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Building BMW /2 Wheels By Lonnie Walker
Before We Begin, Let Me Give You A Little Background I began building wheels in 1968. Fresh out of High School, I took a job at a local bicycle shop, a Schwinn Cyclery in the Bay Area of California. The owner of the shop showed me the tricks to wheel building that revealed the magic for what it really was, a series of small, simple tasks, that when completed, resulted in a finished, ready to use, spoked wheel. In 1968, the Bay Area was still a very diverse place, intermixed with the farm lands were horse racing tracks, dirt bike trails, and one of the United States best Drag Strips, Fremont Drag Strip, later known as Baylands Raceway. In those days, any repair facility, regardless of what they were supposed to be, be it bicycle shop, motorcycle shop, auto repair facility etc, was sought out to repair any number of things that had nothing to do with their core business. We were sought out to fix and build wheels. Between the farms, race tracks etc, we built a lot of wheels that had nothing to do with bicycles. I excelled at wheel building, and soon the word got around the Bay Area, that there was a kid at the Schwinn shop that could build wheels for just about anything.. During my time at that bike shop, I built wheels for kids push scooters, antique automobiles, sulkies, farm carts, a couple of Top Fuel dragsters, motorcycles, and of course lots of bicycles. I decided to do this page because there didn't seem to be much on the web that really dealt with BMW /2 wheel building. I frequent several Vintage BMW web sites, and there are always lots of people asking lots of questions about building or respokeing their wheels. There is a lot of bad information on the web concerning building BMW /2 wheels. Many of the authors of this information seem to feel that there is some particular secret to building these wheels, that it involves VooDoo, or special chants to get it correct. I have even seen it written that you just need to keep putting a wheel together, and if it isn't correct, taking it apart until you luck into getting it correct, NOTHING could be further from the truth. A BMW /2 wheel will practically assemble itself. Follow along as I show you how to unlock the secret of the BMW /2 wheel. Properly assembled, the crossing spokes of a BMW /2 wheel will miss each other with some clearance to spare. Improperly assembled, the crossing spokes will not only touch each other, they will be forced to bend around each other. This is not only incorrect, it is just hard to assemble that way and will result in a wheel that is not as strong as a properly assembled wheel. The BMW /2 wheel uses a straight spoke. The BMW system is much stronger, and will keep adjustment much longer than other bikes that use bent spokes, but, you must pay attention to proper wheel orientation when building the wheel or you will get a wheel that is "built backwards". Once you see how the wheels and hubs are built, you will never have a problem with this again and will be able to build a wheel in about five minutes. If you don't have access to a truing stand, you can still build the wheels and have a shop true them. True story, I one time had to show an owner of a BMW shop how to orient the wheels and hubs, he told me he could only get it right about 1/3 of the time....scary huh? When you really look at a BMW /2 wheel, (I mean really pay attention), you will notice that there are four distinct rows of mounds with spoke holes drilled in them. Starting at the valve stem hole and looking to the right in the photo below, you will notice that there is a mound with a hole in it that is slightly to one side of the center of the rim, it is labeled "Inner Near Side". This is followed by another mound and hole that is slightly to the other side of the center of the rim, this is labeled, "Inner Far Side". Next is a hole and mound that is well to the same side of center as the first hole that we discussed, it is labeled "Outer Near Side". Finally the hole that is well to the center of the rim on the far side labeled, "Outer far Side". Being able to see this pattern is the key to building a BMW /2 wheel. Click on the photos for a larger view The Rim Hole Pattern Photo 1
Here is another photo. In this one I drew a line through the centerline of each hole. In the photo, the lines aren't equally spaced, that is because of the angle that the wheel was photographed on.
The Rim Hole Pattern Photo 2
Once you have seen, and can determine the four rows of holes, it is time to move on. Now you need to see the four different rows of holes in the hub.
The Hubs Four Rows of Holes
Now let's Start Building a Wheel First, start by laying your hub down onto your workbench, brake side down. Next lay your wheel down with the hub in the center, look at the orientation of the spoke holes in the hub, and the wheel. Below is an example of a rim and hub properly oriented
Now an example of improper orientation
Before you begin to spoke up, (lace), a BMW /2 wheel, you need to install the spoke plates onto the spokes. Below is a photo of the spoke plates. Spoke Plates
Install them onto the spokes as shown Spoke With Installed Spoke Plate
Let's Get Started Inserting the first spoke
The easiest way for the beginner to start, is with the outer row of spokes on the non-brake side. Take a spoke/spoke plate assembly, and insert it into an outer hole in the hub. Slide it all the way in, and insert the threaded end of the spoke into an outer hole in the top side of the rim. Thread a spoke nipple onto the spoke. You will now have an assembly that looks like this. Note: It has been suggested that Anti-Seize paste need to be used on the spoke threads. I don't think that this is necessary when using stock spokes and nipples. The stock spokes are chromed steel, the nipples chromed brass. I don't however think that the use of Anti-Seize paste would hurt anything. However, if you are using Stainless spokes and nipples, them the use of Anti-Seize paste is essential to prevent thread galling.
The First Spoke Installed
Now continue to add upper spokes until you have completed the top side of the wheel. Shown below is one of the "Tricks" of wheel building. There will always be three spoke holes between any two "Like" spokes. By that I mean, between an upper and the next upper, or a lower and the next lower on the same side of the hub.
