final drive temps

Discussion in 'Motorbike Technical Discussion' started by rile, Jun 14, 2005.

  1. rile

    rile Guest

    I just finished replacing my drive shaft and final drive unit with
    salvaged parts on a Vulcan 750. I drained the old gear oil out of the
    drive unit and replaced it to the proper lever and greased the parts
    with the correct grease as called for in the shop manual. Today, I
    test rode it for about 30 miles at speeds up to 70 mph along with
    several stops and starts. The ambient temps were in the middle 80's
    also. Upon returning, I thought it might be a good idea to check the
    final drive for any heating. It was more than warm to the touch but
    not hot enough to not be able to lay my hand on it.
    My question to all of you that are much wiser than me is.......does
    that sound about correct for the final drive warming like that? Or,
    should it not warm up at all?
    rile, Jun 14, 2005
    1. Advertisements

  2. rile

    B. Peg Guest

    My question to all of you that are much wiser than me is.......does
    Mine gets hot, moreso since the rotor is attached to the hub and if I hit
    the brakes a lot the heat transference is high, excluding what heat is
    generated from the power loss in the unit as mentioned above. I discovered,
    by accident, that I was dragging the rear brake a lot from my boots design
    which caused me to keep pressure on the brake pedal (someone yelled "You're
    riding the frickin' brake!" ??!!).

    Looking at the newest interaction of BMW's classic rear drive problems, it
    looks as though they've put a large hole through the drive to help circulate
    some air to cool it down as well as reduce some of the obtuse angles of the
    shaft to the rear drive. Don't know if they've done anything about the
    rotor heat like floating the disk though as I've not been to a BMW in a long
    time as they are scarce around here.

    B. Peg, Jun 14, 2005
    1. Advertisements

  3. I would have to say that more than a few horsepower are lost to
    friction between the various gears and clutch disks and chains and
    sprockets or shafts and and hypoid gears...

    As I recall, about 15% of a motorbike's horsepower is lost in
    to the rear tire contact patch...

    So a literbike is going to lose more than 15 horsepower to friction of
    some sort...

    When I road raced at Willow Springs, I was only doing 10 laps at a
    time, a warm up lap, 8 sprint laps, and a cool off lap..

    My chain would be too hot to touch afterwards...

    At Daytona, the Good Ol' Boys of NASCAR will sometimes have to change a
    whole rear end in the pits if something breaks during a 500 mile race.
    The mechanics will be wearing gloves to keep from burning their hands
    from the

    I used to hang out with a street racer who was always tearing up his
    Ford's rear end. He'd go hunting for the whole "3rd member" in
    junkyards and it seemed like he was always mad at the junkyards for
    selling him a
    unit that would howl because the ring and pinion didn't engage just

    Even on one of those quiet running hypoid gear sets, the pinion gear
    friction as each spiral tooth slides into contact with the ring gear.
    If the pinion doesn't contact the ring gear in the right place, the
    unit howls from the friction. Motor manuals show the right contact
    area. It gets polished smooth and shiny from the friction...
    krusty kritter, Jun 14, 2005
  4. rile

    rile Guest

    Jeez........ask a simple question and I get a physics lesson. LOL.
    Anyway thanks to all that replied and I feel less apprehensive now.
    rile, Jun 14, 2005
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.