I know I'm probably going to give my head a slap at the answer....but what does HDI mean after a bulb type......want to order some spare one's.

Don't know what type Is In the front at the moment,but It must be quite good,as last night sat at some traffic lights (and It was still quite light) I accidently had my high beam on,and the car driver on the other side of the lights was shielding his eye's and flashing his lights at me!.......for a split second I felt bad about It....then thought "**** you!"

 

Not sure about HDI, but HID is a commonly used abbreviation for High Intensity Discharge light bulbs. Perhaps Harley-Davidson have decided to switch it around so it looks like something new they invented themselves.

 

Checked again and It's deffo HDI....are these the best bulbs then?

 

I may have solved the riddle.

I found some text in a H-D service bulletin that reads "domestic and HDI bulbs have different current requirements". Assuming "domestic" in this instance refers to "US", then "HDI" must stand for "Harley -Davidson International". So it just means a bulb with the correct rating for whichever "international" version of the bike you are riding, which in your case I guess will be European (UK).

The US laws on vehicle lighting differ from those in the EC and the different current requirements are probably something to do with that, with a brighter light probably required by law in one jurisdiction versus the other.