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Copyright   2011  Gerry Kichok
 
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Master Mechanic
Wheel Building Series - By Eric Hjertberg
Copyright 1986 BICYCLING - JANUARY 1986 - Pages 116 to 120
BUILD YOUR OWN WHEELS
Part 1 - Yes, Even You Can Design and Construct A Great Pair of Wheels

This is part one of a three-article series about designing and building quality wheels.  Author Eric Hjertberg, the well-known wheel builder and co-founder of Wheelsmith, begins by discussing component choices. This information will help when you buy machine-made and custom-built wheels or when you shop for the parts necessary to build wheels yourself. Succeeding articles will tell you how to lace the spokes into the hub and rim, then how to tension and true a wheel to perfection. --Editor

Sooner or later, you're going to want a pair of new wheels. Maybe you'll yearn for something lighter and racier; maybe heavier and more durable. At the worst, you'll need them because your present pair didn't survive a crash or the pounding of a bad road. (We won't mention what happened when you tried to leap those railroad tracks in a single bound.)

The type of wheels you build or buy can increase your bike's performance or durability -- sometimes both. The weight of the individual components you select results in an overall wheel weight that has a direct bearing on your bike's riding characteristics. Judicious component choices will help you tailor the new wheels and the bike itself to your needs.

You can take the process to the limit with hand-built wheels. For a given weight of rim and spokes, they are usually more durable than factory- or machine-built wheels. That means you can enjoy the extra performance of lighter rims or fewer spokes without sacrificing strength. Or, without increasing rim weight, you can increase durability. That may sound like having your cake and eating it, too. Not exactly. To get the better wheels you must pay for a skilled assembler's time, or you must acquire the skill to build them yourself.

As you'll see, wheel building is not as difficult as you might fear. Let's start by looking at the various component options and how to combine them to create wheels for specific purposes.

Rims

There is a confusingly large number of rims out there, but remember that the choice boils down to just three things: type of construction, width, and weight. Then remember two important rules:
1. Don't try to understand manufacturers' descriptions of their rims, because they're usually poorly translated by the importers and may not have come from engineers in the first place.
2. Don't trust listed rim weights. Either weigh them yourself or find somebody who has. Rim weight, because it is an easily obtainable number and it correlates quite well with important factors such as cross section and wall thickness, is still your most reliable and accessible indicator of rim strength.

Aluminum rims are the only type worth considering when performance is a concern. Steel rims should be reserved for juveniles, inner-city cycles, and third-world bikes. As opposed to steel, aluminum is light, can't rust, and offers vastly better braking in the wet. The world of aluminum rims can be divided in terms of the two tire types, tubular and clincher.

Tubular

Tubular (sew-up) tires are difficult to repair and must be glued to their rims. Compared to clinchers, they have little to offer those who ride for recreation, fitness, touring, or even most types of racing. Tubular rims are a different story, however. The lightest models can reduce the rotating weight of a pair of wheels by as much as half a pound compared to the lightest clincher rims. Rotating weight is very important because the greater it is, the greater the amount of energy required to change its speed. This is critical in criteriums or any other event where there are many accelerations and other adjustments to speed. A lighter wheel is simply more responsive. Unfortunately, it is also less durable.

It is useful to sort tubular rims into three categories:
1. Extra light, 280-320 grams. For limited use such as time trials, solo competition, and riders less than 130 pounds.
2. Lightweight, 320-380 grams. For smooth roads, criteriums, and track racing.
3. Team weight, 380-460 grams. For general road racing and training.

Clincher

Among clincher rims the choir is vast and the terminology is confounding. Since there are few common standards for labeling, nearly anything goes. I divide them into these categories:
1. More than 600 grams and outside widths of at least 28 mm (see illustration). For larger tires and all-terrain bikes.
2. Weight of 500-600 grams and outside widths of 22 mm. For all-purpose touring and ATB racing. Tire size is 28 mm (1 1/8 inch) to 38 mm (1 1/2 inch).
3. Weight of 420-500 grams and outside widths of 20 mm. For tires between 19 mm (7/8 inch) and 28 mm (1 1/8 inch). This category is often called "one inch" and covers most racing and sport riding.


Rim width is usually measured from outside to outride.

Other Rim Factors

So-called "hardened" or "heat-treated" rims have gained considerable popularity in recent years. Almost without exception, these rims are gray because of surface anodization, not true heat treatment. This hard shell contributes only a little to the overall strength of the rim. Cynics will note that the reputation for durability gained by "hardened" tubular rims was due to the heavy weight (approximately 400 grams) of the pioneering models. Base your choice on reputation or color preference.

The next decision is between ferruled ("double-eyelet") and washer-reinforced rims. At one time virtually every tubular rim positioned the head of the spoke nipple against the inside wall. When a washer is put between the nipple head and the rim, this design works quite well. The 1970s saw the introduction of a new design with thimble-shaped ferrules that tied together the inner and outer rim walls as they spread the load under the nipple heads. Today there are fans of each design, although it's certainly easier to lace up a ferruled rim. You won't have a choice with V-section aerodynamic rims, which don't have space for ferrules and don't need them for strength, anyway.

