Lower bike weight-what's the real truth?

[uprightbent]

I weigh 210 lbs. Bike weight is 38. I'm pushing 248 lbs. total. Does it matter, everything else being the same, if the bike weighs say-30 lbs? Then I'd be pushing 240 lbs., only 3% less combined weight with the heavy bike. Can you feel this 3% reduction? This combined weight theory was explained to me by a very reputable bent guru and it makes sense to me. He further explained how much it's more important in the case of a 150 lb. rider on a 15 lb. bike. Someone please set me straight on this theory. My concern is that we all know the extreme price differential for anything lightweight. I'm trying to justify it.

[Dchiefransom]

The same person on a much lighter bike will go faster. The same heavy person losing 50 pounds using the same bike will go much faster than they did before on the lighter bike. The same heavy person that rewards himself/herself with a new lighter bike for losing the weight will go faster with a bigger smile.

[Mars]

I don't think that it will make a real life difference if you are just riding recreationally or commuting. Futher, the extra weight is essentially irrelevant on the flats, it only affects us up hill. If you are racing, every once can make a difference because your body still must do work to lift that wieght up against gravity.

I remember a ride with a friend of mine. We always rode as hard as we could. In any case, I was carrying a textbook... maybe 6 pounds(?) in my messenger bag and I'll tell you, I really felt it on the climbs. On the other hand, i felt it going back down too, and I passed him with the gravity boost it gave me!!

[steveknight]

I always wish for the lighter 20 pound recumbent. but deep inside only the hills will show the improvement.

[Dchiefransom]

I always wish for the lighter 20 pound recumbent. but deep inside only the hills will show the improvement.


http://www.lightningbikes.com/r84.htm

[jeff-o]

I've heard talk that a big factor in all this is the weight of the wheels, and the rest of the moving components. Since your wheels are basically two giant gyroscopes, you need to input energy to get them spinning. Lighter, smaller diameter wheels will take less energy to spin at a certain rpm. However, larger heavier wheels will give you better balance (and more resistance to turning...)

[sch]

200+ pounders don't need light weight wheels, not that most bents have a lot of choice in the sub 650 sizes. I agree with uprightbent, the most important thing is to get the bike and ride. Once you have a year or two experience, and perhaps some weight reduction, he can consider whether a lighter bike might be in order. Rider weight is by far the biggest factor, and after conditioning has improved the power to weight ratio.
Steve

[BlazingPedals]

... the extra weight is essentially irrelevant on the flats, it only affects us up hill.

Not completely true. Weight is a factor every time you accelerate. Hillclimbing is nothing more than accelerating against gravity. Rotating weight, as well as sprung and unsprung weight, behave a bit differently, but they matter more often than you'd think. My opinion is that a 20 pound bike will always be faster and less tiring to ride than an otherwise identical 30 pound bike with identical riders. And if the rider loses weight too, the lower weight bike will maintain its advantage.

[budster]

Not completely true. Weight is a factor every time you accelerate. Hillclimbing is nothing more than accelerating against gravity. Rotating weight, as well as sprung and unsprung weight, behave a bit differently, but they matter more often than you'd think. My opinion is that a 20 pound bike will always be faster and less tiring to ride than an otherwise identical 30 pound bike with identical riders. And if the rider loses weight too, the lower weight bike will maintain its advantage.
Ah! But what about two identical riders, one with a 20 lb bike, one with a 30 lb bike. What if the rider of the 30 lb bike loses 10 lbs of pure fat off his body?

Who's faster now? Or are we now into the realm of apples v. oranges?

[ppc]

Someone please set me straight on this theory. My concern is that we all know the extreme price differential for anything lightweight. I'm trying to justify it.

You're absolutely right. The only people who need ultralight bikes are

(1) very thin people, because as you explain, the bike's weight becomes non-negligible compared to the person
(2) Very competitive riders who are already at the top of their physical performances and who need the little weight difference with other athletes to get an edge
(3) Weight weenies and poseurs, because their mental stability and their social lives depend on buying the flashiest, latest, lightest bike stuff

Group 1 and 2 are actually quite small. The industry produces marvels of lightweight technology mainly to sell to group 3. So, unless you're a poseur (which I doubt since you ride a bent in the first place) I say if you like your bike, if it feels too heavy, it'll get better as you shed pounds hauling it uphill. Or, you can think of your heavy bike as a way of training harder and getting fitter than the one with a light bike :)

[BlazingPedals]

Ah! But what about two identical riders, one with a 20 lb bike, one with a 30 lb bike. What if the rider of the 30 lb bike loses 10 lbs of pure fat off his body?

