# heavy bike vs light



## George M (Sep 25, 2008)

I've looked and couldn't find any scientific information saying that a lighter bike is easier to pedal than a heavy one. I know it's easier to climb and sprint with a light bike. I also read that they both are almost the same on the flats. I know that from my own riding anyhow. Anyhow I have a discussion going on with a neighbor about this.
He's an engineer and he's telling me I can ride a lot faster on the flats with a light bike and if I want to get a good workout I should be using a heavy bike. I say I do have a heavy bike and it's really not that much faster with the lighter bike. He's says maybe not, but you will use less energy with the lighter bike.I'm trying to get something to prove this point.Thanks.


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## CActuskid (Sep 3, 2008)

If it did not make ANY difference they would make bikes out of Concrete, it is so obvious what proof do you need


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## mcsqueak (Apr 22, 2010)

I personally think heavier bike will fatigue you sooner than a light bike.

I have an old Schwinn that weighs 34 lbs, and a new bike that weighs 20 lbs.

Longest ride on the Schwinn = 40 miles.
Longest ride on the new bike = 70 miles.

I can just go longer on my new bike before getting tired.


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## waldo425 (Sep 22, 2008)

This coming from a person with a Look bike as their avatar. Is that your heavy bike? If so then we really need to make a trade here. 

I find it hard to believe that you cant find ANY scientific evidence on this. I mean --- Ive always been lead to believe that this is common physics in action here. I am of the opinion that you will go faster for longer with a light weight and stiff bike.


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## SnowMongoose (Mar 7, 2007)

Why do you need science here, common sense should suffice.


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## Peanya (Jun 12, 2008)

Compared to the weight of the rider, virtually all road bikes are light. What's more of a factor is drag and rolling resistance vs. weight.


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## Hooben (Aug 22, 2004)

You're right, never mind what my legs say. Lets all go out and buy heavy bikes. There's no proof, then I ain't buyin it.


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## Salsa_Lover (Jul 6, 2008)

Peanya said:


> Compared to the weight of the rider, virtually all road bikes are light. What's more of a factor is drag and rolling resistance vs. weight.


this is a fallacy being repeat here too often

it is true that when you are just cruising softly inside your comfort zone, the weight differences don't make much difference.

But when you are close to your limits, ( climbing steep gradients, very long rides, high speeds etc ) the weight and aero characteristics work on your favor exponentially.


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## asgelle (Apr 21, 2003)

Peanya said:


> Compared to the weight of the rider, virtually all road bikes are light. What's more of a factor is drag and rolling resistance vs. weight.


And what does rolling resistance depend on?

As for scientific evidence, the OP should show his engineer friend this http://www.recumbents.com/WISIL/MartinDocs/Validation of a mathematical model for road cycling.pdf and while he's at it, ask this so-called engineer why a heavy bike gives a better workout than a light one.


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## spade2you (May 12, 2009)

In the flats? Nah, probably won't make much difference. Lighter and more aero tubulars will probably make a difference, but that's about it.


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## Minjin (Jan 9, 2007)

asgelle said:


> And what does rolling resistance depend on?
> 
> As for scientific evidence, the OP should show his engineer friend this http://www.recumbents.com/WISIL/MartinDocs/Validation of a mathematical model for road cycling.pdf and while he's at it, ask this so-called engineer why a heavy bike gives a better workout than a light one.


Rolling resistance depends on total weight. The argument that people are making is that the difference between a heavy and light bike in regards to the total weight of bike plus rider yields a negligible difference in rolling resistance. 

And what exactly in that PDF are we looking at?


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## PBike (Jul 6, 2007)

Salsa_Lover said:


> this is a fallacy being repeat here too often
> 
> it is true that when you are just cruising softly inside your comfort zone, the weight differences don't make much difference.
> 
> But when you are close to your limits, ( climbing steep gradients, very long rides, high speeds etc ) the weight and aero characteristics work on your favor exponentially.


I think for the most part what you feel when going to a lighter bike is usually not weight but a "quicker" geometry and better stiffness allowing you to accelerate quicker.

It is not a fallacy that the percentage of weight from the bike is small when compared to the overall weight of the rider and bike. 

The bike I ride around for errands weighs in at something like 35 pounds with the bags. I rode it empty to Lowes the other day, and came back with three gallons of DryLock Paint, a ten pound container of cement patch, four paint rollers, a wire brush and three 12 ounce bottles of concrete etch. If you do the math, the load weighed more than the bike. I really didn't notice a lot of difference on the way home on the hills or the flats other than a bit of frame flex since this frame isn't the most rigid one out there. My speeds were pretty much the same as the way there.

I'm not saying the added weight had no effect, I'm saying that if adding over 35 pounds didn't cause a huge difference in my speed then 1 to 5 pounds won't make a whole lot of difference. 1 to 5 pounds is a very small percentage when compared to the overall weight of the bike and rider, that isn't a fallacy, it is a mathematical fact that can be computed.


