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Guide to Bicycle Technology (article index)
In the present section, we shall take a closer look at the bicycle in general. You will be shown how a typical bike is put together and what the names and functions of the various components are. In addition, a brief summary of the commonly available bicycle types is included, pointing out their respective characteristics. Even for those who are familiar with the subject matter, this information will be useful, since it will allow the reader to become familiar with the terminology used in this guide. 2.1. Today’s bicycle is mostly made with modern mass production methods. Here the conveyer belt with finished frames before the various components are in stalled at individual work stations along the way. Although clearly not all bicycles are created equal, there are quite a number of common concepts, and all of them are built up quite similarly, based on the same range of relatively standard components. The bicycle manufacturer generally makes only the frame, installing the various other parts that are supplied by manufacturers specializing in those items. Fig. 2.2 depicts a typical bicycle and identifies the various components by their most common designations. The Parts of the Bicycle The bicycle can be seen as basic structure (the frame), with groups of components that each fuffill a particular function. The best way to describe and understand the way the bicycle is built up and memorize the names of its many components is on the basis of the functional groups or systems in which the bike and its components can be divided. Thus, the following functional groups can be distinguished:
The same break-down is reflected in the technical sections of Part II of the guide, where the various components and systems will be covered in depth. In the sections that follow here, each of these groups will be summarized only in so far as to aid an understanding of the bicycle as a whole. Although Fig. 2.2 only coincides fully with one particular bicycle type, most of this material is general enough to aid in the understanding of any bicycle. 2.2. The parts of a typical bicycle, showing their most common designations. Although only one specific model is shown here, other bikes have largely the same parts. The frame is the supporting structure of the entire bicycle, to which the various other components are attached. It generally comprises a structure of metal tubes, usually attached to each other either by welding them together at the ends or by means of hollow lugs. In recent years variants that are built up differently have been introduced, and the various methods of construction will be discussed in sections 4 and 5. The front portion of the frame is called main frame, the rear portion is referred to as the rear triangle. The main frame consists of the thick tubes called head tube, top tube, seat tube and down tube, respectively. The rear triangle is made up of sets of thinner tubes referred to as seat stays and chain stays, respectively. The lower point, where down tube, seat tube and chain stays come together, is the bottom bracket. Where seat stays and chain stays come together flat plates called drop outs or (rear) fork-ends are installed. 2.3 Campagnolo’s C Record, their top racing bike component group. The steering system, covered in Section 6, serves both to steer and to balance the bicycle. It comprises the front fork, the handlebars with the stem that attaches it to the fork, and the headset bearings that allow the system to pivot in the frame. The seat, or saddle, is held in the frame’s seat tube by means of a tubular piece called seatpost, which in turn is clamped in the seat lug. An adjustment mechanism allows for the correct positioning of the seat. These components are covered in Section 7. The wheels are installed in the frame’s drop-outs in the rear and the fork-ends in the front. Each wheel itself comprises a central hub with ball bearings that is held to the frame, a rim onto which the tire with its inner tube is installed, and a set of spokes connecting hub and rim. Section 8 is devoted to the technical details of the wheel. The drivetrain, covered in Section 9, consists of the components by which the rider’s effort is transferred to the rear wheel. These are the crankset, itself comprising cranks, spindle and bearings, as well as the chain- wheels installed on the RH crank, the pedals, the chain and the rear sprockets with their freewheel mechanism on the rear wheel. The gearing system nowadays almost invariably takes the form of a set of derailleurs that move the chain sideways into the desired combination of chain-wheel and sprocket. In addition, there is a system that relies on a mechanism integrated in the rear wheel hub, still used on many utility and touring bicycles in many parts of the world. The two systems are covered in sections 10 and 11, respectively. The brakes also come in two distinct types, namely rim brakes and hub brakes, the latter not only found on cheap utility bikes, but also available in versions that lend themselves to application in tandems and other special bicycles. Sections 12 covers the rim brake, while hub brakes are described in Section 13. Accessories are anything that can be usefully installed on the bike but are not essential to its operation under normal circumstances. These include lighting, fenders and luggage carrying equipment, as well as such things as lock, pump and bicycle computer (electronic speedometer). The most essential of these