Who's faster now? Or are we now into the realm of apples v. oranges?

Yes, you're getting into the apples/oranges realm. Or, to be more specific, sprung vs unsprung weight. Are you wondering if the 30 pound bike will let the rider lose 10 pounds whereas the 20 pound bike won't?

[royalflash]

You're absolutely right. The only people who need ultralight bikes are

(1) very thin people, because as you explain, the bike's weight becomes non-negligible compared to the person
(2) Very competitive riders who are already at the top of their physical performances and who need the little weight difference with other athletes to get an edge
(3) Weight weenies and poseurs, because their mental stability and their social lives depend on buying the flashiest, latest, lightest bike stuff


what a load of crap

if you want to go faster particularly uphill or city commuting (with lots of stops and starts) then a lighter bike will help- obviously being lighter yourself will also help

[BlazingPedals]

what a load of crap

LOL, I tend to agree. If you drop ten pounds from the bike, that's an immediate ten pounds' advantage that is cumulative with any weight loss from the engine that might or might not come later. Given the choice between otherwise identical bikes, I'd always rather have the lighter one. Of course, there's always a compromise involved; in this case the price usually goes up as the weight goes down. So it becomes a question of finding the right compromise between weight and price.

[ppc]

what a load of crap if you want to go faster particularly uphill or city commuting (with lots of stops and starts) then a lighter bike will help- obviously being lighter yourself will also help

Stop dreaming. Most cyclists aren't fit enough or light enough to tell the difference between two bikes with a 5 pound difference. As for fit cyclists, only a tiny minority will benefit from the weight difference between a good $2000 bike and a $5,000+ one in terms of speed and acceleration, and they have to be pretty serious and committed to shell out that kind of money.

As BlazingPedals said, it's a compromise, but not between weight and price, but between usefulness and price. Most cyclists who buy light bikes or bike equipments have no use for it, and would be faster on a heavier bike with a better, or more regular training regimen. Those who truly benefit from a light bike are not very many, all the others are either poseurs, or people who enjoy owning expensive things, like those who buy expensive hi-fi sound systems just to play Britney Spears on it, but they're not buying the expensive bike stuff to take advantage of its weight.

If you think your bike is 5 pound too heavy, stop reading bicycle magazines, drop whatever you have in your pockets, go take a pee, sweat for half an hour and there's your 5 pounds. As for "performance city commuting", well, I'm not sure what planet you live on really...

[BookFinder]

This discussion reminds me of the useless hours of debate among fellow students while I was taking golf for my PE credits in college. Beyond the two days a week that we got to play a round in the name of education, we learned a lot about the finer points of the game.

The debate about club quality vs player skill was endless: "Will those clubs (Hogans, Pings, blades, cavity backs, etc) help my score enough to justify the expenditure?"

One day my coach got tired of listening to it, and looking at me (or so it seemed), he cut through all the crap and said, "At your skill level, you would be well advised to forget the pro-line clubs, and spend your money on buckets of balls at the practice range..."

Ahem ... cough.

I can't speak for anyone else, but at my skill level, five pounds of difference in bicycles is not going to make a lot of difference...

[budster]

Yes, you're getting into the apples/oranges realm. Or, to be more specific, sprung vs unsprung weight. Are you wondering if the 30 pound bike will let the rider lose 10 pounds whereas the 20 pound bike won't?
Not exactly. I'm sure pedalling a heavier bike is more work and so burns more calories, but -- what I'm really wondering is whether my approach makes sense, my approach being: lose significant weight off the body before shelling out serious cash for a lighter bike.

I'm pretty sure it makes sense, but there are a lot of knowledgeable people on here, so why not ask?

