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-   -   Does weight matter? (http://www.bikeforums.net/clydesdales-athenas-200-lb-91-kg/380854-does-weight-matter.html)

Dr.PooLittle 01-20-08 01:39 PM

Does weight matter?
 
I've heard it both ways. . . some people say that, if your not a featherweight, the weight of your bicycle doesn't really matter, because the combined weight is still rather high. I've also heard theories that your weight is like a baseline and the bike is something you carry with you, so its weight does matter. Lastly, someone once told me there's some kind of difference between suspended weight and weight beneath the suspension (the suspension being your legs). Anybody know enough physics to shed some light on this?

Tom Stormcrowe 01-20-08 02:54 PM

Mass and inertia remain the same whether you are the rider or the bike, once the units are combined.

It's cheaper to lose mass from the biological component than the mechanical component. ;)

Now, if you are at a healthy weight, then you can start looking at the tradeoff between mechanical component mass and stress/strength requirements.

zpl 01-20-08 03:06 PM

Yeah, what Tom said. My personal feeling is that having a heavy bike and even adding weight to it is beneficial because it helps you to lose the weight off your body faster, assuming you work harder and not just ride slower. :)

Bill Kapaun 01-20-08 03:07 PM

More weight takes more energy to accelerate or climb hills.
If you ride on flat roads (and don't do a LOT of stop & go), it's no big deal. It just takes a bit more to accelerate up to speed.

charles vail 01-20-08 03:40 PM

the real deal
 
Quote:

Originally Posted by Dr.PooLittle (Post 6016983)
I've heard it both ways. . . some people say that, if your not a featherweight, the weight of your bicycle doesn't really matter, because the combined weight is still rather high. I've also heard theories that your weight is like a baseline and the bike is something you carry with you, so its weight does matter. Lastly, someone once told me there's some kind of difference between suspended weight and weight beneath the suspension (the suspension being your legs). Anybody know enough physics to shed some light on this?

For a heavy rider a difference of a pound or two is insignificant when it comes to bike weight since it is such a small percentage of the whole. For a super fit and lean racer that same two pounds could mean the difference between winning and losing. The problem is, we regular daily cyclists try to use racing logic when it comes to practical cycling and it doesn't hold up in the real world. A super light bike is a joy but when you weigh 260 pounds you risk breaking the dang thing and killing yourself. Big, heavy riders need stout frames, strong wheels and wider tires with more air volume. A heavy rider using a light race bike is just like taking a Ferrari and and expecting it to do the job of hauling a load of firewood.:eek:

coldfeet 01-20-08 04:40 PM

What the others said, the more you weigh, the less the weight of the bike matters. Unsprung/sprung weight, that matters more for ride quality than anything. Rotational weight, i.e. the rims and tires, adds a bit to the equation because you have to both "spin it up" and move the whole forwards. ( and up when climbing )
Overall, as Bill said, it really only matters on climbs and accelerating. If your rides are flat with little stop and go, don't worry about it. If you do have a lot of climbing, well, how much is it worth to you to make it easier? Keep in mind that the easier you take it the less weight you will be losing. :)

I expended a little effort in reducing weight, more a case of careful packing and arranging my spares at either end, because it was marginal at first to deal with the distance/slope of the commute. Now I have lost 20lbs and gained a fair level of fitness, it's less of a concern and I barely give a thought to picking up 10-20lbs of groceries on the way home.

StephenH 01-20-08 04:51 PM

What is your goal in riding a bike? If you're trying to get from point A to point B as fast as can possibly be done on a bicycle, then yes, weight is important, and you should pay through the nose to eliminate every excess gram off that bike. But if your goal is to tootle around the neighborhood, get some exercise, maybe lose some weight, then it's kind of pointless to get concerned about the grams or even the pounds on the bike itself, and comfort and durability and just fun become equally important in the mix. I wouldn't ever intentionally add weight to a bike just for the weight, but wouldn't avoid a heavy one for my uses.

Wogster 01-20-08 07:10 PM

Quote:

Originally Posted by Dr.PooLittle (Post 6016983)
I've heard it both ways. . . some people say that, if your not a featherweight, the weight of your bicycle doesn't really matter, because the combined weight is still rather high. I've also heard theories that your weight is like a baseline and the bike is something you carry with you, so its weight does matter. Lastly, someone once told me there's some kind of difference between suspended weight and weight beneath the suspension (the suspension being your legs). Anybody know enough physics to shed some light on this?

Of course the bike weight matters, a kilo is a kilo is a kilo whether it's part of the bike, part of the load or part of the rider. With bicycle equipment the rule is "cheap, strong, light, pick any two". For a guy who is 20kg over weight, spending $500 to save 25g on a bicycle component, doesn't make much sense, when having a home made salad with little dressing instead of a burger, fries and large cola, can save 100g of rider weight.

flip18436572 01-21-08 06:57 AM

There is a difference in how the bike feels to the rider with more weight. I can feel the difference when I added my underseat bag and a tire pump. I am still overweight and know that I need to lose the weight off of my body before I will even think about a lighter bike, but I also don't think a lighter bike will do me much good, unless I start racing in tri's. Even then, unless the prize money would pay for the lighter bike, or I win the lotto, I don't plan on buying a new bike.

ang1sgt 01-21-08 09:06 AM

I get to ride many different bicycle as a Mechanic. Even a new Bike can feel dead, slow and uninteresting. Change a few parts on that bicycle, or go to a model with the same frame that has better quality parts and you will indeed feel the difference.