items will be covered in Section 14. Component Groups Until recently, it was quite common to find a quality bicycle equipped with components from many different manufacturers. Brakes could be of one make, derailleurs of another, hubs of a third, the crankset might be supplied by yet another. Not so today, since what I call the ‘gruppo-craze’ has set in, meaning that most parts are now sold together as a so-called gruppo, or component group-set. Due largely to extensive advertising and simultaneous commercial pressure from the two biggest component manufacturers (Shimano and Campagnolo), it has become fashionable to present the unitary look. Manufacturers are virtually forced to choose all their components from one supplier various component groups, rather than selecting what they consider the most suitable individual makes and models, and the public has unjustly come to expect this. Nice perhaps for the two big component makers, who indeed make just about everything, but unreasonably tough on those specialist suppliers who have invested all their efforts into particular components. Due to this recent craze, makers of superb brakes, hubs or crank- sets have run into serious problems, since the bicycle manufacturers who would like to install these products cannot get the other components individually: they either buy everything from Shimano or nothing. Even when obtaining parts from the same maker, they often have to be selected from one of many different gruppos. 2.4. An unusual component group from Sachs-Huret, including optional drum brakes. This has sent some of the smaller manufacturers scrambling to also establish gruppos of their own. Thus, hub and derailleur maker SunTour teams up with brake manufacturer Dia-Compe and crankset maker SR to present its own gruppo with the name SunTour engraved on all parts. Similarly, some of the European manufacturers team up with others to pre sent their own Simplex, Ofmega, Huret, Weinmann or Edco sets, each containing selected items from other manufacturers. The result is that the customer’s and the manufacturer’s choice is considerably narrowed down. What is even worse, the big manufacturers seem to be steering the bicycle industry away from one of its greatest virtues, namely the interchangeability of parts. Components are now no longer designed to be fully interchangeable with other makes and models. Add to this the infuriating tendency not to stock spares of minor bits and pieces, and to change components from one year to the next, and you have arrived at a throw-away bicycle culture. For the cyclist, this has made it more and more necessary to replace or repair parts by trial and error. No longer is it possible to predict with certainty whether a particular major or minor component will fit for re placement or repair. The moral is to always take the bike — or at least the matching components — to the shop when trying to obtain spares or replacement parts, to make sure things fit together before you buy. 2.5. Conventional American utility bike Bicycle Types In this section, the various different types of bicycles available in the US and elsewhere will be presented. Even though quite a number of different models are described here, there are many more. However, most of these are so uncommon that they can only be briefly mentioned in the sections of Part III, devoted to special bicycles. Even the regular bicycles covered here often come in many different variants. However, for the vast majority of these bikes, the following definitions apply quite accurately. Utility Bicycles Though somewhat out of fashion amongst serious cyclists since the present trend of fitness and purely re creational cycling has set in, these humblest of all bicycles still have a place. In this context, it is interesting to observe that each country has developed its own kind of utility bicycles, all characterized by a rather upright riding posture. The American utility bike is the model shown in Fig. 2.5. Weighing about a ton, it rolls on thick low-pres sure tires and is stopped by means of a coaster brake. The German equivalent is shown in Fig. 2.6. It is in- variably equipped with a three-speed hub with integrated coaster brake (in addition to a rim brake in the front), a flimsy luggage rack, chain guard and fenders, as well as dynamo lighting. In the Netherlands, the Western country with the highest degree of utility cycling, utility bikes take the form depicted in Fig. 2.7. It comes with fenders, a rugged luggage rack, dynamo lighting, as well as fully enclosed chain guards and a rear wheel guard. 2.6. German utility bike, inappropriately referred to as Sportrad, (i.e. ‘sports bike’). 2.7. The Dutch utility bicycle is the most fully-equipped model. It reflects a practical approach combined with a relaxed pace. The British variant of the utility bike, depicted in Fig. 2.8, is called a roadster. It is usually equipped with a three-speed hub, rim brakes, fenders (called mud guards locally), battery lights and a saddle bag. 2.8. English bikes for recreational or touristic use, equipped with fenders and luggage racks. Unlike their American counterparts, many women in Britain still insist on a frame with a lowered top tube, as in the bike on the left. In France and a number of other European countries, the utility function is fulfilled by something akin to the English roadster, though generally with a luggage rack instead of the saddle bag, slightly smaller wheels, and without the hub gearing — these bikes have either no gears at all or a limited-range derailleur just in the rear. In many other parts of the world, primarily the third world, a type of utility bicycle is in use that derives from the original form of the British heavy-duty utility bike: a stately looking black machine, equipped with stirrup rim brakes (the type operated by means of pull rods instead of cables), a saddle with big coil springs and a heavy-duty luggage rack. Drop Handlebar Derailleur Bicycles This term more accurately describes what is usually referred to as ten-speed and is shown in Fig. 2.9. It includes models ranging from out-and-out racing machines to models intended for the casual or recreational cyclist — not quite racing bikes, but with their looks — at least from a distance. Since they nowadays usually have at least 12-speed gearing, the term ten- speed is inaccurate and confusing. 