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## asgelle (Apr 21, 2003)

Minjin said:


> And what exactly in that PDF are we looking at?


I'm looking at the equation of motion for a bicycle with rider which could easily be differentiated with respect to mass to quantitatively evaluate the effect of weight on the speed of a rider at fixed power.


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## Jay Strongbow (May 8, 2010)

George M said:


> He's an engineer and he's telling me I can ride a lot faster on the flats with a light bike and if I want to get a good workout I should be using a heavy bike.


Engineer? He must drive a train.
For argument sake let's say he's right that lighter bikes are faster on the flats. The rider is in control of how much of a workout he gets on any weight bike. You don't get more of a workout with a heavier bike, you just go slower. You don't get less of a workout with a light bike, you just go faster. 

But that's moot because for all practical purposes he's wrong about the lighter bike being faster on the flats too. You get to your speed quicker (better acceleration in other words) but cruising speed is more or less the same.


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## asgelle (Apr 21, 2003)

Jay Strongbow said:


> But that's moot because for all practical purposes he's wrong about the lighter bike being faster on the flats too. You get to your speed quicker (better acceleration in other words) but cruising speed is more or less the same.


You sure you have enough qualifiers in there? For many cycling applications 6 mph is the same as 30 mph, so yes cruising speed may be "more or less" the same with a lighter bike, but since cruising speed depends inversely on rolling resistance and rolling resistance is linear with total weight (bike + rider), and further since there are no retarding forces that scale inversely with weight, reducing bike weight can only increase speed on the flats


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## George M (Sep 25, 2008)

Jay Strongbow said:


> Engineer? He must drive a train.
> For argument sake let's say he's right that lighter bikes are faster on the flats. The rider is in control of how much of a workout he gets on any weight bike. You don't get more of a workout with a heavier bike, you just go slower. You don't get less of a workout with a light bike, you just go faster.
> 
> But that's moot because for all practical purposes he's wrong about the lighter bike being faster on the flats too. You get to your speed quicker (better acceleration in other words) but cruising speed is more or less the same.



Thank you, that's exactly what I was trying to tell him.:thumbsup:


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## Jay Strongbow (May 8, 2010)

asgelle said:


> You sure you have enough qualifiers in there? For many cycling applications 6 mph is the same as 30 mph, so yes cruising speed may be "more or less" the same with a lighter bike, but since cruising speed depends inversely on rolling resistance and rolling resistance is linear with total weight (bike + rider), and further since there are no retarding forces that scale inversely with weight, reducing bike weight can only increase speed on the flats


Is today national pedantic day or something? I've posted about 5 times and got one spelling correction and now this. Sorry if 'more or less' isn't up to your standards of internet chat but it's a friggin bike site and I'm not here looking for a nobel nomination.


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## den bakker (Nov 13, 2004)

Jay Strongbow said:


> Is today national pedantic day or something? I've posted about 5 times and got one spelling correction and now this. Sorry if 'more or less' isn't up to your standards of internet chat but it's a friggin bike site and I'm not here looking for a nobel nomination.


well if you're talking c0ck, that's what you get :thumbsup:


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## fontarin (Mar 28, 2009)

Put on 15 pounds, and see if you ride as fast at the same level of effort.

Hint: You won't.


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## asgelle (Apr 21, 2003)

Jay Strongbow said:


> Is today national pedantic day or something? I've posted about 5 times and got one spelling correction and now this. Sorry if 'more or less' isn't up to your standards of internet chat but it's a friggin bike site and I'm not here looking for a nobel nomination.


You think it's pedantic, fine. I think it's important to at least get the trends right. Add weight and bikes go slower except on down hills; remove weight and they go faster. How much depends on the specifics of the bike, rider, and course. In no case does it stay the same. Whether the amount is important depends on the particular goals of the rider. For many riders, 10's of minutes don't matter, for others, races have been decided by tenths or hundredths of a second.


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## Marty01 (Jun 16, 2010)

PBike said:


> I think for the most part what you feel when going to a lighter bike is usually not weight but a "quicker" geometry and better stiffness allowing you to accelerate quicker.
> 
> It is not a fallacy that the percentage of weight from the bike is small when compared to the overall weight of the rider and bike.
> 
> ...


1 pound on a 20 pound bike.. 5%... take 5% off your car`s weight.. HUGE difference!!!and its the SAME 5% you took off your bike...

you guys need to look into rolling HP for cars.. the numbers are bigger and its easier to see..and a steady 60mph.. a lighter vehicule will use less gas on a flat level road(assuming no other changes..like say u just put 200lbs of weight in our car`s trunk.. roughly 5% like mentionned above) why would these physics change to the world of cycling??


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## asgelle (Apr 21, 2003)

Marty01 said:


> 1 pound on a 20 pound bike.. 5%... take 5% off your car`s weight.. HUGE difference!!!and its the SAME 5% you took off your bike...


Interesting. But wait, the bike doesn't ride itself. 1 lb on a 160 lb bike plus rider, 0.6%. 0.6% off a 3200 lb car plus driver, 20 lbs.

