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This was a challenging but rewarding job that I had been a little apprehensive about undertaking. I’d never rebuild a motorcycle wheel, but I had rebuilt bicycle wheels so it wasn’t completely foreign to me.

As usual there were many internet references that were helpful for this job- the two that stood out were; Lonnie Walker’s article Building BMW /2 Wheels and Duane Ausherman’s article on lacing wheels and offsets

The wheels of my bike weren’t in terrible condition to be fair- just the usual kind of wear you would expect after nearly 50 years. There were some dings and scratches on the rims and the hubs were very oxidised. The chrome spokes were irretrievably tarnished. The tires were very old Continentals. Tear down of the wheels and rebuild of the hubs is detailed in my other article here.

Lacing the wheels was really just about being methodical. I did the work on my kitchen table but any relatively flat surface will do.

I have made a video of the wheel building process which covers most of the details- but I will lay out some of the main points here as well.

Offset

Much is written about the offset of the airhead rims- the offset is the distance the rim sits inboard from the hub. It is measured from the brake side of the rim. BMW sold various gauges to measure this but an easy way to establish it is using a flat surface (hence my using the kitchen table). The offset used to be 10mm front and back but when BMW changed to the wider wheels at the back the offset was reduced to 6.5mm (same hub and wider rim = less offset). To achieve this I milled some small aluminium blocks to the correct height and then placed them under the rim with the hub flat on the table brake side down. Then I proceeded to lace the wheels. The offset gets talked about a lot however I believe that if the wheel is laced appropriately and the runout corrected and the spokes roughly equal tension then it will largely set itself.

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Spoke arrangement

The spokes on the rim are arranged in banks of 4- if you inspect a rim you will notice that the bulbs for the spokes are all pointing slight different directions. These correspond to the slots in the hub. In each bank of 4 there are two to each side, one inboard and one outboard. When you inspect the rim it’s hard to explain but this layout effectively means the wheel can only be spoked with the rim one way around. It would be nearly impossible to lace it with the rim the wrong way round. This photo shows a bank of four holes and you can see how they all “point” in different directions.

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Lacing procedure

To lace the wheel I proceeded with the spokes one “layer” at a time. That is I started with the left side outer slots of the hub (topmost- cause you have the hub brake (right) side down) and then moved on layer by later. I had to turn the who arrangement over to install the 2 brake side “layers” but then flipped it back onto my offset blocks before tensioning them.

If you look at each spoke carefully there are two little notches on the heads- these engage reciprocal grooves in the hub and if you don’t have these lined up the spoke head will sit proud in the hub, throwing your tensioning out. It’s important to check this as you go. At first I just installed all the spokes trying to get an even finger tightness then went round and gave them a quarter turn more tightness with my homemade screw driver (see below). At this stage you are just trying to maintain the offset and keep things even. Using the amount of thread showing on each spoke is a good trick to get it even.

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Truing

Once the wheel is laced up with the offset correctly established it is pretty sturdy. However before riding it you need to make sure it is true and that the spokes are appropriately tensioned. To do this you really need some kind of truing stand. Many people make their own but I was fortunate that the truing stand I have used for building bicycle wheels in the past was able to accommodate the slightly larger wheel no troubles.

Truing means correcting the axial and radial runout. Axial is the side to side movement of the rim as it spins and radial is the in and out movement. Sometimes called the wobble and hop. To measure these I used a dial indicator but most truing stands just have pointer gauges and allow you to eyeball the runout.

I inked the rim at various “low” and “high” spots during one rotation. I just used Sharpies of various colours for this. Then I set about tensioning and loosening various spokes to correct it. Basically tensioning spokes going to one side of the rim will move the rim that way as will loosening the spokes going to the other side. To correct the radial runout (the hop) all the spokes in one section can be tightened and the spokes 180degrees (opposite) loosened. Remember that tightening spokes will pull the rim towards the hub. To tighten the spokes I used a small spoke wrench and also this custom screwdriver that I made by grinding a groove in the tip of a non custom screwdriver! This engages the spoke nipples leaving room for the spoke sticking up.

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Fitting tyres

Before fitting the tyres an elastic “rim tape” was fitted to cover the spoke nipples. Make sure the hole for the valve stem is lines up. I also checked for any rough areas on these old rims- anything that looked like it could possibly make a tube unhappy and covered it with tape. To fit the tyres (Metzlers) I tried a technique I had seen on the internet which is supposed to work with no tyre levers. Some air is put into the tube and the tube placed into the the tyre. Then the two beads of the tyre are cinched together using cable ties. Then the tyre is lubed with some washing liquid and in theory just pressed onto the rim using your knees on the ground. In practice I still needed to use the tyre levers a little but it worked relatively well. A key here is to heat the tyres up as warm rubber is much more stretchy than cold rubber.

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