[BlazingPedals]

Not exactly. I'm sure pedalling a heavier bike is more work and so burns more calories, but -- what I'm really wondering is whether my approach makes sense, my approach being: lose significant weight off the body before shelling out serious cash for a lighter bike.

To put it another way, would you rather be better than your bike or have the bike be better than you?That's going to be a personal decision, based on your priorities, as well as your current and anticipated future abilities. I guess if exercise is the only thing you're after, then paying more for an easier-rolling/faster/lighter/better bike wouldn't make economic sense. Personally, I'd rather have a bike that won't hold me back.

[Mooky]

I weigh 326 lbs and my steel ReBike climbs like a mountain goat. Fully loaded. Weight does not matter. If you have big leg muscles you will climb anything including mountains.

Mooky

I weigh 210 lbs. Bike weight is 38. I'm pushing 248 lbs. total. Does it matter, everything else being the same, if the bike weighs say-30 lbs? Then I'd be pushing 240 lbs., only 3% less combined weight with the heavy bike. Can you feel this 3% reduction? This combined weight theory was explained to me by a very reputable bent guru and it makes sense to me. He further explained how much it's more important in the case of a 150 lb. rider on a 15 lb. bike. Someone please set me straight on this theory. My concern is that we all know the extreme price differential for anything lightweight. I'm trying to justify it.

[Dchiefransom]

Ah! But what about two identical riders, one with a 20 lb bike, one with a 30 lb bike. What if the rider of the 30 lb bike loses 10 lbs of pure fat off his body?

Who's faster now? Or are we now into the realm of apples v. oranges?

I think my first post would explain part of that, but it can only really be assessed comparing one rider to themselves.
As far as how much it costs for a "light" bike, the newer Trek 1000 feels about the same weight as my 2002 Lemond Zurich did, and the scales put that one at 20 pounds. ONe costs $650, and the other cost $2,000.

[MaxBender]

I weigh 326 lbs and my steel ReBike climbs like a mountain goat. Fully loaded. Weight does not matter. If you have big leg muscles you will climb anything including mountains.

Mooky

Mooky is not fully loaded.

He failed to mention he removes his big yellow flag prior to ascending those mountains...

[Trsnrtr]

If you have big leg muscles you will climb anything including mountains.

Mooky

That's always been my plan coupled with the lightest bike possible. :-)

[royalflash]

Stop dreaming. Most cyclists aren't fit enough or light enough to tell the difference between two bikes with a 5 pound difference. As for fit cyclists, only a tiny minority will benefit from the weight difference between a good $2000 bike and a $5,000+ one in terms of speed and acceleration, and they have to be pretty serious and committed to shell out that kind of money.

As BlazingPedals said, it's a compromise, but not between weight and price, but between usefulness and price. Most cyclists who buy light bikes or bike equipments have no use for it, and would be faster on a heavier bike with a better, or more regular training regimen. Those who truly benefit from a light bike are not very many, all the others are either poseurs, or people who enjoy owning expensive things, like those who buy expensive hi-fi sound systems just to play Britney Spears on it, but they're not buying the expensive bike stuff to take advantage of its weight.

If you think your bike is 5 pound too heavy, stop reading bicycle magazines, drop whatever you have in your pockets, go take a pee, sweat for half an hour and there's your 5 pounds. As for "performance city commuting", well, I'm not sure what planet you live on really...

Your points don't make any logical sense so I can only assume that you are just jealous because you can't afford a nice light bike.

I don't think it is particularly controversial that all other things being equal that lighter bikes are faster uphills and in stop-start conditions. If you don't believe this then just put 20 kg in a rucksack and give it a try. All the rest of your argument is just your subjective opinion on what other people are justified in spending their money on. If you get to be President of North Korea then this might matter to someone but until then its just hot air.

IMO if someone has plenty of cash and want to get a nice light bike then good luck to them.

[shokhead]

Bisides WW,is there another site that has bike weights listed?

[ppc]

Your points don't make any logical sense so I can only assume that you are just jealous because you can't afford a nice light bike.

