Weight issue - general discussion.

This is a general discussion about weight. After reading it, if you want to get into more detail please use this link.

Our major design criteria are efficiency, comfort, durability, serviceability, longevity, safety and value for money. We are highly conscious of weight but it is an outcome than a starting point. The need to make bikes lighter has often been exaggerated in the media and the marketplace, in as much as it has been applied to non-competition bikes.

Frame failure in “high-end” carbon race frames is not rare. Those bikes generally come with long warranty periods and the replacement cost is built into what people pay initially. It is not so much that they are faulty, although they generally get replaced without argument. It is more that they are built right on the margin of being too light. Whilst touring bikes are not going to have carbon frames or forks, this example illustrates that products that are not very durable are being made and sold. This is understandable when the prime objective is to win a race. But for other uses, it might compromise other objectives that matter more. We are not saying not to use carbon fibre but more to look at, prior to purchase, the case for a cr-mo steel frame and fork. The criteria on which carbon fibre is appealing, is weight, and not its longevity. We are desiging bikes for people who expect longevity.

We are addressing the bike -design issue. You will be also concerned about your own safety, and the convenience to you and your companions of your frame and components always being reliable. This is especially so when travelling.

In our frame materials discussion we came close to this subject. But we wanted to leave the word “weight” for its own page as we do not make decisions in frame design and material selection, based on weight. This however does not mean we think heavier is better or stronger. Or that we are not very aware of weight. You can't not be when designing touring bikes. We are just very wary of allowing maketing language to distort the design story.

And there can be distortion in marketing statements about bikes. A good example is that of tensile strength. It is often mentioned. But, bike frames don’t fail in tension. Frames and parts fail due to fatigue, lack of toughness, "notch-sensitivity", or in an impact. The glass in a window has over five times the tensile strength of cr-mo steel but windows readily break.

Marketing materials may talk about tensile strength but omit to mention any tendency to fail catastrophically. Sound bad? It is. Especially in frames, forks, handlebars, stems, seat posts, pedal axles, cranks, rims and chains. Pedal axle and stem failures are almost unknown. But the others very occasionally happen on the margins, often when weight boundries are pushed.

Defects in manufacturing are unavoidable. Space programs burn up billions of dollars but still have catastrophes happen when something as simple as an O-ring has a tiny flaw, (or, as Richard Feynman says, is used out of context). There is a term “defect tolerance” used in engineering. It is applied to rocket science. But, on our bikes, in traffic, or coming fast down mountains, we ought to be able to trust that defect tolerance having been taken seriously. An obsession with weight can get in the way of taking it seriously.

When we addressed the need for tough wheels and were looking at the rear wheel spokes, we chose 36, not 32, and we chose a 2.34mm (13G) thickness for at the hub end. They are expensive and excellent in quality. Made in Switzerland with Swedish stainless steel. We have not heard of one breaking yet. But, they are slightly heavier and it all adds up.

When we chose the Schwalbe Marathon 700x35C tyres we knew they were 650 grams each. But we also knew they last over 12,000km which is important on a long distance bike; that they very rarely get punctures, also important; that they can be inflated to 85psi, important for rolling on good roads; that they can also run at 45psi because of the bag size; that they ride well on most dirt, gravel and poorer sealed roads. We chose what we thought was the best tyre. The total bike weight is an outcome of these decisions.

We were delighted that the 2011 released Busch and Muller tail light weighs only 51 grams! Some good components are lightweight.

Weight is a big issue when checking in at the airport. Increasingly cyclists are being charged excess if they can’t hold their check-in (bike plus luggage) to 23kg. And when cyclists are riding up mountains they are acutely aware of their load. But it is the sum of the bike, your body, what you had for breakfast, your clothing, the water in your water bottle, and your luggage, that you are carrying up that mountain. So we encourage some wariness when your attention is being directed to the weight of a bike. Also, be wary about comparing a World Randonneur with a different bike. If the other bike has no lights then add them. If you add rechargable lights then also add the weight of the recharger as you have to take that on tour. Finally, close attention to tools, spares, clothing and other equipment can go a long way to keeping weight down.