Also, bike 20/160=12% of total weight. car, 3000/3200=94% of total. 

I've said it before, cars are not bikes.


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## Salsa_Lover (Jul 6, 2008)

PBike said:


> I think for the most part what you feel when going to a lighter bike is usually not weight but a "quicker" geometry and better stiffness allowing you to accelerate quicker.
> 
> It is not a fallacy that the percentage of weight from the bike is small when compared to the overall weight of the rider and bike.
> 
> ...


you are just confirming my point.

when runing errands, or going slow, you maybe don't "feel" that weight 

now take your fully loaded bike on an steep 10Km, 12% climb; or try to sprint at least at 45kmh on it or do a century.

repeat the experience without the load

repeat the experience on a 10Kg racing bike

repeat the experience on a 7Kg racing bike with light wheels.

then come back and report the results


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## Marty01 (Jun 16, 2010)

asgelle said:


> Interesting. But wait, the bike doesn't ride itself. 1 lb on a 160 lb bike plus rider, 0.6%. 0.6% off a 3200 lb car plus driver, 20 lbs.
> 
> Also, bike 20/160=12% of total weight. car, 3000/3200=94% of total.
> 
> I've said it before, cars are not bikes.


but to the rider.. that same 160 pound weight will be there.. the bike weight is the the only variable

sure you could just lose a pound... but lose a pound off your rim and tire.. big difference in accel there.. and to keep it moving too.. big difference in either case.. one pound lost in both cases.. different results


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## asgelle (Apr 21, 2003)

Marty01 said:


> but to the rider.. that same 160 pound weight will be there.. the bike weight is the the only variable
> 
> sure you could just lose a pound... but lose a pound off your rim and tire.. big difference in accel there.. and to keep it moving too.. big difference in either case.. one pound lost in both cases.. different results


Read the paper. Please. Really. I'm begging you.


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## Jay Strongbow (May 8, 2010)

Marty01 said:


> 1 pound on a 20 pound bike.. 5%... take 5% off your car`s weight.. HUGE difference!!!and its the SAME 5% you took off your bike...


Can we assume HUGE means it would be noticed by the rider? If so, next time you're out ride a few miles with a full water bottle bottle and then empty it or chuck it and and get back to us about that HUGE difference.


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## Marty01 (Jun 16, 2010)

see.if we as riders would push ourselves in a consistent way..the lighter bike difference would show up better

as in... at output `X`... weight `Y` will be propelled at speed `Z`... keep the output the same drop the weight and BAM... speed goes up.. this is physics.. doesnt matter if its by 5mph or.05mph.. its still a difference

the reason our speed wont really change ( look at your average before and after that $$$ wheelset for example) is we as cyclist.. are lazy.. we`ll buy an easier ride to keep our speed the same rather than go faster.. further.. longer.. we`re FN lazy! lol

the better workout with a heavier bike is simple.. if you move 30 pounds over distance `X`or move 20 pounds over distance `X`you`ll do more work moving 30 pounds hence get a better workout again simple physics..

I`ve read the paper... I`ll ask you to scratch that noggin you wear a helmet over


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## Marty01 (Jun 16, 2010)

Jay Strongbow said:


> Can we assume HUGE means it would be noticed by the rider? If so, next time you're out ride a few miles with a full water bottle bottle and then empty it or chuck it and and get back to us about that HUGE difference.


see.. I use a camelback so I don`t actually own a waterbottle... but i get what your saying.. 

don`t forget that as cyclists.. we dont average out 60mph.. our numbers are smaller..so the change in speed 5% less bike weight makes is small but its there

5% is 5% no matter how you slice it.. can you feel the change of gears? thats usually anywheres from 5-10% (from 16t to 15t cog is 6%... many people dont want the jump from 17t to 15t because its too big a change.. 13.3%) and yes.. i know this isnt the same 5% at all.. but i think 5% less weight is felt by the `joe blo`average rider..


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## PBike (Jul 6, 2007)

Salsa_Lover said:


> you are just confirming my point.
> 
> when runing errands, or going slow, you maybe don't "feel" that weight
> 
> ...


No offense, but I live in the Pittsburgh, PA suburbs and all I have here where I ride are large hills. Yes, if I drop the 40 pound load, then shave 15 pounds off the bike, I will most likely fee a difference, but that isn't the same as shaving 1 or 2 pounds off a bike that already weighs around 20 pounds. 

One or two pounds out of the total weight of you and your bike will not make an appreciable difference. Training however will.


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## Jay Strongbow (May 8, 2010)

Marty01 said:


> see.if we as riders would push ourselves in a consistent way..the lighter bike difference would show up better
> 
> as in... at output `X`... weight `Y` will be propelled at speed `Z`... keep the output the same drop the weight and BAM... speed goes up.. this is physics.. doesnt matter if its by 5mph or.05mph.. its still a difference
> 
> ...


