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Thread: RT Headlight Low Beam Bulb Lifetime

  1. #1
    Registered User
    Join Date
    Jan 2015
    Pickering, ON, Canada

    RT Headlight Low Beam Bulb Lifetime

    I've seen a bunch of posts on the forum about short lived low beam bulbs and this has always puzzled me. I have a 2014 with 40K miles on it and I'm still on the original bulbs.

    An explanation occurred to me and I thought I'd share it with all. Bulb lifetime is very sensitive to operating voltage. This is why, on a car, if one headlight goes out and you don't notice and replace it fairly quickly, the other will often go shortly after. This is because the line loss through the headlight wiring when both headlights of a car are operating is significant, reducing the operating voltage. When one headlight burns out, the line loss is reduced and the remaining headlight gets a higher voltage (typically 1/2 a volt or more) and, as a result, is more likely to burn out.

    For many years now, I have always ridden in daylight hours with my high beam on (I do not often ride at night, if it can be avoided). I do this to increase my visibility and make me more conspicuous to oncoming traffic - especially at intersections. I don't think the high beam will adversely affect the vision of oncoming drivers in the daytime and, from riding with other RTs and checking my mirrors, I know that it certainly makes the RT much more conspicuous from the front.

    On a recent ride, I wondered about how much of a difference the line loss would be in the RT's headlight system with the high beam on and off. According to the dashboard voltmeter, at highway speeds the system voltage is 14.1V with the high bean off and 13.9V with it on. I'm pretty sure that the 0.2V does make a difference in bulb operating lifetime - and I think I'm safer with the high beam on in the daytime.

    Seems like a beneficial and free thing to do...
    2014 R1200RT

  2. #2
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    You may note that now that DRLs are on all cars, manufacturers arenít using the headlights for that purpose. Even when GM initially cheapskated, they reduced voltage to the high beam.

    Unfortunately USA motorcycle regulations specify headlight, so alternate solutions like the angel eyes donít meet the requirement.
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

  3. #3
    Registered User
    Join Date
    Jan 2016
    Arvada, CO
    Quote Originally Posted by bobs_one View Post
    I have a 2014 with 40K miles on it and I'm still on the original bulbs. .
    I have 40 K miles on my '16 RT and have not had an OEM bulb burn out yet either. We differ in that I only use my high beams to flash oncoming traffic in intersections so I almost never use them. I have followed the forum rumor that letting the electronics fully boot up before hitting the start button does something to spare the low beam bulb (presumably prevents a transient surge). So far so good! It is amazing how many stories of freq low beam bulb changes you read about.
    Last edited by ncpbmw1953; 08-13-2019 at 02:42 AM.

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