Weight Issue

A General Discussion on Weight

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

Frame failure in “high-end” carbon race frames is not rare. Frame replacement cost is built into what people pay for the bike. 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 durable are being made and sold. It is more understandable when the prime objective is to win a race. But we are on a tour, not in a race. Tourers need to be sure their bike will last a long time.

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. We are wary of allowing marketing 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, when weight or -cost-of-manufacturing boundaries 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. There is a term “defect tolerance” used in engineering. On our bikes, in traffic, or coming fast down mountains, we need to be able to trust that defect tolerance has been factored in. An obsession with weight would have been likely to get in the way of that.

When we addressed the need for tough wheels and were looking at the rear wheel spokes, we chose 36, not 32, and we chose DT, the best. Made in Switzerland with Swedish stainless steel. We never hear of them breaking. But, they are expensive, slightly heavier and it all adds up.

Schwalbe Marathon 700x35C tyres weigh 730 grams each. Much lighter tyres are available. But they last over 10,000km (if rotated). They very rarely get punctures. They can be inflated to 85psi which is great for rolling on good roads. They can also run at 45psi because of the bag size. They ride well on most dirt, gravel and poorer sealed roads. We chose what we thought was the best tyre. Lighter would have been a cost in function.

Sometimes lighter items are available at little or no cost in function. Just money. Schwalbe Mondial tyres are one example. Another is the Tubus rear rack. The Tubus Logo in Cr-mo, with the mounting items, weighs 738gms and is rated to carry 40kg. The Logo Titanium with mounting items weighs 538gms, is rated to carry 30kg but adds $160 to the price.

Weight is a big issue when checking in at the airport. Cyclists are being charged excess if they can’t hold their check-in (bike plus luggage) to 20 or in some cases 23kg. There are an increasing number of cases, like Emirates, that allow us 30kg.

Cyclists riding up mountains 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 the luggage that you are carrying up that mountain. So we encourage some wariness on this weight issue. Be wary about comparing a World Randonneur with a different bike. If the other bike has no lights then add them. If you add rechargeable 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.

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Vivente Bikes is a venture of Gemini Bicycle Centres Pty Ltd, ABN 32 003 102 538

Designed by Joshua McFarlane

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