When you claim it's a HUGE difference yes it does matter if it's 5 or .05. Are you familiar with power meters? Most anyone who's ever carried one from an old bike to a newer lighter one could kill your lazy theory.


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## Kerry Irons (Feb 25, 2002)

*Some numbers?*



CActuskid said:


> If it did not make ANY difference they would make bikes out of Concrete, it is so obvious what proof do you need


Rather than entire thread of people mostly arguing from ignorance, how about we use some actual numbers? For a 150 lb (68 kg) rider on a typical road bike on a flat road at 20 mph (32 km/hr), 2 lbs (1 kg) of added weight will slow you down by 0.02 mph (0.03 km/hr). Not going to show up on your bike computer or your stopwatch unless you're keeping REALLY close track over long distances. Just for reference, that would be 18 seconds slower over 100 miles (161 km).


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## muscleendurance (Jan 11, 2009)

its just physics
lighter things take less energy to accelerate than heavier ones.
heavier things conserve more momentum than lighter things --> on flat roads once at speed a heavier bike will stay at a higher speed more easily than a lighter one..but will slow down sooner than the light one!

swings and roundabouts really, they are 'the same' except when there is lots of gravity and hills involved. Also this is all based on everything else being equal [same wheels, tyres, pressures...everything 8)


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## PBike (Jul 6, 2007)

muscleendurance said:


> its just physics
> lighter things take less energy to accelerate than heavier ones.
> heavier things conserve more momentum than lighter things --> on flat roads once at speed a heavier bike will stay at a higher speed more easily than a lighter one..but will slow down sooner than the light one!
> 
> swings and roundabouts really, they are 'the same' except when there is lots of gravity and hills involved. Also this is all based on everything else being equal [same wheels, tyres, pressures...everything 8)


Yes it takes less energy to accelerate lighter objects, however we can go back to 1 or 2 pounds of difference is a small percentage of the total weight of the rider and bike so it will be a small non discernible difference. Unless of course you factor in the weight loss of your wallet.

Do you get progressively faster as you drain your water bottles?


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## muscleendurance (Jan 11, 2009)

PBike said:


> Do you get progressively faster as you drain your water bottles?


when going up or down hill :lol:


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## asgelle (Apr 21, 2003)

Marty01 said:


> the better workout with a heavier bike is simple.. if you move 30 pounds over distance `X`or move 20 pounds over distance `X`you`ll do more work moving 30 pounds hence get a better workout again simple physics..
> 
> I`ve read the paper... I`ll ask you to scratch that noggin you wear a helmet over


So you believe riding the same distance on level ground in an hour on a 30 lb bike uses the same energy as riding it in 40 minutes on a 20 lb one?

Let's see. What say we make it a 15 mile ride? We'll ride that in an hour on the 30 lb bike with a 160 lb rider. Using the defaults at analyticcycling.com that works out to 68.9Wx3600 sec. = 248 kJ. Now our 160 lb rider does the ride in 40 minutes on the 20 lb bike. Now the work is 188x3600x2/3 = 451 kJ. So what do you know, our rider did more work on the lighter bike than the heavier one.


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## Marty01 (Jun 16, 2010)

asgelle said:


> So you believe riding the same distance on level ground in an hour on a 30 lb bike uses the same energy as riding it in 40 minutes on a 20 lb one?
> 
> Let's see. What say we make it a 15 mile ride? We'll ride that in an hour on the 30 lb bike with a 160 lb rider. Using the defaults at analyticcycling.com that works out to 68.9Wx3600 sec. = 248 kJ. Now our 160 lb rider does the ride in 40 minutes on the 20 lb bike. Now the work is 188x3600x2/3 = 451 kJ. So what do you know, our rider did more work on the lighter bike than the heavier one.


not time.. distance..READ the post as you said

and your numbers are skewed.. 68.8 and 188 and NOT the same numbers... look into speed being a constant over the same distance+time with weight being the only variable.. then post your findings.. ill let you unbuckle your theory yourself


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## asgelle (Apr 21, 2003)

Marty01 said:


> not time.. distance..READ the post as you said


The example is for the same distance. 15 miles.


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## brewster (Jun 15, 2004)

I'm no engineer, however consider this hypothetical situation. You're in the shape of your life. You're entering the biggest race of your cycling career. The price money is $50,000 and you have a real shot at winning. The course is a circuit of up and down twists and turns and sections of long flats. You have two bikes to choose from for the race. One weighs 25lbs and the other 15lbs. Which one are you going to choose?


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## Marty01 (Jun 16, 2010)

asgelle said:


> The example is for the same distance. 15 miles.


but you used a different time to make the calculations.. make that same trip in less time on a lighter bike and you`ll skew the results 

simple rule of physics here.. it takes energy `X`to move weight `A`distance `Y`.. add weight and you need more energy


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## muscleendurance (Jan 11, 2009)

brewster said:


> I'm no engineer


glad you said that first before the rest of the post, it just doesnt work that way :thumbsup:


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## asgelle (Apr 21, 2003)

Marty01 said:


> but you used a different time to make the calculations.. make that same trip in less time on a lighter bike and you`ll skew the results


Your example only posited the same distance for the heavy and light bike, you said nothing about speed so I made an assumption. I could have assumed the same time, I could have assumed going faster on the heavy bike. I chose to assume what I did. But it really doesn't matter. How much work I do or how good a workout I get depends only on how much power I choose to put out (that's left as an exercise) and that does not depend on how much a bike weighs.


