Terralux TLE-300 mod
 

I just saw on their webpage terraluxcorp.com how they came out with their newest lighthead. It is supposed to produce a whopping 600 lumens, which is greater than a 50 W MR-16. It's designed to be stuck into the head of a 4-6 D cell Maglite. I seem to remember someone who built a bike headlight with a Maglite head. This new head sells for around $100 last time I checked. Any MTB people want to venture a guess as to how useful this light would be (600 lumens is way too much for on-road commuters).

Not so - My HID is about 675 lumen and it works fine on road. I wear it helmet mounted
so that I don't blind drivers. You need to be seen and lumens is the way it is is done.

Amen brother.

There is no such thing as 'too bright' on a bike for your safety. It's all about the runtime and how big a battery you have to carry. I wished Li-Po 14.8v-18v @ 9Ah batteries weighed 1/4 - 1/2lb but I'd need a time machine for that. >_<;;

interesting. I do think a 4D cell light might be awfully big & heavy to mount....

And as others have said, 600 lumens sure isn't "too much" for a bike light. Never heard anyone say that before! :)

I consider about 400 lumens "adequate":D