Bicycle Weight, The Benefits Quantified
Everyone talks about bicycle weight. It consumes our discussions. Magazine reviews make it clear that if the very lightest parts are not chosen, if it is not as light as possible, the bicycle being examined is suspect. Light weight has become the sine qua non of a good bicycle. A light bicycle is a good bicycle, without any further discussion of its other merits or qualities.
Can we step back for a moment?
Let's get some numbers. Let us see if, as I believe, the handy availability of a single number has led people to make poor decisions in their choice of bicycle.
First of all, weight is important. If it weren't, we would all be enjoying pleasant 75-mile rides on 42-pound Schwinn Varsity bikes. The road bikes offered today are a far cry from those mild-steel tanks. We're not talking about riding heavy bikes. I want to limit the discussion to modern, well-made, well equipped bikes.
My personal favorite bike is a 55-centimeter all Columbus Foco Steel Torelli bike with a steel fork, generously chromed, built up with a Campagnolo Record 10-speed group. It weighs about 19 pounds. Beyond aluminum spoke nipples and double-butted spokes, there is nothing heroic about the equipment to make it lighter. The Squadra HDP saddle is heavy by the usual standards.
UCI regulations limit a racing bike to about 15 pounds. What we are discussing, from a normal all-steel bike to a super-light, barely legal bike is about 4 pounds. This is what we're going crazy about, 4 pounds. Maybe a bit more with a less expensive groups. In any case, given the usual rider-bike package of at least 180 pounds or more, the difference is obviously very small indeed.
But how does this weight difference affect performance? Does removing these few pounds make the bike fly? Is a lighter bike the fountain of youth? The September 2003 Bicycling Magazine has a chart that makes it easy to quantify the performance gains from light weight. James C. Martin, Ph.D., assistant professor in the department of exercise and sport science at the University of Utah provided some interesting calculations that make the cost of weight very clear.
He posited a 5 kilometer, 7% grade. That's a good, stiff climb. The legendary Stelvio climb averages 7.5%. He further assumed a rider who can kick out 250 watts. A 160 pound rider will take 19 minutes and 21 seconds to get up the hill. Every 5 pounds added make the trip up the hill take 30 seconds longer.
That means each added pound adds 6 seconds to the time it takes to get up this hill. That is only 6 seconds on a stiff, 20 minute climb.
So, given our roughly 4-pound range from a full steel bike to a super-light carbon or aluminum bike, the time difference up this hill would be 24 seconds from best to worst.
But, most weight conscious people aren't bringing their bikes down to 15 pounds because down at that weight, the handling gets very sketchy. 17 - 17.5 pounds is the normal range. The real discussion is about 1.5 to 2 pounds.
The performance advantage of a lighter bike is greatest when the hill is steepest. What happens as things flatten out? Then, as the speed of the bike increases, the resistance comes from the wind, tire rolling resistance, bearing drag, etc. Those 6 seconds/pound grow ever smaller.
The variations in body weight, however, being so much greater, make large difference. If that same 160 pound-250 watt rider were to be 220 pounds, he would come in 6 minutes, 10 seconds later.
So what do we do with this information?
There are two basic groups of riders to whom this is important.
The first is the serious athlete. A few seconds advantage is not something he can give up. No matter what the quality of the ride of the bike in question, he must seek every attainable performance gain in his equipment or his body.
Then there is the large body of dedicated cyclists who enjoy the sport at various levels, but do not compete in the higher racing categories. I think this is almost everyone reading this essay. For these riders, the choice of bike and equipment should involve a more complex, qualitative study. Weight is one consideration. But there are others. How does the bike feel? Is it stable? Does it fit? Does it have the snappy, clean, vibrant feel that should be the soul of a great bike?
These basically sensuous questions that are beyond simple quantification. It's not a matter of a 73 degree head tube or 18 pounds or 9 sprockets in the rear. It is the whole bike, taken as a whole that must be considered. One should not pick a bike as if he were one of the 7 blind men describing the elephant.
The fact that these 1.5 - 2 pounds are so unimportant in choosing a bike should be looked upon a truly liberating. Now we can to back to judging bikes on their real merits.
Before leaving this discussion, let's look at the most common "upgrade".
A full carbon fork is considered an upgrade that will add greatly to the competitive advantage of the bike. A full carbon fork replacing a steel fork can take off a little less than a pound. Remember, that's our 6 seconds. Clearly, we have all been oversold on the carbon fork as the easy performance upgrade. There is some improvement, but it is minuscule. And it is not without its costs in quality of road feel. For more about carbon, please see my essay on materials.
Or in other words, Scarpelli, you can't buy a bike light enough to keep up me with on a climb.
By Chairman Bill of Torelli Bicycles