LOL, yeah that's just me, I'm jealous :)
I have four bikes I use and enjoy. 2 of them even happen to be expensive. Who do you want me to be jealous of? Ah yes, my neighbor with the bigger garage :)


I don't think it is particularly controversial that all other things being equal that lighter bikes are faster uphills and in stop-start conditions. If you don't believe this then just put 20 kg in a rucksack and give it a try.

Look, strictly speaking, you're perfectly right, there's no argument there. All I'm saying is, in real life, there won't be any discernable performance increase between Joe Blow on an average bike and Joe Blow on a Trek: Joe Blow is either too heavy, too unfit or doesn't know how to ride efficiently for the weight difference to matter. Joe Blow therefore doesn't need a Trek (yet).


All the rest of your argument is just your subjective opinion on what other people are justified in spending their money on. If you get to be President of North Korea then this might matter to someone but until then its just hot air. IMO if someone has plenty of cash and want to get a nice light bike then good luck to them.

Absolutely. People are free to spend whatever amount they want on ultra-expensive light bike stuff. That doesn't meant those who do without needing it aren't poseurs.

[Bianchiriderlon]

I love physics!

I read with great interest the reference to a "gravity boost" on the downhill as a result of heavier loads carried on bikes. By extension, the same argument could be made with reference to heavier bikes as well. The reality is this: downhill runs do not become faster as a result of having heavier bikes. This thinking goes against what has been known in the field of physics ever since Da Vinci. If you recall, he dropped similarly shaped and sized weights off the leaning tower of Piza. They were made of different materials and weighed differently. They would hit the ground at the same time in spite of being of differing weights.

This is the case because compared with the size and mass of the planet, (the gravity source) they are for all practical purposes, of the same relative weight and mass.

Da Vinci concluded that where there is a difference in the rate of fall of objects, it is due to confounding variables, wind resistance, for example. A feather, or a parachute will fall more slowly than a steel ball because of air resistance, a counfounding variable in our equasion.

When riding up hill, weight does make a difference as we must work to move the weight against gravity. Therefore, a lighter bike will climb more easily than a heavier one. On the flat, weight makes little difference as inertia plays a role. Once an object is set in motion, it tends to "want" to remain in motion unless acted upon by other factors, rolling resistance (friction), for example. Accelerating a bike to one's desired cruising speed will be affected by weight in much the same manner as climbing hills would.

As an experiment, try coasting downhill (don't pedal) with and without an additional load. The weight and configuration of the bike will make no difference. Just make certain you use the same bike for both runs. Sit on the bike in the same position in both the loaded and unloaded conditions. Use the same line on the same hill in both cases. The independent variable is weight and the dependent variable is speed. All extraneous variables have been controlled. Note the speed on the cyclometer at the conclusion of the run in both the loaded and the unloaded conditions. I predict the null hypothesis, that you will see no significant difference in speed. If you do see a difference, do not pass go, proceed directly to the Nobel prize for physics, and collect that $200.00! :)

Cheers

Charles

[BookFinder]

I rest my case, too, thank you! :)

[BlazingPedals]

Here, plug some numbers into this (http://www.kreuzotter.de/english/espeed.htm) site to calculate speeds. Try various weights and some typical grades that you ride. As with fairings, results may vary based on your specifics.

[uprightbent]

Thanks Bianchiriderlon. Way off in left field but why do the Boy Scouts limit the weight in the silly pinewood derby cars to 5 or 10oz? When my kids were little we assumed extra weight made the car faster.

[Bianchiriderlon]

Thanks Bianchiriderlon. Way off in left field but why do the Boy Scouts limit the weight in the silly pinewood derby cars to 5 or 10oz? When my kids were little we assumed extra weight made the car faster.

I think the scouters and scouts make the same assumption, but, alas, it's false. Reduction in friction makes ALL the difference.

Charles

[Bianchiriderlon]

Here, plug some numbers into this (http://www.kreuzotter.de/english/espeed.htm) site to calculate speeds. Try various weights and some typical grades that you ride. As with fairings, results may vary based on your specifics.

