NEXUS

A light weight bike makes for quick starts but as a commuter I don't need to do that. A light weight bike is easier going up hill but it doesn't really apply to me since I usually have a load of groceries on my bike and can just put it in a lower gear for hills. I also read that if the angle of a hill is more than around 18 degrees then it would be more efficient to get off the bike and push regardless of how low your gearing is.


Now can someone check my science:

A lighter bike will be quicker to get up to top speed but will take more energy to stay at top speed while a heavier bike will take longer to get up to top speed but will use less energy to stay at top speed and can reach a higher top speed [slowly] and can coast longer.

So if this is correct, besides at starting and perhaps going up hill, having a heavier bike is actually a good thing, especially for tourers and those whose commute is primarily on open road and not in stop and go traffic.

Anyone want to comment?

apricissimus 

I can't comment intelligently about the ins and outs of the science, but when I bought my Bianchi Volpe last year, I dropped about 7 pounds from the previous rig I had been riding (and will never ride again). The lighter bike was a ton more fun to ride, and yeah I do think that part of it was the weight differential. Seven pounds is a pretty substantial drop though. I'm not one to care much about saving 50 grams on a seat post or whatever.

I hardly ever carry more than about 15 pounds though (on my back, no panniers), so my experience is different from yours.

devianb

If you are always carrying a load of some sort and not always riding at top speed then for the most part I would say you are correct. Are you taking into account the weight of the person too?

daveF

If everything is the same, a lightweight bike is faster to accelerate & faster at top speed, & requires less watts to maintain the same speed. Otherwise, we would be peddling our cars!

PaulH

"A lighter bike will be quicker to get up to top speed"

Yes

"will take more energy to stay at top speed"

No

"a heavier bike will take longer to get up to top speed"

Yes

"will use less energy to stay at top speed"

No

"can reach a higher top speed [slowly]"

No

"can coast longer"

Yes

Paul

tcs

Cyclists have been voting with their pocketbooks for lighter weight for over 130 years.

tcs

rhm

I recently switched commuter bikes; my aluminum frame developed a crack, and while I'm waiting for a replacement from the manufacturer I'm riding a steel framed bike that is otherwise very similar, just considerably heavier.

The ride is very similar, and while riding I do not feel slower. I leave the house at the same time and so far have not missed my train; so my cruising speed must be pretty much the same.

I only feel the weight, really, when I lift it. I think it must be close to 5lbs heavier.

mercator

My winter/rain bike (the dreadnought) weighs about 10 lbs more than my summer bike. They both fit pretty much the same, and I carry about the same amount of stuff in the panniers on both. I much prefer my summer bike

Foofy

Heavier bike will have more inertia, but even with really heavy bikes like Dutch style city bikes and old utility bikes, the majority of the weight of the entire vehicle comes from the individual.

As for maintaining top speed, a lighter bike has the advantage. Aerodynamics, and in some cases rolling resistance, provide a huge challenge to maintaining a fast speed. Even if you're maintaining a speed, you still have to use constant energy to maintain that speed, and it's easier with a lighter bike. Heavy bikes only benefit you when going down hill, and that isn't much of an advantage. The racers try to get the lightest bikes possible because it overall makes them faster.

Weight does matter to those of us who don't race. However, we commuters and utility cyclists are usually willing to accept heavier bikes, due to the nature of our types of riding. Our goals aren't quite the same as the racers, so we put up with heavier bikes.

Some people do commute on racing bikes though, and there's nothing wrong with that.

CliftonGK1

Disregarding all science, the question "does weight matter if you're not racing?" is just a matter of personal preference.

I have a lightweight fixed gear commuter, a mid weight geared commuter, and a 40 pound utility cruiser. Today I sacrificed weight for snow stability and took the cruiser. Some days I sacrifice easy hill gears for simplicity and ride the fixed gear.
I commute and I ride long distance. I'm never concerned with the myriad statistics that competitive cyclists spend hours upon hours analyzing after a ride. I don't care about my weight/power ratio, or my max 30sec vs. 1min vs. 5min wattage. I care that my utility bike gets me and my groceries home from the store, and that my distance bike doesn't break down 70 miles from my house.

tatfiend 

On a bike at any reasonable speed most of the energy needed is due to wind resistance, not inertia or rolling resistance, so weight is a minor factor. Generally speaking lighter bikes have narrower tires though, reducing rolling resistance.

A good part of wind resistance is determined by the riding position. There is a reason why road sports bikes use drop bars. A heavy bike with drop bars will probably have a higher top speed than a lightweight with flat or riser bars due to rider position.

A heavier bike has no advantages that I am aware of other than possibly when riding a steep downhill where the added weight could give a higher top speed with the same riding position as a lighter bike. Normal disadvantages include slower acceleration and less maneuverability.

