Importance of bicycle weight

General Questions
#1

Bicycle weight seems to have a big impact on how easy a bike is to ride, particularly when accelerating and riding up hill. But is there any difference in extra weight of the bicycle frame itself, compared to extra weight the rider is carrying?

Based on my own observations, riding a bike that weighs an extra 4 pounds seems to make a big difference, but I don’t notice that same difference when riding with my 64-oz camelback (also ~4 pounds). People are willing to spend thousands more to get a slightly lighter bike, but don’t worry about carrying an extra 16 oz of water.

That said, I can think of no reason why it would make any difference if the weight is on the bike versus the rider. Can anyone provide a definitive answer on this, not just personal anecdotes? I realize my own experience might be more a matter of, lighter bike are more expensive and have better components all around (including wheels), and are therefore easier to ride because of this and not so much the weight.

Also, I understand why wheel weight and design does make a big difference, because of angular momentum. I’m asking only about the frame.

#2

I just went through the buying process for a new road and was told that the place the weight is the most important, especially when climbing, is at the outside of the wheels—furthest from the hub. In test riding a LOT of bikes, it seemed to me that my fit to the bike and the stiffness of the frame made more of a difference than weight. But I’m probably not attune to the more minor fluctuations a more experiences rider could discern.

I did notice a BIG tradeoff between responsiveness and stability, or comfort. Some aggressive race bikes I tried might have been a little better on the hills or accelerating, but going down big hills was frightening.

#3

Hey, I finally agree with you on something! I’m not a big rider, but I was shocked once in the difference between two bikes similar except for the frame.

#4

Couple factors:

The bicycle is generally “unsprung weight” while your body and items on it are “sprung weight”, with your arms and legs being in this case the suspension. Unsprung weight has more impact on handling and ride characteristics than sprung weight does, which is going to change the feel of the bike.

Also, part of riding a bike is moving it relative to your body, whether that be just rocking it back and forth while in a standing sprint, or muscling it over irregularities in the road/trail. Hence, additional mass on the bicycle will increase the effort involved in these aspects of riding where additional mass on your back will not.

That said, another thing you guys might be noticing with different frames might be geometry and not mass at all. A steeper head tube will make the bike more responsive, possibly even downright twitchy, etc.

#5

I’d say weight matters only when accelerating and riding uphill.

There is a difference in how the bike feels, but it shouldn’t affect your speed.

I found the same when I bought a 20" folding bike - when I pedal hard, I could feel the bike zooming forward. But what matters is how fast the rider+bike move forward, and that’s only determined by total weight.

I think you mean moment of inertia. It just means it takes energy to make the wheel spin faster.

#6

I always make my bike effectively a lot more expensive by taking a dump before I ride.

Weight at the wheel rims counts twice as much as weight on the bike when you’re accelerating or riding uphill.

#7

Part of this is probably just the same as the difference between carrying a bag weighing 4 pounds in your hands as opposed to in a backpack: you notice the former much more. Particularly when trail riding or climbing (depending on riding style) you may throw the bike around a bit. You will feel that through your hands and legs. The weight on your back is easier to ignore because it becomes part of the undistinguished mass of the whole enterprise. 4 pounds when taken as part of the whole bike/rider configuration is, what, perhaps 2%? Too little to notice.

#8

But I thought the first rule of cycling was that all bicycles weigh fifty pounds.
[ul]
[li]A twenty-pound bike needs a thirty-pound lock[/li][li]A thirty-pound bike needs a twenty-pound lock[/li][li]A fifty-pound bike needs no lock[/li][/ul]

#9

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I’d say weight matters only when accelerating and riding uphill.
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If you consider how easy a bike is to ride, wouldn’t you think the weight also matters in certain situations such as a strong crosswind? I’ve riden light and heavy bikes in those conditions and there is a **big **difference in the feel of the bike.

#10

It will have some impact in all situations. Even on flat ground, there are forces acting against your forward motion, like air resistance and friction. A headwind will make it more pronounced. Weight also has an impact on things like getting over terrain on a mountain bike.

Thanks for the responses. The sprung vs unsprung weight and ease of moving the bicycle (side to side while pedaling and over terrain) make sense to me, and I’m sure that’s what I have experienced.

#11

Just to kick the dead horse, I’ll bet it has a lot to do with leverage. i.e. a four pound wight on your back vs. a four pound weight in your hand vs. a four pound weight at the end of a long pole. I bet you’d really notice the weight if you had a five foot long seat tube and handlebars.

#12

Yeah, it can be a big difference. I was also amazed by very minor adjustments in fit on the same bike. A quarter inch here or there can be huge.

Sorry you had to agree with me. I hope it didn’t ruin your day.:wink:

#13

Sorry to hijack with a pet peeve (but the question seems to be answered as best it’s going to be anyway), but like **Dan **I’m going to have to shock myself by agreeing with you for once. It irritates me when I read bike reviews and they prattle on with how the bike “feels” like this or that, as if there is a skerrick of objectivity to the exercise: as you say, a quarter inch here or there makes a huge diference to how a bike feels. So if Mr Reviewer One who is 5 ft 11in rides the bike he’s going to have one experience, and if Mr Reviewer Two who is 5ft 8in rides the same bike he’s going to have a different experience. Yet they write up their “feeling” as if it matters.

#14

The weight of the bike is most noticeable in relation to the weight of the wheels. The more the wheels weigh the greater the force needed to drive them. If you took 2 identically weighted bikes and rearranged the weight so one had heavier wheels you would notice the difference. It also matters how the weight is distributed on the wheel. 2 wheels of the same weight will have different acceleration rates. The more weight shifted to the outer rim, the slower the wheel will roll down hill.

#15

It doesn’t take more force to drive a heavier wheel at a constant speed, it takes more force to accelerate it. It doesn’t make a wheel slower down a hill to shift more weight to the outer rim, it makes the wheel slower to accelerate. Terminal velocity for a given hill would be the same.

Also, if you start two bikes of the same weight down the same hill, and the hill runs out before they reach terminal velocity, the one with heavier rims will keep rolling beyond the hill for longer: it is more efficient to store energy in angular momentum than in the overall speed of the bike, because the latter attracts higher drag.

#16

So all things being equal at cruise there will be a noticeable difference in acceleration.

If you shift weight on a wheel to the outer circumference it will accelerate slower down hill.

#17

Aren’t you contradicting yourself here? Aren’t “cruise” and “acceleration” opposites? All other things being equal, a bike with greater rim weight but the same overall weight will be harder to accelerate, but will not be harder to cruise at a constant speed.

Sure, but my point is that if two bikes of the same overall mass but different wheel circumferences masses go down the same hill at the bottom the one with the greater wheel circumference mass will be going slower, but be storing more energy (having lost less to aerodynamic drag), and will roll further at the bottom than the other. The reason being it will have a greater proportion of its energy stored in the angular momentum of its wheels. The other bike will have a greater amount of energy stored in overall velocity, of which more will be lost to aerodynamic drag.