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Thread: F850GSA - Changing the final drive ratio

  1. #1
    Registered User rwadamsidaho's Avatar
    Join Date
    Mar 2019
    Sweet, Idaho

    F850GSA - Changing the final drive ratio

    Living in SW Idaho, I have the opportunity to ride a lot of gravel and dirt roads. When my bike is loaded for camping or doing trips on forest service or BLM roads at times I felt that my lower end didn't have the torque that I would like. Reading posts in the 850GS form which is international, I found a couple of different threads that dealt with changing the sprocket ratios. The default on my GSA was 17 front 44 rear for a value of 2.58823. By switching my front sprocket to 16 tooth the ratio changed to 2.75. Not a big change, but noticeable when trying to start on a slope or wanting to go extra slow in slippery conditions. The 850GS thread also mentioned a source for sprockets and chains for all euro bikes that had very good prices and shipped all over the world including the USA. CARPIMOTO has a wide selection of high grade drive components that are available for prices about 50% of my local dealer, so I ordered a new 16 tooth front and 44 tooth rear that fit my bike perfectly. The change is noted mostly in the lower three gears where I have more torque at lower RPM, or lower speed at the same RPM. In the high end of the gearing, 5 & 6 there is about a 300 RPM different running at 70 mph.

    I am very pleased with the results and would not switch back for the type of riding I do. If I was making a long road trip on street tires, I then would consider putting the 17 tooth sprocket back on, but as soon as I got back and switched to my 50/50 tires, I would also switch back to my 16 tooth sprocket.

  2. #2
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Jan 2010
    Nice report
    Always good to hear a start to finish project.
    "You can do good or you can do well. Sooner or later they make you choose." MI5
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    2009 F800GS 1994 TW200

  3. #3
    Registered User AntonLargiader's Avatar
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    Jul 2004
    Charlottesville, VA
    Interesting. A number of ADVRiders have noted that they lost their gear indicator after switching to a 16t on their later throttle-by-wire bikes. This was on the F700 and F800.
    Anton Largiader 72724
    Tech articles - YouTube
    Virginia Motorrad Werkstatt BMW motorcycle service and repair in central Virginia

  4. #4
    Registered User rwadamsidaho's Avatar
    Join Date
    Mar 2019
    Sweet, Idaho

    Gear indicator

    That side effect didn't manifest itself on my bike. That would be a good reason to not make a sprocket change.

  5. #5
    Back in the Saddle mcmxcivrs's Avatar
    Join Date
    Apr 2003
    I had heard of that issue with the later 800 models too. Good to hear it is not affecting the 850. One of the benefits of a chain drive is the ability to change ratios. I have not felt the need to do so yet on my GSA, but may in the future.
    Ed Miller, Calgary, AB
    2008 K1200GT, 2019 F850GSA

  6. #6
    I've been running a 15t for years on my 2015 gs800. Certainly not optimal for interstate stints, but 90% of the time I'm in town or on gravel which works great.

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