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## Marty01 (Jun 16, 2010)

gees.. its funny everytime one of the `bike weight has no effect on cruise speed` gets one of those situations put to them.. the answer`s usually `it dont work that way` lol


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## asgelle (Apr 21, 2003)

Marty01 said:


> simple rule of physics here.. it takes energy `X`to move weight `A`distance `Y`..


Make everything as simple as possible, but not simpler." -- Albert Einstein You're way too simple.


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## Marty01 (Jun 16, 2010)

asgelle said:


> Your example only posited the same distance for the heavy and light bike, you said nothing about speed so I made an assumption. I could have assumed the same time, I could have assumed going faster on the heavy bike. I chose to assume what I did. But it really doesn't matter. How much work I do or how good a workout I get depends only on how much power I choose to put out (that's left as an exercise) and that does not depend on how much a bike weighs.


good lord man connect the dots! lol

the calories you put out are dependant on the bike`s weight.(amongst other things yes)... you weight the same regardless of which bike you ride... your power output is roughly constant thru your ride weather on a 15lbs or 50lbs bike.. do you see the variables being knocked out here??? whats left... the bike`s weight!!!  now.. if that heavier bike is say 21lbs.. and that lighter bike weighs 20 lbs.. why would the rules change?


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## medimond (Apr 26, 2009)

Where are you guys riding 15+ mile loops that are bone flat? Furthermore, your also assuming that your able to ride at steady state continuously, pedaling perfect circles. In all likelihood your not pedaling perfect circles and are continuously accelerating/decelerating the bike throughout this event. This accel/decel requires energy, and while the difference in a lb might not be much, it does add up over the course of the event. 

IMO you cannot get in really good shape until you start going up hill, that separates the men from the boys.


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## cs1 (Sep 16, 2003)

SnowMongoose said:


> Why do you need science here, common sense should suffice.


If common sense was common internet forums would be out of business.


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## den bakker (Nov 13, 2004)

medimond said:


> IMO you cannot get in really good shape until you start going up hill, that separates the men from the boys.


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## orange_julius (Jan 24, 2003)

Salsa_Lover said:


> this is a fallacy being repeat here too often
> 
> it is true that when you are just cruising softly inside your comfort zone, the weight differences don't make much difference.
> 
> But when you are close to your limits, ( climbing steep gradients, very long rides, high speeds etc ) the weight and aero characteristics work on your favor exponentially.


Also, human brings are not ideal point energy sources that provide motion to the bicycle. We are mounted on it, and we fight evolutionarily-optimized biomechanics geared towards walking and running to provide the pedaling motion that the bicycle needs. How much efficiency is lost with a lighter bike compared with a heavier bike? 

I'm not going as far as saying that the outcome is wrong, but the argument points to support the belief that bike weight doesn't matter -- flat idealized model of mass and source of energy for motion and displacement -- has fallacies.


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## asgelle (Apr 21, 2003)

orange_julius said:


> I'm not going as far as saying that the outcome is wrong, but the argument points to support the belief that bike weight doesn't matter -- flat idealized model of mass and source of energy for motion and displacement -- has fallacies.


Read the paper. It includes model validation.


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## Blue CheeseHead (Jul 14, 2008)

asgelle said:


> Read the paper. Please. Really. I'm begging you.


Looking at the results of the paper it is clear. 10% of the total power is used to overcome rolling resistance, which is the only weight dependant variable on flat ground. So, If a rider plus a bike weighs 200 # and you get a 4# lighter bike (2%) your are really only seeing a .2% benefit to your power. I would hardly call that significant for the average rider.

As others say, weight really comes into play when accelleration is at play.

As I see it, the OP's arguement was with regard to a theoretical flat surface at a steady speed. One cannot say there is zero effect of weight, but one can say it is negligable.


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## orange_julius (Jan 24, 2003)

asgelle said:


> Read the paper. It includes model validation.


What paper are you talking about, is this from another thread??


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## asgelle (Apr 21, 2003)

orange_julius said:


> What paper are you talking about, is this from another thread??


Post #9


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## orange_julius (Jan 24, 2003)

asgelle said:


> Post #9


Are you a specialist in being mysterious? Post #9 is by Salsa Lover, in fact the one that I wrote my first reply to.


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## Salsa_Lover (Jul 6, 2008)

Jay Strongbow said:


> Can we assume HUGE means it would be noticed by the rider? If so, next time you're out ride a few miles with a full water bottle bottle and then empty it or chuck it and and get back to us about that HUGE difference.


