They are just different bulbs and different light aperatures/aiming. (Bulb depends which year model you have).
I have HID on the Low but choose not to on the High as I use it more for signalling than I do for night riding, and HID is not good for flashing.
1. it is not good to re-strike the bulb over and over with out cool down.
2. the initial light output in the first second in not very bright.
I would re-consider if I did alot of back road night driving.
I have an 05, so there are separate light assemblies. I just put in the CQlights high and low, h-3 and h-7? "they helped me with the selection when I called. Man, what an improvement. I am really impressed. It is the best money I have spent so far. But I ride at night allot.
I had a high beam HID, didn't use it for flashing, and had PIAA's slaved to it. The PIAA's came on instantly and about a second later, the high beam. It was very intense. Then again, there are so many horned rats out here, anything you can do to even the score is worth it.
I also have a 05 LT and installed HID in low and high beam locations in winter of 06. If I had it to do again, I would only install the low beam HID because both of them on is overwhelming to oncoming traffic even with correct light aiming of both. And as John already stated, short duration duty cycle for these bulbs really shortens their life.
It's also important to purchase HID with as close to 4000K operating temp as possible since above 4300K already introduces blue and that is not desirable from the standpoint of usable white light or from the standpoint of aggravating oncoming motorists. The blue wavelength is the first color the human eye is attracted to...another reason why correctly-selected Alpine (downhill) ski goggles are designed to block blue, thus enhancing one's visual acuity in "flat" and bright skiing conditions.
I did incorporate a manual, weather-protected toggle sw in series from the 12V power supply to the input of the ballast on the low beam...this allows turning off the low beam right before shutting down and then deploying the center stand (avoids low beam ON for center stand deployment) or when one is performing work on the bike at home.
Of course, one has to get used to powering up the low beam which I do after starting the beast and also lighting up the caliper-mounted, 50W Motolights.
When ordering the Motolights, 50W halogen, 8 degree (spot) bulbs instead of the 35W bulbs are available from sources such as 'Raffy' or directly from Motolights.
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