after a few years' service. I find the alternative metal drive wheel best - the standard rubber wheel does slip.