I ride without water bottles when I go climbing.... Yes there is a difference ( some 1.5 Kgs ) and you can feel it.


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## Opus51569 (Jul 21, 2009)

George M said:


> I've looked and couldn't find any scientific information saying that a lighter bike is easier to pedal than a heavy one. I know it's easier to climb and sprint with a light bike. I also read that they both are almost the same on the flats. I know that from my own riding anyhow. Anyhow I have a discussion going on with a neighbor about this.
> He's an engineer and he's telling me I can ride a lot faster on the flats with a light bike and if I want to get a good workout I should be using a heavy bike. I say I do have a heavy bike and it's really not that much faster with the lighter bike. He's says maybe not, but you will use less energy with the lighter bike.I'm trying to get something to prove this point.Thanks.


I'm neither a physicist nor an engineer (which should be painfully obvious in a moment). Going back to the OP, George is using terms such as "almost" and "not that much". Somewhere along the way, math got involved and we all know nothing good can come of that . 

Yes, it takes less energy to accelerate a lighter object than a heavier one. 
Yes, a heavier object will achieve greater momentum downhill than a lighter one. 
Yes, it takes less energy to propel a lighter bike up hill than a heavier one.

On the flats, you're right that you probably won't be "that much faster" with a lighter bike but you will be faster. If you want to ride the heavier bike for a better workout, you can, but only if you maintain the same speed over distance that you do on the lighter bike. Doing that will require more effort leading to a better workout.


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## George M (Sep 25, 2008)

Opus51569 said:


> I'm neither a physicist nor an engineer (which should be painfully obvious in a moment). Going back to the OP, George is using terms such as "almost" and "not that much". Somewhere along the way, math got involved and we all know nothing good can come of that .
> 
> Yes, it takes less energy to accelerate a lighter object than a heavier one.
> Yes, a heavier object will achieve greater momentum downhill than a lighter one.
> ...



Your right about the math part and I know it's a part of the answer, but what you just wrote just about hits the nail on the head.
I did decide to just agree with everything he says, so it will make life easier . Thanks for the reply.:thumbsup:


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## Mount Dora Cycles (Aug 11, 2009)

F=ma Force = mass x acceleration
If acceleration doesn't change and mass does, the force required will be greater. The force needed on flat straight isn't that great in the common rider doing 16mph. Thats why mass of object is not so special. Add hills or greater speed (25pmh for instance) and the force needed increases as the acceleration needs increase. This makes even the smallest change in mass substantial. 

Hope that helps clear some things up using simple physics.

Thanks to this thread for my new signature!


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## asgelle (Apr 21, 2003)

Mount Dora Cycles said:


> This makes even the smallest change in mass substantial.
> 
> Hope that helps clear some things up using simple physics.


1 nanogram change in mass makes for a substantial change in force at 25 mph. Got it. Thanks for clearing that up.


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## PBike (Jul 6, 2007)

The one thing that truly affects acceleration in terms of weight, would be unsprung weight, or in other words, the wheels/tires. Shaving 2 pounds off the wheels (if possible) would make a much bigger difference in terms of acceleration than 2 pounds off the bike, which would yield no discernible change. You are still dealing with the rider/bike weight combination and 2 pounds is negligible.


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## roscoe (Mar 9, 2010)

Mount Dora Cycles said:


> F=ma Force = mass x acceleration
> If acceleration doesn't change and mass does, the force required will be greater. The force needed on flat straight isn't that great in the common rider doing 16mph. Thats why mass of object is not so special. Add hills or greater speed (25pmh for instance) and the force needed increases as the acceleration needs increase. This makes even the smallest change in mass substantial.
> 
> Hope that helps clear some things up using simple physics.
> ...


and this means nothing when you're up to constant cruising speed

steady speed means acceleration = zero 

you're oversimplifying because we're not riding in a vaccuum

the added work required in traveling faster is due to wind drag (which increases at the square of velocity) 
weight means nothing compared to wind drag once you're up to speed


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## asgelle (Apr 21, 2003)

roscoe said:


> the added work required in traveling faster is due to wind drag (which increases at the square of velocity)
> weight means nothing compared to wind drag once you're up to speed


What on Earth does "nothing" mean? Literally 0? 1%? 5%? 10%? The answer is out there if you look.


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## SwiftSolo (Jun 7, 2008)

George M said:


> I've looked and couldn't find any scientific information saying that a lighter bike is easier to pedal than a heavy one. I know it's easier to climb and sprint with a light bike. I also read that they both are almost the same on the flats. I know that from my own riding anyhow. Anyhow I have a discussion going on with a neighbor about this.
> He's an engineer and he's telling me I can ride a lot faster on the flats with a light bike and if I want to get a good workout I should be using a heavy bike. I say I do have a heavy bike and it's really not that much faster with the lighter bike. He's says maybe not, but you will use less energy with the lighter bike.I'm trying to get something to prove this point.Thanks.