A lot of the feel of a bike has to do with wheel and tire choices. In the days of the Schwinn Varsity there was a saying that "I would rather ride a Varsity with Paramount wheels and tires than a Paramount with Varsity wheels and tires".

Kotts

To elaborate a bit on Paul H's post:

"A lighter bike will be quicker to get up to top speed ..."
"... a heavier bike will take longer to get up to top speed ..."

All else being equal, this is true. The amount of energy required to accelerate a mass is proportional to the mass. More mass = less acceleration for the same energy input.

"A lighter bike ... will take more energy to stay at top speed ..."
"... a heavier bike ... will use less energy to stay at top speed ..."

All else being equal, this is false. Once a mass has reached a certain velocity, the energy required to keep it at that velocity veries with the total resistance it faces. If the heavier bike and the lighter bike have the same aerodynamic drag and rolling resistance, it will take the same amount of energy to keep them at the same speed, once there. However, usually, the heavier bike has worse aerodynamics and more rolling resistance, so it will usually take more effort to maintain the same speed.

In a rolling hill scenario, you might percieve the heavier bike as taking less erengy to maintain speed, because you're carrying more momentum into the beginning of the hill.

"...a heavier bike ... can reach a higher top speed [slowly] ..."

All else being equal, the same top speed will require the same energy. However, as noted earlier, the heavier bike generally will have a lower top speed (for the same energy input) because of increased rolling resistenace and decreased aerodynamics.

"... a heavier bike ... can coast longer."

As long as the aerodynamics and rolling resistance doesn't overcome the advantage the heavier bike has in terms of momentum.

I commute on a brazed-and-lugged steel frame bike that all-in (including change of clothes for work) weighs about 32 lbs. Believe me, I'm a h@ll of a lot faster, and have more fun on my 17lb aluminum bike.

But, speed isn't everything, and I'd probably absolutely hate my commute if I took the lighter bike. The roads are crappy on my commute, and when the road is rough, steel is real (forgiving).

ItsJustMe

First off, I don't care how much my bike weighs. I don't think I'd pay a dime to take a pound off my bike personally.

However I don't think your arguments are completely valid. Weight has nothing to do with maintaining speed. To maintain any given speed, all you have to do is overcome friction, both air and rolling. If you're exactly holding speed, this will be the same on either a 100 pound or a 10 pound bike, assuming the frames have a similar efficiency. It's possible a lighter frame may lose energy because it flexes.

Coasting and regaining speed is a different matter though. A heavier bike will lose speed slower when faced with the same frictions, because it contains more kinetic energy when at speed. However, if you take a light bike at 30 MPH and coast for 30 seconds and it goes down to 20 MPH, or a heavy bike at 30, cost for 30 seconds, and it only goes down to 25 MPH, you'll have to put more energy back into the heavy bike to get it back up to speed, because while the heavy bike used its kinetic energy to maintain a higher speed, at the end of the 30 seconds, it had LESS kinetic energy than the light bike, because it spent more time at a higher speed and therefore losing more energy to the higher wind resistance.

If you just maintain any given speed though, none of that matters.

Likewise, on level ground, a cyclist with a given strength will be able to reach the same top speed regardless of bike weight, assuming they do not tire out before reaching that speed due to trying to accelerate the extra mass, and also assuming that the extra weight does not significantly increase either air or rolling friction. A heavier bike IS likely to have more friction though; typically they will have more spokes, which adds up, and even with the same tires they'll have a little more resistance, and they often will have wider tires.

All that said though, the weight of the bike isn't that significant when you put a 180 pound guy like me, much less a 200+ pound person on top of it. I think it's the 120 pound folks that really like to shave 5 pounds off a 30 pound bike.

jeffpoulin

I once rode an old, heavy mountain bike with 26x2 tires on a 200 mile single-day ride. I've also done the same on a light-weight road (racing) bike with 700x23 tires. Of course, the road bike was much faster, but at the end of the day, it was the mountain bike that proved to be more comfortable, and thus more enjoyable.

For my daily commuter, comfort, reliability, and handling are the most important qualities with total weight somewhere way down the list. Of my two commuters, one is a 90s era touring bike, the other a high-end hybrid that I bought new last year. Neither are very light (22-25 lbs unloaded), but they're both super comfortable, handle like a dream, and "just work". That's what's important to me.

RogerB

I would say, yes, in the same way the weight matters to any vehicle, but the line of diminishing returns is drawn much sooner for the non-racer. The racer--of bikes, cars, or whatever--will pay or do a lot of extra to shave weight to the bare minimum because it impacts so many dynamic factors: acceleration, braking, cornering, and even energy efficiency (important in endurance racing). For the rest of us, lighter weight is a "good thing" for the same reasons, but there is more compromise with other utilitarian requirements: Cargo capacity, stability, durability, affordability, comfort, etc.

crazybikerchick

Weight certainly matters if you have a lot of stairs to carry your bike up/down for storing it daily.