Excellent calculator if knowing calorie expenditure is important to you. However, it does not speak to the "gravity boost" issue. It is the programmer's intent to simulate a workout for the purpose of estimating calorie "burn" on a ride. It was not his or her intent to compare the speeds of bikes based on their weights. The error in the program can be easily detected. Set the weight to, say, 50 pounds. Set the grade to -100%. This would represent a fall. Note the speed. Now double the bike's weight. The speed of the falling object goes from 118.3mph to 131.7mph! All objects, regardless of mass fall at the rate of 10 m/s/s. Therefore, the program is flawed in that the programmer assumes that mass (represented in this case by weight) makes a difference in the rate of fall. It does not.

A related concept is "terminal velocity." The terminal velocity of a human in free fall tightly balled up is about 200mph. A bike with a rider would fall at a different rate due to increased air resistance.

However, knowing calorie expenditure is of interest to me so I will bookmark the page. I will, keep the flaw in mind when interpreting its output. Thanks for the link!

BTW, I gave a wrong reference in my initial reply. I stated that this work was done by Da Vinci. It was actually by Galileo Galilei. Also check out Isaac Newton.

Cheers

Charles :)

[BK Xray]

Thanks Bianchiriderlon. Way off in left field but why do the Boy Scouts limit the weight in the silly pinewood derby cars to 5 or 10oz? When my kids were little we assumed extra weight made the car faster.

Weight is an issue, unless of course you are throwing the Pinewood Derby car (or bike) off a cliff.. You have to overcome the rolling resistance and the wind resistance. More weight equals more downward force and greater acceleration.

[Bianchiriderlon]

Weight is an issue, unless of course you are throwing the Pinewood Derby car (or bike) off a cliff.. You have to overcome the rolling resistance and the wind resistance. More weight equals more downward force and greater acceleration.

Not so! The resistive factors would be the same regardless of the car's weight. Also, note that the cars are not falling. They are travelling on an incline. The angle of the incline will make a difference in the rate of descent, as will also be the case with the bike. The velocity will be, however, a factor of the angle of the incline, not the weight of the objects. Mass (weight) makes no difference. More weight does not equal more downward force. This view is in error. Go look it up.

[Trsnrtr]

The reality is this: downhill runs do not become faster as a result of having heavier bikes. This thinking goes against what has been known in the field of physics ever since Da Vinci. If you recall, he dropped similarly shaped and sized weights off the leaning tower of Piza.

And here all along, I thought it was Galileo that did that. ;)

[Bianchiriderlon]

And here all along, I thought it was Galileo that did that. ;)

You're right. Check my correction above.

[squeaker]

Not so! The resistive factors would be the same regardless of the car's weight. Also, note that the cars are not falling. They are travelling on an incline. The angle of the incline will make a difference in the rate of descent, as will also be the case with the bike. The velocity will be, however, a factor of the angle of the incline, not the weight of the objects. Mass (weight) makes no difference. More weight does not equal more downward force. This view is in error. Go look it up.
I did look it up, and it's troubling me :eek: : ever seen a table-tennis ball supported on a vertical jet of air? Would a lead, rather than air, filled ball do the same trick (at the same height)?
I thought that Gallileo showed that "all bodies dropped at the same place fell to earth with the same acceleration", in contrast to the then prevailing view of Aristotle that a heavier body would accelerate at a higher rate. In other words that the gravitational force on the body was proportional to its mass, consequently the acceleration was independant of mass? Unfortunately the actual acceleration also depends on other forces (such as aerodynamic drag and rolling resistance for a bicycle). I suspect that Walter Zorn is correct in his calculations, although I have not done an exhaustive analysis ;)

[Bianchiriderlon]

I did look it up, and it's troubling me :eek: : ever seen a table-tennis ball supported on a vertical jet of air? Would a lead, rather than air, filled ball do the same trick (at the same height)?
I thought that Gallileo showed that "all bodies dropped at the same place fell to earth with the same acceleration", in contrast to the then prevailing view of Aristotle that a heavier body would accelerate at a higher rate. In other words that the gravitational force on the body was proportional to its mass, consequently the acceleration was independant of mass? Unfortunately the actual acceleration also depends on other forces (such as aerodynamic drag and rolling resistance for a bicycle). I suspect that Walter Zorn is correct in his calculations, although I have not done an exhaustive analysis ;)

Apples and oranges! In one case we are referring to objects falling in free space. In the other we are referring to the energy needed to lift objects against gravity. The lead ball would "float" in the air jet provided that the velocity of the jet was sufficient to allow it to do so. In any case in which a massive object is lifted against gravity, energy is needed to do the job. The heavier the object (more massive) and the higher it is lifted, the more energy is needed to do the job. The ball floating in the jet then has potential energy which becomes kinetic energy when the air jet is removed. The ball will fall to the ground expelling its potential energy.

