F800GS mods for off-roading

Discussion in 'Parallel Universe' started by chrisjk, Jul 1, 2009.

  1. chrisjk

    chrisjk Been here awhile

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    I want to do two things to the bike that will make it a bit better for off-roading and wonder if any one else has done anything on these lines.

    1. I am contemplating getting my F800 GS's rear wheel laced with an 18 inch rim to improve tyre choice. This will affect the ABS ( which I use on the road). The owners handbook implies that a change in wheel size might be catered for by re-programming the ABS computer but makes no promises - anyone else done this?

    2. Reversing default condition of ABS - so that it is off by default and has to be switched on. As I found out on a steep slippery descent after stalling the motor with over-ambitious braking and restarting it as you slide/roll down, leaves you with no brakes to speak of.
    #1
  2. Wildman

    Wildman In my castle

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    Hi Chris

    Looks like you guys had a great time at the European Rally. Can't answer your questions but someone who can will be along shortly, I'm sure.

    Paul
    #2
  3. chrisjk

    chrisjk Been here awhile

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    Hi Paul,

    The rally was great, trails, weather and people all terrific.
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  4. Bartron

    Bartron 'Tenacious B' the Bike Punisher

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    Great questions. I'm also curious what the collective will contribute.

    I have found the following to be of great help off-road:

    Snatchy throttle fix a la hacksaw
    15 tooth Chain Sprocket
    Lowering tire pressure to 24f/26r
    Turning off ABS but NOT turning off ignition at stops/restarts so as to keep ABS off

    Of these, the 15 tooth CS has yielded the most dramatic improvements at very little cost.
    #4
  5. johngil

    johngil Reseda, CA

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    I'm planning on lacing up a 17" x 3.5" rear wheel. The #'s for a 130/90 mounted on the 3.5" rim seem to be pretty close to the overall diameter of the 150/70. It's been hard to get much info.There are lots of tire choices in this size. I'll have to learn the hard way on whether a 130 is enough tire. I don't believe the ABS will be a problem w/ this set up. Hopefully someone here will tell me if I'm wrong.
    Nothing in 18" seemed close.
    #5
  6. bxr140

    bxr140 Flame Bait

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    In the grand scheme of things, I think this is a low priority. Unless you've already spent your money on your suspension, I wouldn't bother. The three or four 17" options should be plenty capable for virtually anything you can navigate with the 800.
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  7. Dert Gerl

    Dert Gerl Been here awhile

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    +1
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  8. lawe

    lawe lawe

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    I think a reprogramming like that would be a liiitle bit difficult. But maybe if you figure out which of the cables that attach to the ABS Pressure Modulator that brings the power to it, you could place a ordinary switch on that? I wouldn't like to be the first one who test's it and it will for sure give the OBC a lot of fault codes. And You can probaly forget everything about warranty when it comes to the brakes or the Canbus.

    Just a thought... Maybe there's someone who already has tried it on this or some other kind of bike.
    #8
  9. Dert Gerl

    Dert Gerl Been here awhile

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    But if you had the abs off to begin with, then stalled, then hit the starter button while going down the hill your abs would still be off. You wouldn't need to turn it off again unless you turned the ignition/key off.

    That's the way my bike works anyway.

    I'm with you in that I'd prefer the abs to default to off for what I ride.

    I did the 15 tooth sprocket too and am very happy with it.
    #9
  10. DolphinJohn

    DolphinJohn Caveman

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    How is it riding at highway speeds? What is the approx. rpm's at say 75 mph?
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  11. Dert Gerl

    Dert Gerl Been here awhile

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    I want to say it's just under 5K.
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  12. DolphinJohn

    DolphinJohn Caveman

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    Seems like a good compromise.
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  13. Singletrack_mind

    Singletrack_mind Cave Man

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    It seems to me that it might be nice to have a real off switch on the ABS, something you could turn off when you began your day in the dirt & forget about (which of course is why they aren't shipped this way). What comes to mind would be to wire a switch in to one of the sensors so that when the ABS runs it's preflight check it can't see the sensor if the switch is off so the system reverts to the normal braking mode. I'm sure you'd have a big annoying ABS light on your instrument cluster all day, but hey, that'd remind you to turn it back on!

    Some electrical engineer can tell us why this isn't a good idea. I KNOW a BMW lawyer could explain it . . .

    I skipped ABS on mine, I just wanted my brakes to be simple, direct & what I'm used to every time I need them. So far so good.
    #13
  14. StabbyMcCutty

    StabbyMcCutty Adventurer

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    What was the hacksaw fix??? :scratch
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  15. Bartron

    Bartron 'Tenacious B' the Bike Punisher

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  16. chrisjk

    chrisjk Been here awhile

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    I think this is a pretty fair comment although my desire for a wider tyre choice is not simply based on what I think might work better off-road. For example, I have had the opportunity to compare the wear characteristics of a Dunlop 908RR on a KTM 950 SE and the TKC 80's on my bike over enough of the same miles to convince me that I would really, really like to run the 908s.

    In truth, I don't know enough to say whether the different aspect ratio (140/80 rather than 150/70) would make a difference to the handling of the bike, so any change would be a it of a gamble.
    #16
  17. lawe

    lawe lawe

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    I'm the author of that post. I think it helped, more relaxed driving now. But read the posts after no.73 also before using the hack-saw. There are different opinions on this, but i'm sure the pulley needs some kind of modification if you wan't to get it less "snatchy". As all other mods presentated on forums, you need to decide for your self what to do with it.
    #17
  18. Dert Gerl

    Dert Gerl Been here awhile

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    I was pretty dissappointed about the 17" rear wheel when I initially bought the bike, but in my search for tires for a baja trip I ended up with these ...

    Michelin Deserts
    http://www.michelinmotorcycle.com/index.cfm?event=Desert

    I come from the dirt bike side of things rather than the street bike side of things and I think you'd be hard pressed to find a tire that wears substantially better than this if you're talking a knobby tire.

    I did 2100 miles from Phoenix to 3/4 of the way down the baja penninsula and back up with a KTM 990. We did as much dirt as possible while in baja and the tire wear was comparable bike to bike.

    The Michelin Deserts have a super stiff sidewall and performed great!
    #18
  19. chrisjk

    chrisjk Been here awhile

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    I will give Deserts a try at my next tyre change, although I would observe that I know a number of folk with 18 inch rears who moved to 908RRs from Deserts and prefer them on wet pavement and in mud.
    #19
  20. lawe

    lawe lawe

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    If You wan't to disable the ABS for a whole day you can easily remove the ABS sensor from the back wheel and zip tie the sensor to the brake caliper or hose to secure it. Of course your ABS warning lamp will be flashing all day, but that might be a good reminder the next day you are using the bike. I can't see what harm this could do to the bike.
    #20