As others have mentioned, do we really need a fly-weight bike when more can be done with ourselves?
I look at it this way, I ride the bicycle that I want to ride. The one that calls to me to get back on it and ride the trails again. I am fortunate enough to have three bicycles that I enjoy riding. One recumbent, and two Mountain Bikes. I could ride and enjoy a Road Bike, but I've found that I just don't enjoy it enough to buy a Road Bike. I came OH SO CLOSE this year when we got our first new 08 Madone's in the shop.

Gram shaving on a bicycle is something that folks get wrapped up in also. I only change parts out either when I need too, (breakage) or when I know there will be a strength or durability change. Sometimes it's a vanity thing for me. I have one part on my new bike that is purely that. I just put on the new 08 Shimano XT crank on my new bike. Absolutely nothing wrong with the LX crank that came on the bike, I just wanted an XT crank!

Take all of this with a grain of salt please. Working at a LBS, I like to keep my bikes well maintained and tuned to perfection.

Chris

makeinu 01-21-08 09:49 AM

Quote:

Originally Posted by charles vail (Post 6017550)
For a heavy rider a difference of a pound or two is insignificant when it comes to bike weight since it is such a small percentage of the whole.

Oh yeah? Stand with your arms over your head and see how long you can hold the position. Now, put a textbook in each hand a do the same thing. The percentage difference in overall weight is almost insignificant, yet the difference in energy expended by the body is huge.

Strangely enough, no physical energy is required to hold the position in either case, despite the fact that a huge amount of physiological energy is clearly required. A wooden bookcase doesn't need to use fuel, but a human bookcase does.

I have no idea what the physiological reasons are, but weight is obviously important, especially weight external to the body.

ChunkyB 01-21-08 10:07 AM

It depends on what you're trying to do also. If you're riding solely for training and losing weight, it might actually help to have a heavier bike, because you get a better workout. If you're commuting, or racing especially, absolute time might matter, so it might be worth getting a lighter bike.

But, as has been said, if you have weight to lose from your body, I'd do that before you worry too much about your bike.

charles vail 01-21-08 05:48 PM

huh?
 
Quote:

Originally Posted by makeinu (Post 6021157)
Oh yeah? Stand with your arms over your head and see how long you can hold the position. Now, put a textbook in each hand a do the same thing. The percentage difference in overall weight is almost insignificant, yet the difference in energy expended by the body is huge.

Strangely enough, no physical energy is required to hold the position in either case, despite the fact that a huge amount of physiological energy is clearly required. A wooden bookcase doesn't need to use fuel, but a human bookcase does.

I have no idea what the physiological reasons are, but weight is obviously important, especially weight external to the body.

On a bicycle though its not the same as holding up weight with your deltoid muscles. The weight is supported by the frame etc. I seriously doubt anyone can feel the difference on a climb between a 16 pound bike and an 18 pound bike. In the practical world of real life cycling the difference is about what your water bottle and tool bag weigh. I'm sure someone can give a mathematical breakdown about the number of watts expended on a climb and the few seconds difference it might make theoretically but reality doesn't allow that since there are too many other variables. When you are talking about your body having extra weight then yes, that is going to make a big difference since your entire circulatory system becomes less efficient. When I weighed 230 pounds I could fly up hills much faster and in a higher gear than I do now but I can barely tell any difference between my 20 pound race bike and my 30 pound touring machine. On flat ground, there is no difference, except when accelerating. I don't think I could tell a 2 pound difference, in fact, there are probably plenty of times when I have loaded my bike with extra junk and not noticed. The super weight conscious logic escapes me. I have to be honest, I literally laugh when I hear people talking about cutting grams off their bike like there is going to be some magical difference in their performance. Whether you visit the john or not will make a bigger difference using that logic.:beer:

MikeLD 01-21-08 08:11 PM

From a practical standpoint I'm sure that a a few pounds here and there don't matter in the real world ... particular for a "husky" guy like me. That said, there's a psychological impact, at least there is for me. I regularly ride 4 bikes (CF Roubaix, Carl Strong light weight custom steel road bike, Aluminum Sequoia, and a steel Surly Cross Check. The Cross Check is the heaviest and I run it with 48 spoke rear / 40 spoke front wheels with heavy Phil Wood hubs. I do a little touring and trail riding on the Surly, but it's built like a tank, and a good 6 or 7 pounds heaver than the Roubaix and custom steel bike. I love it but feel measurably slower on it -- hard to prove since every ride is different, but I FEEL a bit slower.

