neninja...interesting...cast alloys must weigh a ton tho, and the speeds, forces, gyroscopic effect are likely orders of magnitude higher than mtbs...where we are discussing 500g off a ~3.5kg wheelset, part of a 90kg rider & bike.
skywalker - Member
What they don't take into account though is the effect lighter wheels have on suspension performance, handling and braking.
None of which you have referenced any formulae or data for...so your only guessing.
skywalker - Member
Why do you think manufacturers try so hard to reduce the sprung and unsprung weight of downhill bikes? If you and Al were right, they would build heavier bikes to keep momentum, but like I said you are not looking at the whole picture.
Your logic is crap, that would not follow from our argument, in fact in DH where there's a fair bit of accelerating & change of direction, and races are very very tight, these factors may matter.
Anyway back to your sacred article, here are the salient quotes about light wheels...
In other words, a mass on the tire has twice the kinetic energy of a non-rotating mass on the bike. There is a kernel of truth in the old saying that "A pound off the wheels = 2 pounds off the frame."
Another place where light wheels are claimed to have great advantage is in climbing. Though one may hear expressions such as "these wheels were worth 1–2 mph", etc. The formula for power suggests that 1 lb saved is worth 0.06 mph (0.1 km/h) on a 7% grade, and even a 4 lb saving is worth only 0.25 mph (0.4 km/h) for a light rider. So, where is the big savings in wheel weight reduction coming from? One argument is that there is no such improvement; that it is "placebo effect". But it has been proposed that the speed variation with each pedal stroke when riding up a hill explains such an advantage. However the energy of speed variation is conserved; during the power phase of pedaling the bike speeds up slightly, which stores KE, and in the "dead spot" at the top of the pedal stroke the bike slows down, which recovers that KE. Thus increased rotating mass may slightly reduce speed variations, but it does not add energy requirement beyond that of the same non-rotating mass.
Lighter bikes are easier to get up hills, but the cost of "rotating mass" is only an issue during a rapid acceleration, and it is small even then.
There are two "non-technical" explanations for the effects of light weight. First is the placebo effect. Since the rider feels that they are on better (lighter) equipment, they push themselves harder and therefore go faster. It's not the equipment that increases speed so much as the rider's belief and resulting higher power output. The second non-technical explanation is the triumph of hope over experience—the rider is not much faster due to lightweight equipment but thinks they are faster. Sometimes this is due to lack of real data, as when a rider took two hours to do a climb on their old bike and on their new bike did it in 1:50. No accounting for how fit the rider was during these two climbs, how hot or windy it was, which way the wind was blowing, how the rider felt that day, etc.*below
Another explanation, of course, may be marketing benefits associated with selling weight reductions.
Many many people on here suffer from *above.
I love how you say we don't understand your argument. We understand it perfectly, and have showed that, whereas you've not even responded to points made by me 2 pages ago! If you had, you'd have some credibility.
Anyway this is too easy...like eating minnows in a barrel. Night, hope you're tucked in!