Steve B.

In my 25 years of bike commuting I found there was nothing to be gained by trying to go faster. I saved my hard workouts for the weekends ont he faster group rides. Trying to save time on a commute often put me in conflict with cars, I would try to beat a soon channging traffic light, I wasn't paying attention, etc..... i found a slower steady pace was safer. I did use a lighter road/sport touring bike whenever possible as it was easier to get back upo to speed after countless traffic lights. I was leaving clothes and shoes at work so didn't have to carry panniers.

3alarmer 

.
...if you were a real friend, Larry, you would offer to install some foam liners in the tires of the bike you gave her.
No more flats, ever. And the rolling resistance increases to the point where she will get an excellent workout. Winning.

tomato coupe

Maybe she's only afraid to ride fast on the road bike that you gave her. She might be fearless on a bike she trusted.

Broctoon

I have a heavy old road frame converted to 3-speed, with fenders, riser bar, and tough inefficient tires. I don't know how much wattage it requires to move at a given speed, or where my heart rate goes on it vs. my road bike. But I know it's harder to ride fast, much harder.

If I just wanted to expend a certain number of calories or get my heart to some particular level, this bike would be the way to go. I'd much rather get on my road bike and go farther and faster with the same energy consumption.

Like you said, Larry, she's afraid to go fast. For her, that bike is probably best.

Broctoon

Maybe she rode with Larry once and to get away said, "You go ahead... I'm gonna hang back. I'm scared to ride that fast."

Just playin', Larry.

AndreyT

???

Not clear to me why "heavier" and "less efficient" are lumped together here. Less efficient bike will indeed need more effort. A heavier bike will not need more effort. Bike weight has no effect of effort, unless you are talking about exclusively uphill riding.

Maelochs

Yeah! I mean ... physics, yeah, right ... what do physicians know about cycling.

Maelochs

I pretty much rode each ride as itself. because I was younger, and in much, much better shape, I enjoyed going fast more often, but each ride was just a ride. Traffic was always different, weather was always different, I was always different. Every ride was different.

The only part that was the same is I ended up at work and deflated .....

AndreyT

Exactly: physics. Which clearly and explicitly tells us that weight/mass has no effect on effort when riding with constant speed. Physics tells us that on a flat course mass matters only when accelerating or decelerating, but still adds that any increase in effort during acceleration is precisely balanced out by the decrease in effort during deceleration. And that pesky physics goes even further: it even tells us the same thing about riding a conservative non-flat course, i.e. any effort spent while climbing on a heavier bike will be compensated precisely by reduced effort while riding downhill on the same bicycle.

So, no matter how you slice it physics just can't stop reiterating: mass has no net effect on effort. But... what do physicians (sic) know about cycling, right?

wolfchild

I agree with everything you just said, it parallels my own commuting experience....For anybody who lives in an urban area there are way too many things and hazards that can get in a way and prevent a person from going too fast...Trying to race against cars, drafting busses or trucks and racing against lights is just foolish and stupid. In all my years of commuting I was never late for work and always arrived at work refreshed and energized instead of burned out from a hard ride.

Maelochs

Yeah ... except, No.

The energy will be returned To The System. But not ... To The Rider.

Think it through. If the energy were returned to the rider, I could ride hills endlessly because no matter how hard I had to work to make the climb, I would be refreshed at the bottom right? Oh, I am sorry ... physiology also plays a part ... as in, the energy In A System remains the same, but a human being has a finite store of energy which must be replenished via Rest and Refueling.

It takes more Human energy to get a heavier bike up the hill. If this weren't the case, fat people would be winning the Tour de France, instead of emaciated people.

Just watch Filipo Ganna, who is 6'3" and 80 or 90 kg, trying to hang with the real climbers (if you have been following the Vuelta, this has been on your TV/PC screen many times this month.) Ganna Always drops off when the climbs get really steep ... not because Physics doesn't preserve energy, but because riding a bike uphill requires physical exertion.

I think maybe you forgot that the world "energy" has multiple definitions.

If your idea is correct ... a person could ride forever without eating, as long as there were hills to climb, because s/he would recoup all the energy used to climb the hill on the descent. I hope this is clear. If not, consult some of the engineers on the site, or the mathematicians, who also ride bikes. They can explain it in terms of physics equations and such ... but i am not so stupid to think the Conservation of Energy means that so long as I lift a barbell and set it down, it takes no energy ......

AndreyT

There is.