This is why lighter bikes will climb more easily. They will require less energy to become elevated than would heavier ones. In free fall, however, they will fall at the same rate regardless of the potential energy invested therein. It becomes kinetic energy when the object is released and is exhausted by the process of returning to earth. Of course, bikes are not falling in free space (we hope :) ). They are rolling on an inclined plane and that, together with friction will determine the rate of descent.

The Zorn site calculator is ok until we push the angle of descent to -100% (free fall). At that point it will report different velocities by weight which is theoretically impossible.

Cheers

[Trsnrtr]

Set the weight to, say, 50 pounds. Set the grade to -100%. This would represent a fall.

Not true. a 100% grade is a 45 degree angle, far from a fall. Freefall can't be defined by gradient because there is none.

[BlazingPedals]

Not so! The resistive factors would be the same regardless of the car's weight. Also, note that the cars are not falling. They are travelling on an incline. The angle of the incline will make a difference in the rate of descent, as will also be the case with the bike. The velocity will be, however, a factor of the angle of the incline, not the weight of the objects. Mass (weight) makes no difference. More weight does not equal more downward force. This view is in error. Go look it up.

Acceleration due to gravity can be treated as a constant. It's 9.8m/sec/sec, and that number is vertical feet, not horizontal. Mass makes no difference to gravitational acceleration, but the lower the grade, the higher resistive forces will be proportionally. At 0% grade, resistance is effectively -9.8m/sec/sec. Also, assuming that frontal area, C/D, and rolling resistance remain similar, the higher force of a heavier object will more easily overcome resistive forces, and cause it to outcoast a lighter object (F=MA, which means more weight DOES mean more downward force.)

[Mars]

Acceleration due to gravity can be treated as a constant. It's 9.8m/sec/sec, and that number is vertical feet, not horizontal. Mass makes no difference to acceleration, but the lower the grade, the higher resistive forces will be proportionally. At 0% grade, resistance is effectively -9.8m/sec/sec. Also, assuming that frontal area, C/D, and rolling resistance remain similar, the higher force of a heavier object will more easily overcome resistive forces, and cause it to outcoast a lighter object (F=MA, which means more weight DOES mean more downward force.)

Sure, test it yourself. Place a full and empty soda can side by side on an incline. The full one will get to the bottom much faster.

[shokhead]

Mythbusters did it with a car and a hot wheels in SF on a hill. Car won.

[Bianchiriderlon]

Not true. a 100% grade is a 45 degree angle, far from a fall. Freefall can't be defined by gradient because there is none.

True, but when working within the confines of a program one will do what one will to test its outcome. Perhaps a setting of -200% would be closer. However, I can't help but think that the output would not differ by much. The rate of descent is about what one would expect in a falling bike and rider.

This has been an interesting topic, but I'm outta here. I think we've kicked this one to death and we can all agree on the role played by resistive factors.

Cheers

Charles

[Trsnrtr]

Perhaps a setting of -200% would be closer.

-9999% would be closer yet. ;)

[ezgreen]

This is an interesting discussion, however my real world experience and my knowledge of physics predicts that a heavier bike will attain a higher speed when coasting down hill. If we were in a complete vacuum that would not be the case. However the heavier bike will accelerate faster when coasting down hill because friction and wind resistance have less ability to affect its acceleration. The heavier object contains more potential energy. That is why at the bottom of the hill the heavier object will roll further because the more potential energy has been converted to more enertia. The higher enertia is a result of the weight. The reverse is true when going up a hill. It takes more energy to move a heavier object to a given height. Therefore a lighter bike climbs a hill with less energy output from the rider. Its no different that carrying a box up a flight of stairs. The lighter the box the easier the climb. Lighter objects also accelerate from a stop quicker because they take less energy to get moving. However once moving in a straight line at a given speed then areodynamics becomes more important. Once an object is at speed, weight has no bearing on how much energy is required to maintain that speed. Therefore if you ride mostly on flat terrain and you do not do a lot of stopping and starting, the weight of your bike probably isn't going to make much difference in your riding. If you do a lot of hill climbing, starting and stopping, then a lighter bike has advantages. However if you are trying to lose weight and expend calories then heavier is better. While riding with a friend one day I noticed his rear brake was dragging on the rim. I told him of the problem and he just shrugged and said he didn't care. He needed the exercise!

