idoru2005

I wonder if any TdF rider has taken on a waterbottle filled with rocks or other such heavy objects to help them descend faster, and toss it at the end of the descent. Might be a good 'tactic' for some of the lighter climbers.....

mwchandler21

I suspect that the amount of weight that a rider could actually attach to the bike in a brief few seconds is too small to make a significant difference.

prathmann

Jean Robic was supposedly handed lead-filled 'water' bottles at the summits of some climbs to be able to descend faster.

idoru2005

It depends on what they put in the water bottle. A bigger factor is whether the puny arms of a climber could handle such weight.

idoru2005

Thanks for that fine example. That's exactly what I was wondering, ie, if it's ever been known to be done.

dolfinack

They won't descend faster due to being heavier. Gravity is gravity. I expect this to be refuted hotly. Hum. (They will achieve a higher terminal velocity but I doubt they reach that kind of speed!!)

DiabloScott

Terminal velocity is when the force of the wind and road friction slowing you down equals the force of gravity speeding you up (ie you are no longer accelerating) - and it happens on virtually all descents to all riders. Heavier riders have a higher terminal velocity - they DO descend faster. The lead bottle (actually I think it was shot pellets in the bottle) idea works, but it's not a huge factor.

SouthFLpix

The descents are already so fast that if you don't touch your brakes you often go into the corners too hot. A lot of the riders just have very little experience in handling corners at high speed. Maybe some of the teams should hire a motorcycle racer as a consultant to give them a few lessons.

dolfinack

Yup I know the terminal velocity definition, I just really didn't think riders hit it. But if you know better, which I have no doubt that you do, then I bow to your greater knowledge Sir!

DiabloScott

Maybe you just need to ride with some fat guys to observe this phenomenon in person.

Jed19

Descending is a combo of skill, psychology, courage, gravity and other parameters. In my view, even if you wear a jersey made of lead, you only cover one aspect. And it can even be dangerous, if you are descending way faster than your skill level.

idoru2005

Yahhh right. Try to convince me of that when clydesdales almost always pass me on descents.

idoru2005

Maybe he's one of those fat guys, and never sees anyone go faster than him....

dolfinack

haha this one I can gladly refute myself.

gpsblake

Extra weight would throw them off balance and probably make them slower in the long run I would think.

Dolomiti

Yeah maybe it would help on descents that are very mild technically - with no significant braking sections - just a flat out -4% gradient downhill or something - while not being worth it because of the problem it would cause on the seemingly more typical twisty descents? Just a guess.

bobvonb

yeah, gravity effect is minimal. what it does do is increase inertia. once going the bike doesn't want to slow down and will go thru the air better. that has some impact on cornering too, the bike wants to turn less the heavier it is. if the weight is below the center of gravity it would tend to stabilize, if above to de-stabilize.

Hezz

It's true, weight doesn't matter for gravity. Light and heavy fall at the same rate unless effected by wind resistance or other forces. So the bigger guy actually has slightly more wind resistance. But the extra weight does give him more inertia which can help to maintain high speeds over slightly changing pitches. But, as has been pointed out being able to brake quickly is very important on steep twisty roads and the lighter guys can brake more quickly. So it's kind of a trade off. Having more nerve, daring and bike handling skills seems to be more important than weight for descending.

Another issue is strength. The big guys can usually output more wattage for short durations on the downhills to get their speed up. So if they have the nerve and the handling skills combined with their greater inertia they can really fly on straight downhills with varying pitches. On steep curvy stuff the lighter guys seem to have an advantage. Not only can they brake easier but they can accelerate faster coming out of the curve. And because they have less inertia they can corner faster without crashing since inertia tends to want to keep going in a straight line. So it seems that in the end things come out rather even for descending and races are only occasionally decided on the descent.

bobvonb

actually gravity is computed by mass, not weight. but adding lead weights does add mass, so for common understanding they are about the same. However, more massive objects do fall faster than less massive objects. It's just that the formula for gravity is computed between 2 objects and includes both masses (the object in question and the earth) and the earth's mass is so much greater than the lighter object's mass (be it a feather, cannon ball, bike and rider or whatever) that the difference in gravitational force between the earth and these different objects is negligible. Further, with any resistance (like falling through air) that effect is much greater. gravity is actually a pretty weak force. even a small magnet can overcome it. Pick up a paper clip with a magnet and it's overcoming the entire force of the earth-paper clip gravitational force.

Bacciagalupe

I agree that extra weight won't improve a rider's speed on the descents, at least for the pros.

Basically they're going so fast that descending is all about handling skills and getting aero.

For example, look at Christian Vande Velde's power chart from Stage 14. Change the elevation to "time" and you'll see that his power output drops significantly, and often to zero, on the descents.

https://connect.garmin.com/activity/99936583

msu2001la

Extra weight isn't going to help them around corners, and that seems to be where the biggest difference is between riders.

Put them all on a straight line decent, and they're all within a couple of seconds of each other.

Kind of Blued

I love when people give their opinions on science.

oldbobcat

They tried that with Jean Robic in the early postwar years.

TommyL

The problem is that the real world is complicated. A real situation isn't just going to match up with one law of physics. Going downhill, the big boys go faster. There are a variety of reasons for this, but whatever reasons people to chose to cite won't effect the reality of it.

Kind of Blued

Good Lord...