55W should be fine. Do yourself a favour and order the triumph driving light wiring harness too so you can use the custom plug beneath the tank to wire them up. Saves mucking about with your own wiring. Instead of putting the switch in the light body as Triumph wold have you do it, re-route it up to the hole for the alarm LED in the tank console and use a smaller switch with a waterproof boot. The part number for the wiring harness is in the tech vault.
