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Bicycle weight doesn't matter? (myth)

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Bicycle weight doesn't matter? (myth)

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Old 07-12-18, 10:02 AM
  #26  
Metieval
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Originally Posted by Happy Feet View Post
Well, let me rephrase it so you can't argue what should be a simple concept by obfuscation.

I have never heard a reasonable person suggest that weight does not matter in broad general terms without defining just what it is they are discussing. Reasonable people define parameters because they know context matters if they actually are interested in answers.

And to add to the reasoning that context matters: As I already indicated, If you are riding 2kms weight will not matter in regard to fuel requirements as you will not deplete your stored glycogen stores and thus, require no additional fuel. Most reasonably fit humans have a constant fuel reserve such that riding a short distance on a heavy or light bike will not unduly effect them. If however, you ride 200kms, you will deplete those glycogen stores, more so on a heavy bike, and will need to adjust accordingly.

Until you define what you are doing on the bike how can anyone intelligently discuss whether fuel considerations matter or not.
the forum has a search feature top right corner. If you wish to see/read/hear what
people use to quantify their "weight doesn't matter arguments"
I really don't care what the opinions are.

I side with Physics on the matter. It takes more energy to move more weight, all else being equal.
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Old 07-12-18, 10:38 AM
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Originally Posted by Metieval View Post
I side with Physics on the matter. It takes more energy to move more weight, all else being equal.
Actually, physics says it takes more energy to accelerate more weight, all else being equal.

Fuel mileage estimates include things like starting and stopping, and an average acceleration up to speed. But a cyclist in a flat area could only need to get up to speed once at the beginning of the ride, and physics will reward them for the momentum of their heavy bike by decreasing the minor decelerations from corning, wind, etc. Heavy bikes on flats are more efficient.

So you want to make blanket statements, but it doesn't sound like you've actually thought through the actual conditions mileage tests are performed under. I would expect your next myth buster is to tell cyclists it doesn't take more energy to ride faster since car MPGs are always lower for faster highway conditions. That wind resistance thing must be a myth!
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Old 07-12-18, 10:44 AM
  #28  
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Originally Posted by Kontact View Post
Actually, physics says it takes more energy to accelerate more weight, all else being equal.

Fuel mileage estimates include things like starting and stopping, and an average acceleration up to speed. But a cyclist in a flat area could only need to get up to speed once at the beginning of the ride, and physics will reward them for the momentum of their heavy bike by decreasing the minor decelerations from corning, wind, etc. Heavy bikes on flats are more efficient.

So you want to make blanket statements, but it doesn't sound like you've actually thought through the actual conditions mileage tests are performed under. I would expect your next myth buster is to tell cyclists it doesn't take more energy to ride faster since car MPGs are always lower for faster highway conditions. That wind resistance thing must be a myth!
Not always. The Prius C has a drivetrain tailored to city driving and fares worse at highway speeds, especially as the speeds get above ~60 mph. Then it becomes simply more work and the engine has to run full time. You get to see that wind resistance is quite real - in real time with the running MPG on the dash and in the wallet at the gas pump.

Ben
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Old 07-12-18, 10:57 AM
  #29  
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I own so many bikes, that I don't know how many I own. Their weights range from 16ish (carbon road) to almost 30 pounds for a commuter kitted with fenders and racks. They are all high quantity gear, and very well maintained.

Anyway being on the carbon Uber bikes spoils you for life. After this, riding 30 pounds feels like misery.

Light wheels make a huge difference, more than any other factor. My most recent bike is kitted out with fat 28mm clincher tires on fat beefy rims (on a so-called endurance bike). The wheels alone must weigh a porky 2kg. They are pigs; the otherwise lightweight bike now rides like a farm tractor.

1,200 gram tubular wheelset: a life-altering revelation.
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Old 07-12-18, 10:58 AM
  #30  
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The weight of a bicycle matters, but not nearly as much as it does on a cargo van.