When you are finished with the upper spokes on the first side, your wheel will look like this.
A Wheel With the First Row of Spokes Installed
Now take a spoke/plate assembly and insert it into an inner hole on the top side of the hub. Slide it all the way in, and insert it into an inner hole on the top side of the rim, and thread on a nipple. You will now have a wheel that looks like this
A Wheel With the First Inner Spoke Installed
When you are finished installing all of the inner spokes on the top side of the wheel, every other spoke hole in the rim will be filled with a spoke assembly.
Finish installing all of the inner spokes on the top side of the wheel. When you are finished, your wheel will look like this. A Wheel With All Of The Spokes Installed On The First Side
Turn the wheel assembly over, repeat the above instructions to complete the other side of the wheel, and your wheel will look like this.
A Wheel With All Of Its Spokes Installed
Thread all of the nipples onto the spokes as shown in the illustration below.
Shown below are the tools that I use for truing the wheel. The first photo, is a spoke wrench that I made from an old Proto butterfly pin wrench. The second photo is an enlargement of the tip of an old, cheap screwdriver that I have ground to fit into the spoke nipples, and around a protruding spoke.
Spoke Wrench
Modified Screwdriver
Using the modified screwdriver, screw all of the nipples onto the spokes until the end of the spokes are even with the bottom of the screwdriver slot in the nipples, as shown below.
Screwing On The Nipples
Go This Far
At this point, some spokes will be tight, some quite loose. This is normal, spokes do vary in length somewhat, and no rim leaves the factory exactly round. Using your modified screwdriver, go around the wheel progressively tightening all spokes until they are all the same tension, this should be quite tight. Now it is time to "set" the spokes into the spoke plates. Using a large drift punch and a ball peen hammer, strike the head of each spoke as shown below, don't be timid, you need to make the spoke heads conform to the spoke plates.
Setting The Spokes
Shown next is the special axle that I made for truing BMW wheels. The older BMWs used tapered roller bearings for their wheel bearings, and this axle, (or a sleeve to fit your bikes axle), is required in order to take up the slack in the bearing system.
The Truing Axle
The Axle Taking Up The Bearing Play
Next is my truing stand. This is of my own design and manufacture. I designed, and made this stand to use either pointers, or a dial indicator. I learned using pointers, I am comfortable using pointers, I show pointers being used. If they are good enough for a 275 MPH race car, they are good enough for our bikes. Feel free to criticize, I really don't care.
My Truing Stand
The Wheel mounted On The Stand
The first thing that you need to do is to remove the "Hop", or radial run out from the wheel assembly. Analyze the hop, and determine if it is localized, or if the hub is off center from the rim. If the hub is off center, the you need to slightly loosen the spokes that are on the low side, and tighten the spokes that are on the high side. The high side will be the area of the rim that contacts the pointers. All spokes affect all areas of wheel true, but the inner spokes will have a greater affect on the hop, and the outer spokes will have a greater affect on the "Swerve", or axial run out. There is nothing that can be done to correct the wheel in the weld area, so just ignore this area and work on the rest of the wheel. BMWs specs for run out are unrealistic, try to keep run out in both planes to .020" (.5mm).
Removing The "Hop"
Removing The "Swerve"
Before the final truing, you will want to check the wheel offset. Much has been made of this issue, however, almost every /2 wheel will spoke up with the proper offset if the spokes that are used are all of the correct length. This wheel spoked up perfectly, and I didn't do anything special to make that happen. Measure the hub to truing stand dimension, and the rim to truing stand dimension. The hub dimension should be 6mm greater that the rim dimension on the brake side of the wheel, or slightly less than 1/4". If you don't have access to a truing stand, or yours is not built in such a way that you can use it to take the measurement, you can use a straight edge and ruler. Simply lay the straight edge across the wheel with it resting on the rim edges, then measure from the bottom of the straight edge to the hub at the indicated location. If the offset is too great, slightly loosen all of the spokes on the brake side of the wheel, (make sure that you loosen them all the same amount), then tighten all of the spokes on the hubcap side of the wheel. If the off set is too little, reverse the procedure.
Measuring The Offset
A spoke wrench will be necessary for the final truing. When You are finished truing the wheel, strike each spoke gently on its side with the spoke wrench, if properly tensioned, it should make a musical note. I have been told that it is a high C, but being musically challenged, I will have to take that on face value, I just know what they should sound like. Tighten up any spokes that are loose, and then recheck the trueness of the wheel.
Using The Spoke Wrench
When you are finished truing the wheel, grind off any spoke ends that stick out beyond the spoke nipples, then wrap 4-6 layers of vinyl electrical tape over the spoke nipples in order to protect the inner tube from damage. I like electrical tape because it is easier to use, and longer lasting than a rubber rim strip. Some people use duct tape, but that is too hard to remove, and it gets brittle with age.
The Wrapped Rim
Now cut out the valve stem hole with an Exacto knife, and you are ready to mount and balance a tire.
Cutting Out The Valve Stem Hole
When finished, a properly built BMW /2 wheel will have clearance between the spokes at the cross. In the photo below, the knife blade slips easily between the spokes. This photo demonstrates the clearance between the spokes
Spoke Clearance
Good luck with your wheel building I am not responsible for errors, omissions, or a lack of understanding or skill on your part. E-Mail your comments/suggestions to mailto:lonnie@agwalker.com Some Links
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