cyccommute 

You are correct. My mistake. Doesn’t change the argument, however. Shorter distances require more force to move the bicycle to balance the power equation.


Have you never heard the term “unit distance”. It’s short hand for “pick any distance”. In the work equation, force is acting over a distance. That distance can be a mile or a foot or a nanometer. In Virtus original scenario, he uses miles. The force needed to move the bike over each mile is higher in the mountain bike compared to the road bike.

”Velocity”…speed, really, because velocity is a vector quantity…doesn’t figure into the equation except in the definition of acceleration in the force equation. The force in the work equation is used in overcoming the forces working against the bike and rider, i.e. rolling resistance and wind resistance.

Kapusta

Now this is something we can actually agree on

genejockey 

You know, the OP did a remarkable job asking his question in a clear straightforward way to which there was a clear simple answer, and avoided the assumptions that generally lead to controversy - and yet here we are, 6 pages later.

I'd say "Gotta love Bike Forums!", but it's not really required....

cyccommute 

No, I’m not trolling. Ask yourself which bike you would rather ride in Virtus’ scenario? Assuming smooth road riding and not mountain biking, most people would opt for any bike but the mountain bike…largely because of the large rolling resistance loses in the mountain bike case.

Think of it this way: You are tasked with moving eight 10 lb rocks from one end yard to the other by carrying them. Eight trips with a 10 lb rock is relatively easy. Four trips with two 10 lb rocks is harder but still doable. Two trips with four 10 lb rocks would be hard but is a whole lot harder. See where I’m going? A single trip takes a whole lot more effort than any of those other methods. Same work, same energy input (ignore the return trip) but, from a physiological perspective, it’s a whole lot harder to do one trip.

tomato coupe

I loathe to do so, but I'll repeat myself:

1) If you ride a heavier bike at the same power that you ride a lighter bike, and you select gears so that you ride at the same cadence, then you will produce the same force on the pedals. If you ride both bikes at the same cadence and pedal force for the same amount of time, you will do the same amount of mechanical work, and your body won't know the difference between the two.

2) "Force per unit distance" is not a unit that any physicist would use. It is meaningless, and you need to let it go.

3) The OP was very clear that he was interested in the difference between riding different bikes at the "same average HR and perceived effort" for a fixed amount of time (30 minutes). From a work/energy perspective, distance doesn't matter in this scenario. The only part anyone can really quibble over is whether "same average HR and perceived effort" directly translates to "the same power".

genejockey 

Lemme see if I can explain it using your rock metaphor: the OP is asking whether there's any difference in how hard it is to move 8 10 lb rocks in one trip with a wheelbarrow, vs 10 8 lb rocks in the same wheelbarrow. And your response is that most people prefer 8 lb rocks over 10 lb rocks.

genejockey 

Or, as The Older Boy just said, "Cut my pizza in 6 slices not 8. I can't eat 8 slices of pizza."

WhyFi

Which would I rather ride? If my goal is to ride at a specific intensity for a specific duration of time, I don't care - assuming that none of them is severely under-geared, all will be capable of providing that.

Do I see where you're going? No, I don't think that you do, either, because it's a horrible analogy that requires a suspension of reality via teleportation.

The OP is asking about exerting X amount of energy for a Y amount of time. Because of the differences in resistance that you'll see on each of these bikes, they'll necessarily travel different distances, but that doesn't change X energy for Y time.

3alarmer 

...I think you're dodging here. What's your FTP ?

rm -rf

Ha, this thread!

For 30 minute rides? Your hybrid is perfect.
Get a road bike for:
Longer rides. I mostly ride more than 2 hours, and usually longer. The road bike is more comfortable for these longer rides, with more hand positions, and the ability to be somewhat more aero.
Group rides! It's easier to keep the group's pace. Group rides are my motivation -- I often find reasons to postpone a bike ride solo. A scheduled ride is good, and I need to ride often enough to keep up.

wolfchild

This is a serious topic for serious cyclists and deserves a separate thread to itself.....I would browse it just for entertainment, since I don't really care about my FTP.

tomato coupe

At least there's one thing we can all agree on - no one cares about your FTP.

genejockey 

"When I were a lad, we'd ride 30 mph on knobby tires, uphill both ways through snow up to our hips! We didn't care about FTPs!"

CAT7RDR

I prefer four slices so I can fold it in half.

PeteHski

Your human potential to produce power through the cranks doesn't change with different bicycles (providing they fit reasonably well and have appropriate gearing). The only thing that changes is how fast they move for a given power input. Don't think about balancing the power equation. Power is an input parameter in this model and doesn't change with the bike. As long as you can pedal the thing, one bike will produce the same fitness results as any other bike. Of course more power is needed to move an mtb over each mile than a road bike AT A GIVEN SPEED. But that wasn't the question here. You can ride both bikes with the same power, one just moves faster for the same power input. Power and time are what give you the fitness. Not speed and not distance. Is it that hard to understand?

3alarmer 

frogman

This is typical for cycocommute.

The Chemist

I ride a 15kg hybrid that I converted to a 1x drive train with drop bars, and I absolutely love it. Might I be a bit faster with a lighter bike? Possibly. But I can already average nearly 29km/h over distances of 100+ km, and I can ride up to 240km a day without issue on the bike I have, and have a good time doing it, so I don't see the need to go lighter.

livedarklions

To steal a line from Robert Merton, he's not even wrong.

He doesn't know what the question is.

PeteHski

I take it there are not many hills where you live then.

livedarklions

They live in Shanghai, it's very flat.

Branko D

Personally, a bike which is pleasing to the eye, where everything works perfectly and which goes faster at the same effort inspires me to ride more. More time spent riding, better fitness.

Drop bars, a really comfortable saddle and everything fitting properly are important, too.

​​​​​​

silverider

Even a 30 min. ride on a bike with bad fit, especially the wrong seat, seat height and/or setback can be a real pain----in the knees and/or arse.

asgelle

Wrong
Wrong. And horribly ill-informed
Maybe not wrong, but more in line with a stopped clock is right twice a day.

Virtus

The only comfort issue I have on my hybrid is my arms start to really fatigue when I get to 45-50 minutes of "hard" riding. I put on a set of Ergon GP3 grips which helps but they're still wider than ideal I think.