If I'm riding by myself I take the Surly 75% of the time ... if I'm riding with a group that goes a bit faster, I ride the Carl Strong Custom ... because in my head, I'm faster on it. I'm 260lbs, by the way.

bautieri 01-24-08 08:15 AM

One of the first lessons you learn in physics is to always ask ma, she'll know. Ok so not-so-funny physics humor aside no matter what, the force you must excerpt to move a bicycle (or anything) is always going to be Force = Mass x Acceleration (F=MA see, there's ma:) ).

In this case the mass is going to be rider plus bike going your desired speed, acceleration in physics can be a constant speed. So now its easy to see that if the total mass goes down less force will be required to move it. As pointed out before its a lot cheaper for the rider to lose a pound than it is for the bike to loose a pound.

Now this equation only works on flat ground. Should a slope be involved the equation gets much more complex as we'll need to know the degree of the slope, the coefficient of friction, and the retarding force due to gravity. After all this is figured out it will only confirm what we already know, more mass = more force to move be it flat frictionless ground or up a hill factoring gravity and friction.

So that pretty much puts an end to any type of argument over this. Less weight will always equal less energy output therefor making it easier to ride no matter how marginal it may be.

Bau

CliftonGK1 01-24-08 10:29 AM

Quote:

Originally Posted by charles vail (Post 6017550)
A heavy rider using a light race bike is just like taking a Ferrari and and expecting it to do the job of hauling a load of firewood.:eek:

Don't be the bicycling equivalent of this guy.
http://www.swapmeetdave.com/Humor/Wo...mber-Car-A.jpg

piper_chuck 01-24-08 11:56 AM

Quote:

Originally Posted by makeinu (Post 6021157)
Oh yeah? Stand with your arms over your head and see how long you can hold the position. Now, put a textbook in each hand a do the same thing. The percentage difference in overall weight is almost insignificant, yet the difference in energy expended by the body is huge.

Strangely enough, no physical energy is required to hold the position in either case, despite the fact that a huge amount of physiological energy is clearly required. A wooden bookcase doesn't need to use fuel, but a human bookcase does.

Huh? "No physical energy is required to hold the position"? When you have your arms at your sides, a force is being applied to overcome gravity. Since they are not rising, or falling, the upward force is exactly equal to the downward force of gravity. To lift your your arms, you have to apply more force than that being exerted by gravity. Once you have your arms all the way up, and they stop moving, the upward force you are applying is once again equal to the downward force of gravity. Since we are not made of stone, we exert some amount of physical energy to generate the forces in question.

eurojuce 01-30-08 10:59 AM

CF and weight
 
Is there a general rule about how heavy you are and the type of bike material you ride? I'm 210-213 and am looking at CF, but heard somewhere that I should stay away from CF because of the stresses it goes through under a heavier rider. I want to build a CF78 (Botteccia)

Tom Stormcrowe 01-30-08 11:09 AM

Check with Bottechia about any weight limits. We have Clydes a lot heavier riding CF frames on the forum.

The biggest drawback I can see to CF, really is catastrophic crash damage. Ither than that, it's a great material for strength given modern fiber weave matrices used.
Quote:

Originally Posted by eurojuce (Post 6077631)
Is there a general rule about how heavy you are and the type of bike material you ride? I'm 210-213 and am looking at CF, but heard somewhere that I should stay away from CF because of the stresses it goes through under a heavier rider. I want to build a CF78 (Botteccia)


bcart1991 01-30-08 11:48 AM

Back to the original topic a bit...

Did anyone see the report (in Road Cycling I believe) (from the Serotta Cycling Symposium or some such) showing findings froma study that 3kg lost from the body of the rider makes more difference in efficiency and/or power than 3kg lost from the bike?

Intersting stuff in that report.

WalterMitty 01-30-08 02:31 PM

Quote:

Originally Posted by CliftonGK1 (Post 6041191)
Don't be the bicycling equivalent of this guy.
http://www.swapmeetdave.com/Humor/Wo...mber-Car-A.jpg

I certainly agree! I think those spoked wheels look like crap on that body style.

;)

TheScientist 01-30-08 10:33 PM

If you are talking overall bike weight it's not that significant if you're heavy. But there are some parts of the bike where weight matters more than others. the frame, handle bars and seat and seat post and stuff like that is stationary when you ride. Things like your rims and Hubs and pedals are very important though. The less weight you have to make go around the better off you're going to be. Overall though, lose weight on yourself and then worry about your bike

Kotts 01-31-08 01:44 PM

On the other hand...
 
I agree with most of these posters that if you're heavy, a light bike won't matter much, if at all.

On the other hand, a bike that can efficiently put power to the pavement matters a LOT! Get a bike that handles and performs well**, and you'll ride more, because it's more fun.

**Note that "handles and rides well" can be pretty subjective. So pick a frame design, and material, and components that do what you want, the way you want it, and let the "weight weenies" go hang.

(A former Clyde...)


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