2.9 and 2.10. Above: Simple racing style bike for fitness cycling; Below: Track racing bicycle. Bicycle racers and people who cycle for fitness (as well as many others who have learned to appreciate its virtues of this design) still ride bikes based on this design. The difference between different versions of this basic design are apparent upon closer examination. The real racing bike is much lighter and built more accurately than the run of the mill. Recreational models are often quite a bit heavier and more forgiving. Those intended for touristic use are also a little heavier and sturdier, as well as more extensively equipped. On racing models, very narrow tires are used, and the gearing tends to be very closely spaced, while the whole bike has a rather short geometry with minimal clearances. Essentially all components are made of strong aluminum alloys, which allows them to be kept very light. The simpler versions may have certain parts made of steel and use weaker types of steel for the frame, making them considerably heavier and giving them a less lively feel. A rather exclusive and rarely seen type of racing machine is the track bicycle, depicted in Fig. 2.10. This model has the same basic design but lacks brakes and gearing. The frame geometry is usually even tighter than that of other racing bikes, and they are not in tended, nor suitable, for use on the road. Lightweight Touring Bikes Although this type of bicycle has become almost extinct in the US with the advent of the mountain bike, it is still widely used in other countries. A comeback of this design, be it via the hybrid mentioned below, is anticipated in the US as well. Shown in Fig. 2.11, it is essentially a high-quality conventional derailleur bicycle equipped with some practical utilitarian accessories — in addition to the luggage racks shown, it may come with fenders and lighting. The tires have a greater cross section and more tread than the racing bike, yet less extreme than the mountain bike. 2.11 and 2.12. Above: Beautiful aluminum-frame touring bike by Klein. Below: A high-quality mountain bike by Gary Fisher. Mountain Bikes and Hybrids Suddenly, in the eighties, there was a revolution in America that has subsequently swept the rest of the western world as well: The mountain bike has become the most universal adult bicycle, replacing narrow tires with fat ones and dropped handlebars with straight models. This development has had a significant effect on cycling habits as a whole, winning friends for the bicycle amongst those who had never felt at ease on the conventional derailleur bike. Depicted in Fig. 2.12, the mountain bike is a derailleur bike with very wide-range gearing, a rather upright riding position, due to the use of flat handlebars, and fat high-pressure tires. Although it was originally conceived for off-road use, it was soon adapted for regular cycling as well. The advantages of this design for the average cyclist are obvious enough: easily accessible brakes and gears, a riding posture that allows a clear view of the road ahead, a softer ride due to the thicker tires and a less fragile construction that makes the whole machine more forgiving. The hybrid is a recent variation on the same theme. It is intended for less rugged terrain but performs better on the road. Different types of this machines may have either flat or drop handlebars, somewhat less wide spread gearing range and less bulky tires. 2.13. The ultimate multi-purpose bicycle: This is a Bruce Gordon hybrid bike with interchangeable wheels. Portable Bicycles This category is far less common than the models described so far, but it is significant enough not to be overlooked. These bicycles may eventually increase in popularity again, enabling more extensive use of the bicycle for commuting. As shown in Fig. 2.14, they usually come with smaller than usual wheels (anything from 12 to 20 inch diameter, as opposed to the 26 and 27 inch wheels common on conventional bicycles). Their portability may be achieved by means of a folding or separating mechanism that allows getting the overall package dimensions down to something that can be handled on public transport vehicles. 