[banerjek]

I weigh 210 lbs. Bike weight is 38... Does it matter, everything else being the same, if the bike weighs say-30 lbs?

To find out how much difference this would make, just pick up a gallon of milk (or 4 quarts of Gatorade depending on what kind of packs you have) on your way home. The weight difference will be the roughly the same that you're talking about.

Note that my experiment does not take into account the mental component of cycling, so it might be better to carry an extra gallon of water for 2 weeks.

Weight definitely matters, but not as much as many people think.

[shokhead]

This is an interesting discussion, however my real world experience and my knowledge of physics predicts that a heavier bike will attain a higher speed when coasting down hill. If we were in a complete vacuum that would not be the case. However the heavier bike will accelerate faster when coasting down hill because friction and wind resistance have less ability to affect its acceleration. The heavier object contains more potential energy. That is why at the bottom of the hill the heavier object will roll further because the more potential energy has been converted to more enertia. The higher enertia is a result of the weight. The reverse is true when going up a hill. It takes more energy to move a heavier object to a given height. Therefore a lighter bike climbs a hill with less energy output from the rider. Its no different that carrying a box up a flight of stairs. The lighter the box the easier the climb. Lighter objects also accelerate from a stop quicker because they take less energy to get moving. However once moving in a straight line at a given speed then areodynamics becomes more important. Once an object is at speed, weight has no bearing on how much energy is required to maintain that speed. Therefore if you ride mostly on flat terrain and you do not do a lot of stopping and starting, the weight of your bike probably isn't going to make much difference in your riding. If you do a lot of hill climbing, starting and stopping, then a lighter bike has advantages. However if you are trying to lose weight and expend calories then heavier is better. While riding with a friend one day I noticed his rear brake was dragging on the rim. I told him of the problem and he just shrugged and said he didn't care. He needed the exercise!

Never been on a down hill loop. Aero doesnt come into play unless your doing 30mph.

[Dchiefransom]

Not true. a 100% grade is a 45 degree angle, far from a fall. Freefall can't be defined by gradient because there is none.

I usually fall when attempting a 100% grade. :eek:

[ezgreen]

I think weight is over emphasized for recreational riders. I have two long wheelbase recumbents. One weighs 30 pounds, the other is closer to 40. With the daily baggage I am sure that adds another 5 pounds. They both get me to work in about the same time.

[shokhead]

Even rec riders as myself{80-100 miles aweek} dont want a 25 pound bike. We want a nice bike under 20 and i dont need a 15 pound bike but i'll take one. For riding,lighter but maybe not lightest is better,period. If i have 2000g wheelset on my rig,i dont want to spin those things 50 miles. Less 400g would keep my legs just abit more fresh. Flat,hills,grade,you still pedal and your still pushing that bike.

[banerjek]

Even rec riders as myself{80-100 miles aweek} dont want a 25 pound bike. We want a nice bike under 20 and i dont need a 15 pound bike but i'll take one. For riding,lighter but maybe not lightest is better,period. If i have 2000g wheelset on my rig,i dont want to spin those things 50 miles. Less 400g would keep my legs just abit more fresh. Flat,hills,grade,you still pedal and your still pushing that bike.

Point taken, but weather, level of fitness, aerodynamics, mental state, nutrition, and a number of other factors are far more important than weight. Adding several pounds to your bike will not change who you bike with unless you race. My 45 lb commuter doesn't slow me down nearly as much as people think. However, if you're buying a bike, get the one you want.

[shokhead]

I did,today. 05 Roubaix comp. Anyone know what they weight,58cm.