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Old 07-01-2009, 09:18 AM   #1
chrisjk OP
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F800GS mods for off-roading

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.
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Old 07-01-2009, 09:52 AM   #2
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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
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Old 07-01-2009, 10:14 AM   #3
chrisjk OP
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Hi Paul,

The rally was great, trails, weather and people all terrific.
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Old 07-01-2009, 10:33 AM   #4
Bartron
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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.
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Old 07-01-2009, 11:28 AM   #5
johngil
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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.
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Old 07-01-2009, 12:09 PM   #6
bxr140
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Quote:
Originally Posted by chrisjk
I am contemplating getting my F800 GS's rear wheel laced with an 18 inch rim to improve tyre choice.
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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Old 07-01-2009, 12:55 PM   #7
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Quote:
Originally Posted by bxr140
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.
+1
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Old 07-01-2009, 01:02 PM   #8
lawe
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Quote:
Originally Posted by chrisjk
2. Reversing default condition of ABS - so that it is off by default and has to be switched on.
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.
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Old 07-01-2009, 01:05 PM   #9
Dert Gerl
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Quote:
Originally Posted by chrisjk
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.
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.
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Old 07-01-2009, 01:24 PM   #10
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Quote:
Originally Posted by Dert Gerl
...................................

I did the 15 tooth sprocket too and am very happy with it.

How is it riding at highway speeds? What is the approx. rpm's at say 75 mph?
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Old 07-01-2009, 01:42 PM   #11
Dert Gerl
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Originally Posted by DolphinJohn
How is it riding at highway speeds? What is the approx. rpm's at say 75 mph?
I want to say it's just under 5K.
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Old 07-01-2009, 02:01 PM   #12
DolphinJohn
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Quote:
Originally Posted by Dert Gerl
I want to say it's just under 5K.

Seems like a good compromise.
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Old 07-01-2009, 02:03 PM   #13
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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.
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Old 07-01-2009, 08:17 PM   #14
StabbyMcCutty
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Quote:
Originally Posted by Bartron
... Snatchy throttle fix a la hacksaw ...
What was the hacksaw fix???
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Old 07-01-2009, 09:25 PM   #15
Bartron
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Quote:
Originally Posted by StabbyMcCutty
What was the hacksaw fix???
Although not exactly a fix, it does make things a bit better...

http://f800riders.org/forum/showthre...t=20868&page=3

scroll down to post #73
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