NEXUS

Wow, thanks for all the informative replies guys. Nice explanations Kotts!

After doing some more critical evaluations, I have reached to the conclusion that the weight of the bike does not apply to men like me and maybe 3 or 4 other guys here since the law of physics that states the closer to the speed of light you get, the more energy required to gain the same amount of speed. ie going from 1mph to 2mph uses nearly no energy, while going from "speed of light -1mph" to "speed of light" requires an infinite amount of energy.

nkfrench 

One intersection on my commute I have a stopsign, the cross traffic is very heavy, and they have no stopsign. I really appreciate having a light CF bike that's easier to accellerate before I head uphill across 4 lanes of traffic. I pedal as fast as I can.

In a stiff crosswind I do feel more secure on my steel road bike. The center of mass seems lower and the bike slightly more stable.

Kotts

Nexus, I like the way you think! :-)

I think a lot of the difference is also in how the bike "feels". Both my commuter bike and my lightweight bike are set up the same in terms of "fit", and each is fairly well optimized for its use. As a result, I wouldn't choose to commute on my lightweight, and I wouldn't want to do a lot of my recreational riding on my commuter.

The lightweight bike is completely impractical for my commute, but it's a heck of a lot of fun for recreational rides. Just like I wouldn't want to drive my '77 MG to haul construction materials (not like I could anyway), but for either a romantic drive with my wife or an autocross, I'm not taking a pick-up truck. Sometimes, you just want a "sports car", or its bicycle equivalent.

Or at least I do.

andrelam

Others have already answered you questions regarding weight plenty. I did want to add that quality of components can make a big difference. I've gone on plenty of rides with a co-worker. He tends to ride on the slow side, but we both ride hybrids and we both pedal about the same amount. Last Spring I had my road bike with me and we had to ride about 10 miles to a remote office. On the road bike I was coasting in a regular basis even through I was on the hoods so I was in about the same aerodynamic position as on the hybrid. The hybrid is a descent quality $500 bike. I also notice that I easily average 2 mph faster on the road bike. Sure the road bike weighs at least 15 lbs less than by hybrid, but that means I should loose speed faster (applying the laws of conservation of momentum). The only reasonable explanation is that the components on my road bike have much lower friction, especially the wheels. I noticed that when I replaced my OEM front wheel with a Shimano Generator hub (that has ultegra bearings), that even with the tire on, but the light off that my generator hub wheel ran LONGER on its own once I gave it a push than my OEM wheel. Therefore the OEM wheels had pretty inefficient bearings.

Most lighters bikes cost more than the heavier bikes, part of that cost goes into better componts, from Wheel bearings, to bottom brackets, to deraillers and chains, all those components on a higher end bike = more speed, higher acceleration, and easier maintenance of speed (all other geometry being equal).

I am still quite happy commuting on my hybrid as the components cost less and therefore after a winter's worth of salt, road grit I don't have to spend too much money replacing those bits even if they are not quite as efficient as my road bike.

Happy riding,
André

degnaw

A lot of this may have already been said, so bear with me:

1. A heavier bike doesn't really afford any advantage in downhills;

The force of gravity = mgsinθ, with horizontal force provided by gravity being mgcosθ - plug that equation into F=ma and you get gcosθ=a (since the mass cancels out), so acceleration provided by a hill is dependent solely on how steep the hill is.

2. a heavier bike will provide an advantage in coasting, In theory - in reality, however, heavier bikes typically have more rolling resistance and air resistance, meaning little to no such advantage.

I only weigh 110lbs, so weight is pretty significant to me. That said, i'm not willing to spend an extra $1000 to shave 5 or so pounds off a bike.

somedood

It matters in the same way that a feather falls faster than a bowling ball - aerodynamics. They won't accelerate at the same rate if they have the same amount of drag, rolling resistance, and friction on other moving surfaces.

I like having a relatively light bike so I can lift it up onto the bus rack, on top of the car, on my shoulder etc. I still have the rack and fenders, but if the bike were another 10 pounds I wouldn't be as eager to carry it some of the places that I do.

tsl

In my experience, one pound of wheel weight more than makes up for three or more pounds of overall weight.

I have a 23lb bike with 2100g wheels and a 26lb bike with 1600g wheels. The heavier bike with the lighter wheels spins up much faster and feels lighter and more lively overall than the lighter bike. I can't swap wheels between them because one is disc brakes (guess which.)

Ultimately, I achieve about the same cruising speed on both bikes, but I achieve higher average speeds on the one with lighter wheels due to more rapid acceleration. And more work seems to go into forward motion rather than just keeping the wheel itself spinning (subjective, I know.)

BarracksSi

It really matters when you're climbing...

... up some stairs and carrying it.

NEXUS

what about wind-resistance and weight?