I checked and running with no cargo versus running with full cargo for the Mercedes Sprinter (as an example) results in a 70% increase in weight. A 200 lb. bicycle rider riding a 30 lb. bike versus a 20 lb. bike is an increase of 4.5%. So yeah, it matters, but not enough to affect performance nearly as much as loading a cargo van.
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Originally Posted by bragi "However, it's never a good idea to overgeneralize."
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Old 07-12-18, 11:08 AM
  #31  
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Originally Posted by livedarklions View Post
Now, that being said, is there anything funnier than a really overweight guy trying to convince you that you should spend an additional $400 on an accessory like he did in order to save 200 grams? I know, that's kind of mean, but still....
A while back we had a thread on this forum (I searched for it but can't seem to find it) from someone asking about drilling holes in his frame in order to save weight. Later in the thread someone was asking about his weight (due to safety of drilling holes in a frame) and he was up somewhere north of 230 pounds or so. So yeah, makes much more sense to drill a bunch of holes in your bike to save a few ounces rather than diet and lose 30 or 40 pounds.
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Old 07-12-18, 11:13 AM
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Originally Posted by 79pmooney View Post
Not always. The Prius C has a drivetrain tailored to city driving and fares worse at highway speeds, especially as the speeds get above ~60 mph. Then it becomes simply more work and the engine has to run full time. You get to see that wind resistance is quite real - in real time with the running MPG on the dash and in the wallet at the gas pump.

Ben

Isn't that also because braking the Prius generates electricity so stop and go actually uses less gas?
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Old 07-12-18, 11:17 AM
  #33  
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The other thing everyone is forgetting? Just like in cars, moreso than weight on flat grounds, aero plays a massive difference in fuel economy.

Take that car and put 500# in it and get your readings. Take out said weight, and take all the front fenders off, and I can almost guarantee you you use more fuel.

In the same manner, TT bikes will often be slightly HEAVIER than their non aero counterparts, because the slight increase in weight to shape the components more efficiently saves more time than the lesser weight.
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Old 07-12-18, 11:21 AM
  #34  
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Bicycle weight does matter, but perhaps not as much as you'd think, unless you're in peak physical condition and racing. With bicycles, the weight of the bike is only a fraction of the weight of the rider, while with automobiles, the opposite is true. It's often more cost effective to reduce body mass rather than bicycle mass, and depending on your BMI, it can be healthier as well.

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Old 07-12-18, 11:26 AM
  #35  
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I know people hate average speeds on rides around here... but I am 1mph faster on average riding my carbon frame bike vs. my aluminum bike.
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Old 07-12-18, 11:33 AM
  #36  
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Originally Posted by Milton Keynes View Post
A while back we had a thread on this forum (I searched for it but can't seem to find it) from someone asking about drilling holes in his frame in order to save weight. Later in the thread someone was asking about his weight (due to safety of drilling holes in a frame) and he was up somewhere north of 230 pounds or so. So yeah, makes much more sense to drill a bunch of holes in your bike to save a few ounces rather than diet and lose 30 or 40 pounds.
Google search definitely works better than BF search. Thanks for the laugh!

Drilling a steel classic road frame like swiss cheese...still safe to ride?
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Old 07-12-18, 11:35 AM
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Originally Posted by Metieval View Post
the forum has a search feature top right corner. If you wish to see/read/hear what
people use to quantify their "weight doesn't matter arguments"
I really don't care what the opinions are.

I side with Physics on the matter. It takes more energy to move more weight, all else being equal.
Glad you posted on an open forum, and do not wish to hear other opinions, which generally aren;t opinions, but rather fact.

You are correct of course that it takes more energy to move more weight, or more specifically, as Kontact pointed out, to accelerate that weight to speed, but what you are missing is that what is significant it the percentage of total weight difference, and that in most cases on a bicycle the difference is negligible, since the rider generally is the bulk of the mass on the bike. The major exception would be a person touring, or commuting with a lot of weight in their bags. A two pound difference on the weight of the bike won't be felt much by the rider, unless perhaps it is a two pound difference on the wheels.
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Old 07-12-18, 11:36 AM
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Originally Posted by DomaneS5 View Post
I know people hate average speeds on rides around here... but I am 1mph faster on average riding my carbon frame bike vs. my aluminum bike.

Is weight the only difference between the two bikes?
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Old 07-12-18, 11:48 AM
  #39  
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Originally Posted by livedarklions View Post
Is weight the only difference between the two bikes?
Aside from the trailer, yes.
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Old 07-12-18, 12:00 PM
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Originally Posted by Kontact View Post
Aside from the trailer, yes.