Irons has this right. You can find all of the answers by using this. It'll end all of the BS. 
http://bikecalculator.com/veloUS.html


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## Keski (Sep 25, 2004)

Watts out are watts out. You won't be working any harder on a heavier bike you will just be going slower for the same effort.


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## spade2you (May 12, 2009)

I don't think RBR will come to a consensus of heavy vs. light.


....but what's the difference between light and hard?

























You can sleep with a light on!


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## den bakker (Nov 13, 2004)

Keski said:


> Watts out are watts out. You won't be working any harder on a heavier bike you will just be going slower for the same effort.


total work done is a different matter though.


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## Mount Dora Cycles (Aug 11, 2009)

roscoe said:


> and this means nothing when you're up to constant cruising speed
> 
> steady speed means acceleration = zero
> 
> ...


 My friend, you are confused. If acceleration was "0" then a zero force would be needed to continue moving. Can you take your feet off the pedals and continue moving at the same speed? Acceleration is needed constantly to continue moving against outside forces opposing you (like wing drag and friction to mention only 2 of the many). For the acceleration to be "0" you would have to be in a vacuum as you suggested I was (but wasn't) implying.

When you say "up to speed", that's not very accurate. The coefficient of drag due to wind starts becoming a great factor at speeds reaching 23mph. This is why many studies show when riding downhill above 25mph, it is best to cruise and conserve energy, rather than pedal away to try to catch up if you're behind.

If you really need a lesson in Dynamics, I can surely help you. Your grammar is your own to correct.


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## Mount Dora Cycles (Aug 11, 2009)

asgelle said:


> 1 nanogram change in mass makes for a substantial change in force at 25 mph. Got it. Thanks for clearing that up.


No need to be a smartass.


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## asgelle (Apr 21, 2003)

Mount Dora Cycles said:


> Acceleration is needed constantly to continue moving against outside forces opposing you (like wing drag and friction to mention only 2 of the many).


Why is an acceleration needed to counter a force? The units don't match up. A force is needed to oppose a force. Kind of like how the force on the pedals overcomes the forces acting on the bike and rider.



Mount Dora Cycles said:


> The coefficient of drag due to wind starts becoming a great factor at speeds reaching 23mph.


This is simply incorrect. Over the range of normal cycling speeds, the drag coefficient is not a function of speed.


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## Mount Dora Cycles (Aug 11, 2009)

asgelle said:


> Why is an acceleration needed to counter a force? The units don't match up. A force is needed to oppose a force. Kind of like how the force on the pedals overcomes the forces acting on the bike and rider.


Force IS mass x acceleration. If mass isn't changing, then the acceleration is. The units match up fine when you take mass out. The force on the pedals is just the person accelerating the pedals, once again, no change in mass. Acceleration doesn't always coincide with movement, which is what it seems you are confused with. Gravity always has a constant acceleration on Earth, but we aren't always falling towards the core are we? Outside forces prevent that. If gravity's acceleration was "0", then we would all just float away.



asgelle said:


> This is simply incorrect. Over the range of normal cycling speeds, the drag coefficient is not a function of speed.


WHAT? Is this a joke?


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## asgelle (Apr 21, 2003)

Mount Dora Cycles said:


> Force IS mass x acceleration. If mass isn't changing, then the acceleration is. The units match up fine when you take mass out. The force on the pedals is just the person accelerating the pedals, once again, no change in mass. Acceleration doesn't always coincide with movement, which is what it seems you are confused with. Gravity always has a constant acceleration on Earth, but we aren't always falling towards the core are we? Outside forces prevent that. If gravity's acceleration was "0", then we would all just float away.
> 
> 
> 
> WHAT? Is this a joke?


Apparently so.


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## roscoe (Mar 9, 2010)

Mount Dora Cycles said:


> My friend, you are confused. If acceleration was "0" then a zero force would be needed to continue moving. Can you take your feet off the pedals and continue moving at the same speed? Acceleration is needed constantly to continue moving against outside forces opposing you (like wing drag and friction to mention only 2 of the many). For the acceleration to be "0" you would have to be in a vacuum as you suggested I was (but wasn't) implying.
> 
> When you say "up to speed", that's not very accurate. The coefficient of drag due to wind starts becoming a great factor at speeds reaching 23mph. This is why many studies show when riding downhill above 25mph, it is best to cruise and conserve energy, rather than pedal away to try to catch up if you're behind.
> 
> If you really need a lesson in Dynamics, I can surely help you. Your grammar is your own to correct.



sounds like if you gave me a lesson in dynamics I would get worse grades in school than I got on my own 

as has been posted before, the coefficient of drag has NOTHING at all do to with speed. it's a constant factor 

drag force is a function of that coefficient multiplied by your net velocity through the air squared 

are you aware what acceleration is? it's a change in velocity 
if you're going 18 mph on flat ground you are not accelerating 
(you are pedaling to create a force, equal and opposite to the wind drag and mechanical drag) F(pedaling)-F(drag/friction...)=mass*acceleration(which is zero) 

you stop pedaling, and then the force isn't zero, and then the acceleration isn't zero

lean the difference between acceleration and force and then we can talk


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## roscoe (Mar 9, 2010)

asgelle said:


> What on Earth does "nothing" mean? Literally 0? 1%? 5%? 10%? The answer is out there if you look.