The biggest problem with bike commuting is plain boredom. The boredom of riding the same route again, again and again, day after day. Of course, one can always alter their route to make things more interesting, but the number of practical ones is usually too limited.

And this is where "trying to go faster" comes into the picture. One finds a number of good segments along the route and tries to compete with oneself by riding them faster, faster and faster. This is something to look forward to while riding a commuting route. That's something that makes things more interesting.

This is something I found in my 25 years of bike commuting.

wheelreason

So no traffic lights, stop signs or slowing down for traffic on this commute? Weight will be a factor evry time you have to accelerate back to speed, though a more upright position and rolling resistance are probably a bigger issue.

AndreyT

Yes, that is absolutely correct. That's actually the reason we strive to make bicycles lighter. But that's not physics anymore. That's human anatomy and physiology.

(One can actually attempt to take the human out of the picture by adding some kind of energy recovery capability to the bicycle, but that's a wholly different story.)

Not sure what "idea" you are talking about and where did you manage to find such "idea" in what I stated above. When riding bicycles, we spend most effort fighting the air resistance. And that has nothing to do with the bicycle's weight.

tomato coupe

... which is why freight trains are powered by hamsters.

Maelochs

The idea that the weight of a bicycle has no effect on the amount of energy needed to move it, would be the idea which seems to me, being uneducated, to fly in the face of both physics and physiology. The idea that the weight of a bicycle has no effect on the amount of energy needed to move it, would be the idea which seems to me, being uneducated, to fly in the face of both physics and physiology. Actually, we are fighting inertia up until about 15 or 18 mph (depending on the rider, bike, posture, etc .. . cD, I think it might be called coefficient of drag ... ) After that, the resistance due to air keeps growing while the effect of inertia drops off ... but of course, no one rides in a perfectly steady state on perfectly flat ground ...

I might not be abler to calculate arithmetic versus exponential growth in effort required, but I understand the concept ... and I also know that f you tool around at 10 mph you are mostly fighting your own mass and the mass of the bike. Considering that the OP referenced a person who was Riding Slowly,and Commuting (which often means many stops for traffic ... ) I'd say this person is not mainly fighting the wind.

Whatever. You go home and strap a few truck batteries to your bike so you can get more energy from the downhills. Let us know how that works for you ... but oh ... be sure to use some sort of aerodynamic fairing.

Broctoon

I want to race with you. I get to pick the bikes. Since weight has no effect on effort, you shouldn't mind if I ride a really light one and pick a really heavy one for you. I'll even let you pick the course. It could be flat or even conservative hills. Lots of turns to require accelerating and decelerating, or one straight line, whatever you like. With physics on your side, you should have no trouble. Effort will be the same for both of us right? How much you want to wager for the winner?

Reynolds 

It's a commute, not a TT. Many stops/starts.

Broctoon

The biggest--though not the only--problem with claiming that any effort you put into positive acceleration will be returned 100% when negative acceleration inevitably takes place is this: Your muscles get you moving, converting chemical energy in your body into kinetic energy, through a series of biological and artificial machines, but at the other end of the equation, the kinetic energy gets "thrown away" as it's turned into heat through friction (by another artificial machine we call brakes). Also, wind resistance applies negatively at both ends of the equation; we're not riding in a vacuum. This is a more specific explanation of what Maelochs referred to above as the system but not the rider seeing energy returned.

And I know... there was a qualifying statement of "when riding at constant speed." The trouble with that is we never ride bikes at constant speed, most certainly not when commuting.

SkinGriz

I worked with a guy that was a semi pro football player. He showed me pics of him sprinting with what kind of looked the chutes to drag cars.

3alarmer 

...where exactly did you commute (what city) ? Because I was usually too busy trying to keep from getting killed by some guy driving a car, here, to get bored.
I did commute for a while in Merced, CA. That might have gotten boring, were it not for the thick morning fog in winter. That was always exciting.

SkinGriz

I think it’s just important that she exercises and has a good (enough) time.

SkinGriz

When I was in HS on the way to school I passed by a property with a lot of massive dove coats full of birds.

Free smelling salts to wake me up every morning.

AndreyT

Silicon Valley. Sunnyvale, Cupertino, Campbell, Santa Clara, Los Gatos. I choose my routes to include quieter residential streets as much as possible. Most of the route I don't have to worry about cars.

Rick_D

This, every day plus the added unexpected stops resulting from vehicular assaults. No way of knowing how many of those/commute ahead of time.