Oh, you're that guy:

https://goo.gl/images/HcKlCQ
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Old 07-12-18, 12:05 PM
  #41  
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Originally Posted by fietsbob View Post
with the frontal area of a van the air resistance increases the faster you drive.. and gas mpg gets worse.
work thru your analogy to bikes with that.
I'll throw a spanner in to that, since it seems to be a spanner flinging kind of thread.
My SAG-mobile is a Honda Element, which is boxy and low-powered. 75 mph is it's max comfortable speed on the highway. It'll go faster, but fuel economy and handling go down sharply above 80mph. Drove to South Carolina for vacation one year. 2 pax + luggage, averaged 23 mpg. Did the same trip 2 summers later, with 3 pax, and the 20 cu.ft. cargo pod on the roof. Got better than 25 mpg.
Steady state cruising on I-95; Big increase in frontal area, but significant change in airflow, probably reduced drag at the rear edge of the roof.

That's why TT / Tri bikes are heavy and chunky looking compared to road racers, particularly the climbing specialists. You only accelerate once, then it's all about how smoothly you move through the air.
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Old 07-12-18, 12:05 PM
  #42  
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Originally Posted by JohnDThompson View Post
Bicycle weight does matter, but perhaps not as much as you'd think, unless you're in peak physical condition and racing. With bicycles, the weight of the bike is only a fraction of the weight of the rider, while with automobiles, the opposite is true. It's often more cost effective to reduce body mass rather than bicycle mass, and depending on your BMI, it can be healthier as well.
Yep, I just said that.

Originally Posted by Doohickie View Post
The weight of a bicycle matters, but not nearly as much as it does on a cargo van.

I checked and running with no cargo versus running with full cargo for the Mercedes Sprinter (as an example) results in a 70% increase in weight. A 200 lb. bicycle rider riding a 30 lb. bike versus a 20 lb. bike is an increase of 4.5%. So yeah, it matters, but not enough to affect performance nearly as much as loading a cargo van.
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Originally Posted by bragi "However, it's never a good idea to overgeneralize."
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Old 07-12-18, 12:19 PM
  #43  
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Originally Posted by Kontact View Post
Aside from the trailer, yes.
The aluminum bike generates it's own magnetic field.
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Old 07-12-18, 12:22 PM
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Originally Posted by livedarklions View Post
Google search definitely works better than BF search. Thanks for the laugh!

Drilling a steel classic road frame like swiss cheese...still safe to ride?
Thanks for finding that. I looked and looked and couldn't find it, but I wanted to go back and read it again.

*edit* My bad, the guy was only 200 lbs, but still more worth it to lose 20 lbs of fat than to drill out a few ounces of metal and have the bike fail.

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Old 07-12-18, 12:50 PM
  #45  
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You can overcome a bike weight disadvantage by inflating the tires with helium.

I am thinking about cutting off the ends of my toothbrush, plastic spoon and fork to lighten the load. Will that make me faster and require fewer calories?



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Old 07-12-18, 12:50 PM
  #46  
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Originally Posted by Milton Keynes View Post
Thanks for finding that. I looked and looked and couldn't find it, but I wanted to go back and read it again.

*edit* My bad, the guy was only 200 lbs, but still more worth it to lose 20 lbs of fat than to drill out a few ounces of metal and have the bike fail.


Didn't the drillium trend also fade because all those holes

created an aero penalty more than a weight advantage?
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Old 07-12-18, 01:16 PM
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This is why I always struggle on whether or not to bring a sandwich on my rides. Without one, I can finish the ride just fine. But if I do bring along a sandwich, the extra weight ensures that I'll run out of fuel at some point and need to eat it.
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Old 07-12-18, 01:37 PM
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Bonking in the UK has an entirely different meaning. It's the bit between two people dancing, eating, drinking, disrobing then smoking a metaphorical cigarette. It requires fuel both before and after. Bicycle weight doesn't matter, as bonking on a bicycle in the UK is probably beyond all but the most supple.
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Old 07-12-18, 01:41 PM
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Only thing I know is;
1) I'd rather push a Prius up a hill than a van
2) all winning bikes at Tour de France don't have valve caps on them.
hope this helps
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Old 07-12-18, 01:43 PM
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Originally Posted by AlmostTrick View Post
This is why I always struggle on whether or not to bring a sandwich on my rides. Without one, I can finish the ride just fine. But if I do bring along a sandwich, the extra weight ensures that I'll run out of fuel at some point and need to eat it.
If you put it in your pocket, then it won't count as bike weight and there is no problem.
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