Because of its deep, V-shaped cross section, an aero rim has more radial and torsional rigidity, but slightly less lateral rigidity, than a conventional rim. This means greater resistance to the perils of potholes. It's a benefit that may even outweigh an aero rim's real, but slight, aerodynamic advantage.

When you hear claims about exotic materials and treatments, remember that cross section and wall thickness are the major determinants of rim strength. Because the bicycle industry is so closely knit, we find most companies operating with similar technologies and similar materials. To a great extent a company's reputation is based on its recent success (or lack of it) in making the joint that's part of every rim. On a narrow rim, this seam is usually riveted and/or glued, whereas heavier rims are often welded. In our experience, every company occasionally produces uneven, undesirable seams. A good seam is tight and almost imperceptible when you run your finger across it. Once you've selected a rim model, carefully compare several pairs and choose the smoothest before making the purchase.

Spokes

Fortunately, there's more consensus on spoke design than on rims. The best advice I can give is to use the strongest spokes you can get. Spoke strength has a great bearing on a wheel's reliability. Professional wheel builders demand these brands over most others: DT, Wheelsmith, and Alpina.

Stainless steel is the best material for spokes. Although the extra-shiny finish of chrome-plated spokes keeps them close to the hearts of fair-weather riders, their vulnerability to corrosion makes them second best.

Plated brass nipples are almost universally favored because of their low-friction threads, which make truing easier. Aluminum nipples, which save approximately one ounce per wheel, should be used only on special-purpose wheels destined for light duty. The price for saving that precious weight may be paid later in truing difficulties.

Two gauges, or sizes, of spokes prevail. Remember that gauge numbers run opposite diameter size. That is, the lower the gauge, the thicker the spoke -- 14 gauge spokes are larger and stronger than 15 gauge. It may be less confusing to refer to the diameter measurement. Rather than 14 gauge, think 2.0 mm. Fifteen gauge is 1.8 mm.

Straight-gauge spokes have a constant diameter from threads to head. They account for more than 90 per cent of all spokes used. The major decision you must make is between 2.0- and 1.8-mm diameters, a weight difference of about 40 grams ( 1 1/2 oz.) per wheel. For most of us, that 40 grams is worth it in spoke strength. Leave 1.8-mm spokes to riders who weigh less than 130 pounds. But even they must be cautious using them in competition. A broken spoke can exact the same time penalty as a puncture, so more and more competitors are opting for 2.0-mm butted spokes.

Butting reduces a spoke's center section. For example, the diameter of the elbow and threaded end will be 2.0 mm while the center section is 1.5 or 1.8 mm. This provides 2.0- mm strength where breakage is most likely, while delivering overall weight closer to straight-gauge 1.8 mm. Despite this advantage, butted spokes don't enjoy great popularity. Extra cost has been the main reason; butted spokes can add $10 to the price of a wheel. Of course, that doesn't seem like much when a pair of rims can cost $60 or more.

Butted 1.8-mm spokes have traditionally been mated with extra-light rims. Today, because most racers are concerned with reducing wind resistance, 32- and even 28-spoke wheels are commonplace. This loss of spokes, combined with the trend toward 6-speed freewheels and the extra rear-wheel dish they require, puts a premium on the strength of the spokes that remain. That's a good argument for 1.8-mm straight-gauge or even 2.0-mm butted spokes.

Aero spokes, like aero rims, offer a small decrease in wind resistance that is mainly of value to competitive cyclists. There are two considerations (besides greater cost) when changing from round to aerodynamic spokes. First, in almost every case, the aero spoke must still fit through the hub flange, which means it cannot be very flat. Second, the less round the spoke, the more easily it twists during wheel construction. That's an aggravation. Most riders find their needs best filled by standard, round spokes.

 *After you've decided on hubs, rims and pattern, your source for spokes should be able to determine the spoke length you require. If not, try to find Sutherland's Handbook for Bicycle Mechanics.

Hubs

Small-flange hubs have supplanted large-flange during the last 10 years. There is nothing "wrong" with large-flange hubs. It's just that small-flange hubs do the job well enough, and the amount of extra strength afforded by large flanges isn't worth their extra weight. One conspicuous exception is track racing, where large-flange hubs are still practical and popular.

When choosing among small-flange hubs, weight is a relatively minor factor because most models are of similar size and their mass is concentrated close to the wheel's rotating center. Wind resistance is also a minor consideration. An aerodynamic shape is worth a lot more in looks than performance.

As a rule of thumb, choose hubs that cost the same or a little less than the pair of rims you've selected. It makes little sense to combine a $20 pair of hubs with $70 worth of rims. Cheap hubs may give good service, but only for a couple of years. On the other hand, a pair of quality hubs ( $50 and up) will outlast several rims. Before buying, make sure replacement parts are available for conventional bearing hubs and that "sealed" units are easily serviceable.

