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Old 05-09-2012, 08:50 AM   #12
BMWzenrider OP
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Quote:
Originally Posted by GAS GUY View Post
Does this work on the 1200 gs ?

And I wonder if the modification will be harder on the final drive, considering its more weight and the spacer possibly moving some of the load farther outwards ??
Hello GAS GUY,
Yes, this is a direct bolt-on conversion for the R1200GS/GSA bikes as well.

It will also fit any of the newer K-bikes which use the same style of final drive. (You just need to stand on your head when installing because the shaft is on the wrong side... )

As far as changing the suspension or effect on the final drive:
Based upon my abuse of one of these setups on my sidecar rig, I don't see it being any problem.

1st; The centerline of the wheel assembly is NOT offset vs. the stock wheel setup.
The wheel used for the conversion has more backspace to it, which is what allows there to be enough space for the adapter, but the thickness of the adapter brings the new wheel right back to the original wheel/tire centerline of the bike!

2nd; The unsprung mass of the wheel assembly doesn't really change much.
If you compare the weight of the stock GS/GSA wheel and tire to the total weight of the new setup (adapter/wheel/tire) they are right in the same ballpark. The exact figures depend somewhat on which tires you are comparing.

-The stock GS/GSA spoked rear wheel is listed as being 13.01 pounds.
-A 150/70R17 Metzeler Tourance rear tire has a listed weight of 15.43 pounds.
That gives a total wheel/tire package weight of 28.46-lb (including valve stem).




- As you can see from this photo of an actual complete wheel/adapter assembly, including the lug nuts, stem, etc., the total weight of the new wheel AND adapter assembly is only 14.38 pounds.
- The typical tire used with this setup on the GS bikes is a 165/80R15 all-season radial. This size tire weighs in at about 17.0 pounds when new.
That gives a total package weight for the new setup of 31.38 pounds.
Less than 3 pounds difference between the two wheel/tire assemblies, and you can easily pick up more mud than that.

On my sidecar rig, I am using a different size tire with the new setup to change my overall gearing. That tire is only 13.5 pounds when new, for an total wheel/tire assembly weight of only 27.88, which is actually LESS than the stock setup!
(My winter tire is even another 1/2 pound lighter still...)


3rd; The unsprung mass of the wheel is not even CLOSE to the greatest force/load on the final drive.
The weight of the bike bearing down on the rear wheel is far and away more of a factor to loading on the final drive bearings. The unsprung mass will simply affect the reaction rate of the rear suspension.
And even there, the wheel is less than half of the total unsprung mass when you start adding up the weight of the final drive assembly itself (18.21-lb), the swingarm and torque links (8.79-lb), the driveshaft (4.65-lb), and the various pivot bearings, bolts, drive fluid, etc which adds and additional 1.86 pounds. For a total unsprung weigh of the swingarm/final drive of 33.51 pounds.


4th; I believe that I have "torture tested" this setup with loads transmitted to the final drive above anything that you will be able to dish out. And my original final drive is still humming along happily with nearly 50,000 miles on it. (about 42,000 of those with this wheel/tire conversion installed)

When fully loaded for a trip my sidecar weighs in at close to 1,400 pounds with just myself aboard. That equates to an actual measured static rear wheel loading of about 660-lb. More than the entire weight of a stock GS bearing down JUST on the rear wheel!
Add in that a sidecar doesn't lean into turns, so that my final drive has been subjected to side-thrust loading in addition to the normal radial loads on the support bearings and you can see that I have been testing the final drive of my rig pretty hard...


(I DO like to sometimes ride the rig at a bit more 'spirited' pace...)

In addition to the on-road miles, I have ridden this rig over quite a few dusty miles of rutted/washboard gravel at speed, run it through mud, and hit whoops big enough to bottom out the suspension on more than one occation.






AND, I don't own a car, so my sidecar is my only winter transportation. Meaning my final drive has been subjected to running with below-zero lube in it, road salt thrown at the seals, and all sorts of other mean, nasty stuff.



I don't baby my bikes, and so far I have not detected any issues with this conversion!

------------------

Sorry if this reply got a bit long, but I just wanted to give you a thorough answer to your question.
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2005 BMW R1200RT w/Hannigan-LT sidecar
2002 BMW R1150RA
In Memoriam: Harley, 1993-2010 You will be missed.
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