2.14. Simple folding bicycle with relatively small wheels. Quite rare these days, even in Europe, where they were once very popular. In the 1960s, crude versions of this type were all the craze in much of Europe. Today’s models are, al most without exception, very much superior in design and execution. The queen of these is probably the Moulton, with built-in suspension but rather limited portability. Other designs generally sacrifice some of the desired riding and handling characteristics to achieve a more compact package. More satisfactory de signs are coming on the market, so this concept has a fair chance to ripen to maturity before long. Special-Size Bikes Many women and some men have physical proportions that don’t allow them to be comfortable on most standard bicycles, because they are too small. Something similar applies to very tall persons of either sex. By and large, the bicycle industry does not adequately cater to these people. Too much attention is paid to the greatest common denominator, and few in the trade seem to be aware how ergonomically disastrous the bicycle can be if it is drastically disproportioned in relation to the rider. Not only the frame itself, but also many of the components should be adapted correctly. For small riders, that often brings unforeseen problems, since simply downscaling things doesn’t work, as will be explained in some detail in Section 15. For very tall people, similar problems apply as for those who are short, with the additional drawback of their generally greater weight and the fact that parts become structurally weaker as they are made larger. Some frame builders have recently shown an interest in the problems of the tall and the small, but much is still left to be desired. The major component manufacturers make their high-quality parts only in a very limited range of sizes, leaving even the best intentioned frame builder little to choose from for his discriminating big and small customers. 2.15. Alex Moulton’s high tech small wheeled bicycle with built-in suspension. It can be separated for ease of transport. Children’s Bikes Although much of what was said with respect to the problems of small adults also applies to children, some additional difficulties should be pointed out. One of the most obvious of these is the fact that children often are not able to define the discomfort of a particular design. If one considers the fact that bringing up children is accepted to be an expensive hobby by most adults in the US, it is astonishing that not more pressure has been brought to bear upon the manufacturers to properly cater to this category of cyclists. Whereas adult bicycles are available in a wide range of both price and quality, children’s bikes are generally available in only one: mediocre. It appears that until a customer fits a bike with 27 inch wheels (or a mountain bike with 26 inch wheels), very little is done to provide quality. The argument that a child’s bike is not worth the expense since the child outgrows any bike too fast is a flimsy one indeed, especially coming from an industry that encourages adults to upgrade their bicycle every two to three years. Although a few frame-builders and manufacturers actually make good childrens’ bikes, it is very hard to find them. Amongst the bicycles for children and young teenagers, two designs should be considered separately, since they are available only for this age category: the BMX and freestyle bike and the more recently introduced Formula-1 bike. BMX and freestyle bikes may be fun for riding on dirt and doing tricks, respectively. Al though both have been a great help in raising the standard of the industry, they are very little use for transportation. Not so the Formula-1 bike, which can be seen as the racing bike for kids. Built for fast acceleration, high speeds and easy maneuvering, this machine is superbly suitable for getting around as well. 2.16. Formula-1bike, intended for higher speeds than the BMX bike. 2.17. BMX derivative — uncharacteristically equipped with derailleur gearing — from Diamond Back. Tandems Since the early eighties, there has been a renewed interest in the bicycle built for two. Whereas formerly tandems often seemed to be modeled on the touring bike, many of the newer tandems may have borrowed the characteristics from either the mountain bike or the pure racing bike. 2.18. Tandem bicycle The design of the tandem is an art by itself, due to the structural problems that occur when making a large, complex structure carry such a heavy load. But there are other problems too, for which experienced tandem riders and tandem frame builders have found adequate solutions over the years. Special Bicycles In addition to the relatively common bicycles built on conventional lines discussed above, quite different de signs are introduced from time to time. These include bikes with built-in suspension systems, recumbents, tricycles and even real or presumed HPV’s, in which the rider may be fully enclosed. In addition, bicycles incorporating different solutions for one problem or the other are presented by daring inventors or reckless investors. Section 17 will discuss some of these ideas in more depth, while Section 18 will take a look at the chances of success for such concepts in the future. 2.18. Recumbent bicycle Bicycle Sizing At least as important as the type and quality of a bicycle is its size. Standard bicycles — at least those of any quality — come in quite a range of different frame sizes; yet determining the correct size for any individual is not universally clear. One reasonable way to find the correct frame size is by means of Fig. 2.19. Straddling the top tube with the feet flat on the ground, it should be possible to raise the front wheel off the ground by the distance listed below:
Table 8 gives an approximation of the correct basic frame size as a function of the rider’s leg size. Use the table to find the nearest size, then experi ment with saddle height, handlebar height and stem size to find a position that provides overall comfort. 2.19 Frame sizing. |
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