[briansm]

I find the obsession minimizing bicycle weight funny. It's not the bicycle weight that matters, it's the combined weight of bicycle and rider that counts.

Rider weight massively outweighs the relevance of bike frame material, especially in the West where obesity epidemic has biased BMI upwards over the last half century.

[tomaskafka]

That’s what I tell myself when picking the bike - just get a competent basic $700-ish bike, and if you want it 2 kg lighter, lose those 2 kg instead of paying thousands.

[briansm]

In evolutionary terms, being taller, fatter and more muscular is advantageous, but in practical terms it's just a lot of extra weight to drag around for a lifetime, along with all the extra calories of energy needed to do so.

[magic_smoke_ee]

Yep. That's what I keep telling myself. ;) In the end, those will all kill me sooner because they're each opposed to longevity in a safe environment.

[ndsipa_pomu]

Weight isn't that important for bike racing unless you're specifically doing hill climbs. Aerodynamics will make more of a difference, so there might be some advantage in having a bit of belly fat to enable a smooth airflow.

Also, heavier riders are generally faster downhill as they have a greater terminal velocity.

[magic_smoke_ee]

> have a greater terminal velocity

No, unless they're Russian, they're not free falling. They have greater potential energy. And also increased traction, increased rolling resistance, and increased losses in wheel bearings and drive components due to friction.

[ndsipa_pomu]

Terminal velocity can still apply when cyclists are going downhill. Essentially it's the speed that a cyclist will reach when the gravitational force is equal to rolling resistance (roughly proportional to speed) plus the air resistance (roughly proportional to the square of speed) assuming that they're just free-wheeling and not pedalling. If two cyclists have a similar air resistance, but different weights, then the heavier cyclist will reach a quicker speed. There's the argument that a heavier rider will be bigger and thus have more air resistance, but that effect is smaller than the weight difference. (NB. this can be trivially tested).

[loeg]

Terminal velocity still applies. Yes, it is because they have more potential energy (per CdA).

Rolling resistance increases are pretty marginal with compensating tire pressures (i.e., higher). Wheel bearing losses are de minimis.

Drivetrain component friction is not a function of rider weight.

[magic_smoke_ee]

> Drivetrain component friction is not a function of rider weight.

Wheel bearing friction, duh. If the rider stands up while pedaling, it does. :)

[magic_smoke_ee]

Yep. A heavier bicycle is cheaper, less fragile, and also increases the workout effect. As long as a bicycle isn't 20 kg / 50 lbs, what is the real problem? I believe the real goal for lightness is luxury conspicuous consumption to maximize cost using exotic materials like beryllium.

[wiether]

> and also increases the workout effect

If you push 300W on a 5kg bike or 20kg bike, the "workout effect" will be the same.

At the end of the day, if you are looking for "workout effect", it means that you're trying to achieve something, like winning races or going faster.

And for a given rider, with a certain weight and certain physiological abilities, they will go much faster on a 5kg bike than on a 20kg bike.

There is a whole world between <$1k bikes and those >$2k ones. Weight being an important part. Not only because it reduce the total weight of bike + rider, but also because a 5kg bike behave in a very different way than a 20kg.

It's like saying that cooking with a chef knife is the same as cooking with a sword.

Sure, after a certain point, the race for removing a few grams here or there is a luxury and many people tend to believe that spending $$$ on a lighter bike will fix their lack of fitness.

But modern bikes provide a completely difference than the old, heavy ones.

[wink]

It's not bike weight per se, but there's also a somewhat direct link between weight and component quality and age. I.e. no one really tests a 20y old bike with current top-end components, no one really puts 10y old groupsets on a 2024 frame.

Yes, rider weight trumps it, but modern bikes in general just ride nicer and most of us who are not pros only test a dozen different bikes at most. It's a hobby, people like to splurge.

[dartharva]

Depends on what you're using the bike for. If it is for work or transport (as it used to be for paperboys and delivery gigs a few decades ago), you'd want it to be as smooth and light as possible.

[matsemann]

In Tyler Hamilton's book he describes going out for hour long rides, then taking some sleeping pills and going to bed, all without eating, just to shed weight before the tour. Just crazy.