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Mono Rear Wheel Conversion

Spoked wheels on a 1985-1995 Monolver rear drive

You arrived on this website for one of the following reasons:

  1. You don't like the y-shaped cast wheels that BMW introduced with the 1985-onwards streetbike monolever Airheads
  2. You would like to convert your 1988-on GS to a monolever rear drive and continue to use your 17in rear wheel with a 130/80-17
  3. You want different final drive ratios for your GS (37/11 and 33/11)
Since case 2 and 3 apply for me, I did not have to deal with the front end conversion as I have a spoked wheel front end already. However, it is quite straight forward: the 19" front wheel off the R100R fits onto a 1985-on monolever and only requires some different size sleeves to be correctly aligned, so is not entirely "plug 'n play".

The easiest way to approach the rear wheel conversion is using a 1988-1995 paralever (R80GS, R100GS, R80R, R100R) rear wheel.

I have marked the area of concern with the red arrow. How does that show when you mount the GS/R rear hub to the monolever rear drive:

In my case, 21.5mm of the inner hub had tp come off. I gave the job to my local machinist Rich, and he took excellent care of it. I won't bore you with any details, just because I don't have any:

Now, in order to be able to use this wheel again on a paralever hub, I had Rich machine a spacer:

Now, how does that fit all together?

That took care of just the hub fitting to the final drive. The second before last thing you need are the 4 monolever wheel bolts (should you not already have them.

Now, the most important part is to make sure, that whatever tire size you're going to use is not rubbing at the swing arm. For a "standard" say 1987 R80 Monolever conversion, the rim has to be laced approx. 10mm off center.

My case is the conversion of a Paralever GS to a monolever. I would like to use 130-80/17 street tires or 50/50 to 70/30 knobbies, so I had some fellow riders check on tire width:

Tire size
Make/Model
Tire Width [mm]
Rim size
140/80-17
Bridgestone BT45
140.00
2.50x17 (R100R)
140/80-18
Metzeler Enduro Sahara 3
140.00
KTM (?)
140/90-18
Mitas E 08
136.00
KTM (?)
130/80-17
Avon Gripster am24
143.00
2.50x17 (R100GS)
130/80-17
Metzeler Enduro Sahara 3
125.00
2.50x17 (R100GS)
130/80-17
Metzeler Tourance
130.00
2.50x17 (R100GS)
130/80-17
Michelin Anakee
130.00
2.50x17 (R100GS)
130/80-17
Metzeler Karoo 2
130.00
2.50x17 (R100GS)
4.00-18
Metzeler Enduro Sahara 3
113.00
2.15x17 (R80G/S)
120/100-18
Avon Gripster am24
125.00
2.15x17 (R80G/S)

I took a couple of measurements of the new hub when installed. Assuming a safe 2-3mm clearance between rubber and swingarm, I will assume a 140mm wide tire as maximun and therefore have the rim laced 15mm off-center to the left. I will consider a 30-50mm swingarm extension to the monolever swingarm as the paralever swingarm is 30mm (measured from swingarm pivot bolts to final drive center) longer than the monolever: 420mm vs. 450mm.