If you're heavy and/or very strong and regularly have rear wheel problems, here's your opportunity to do something about it. Order your rear hub with a 126-mm (6-speed) axle and obtain some small axle spacers. Disassemble the rear hub (see "Master Mechanic" in Bicycling, April 1985) and decrease the spacing between the right-side bearing cone and locknut by 5 or 6 mm. Then add the same amount of spacing between the left-side cone and locknut. You'll only be able to use a standard-width 5-speed freewheel, but the dish will be substantially reduced, increasing the wheel's durability. Have your local shop spread your rear triangle to 126 mm, if necessary. If you have a 120-mm hub and you want to use it in a frame with 126- mm spacing, obtain the longer axle and spacers, then proceed as above.

Spoke Pattern

Spoking patterns shouldn't receive so much attention. The stiffness and longevity of a wheel is barely affected by a pattern as long as it is conventional. The accepted patterns are: 24 spoke, cross 2; 28 spoke, cross 2 or 3; 32 spoke, cross 3; 36 and 40 spoke, cross 3 or 4; and 48 spoke, cross 3, 4 or 5.

Radial (no cross) spoking looks great on front wheels and provides adequate performance, but many hub flanges can't stand the extra strain. Do not radially spoke a wheel that may see punishing service.

Touring Wheels

In the classic sense, touring includes all conceivable road and weather conditions, with or without extra baggage. Hubs need to be serviceable and have a strong rear axle. Some brands feature heat-treated axles, and these are worth the expense. Stick to low-flange hubs and 36 spokes. Why 36? Try buying a 40-spoke rim in a faraway place.

A touring rim must be able to accept wide-section tires, so choose from the second category of clincher rims above (22-mm outside width). To complement this durable menu, use 2.0-mm straight-gauge spokes with plated brass nipples in a 3-cross pattern.

Off Road

More and more paved-road touring is being done on all-terrain bikes even if they are a bit slower. As with all touring designs, ATB wheels must emphasize strength. I recommend a 3- or 4-cross pattern with 36 2.0-mm straight-gauge spokes. For true off-road hammering, rims with a 32-mm width are mandatory, but when your riding includes generous amounts of pavement the rim can be lighter, making a 22- or 28-turn width appropriate. I like the two-pair approach: One pair with 32-mm rims and full-size 2.125-inch tires, the second pair with lighter rims and narrow (down to 1.4 inch) street tires. Quick-release hubs can be used in the lighter pair. When you're set up like this, you can make the best use of your ATB.

Sport and Racing

Racing, sport riding, and fast touring can be done on narrow, 20-mm rims unless you weigh more than 200 lbs. For noncompetitive use, the tried-and-true formula is a 36-spoke, 3-cross pattern using 2.0-mm straight- gauge spokes. This robust setup makes perfect sense with a 20-mm rim, especially if you plan to commute, ride in foul weather, or do some touring.

Since fast recreational rides frequently include the speed and excitement of competition, we can take some design lessons from racers. For team use, 32-spoke wheels using a 3-cross pattern and 1.8-mm straight-gauge spokes are common. Unless you're in top- level competition, use high-pressure clinchers. Recent evidence confirms that their rolling resistance is about the same as tubulars'. At 440 to 470 grams the lightest clincher rims do weigh more, but it's a slight penalty considering that the tubular rims most teams use weigh a hefty 400 to 420 grams. On the other hand, the weight saved by using a tubular tire and a lightweight tubular rim can give you a substantial advantage if your weight or riding style doesn't endanger the wheels.

If you choose tubulars, the next important decision is between 28 and 32 spokes. In top-level racing, the vote runs about 80 percent in favor of 32 spokes. Twenty-eight spokes are most popular with light riders (130 pounds and less), time trialists, and triathletes. During the next few years the ratio will tip toward 28 spokes, perhaps to as much as 50 percent.

That doesn't mean you'll see a trend toward even fewer spokes, since 24-spoke wheels remain in the realm of the expert wheel builder and are appropriate only for special use. Still, you will even hear tales of 20- or 16-spoke wheels. Discs will get their share of publicity, too. But the cost of such exotic wheels comes in two forms: a very high purchase price and the possibility of rapid obsolescence; a much higher frequency of maintenance and risk of failure.

Tandems

With tandems, put the emphasis on brute strength. Use a solid rear axle, 700C or 27-inch rims, and 48 straight-gauge spokes per wheel. With all those spokes, rim brand becomes secondary, but use at least a 22-mm width to withstand the inevitable bashing a tandem's weight can inflict. It matters little whether the spoke pattern is 3-, 4- or 5-cross. A 5-cross wheel does have a unique look, though.

Get Ready to Build

In Bicycling's next issue I'll begin the instructions for wheel construction. You may be surprised at how some of the latest breakthroughs in wheel analysis and automation have affected and simplified the manual construction process.

If you want to participate, you'll need to acquire your wheel components in the coming month. You also must purchase or gain the use of a spoke wrench, truing stand, and dishing gauge. Minoura, Park, Tacx, Avocet, VAR, and Wheelsmith make consumer truing stands that cost $25 to $50. Dishing gauges for $10 to $30 are made by Wheelsmith, VAR, Park, and Minoura. At least one of these brands is probably available from your source for rims, spokes, and hubs.

 
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