It's too small to care about 

my googler is tired this afternoon


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## Salsa_Lover (Jul 6, 2008)

roscoe said:


> and this means nothing when you're up to constant cruising speed
> 
> steady speed means acceleration = zero
> 
> ...


but to keep your steady speed given the air resistance and rolling resistance you need to accelerate the bike continuously..

That is why you have to keep pedaling to sustain your steady speed. is that clear now ?


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## roscoe (Mar 9, 2010)

Salsa_Lover said:


> but to keep your steady speed given the air resistance and rolling resistance you need to accelerate the bike continuously..
> 
> That is why you have to keep pedaling to sustain your steady speed. is that clear now ?


the only thing that your post makes clear is that
you don't understand what acceleration is either


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## Mount Dora Cycles (Aug 11, 2009)

roscoe said:


> sounds like if you gave me a lesson in dynamics I would get worse grades in school than I got on my own
> 
> as has been posted before, the coefficient of drag has NOTHING at all do to with speed. it's a constant factor
> 
> ...


It seems Dynamics is just beyond your thinking. I won't try to explain Newton's theories to you on a bike forum.


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## roscoe (Mar 9, 2010)

which one of newton's theories says the coefficient of drag changes with speed? 

have you figured out what acceleration is yet?


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## Mount Dora Cycles (Aug 11, 2009)

roscoe said:


> which one of newton's theories says the coefficient of drag changes with speed?


It's in the formula, which by the way, had nothing to do with Newton other than his original theory. Seriously, if you really want to learn more, try Google or wikipedia. Or you could go to college and major in Civil Engineering like me and learn all this fun stuff. Then throw it away to open a bike shop. Gotta do what you love though.

If you're still curious, the formula is 









V is velocity, and as you can tell, if V changes, so does Cd. 



roscoe said:


> have you figured out what acceleration is yet?


 Now you are starting to sound like a smartass too. Better know what you are talking about first.


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## asgelle (Apr 21, 2003)

Mount Dora Cycles said:


> If you're still curious, the formula is
> 
> 
> 
> ...


What if Fd changes exactly the same as V^2?


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## asgelle (Apr 21, 2003)

Mount Dora Cycles said:


> Seriously, if you really want to learn more, try Google or wikipedia. Or you could go to college and major in Civil Engineering like me and learn all this fun stuff.


Not that it matters, but you might want to be careful about throwing degrees around without knowing who you're talking to.


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## Mount Dora Cycles (Aug 11, 2009)

asgelle said:


> What if Fd changes exactly the same as V^2?


 What do you mean by "changes exactly the same"? Are you implying the Force and Velocity are related in the cyclist case? How can they change exactly the same? They can't with so many other outside factors. 

This thread is way off topic now and I'm done arguing with internet know-it-alls. I was just showing the OP that scientifically weight matters. Sorry for cluttering the thread.


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## asgelle (Apr 21, 2003)

Mount Dora Cycles said:


> What do you mean by "changes exactly the same"? Are you implying the Force and Velocity are related in the cyclist case? How can they change exactly the same? They can't with so many other outside factors.


Actually it's not me who's saying it; it's been established for decades that drag force is proportional to velocity squared (at least over the range of normal cycling speeds). In fact, the proportionality constant is 1/2 times the fluid density times the frontal area times a geometric constant known as the drag coefficient. Further, this drag coefficient is independent of speed (again over the range of normal cycling speeds). What do you think that equation you pasted meant?


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## nOOky (Mar 20, 2009)

Leave it to the engineers to over complicate a really simple answer and get into an argument over who's smarter


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## roscoe (Mar 9, 2010)

nOOky said:


> Leave it to the engineers to over complicate a really simple answer and get into an argument over who's smarter


but when a civil engineer incorrectly tries to "explain" things to people with degrees that are more applicable to the situation at hand, that's when it gets entertaining


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## Maximus_XXIV (Nov 10, 2008)

Salsa_Lover said:


> you are just confirming my point.
> 
> when runing errands, or going slow, you maybe don't "feel" that weight
> 
> ...


He will be too dead...


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## roscoe (Mar 9, 2010)

Mount Dora Cycles said:


> What do you mean by "changes exactly the same"? Are you implying the Force and Velocity are related in the cyclist case? How can they change exactly the same? They can't with so many other outside factors.
> 
> This thread is way off topic now and I'm done arguing with internet know-it-alls. I was just showing the OP that scientifically weight matters. Sorry for cluttering the thread.



what he means is that you don't grasp the mechanics and fundamentals behind that formula you posted

as a civil eng, you're out of your specialty here and it shows, maybe you could explain a stationary bike a bit better


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