Sunday, July 15, 2012


This post is sponsored by Phototech, for all your Camera and Lens Repair needs.

Hello and welcome to Part III of my Mobec Duo-Drive sidecar conversion on my 2004 BMW R 1150 GS Adventure.
To see Part I, click here, for Part II, click here.

This build report is about the conversion of my 2004 BMW R1150 GS Adventure motorcycle into a 2 Wheel Drive Overland sidecar. I initially dreamt up this project while snowed in up in Steamboat Colorado in January of 2010 and honestly never thought I would see it materialize. But many life experiences along the way has taught me that you have one shot at this, may as well do it now, so what started out as a budget build sidecar has now turned into a full on Mobec Duo-Drive, Suzuki Vitara Sidecar Locking Wheel Hub outfit.
In this installment we are putting together the separate components of the drivetrain, most of which are sourced from other vehicles, replacing the OEM BMW parts.

To recap, this is how my 2004 68,000 mile BMW R1150GS Adventure looked before we started on June 1st,

......and this is how it looks now on July 7th.

The biggest difference is the front end, now leading link steering and not the stock twin tube forks.
Visible also is the sidecar sub-frame, used to attach the sidecar to the motorcycle, or more commonly known as the tug.

The other obvious difference here are the tires, 195 65-16, now light truck tires and not motorcycle tires.

There are 2 main ways to build a sidecar, non-dedicated and dedicated.
The first way, non-dedicated, is to leave the motorcycle pretty much stock with the stock front forks and the stock motorcycle tires, this will be easier, cheaper and allow you to detach the sidecar should you feel like riding solo in 'Motorcycle Mode', usually only 6 or 8 bolts to detach the chair.
The only thing you have to change is the rake of the front forks to make the steering lighter, thats about it. And you really don't have to do that if you don't mind heavy steering.
The second way is to build whats called a 'Dedicated' outfit, where you know that you will never want to detach the sidecar and ride solo. This way you can build it stronger, safer, it will ride and perform much better than a non-decitated outfit and you can use car tires to replace motorcycle tires which benefit you in 3 main ways.
First, car tires are cheaper than motorcycle tires and they give you almost twice the mileage than the softer compound in a motorcycle tire. Second, a sidecar outfit will handle and perform much better with car tires on it. The sidewall on a car tire is larger and stronger than on a motorcycle tire, so they have a stronger and bigger load capacity.
 And third, for winter riding in snow and ice,like the snow and ice I got stuck in Steamboat in January of 2011, you can get studded car tires but not studded motorcycle tires, those you have to make yourself.

A motorcycle tire (top tire)has a curved profile for 'leaning' into turns and curves, you don't 'steer' a motorcycle around a curve, you 'counter steer' or 'push-turn', as you lean into the curve you turn or push the bars in the opposite direction of the turn in the bend. Seems weird, but it works.
On a Sidecar outfit, you don't 'lean' or 'counter steer' into turns anymore, you steer around them like a car, you turn the bars in the same direction as the turn in the bend, so you don't need a motorcycle profile tire on a sidecar, it's a complete waste of a tire. 

Ok, so back to my build.
These last two weeks we accomplished a lot, we got the sidecar attached to the subframe of the motorcycle, the duo-drive attached to the frame of the sidecar and one half of the drive axle attached from the motorcycle final drive to the duo-drive.

And the wheels arrived too, all the way from Japan. 

 I decided not to use the stock BMW rear caliper and rotor and instead use a Brembo caliper and an aftermarket rotor for a Harley Davidson V-Rod. the V-Rod rotor is larger for better braking, looks much better than the stock BMW rotor and the pads in the Brembo caliper have a larger braking contact area than the BMW pads, which is better for the added weight that comes along with attaching a sidecar.

But in order to make the V-Rod caliper fit on the stock BMW final drive housing we had to spend a little time on the milling machine and make an adapter.

The Brembo caliper, origin unknown.

The finished product, we managed to space out the V-Rod caliper so as we could mount the Brembo caliper in the original BMW caliper mounting tabs on the final drive housing, thus utilizing the OEM T45 Torx bolts.

And staying in the adapter mode, we also had to make an adapter in order to mate a 5 bolt Suzuki Vitara wheel pattern to a 4 bolt BMW Rear Wheel bolt pattern. It started out life as a chunk of aluminum......

And ended up a smaller chunk of Aluminum.

4 bolt OEM BMW bolt pattern on the inside and 5 bolt Suzuki Vitara on the outer ring.

The front wheel needed an adapter too, to adapt the Suziki Vitara 5 bolt hub and front wheel disc, but it was easier than the rear wheel to do.

We used the front rotor from the Suzuki Vitara front wheel instead of trying to use the stock BMW rotor, again because it's a bigger rotor and I decided to use a set Brembo calipers from a late model Ducati instead of the BMW calipers. Better brake pads, better braking and I like the look of these calipers better.

Ad Donkers did a really nice job on the sidecar swing arm, incorporating the machined down Suzuki Vitara hub.

On the left is a Suzuki Vitara hub as it came off the car, on the right our machined down version.

Ok, so the next installment will be getting closer to seeing the outfit together, we're working on haveing it nearly all together before disassembly for paint and powder coat.

Just a sneak peek at a mock up we did, not too revealing.
The front view will be in the next installment.




Charlie6 said...

Very cool stuff Murph! The man working the CNC machine is an artist.

Re the tire choice, I understand the way in terms of performance/dimensions involved...was the choice also that they're easily available around the world? Are these tires known in the business as great for sidecar rigs?

Looking forward to the next post!


Redleg's Rides

Colorado Motorcycle Travel Examiner

IRISH Murph said...

Dom, re the tire choice, none of the tires in the pictures are the ones being used, they're just 3 different tires we got as test tires. They're 3 different sizes also. I haven't decided on a final tire yet, mainly because for the first leg of the trip up to Nordkapp for the winter, I'm looking for a M/T Winter tire that can be studded and has a good aggressive tread pattern , but that doesn't wear own too fast either.
The final size has yet to be determined, we have one coming this week that may be the one, fingers crossed, as it's a great looking tire, but have to see if it fits.

sequence kids said...

That has got to be one of the coolest motorcycles I have seen in a very long time. Good job.


Hi Murph I hope ill met you in Potugal in 2013 best Regard´s

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