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23

This research claims around walking 334 kilojoules of energy expended for a 1.6km walk Using the same 1.6km distance, if you cycled at 20km/h at 70watts (arbitrary but vaguely-plausible numbers), you would be involve around 20 kilojoules being "sent to the pedals". Assuming you are about 20% efficient, that would be 100kilojoules burned For that distance, ...


22

Keep your front brake. It does the most work, it will stop you much faster than your rear brake ever could hope to. Take a look at a motorcycle, the front brakes are always much larger than the rear. Whenever you brake, on a bicycle, motorcycle, in a car, more weight is transfered to the front wheels, so the front tire has more traction to stop you with. ...


21

Other than the obvious fact that your better quality (and better handling) bikes tend to be lighter, there's no real correlation between weight and performance (other than a modest effect on acceleration and the obvious effect on hill climbing). But you can generally (with some exceptions) assume that a bike that is quite a bit (like 2x) heavier than others ...


14

The ideal gas law (which is a good approximation in this case) says PV=nRT where P is pressure, V is volume, n is mols of gas, R is the ideal gas law constant, and T is temperature in Kelvin. Thus, solving for n, we see n = (PV)/(RT). Then, assuming air is made up of {gas1, gas2,...} with fractions {p1,p2,...} (so p1+p2+...=1) and corresponding molar ...


12

Obviously the prices seem to support the idea that aerodynamics matter more than a few hundred grams of weight, but at what point does the added weight offset the gain? An exact calculation will depend on the total mass of you and your bike, your speed, the wind, its angle, whether you're climbing, on the flat, or descending, and the speed you're ...


11

It's something that should be experienced. Go grab an old school beater bike (like my old MTB that weighs 35lbs), ride it for awhile. Then, stop by a bike shope and see if they'll let you test drive a nice lightweight bike (usually on the order of 16-20lbs). You'll be astonished at how much more FUN it is to ride the light bike due to the responsiveness ...


11

I worked as a physician (not anymore nowadays, got into medical systems design), and I can guarantee you that either people and health professinals overemphasize the importance of the weight as if it was a single "magic number" regarding health, and it is not. Body fat percentage, cardiovascular endurance, muscle and joint flexibility, dietary habits and ...


11

I had the same issues riding on pre-built 26" mountain bike wheels. I'm 6'5" and weigh ~400lbs, so I break stuff left and right (including frame welds). I have found two things that broke my wheel-breaking streak. The first thing I found was the Surly Pugsley and the Endomorph (or Larry) tires that fit on it. The 26"x4" tires are massive, and absorb any ...


10

The spokes and gears are likely unrelated issues. You have done 2000km on the bike - have you replaced the chain and rear cluster yet? At you weight and those hill climbs, I would not be surprised if they are just worn out. It is also possible that at your weight and that distance the spokes have come out of adjustment, and/or now have fatiguied to the ...


10

The main thing you have to consider at speed is drag: The force F on you+bike (mass m) is: F = ma = mg sin Q - F_d - F_rr where a is your acceleration, g is the acceleration due to gravity and Q is the hill angle to the horizontal. F_d is the drag force which doesn't scale with mass. Try dropping a balloon and a (soccer) football of the same size and ...


9

We can generalize the main areas where one can load weight as such: Front rack vs. Rear Rack High (on top of rack) vs. Low (in panniers) The most commonly accepted points for load distribution are as follows: Keep dense, heavy items low to the ground. The lower you & your bike's center of gravity is, the more easily you can keep yourself upright. ...


9

The rational side of me says that over the short distance you're talking about, walking would cost more energy than cycling. The caveat here of course is how fast you walk. However when I first got back on my bike (and I was pretty overweight), I started off cycling between the train station and my office. It was something like 2 miles each way, and used to ...


8

For commuting, a heavier bike might actually get you overburned if you ride everyday. I have a 18kg bike (full-fledged mtb converted to city bike) and a 10.5kg bike (steel 10 speed converted to fixed). I use both for commuting, depending on weather and mood. Specifically when I carry some stuff on the rear rack (then the bike is even heavier), compared when ...


8

'Bulk' is mostly about whether all of your luggage will fit in your bags. ie is the volume of your luggage less than the capacity of your bags. So it depends on how much stuff you want to take, and how big your panniers are. Aerodynamics doesn't really matter for touring. Unless you are cycling rather fast, or it is very windy. Usually the weight of your ...


7

The answer I got was 2x -- adding one ounce (or gram) to the wheel at the outer diameter (ie, the tread) is equivalent, in terms of force/energy needed to accelerate, to adding twice that amount to the bike frame. The answer was a bit involved and takes careful reading to fully understand, but the answer can also be explained with this thought experiment: ...


7

I'd say no sweat -- the bike can handle you and another 100kg, so long as you don't go off-roading with it or some such. The wheels appear to be 36-spoke and plenty wide, so they can easily handle the weight. The frame is a standard diamond, the strongest design you'll find. No fancy suspension to bottom out or break. Barring a manufacturing defect or ...


7

On a road surface you will be fine - try not to jump any kerbs ;-) Compared to the force when a bike with even a light rider goes over say a pothole or a jump the static load from a 120Kg rider is small. You might want to check the spoke tension reglarly - those are the parts that will suffer most.


7

There are generally two types of dropper seatposts, mechanical (e.g. GravityDropper) and hydraulic (e.g. RockShox Reverb). Mechanical dropper seatposts use a spring to move the seatpost and a bolt to keep it in place. This is a very simple design and there are few things that can break or jam, and the weight is also kept very reasonable since there are few ...


7

You want a geared bike -- not necessarily 50 speeds, but at least 3, preferably 15 or so. If derailleur-style bikes scare you, there are geared hub bikes available (though they tend to be a bit more expensive). (But, honestly, there's nothing to be afraid of with a modern derailleur-style bike, if properly maintained.) If you're only going to be riding on ...


6

There are two main reasons: Hills: Pushing a light bike up a hill is obviously easier than a heavier bike. Everyone likes to brag about that HC climb he did the other day. Without resorting to lying about actually climbing the hill, the easiest way for a cyclist to make his life easier is to carry less mass up the hill. Nobody will say, "That didn't ...


6

To calculate the weight of a gas you need the volume, pressure and temperature. A bike tyre is a torus (doughnut) with volume given by the formula: V=(πr^2)(2πR) where R is the radius of the wheel and r is the radius of the tyre. For a 700c25 tyre, R will be 311mm and r will be 12.5mm that gives a volume of 9.59×10^5 cubic millimetres or 0.000959 cubic ...


5

I am a big guy. Usually 230-270 lbs. (Alas currently at the high end). I feel your pain. My solution has been to get a 32 or 36 hole hub and rim, with the heaviest gauge spokes they make. Once you go to this level, it is 'heavy' and light weight racers will point and mock you, but it will stop breaking spokes. Until I did this on my two regular road ...


5

I have the same bike, and have done a little loaded touring (though not recently, as my health no longer permits it). I find that keeping the load low and balanced is the key. On the front it's important that the load be tightly attached, since if it is loose at all it will tend to wobble and resonate and can make the bike unmanageable on a rough surface. ...


5

I am continuously amazed at the overemphasis placed on the weight of bikes. Yes it is important, but relative to other factors in deciding which bike to buy it is not that significant. Lets compare a 20lb bike to a 24lb bike. If your budget is $1000 for a new bike, would you choose a 20lb bike with very good components and a so-so feel/fit, or a 24lb bike ...


5

This is an extremely bad idea, and it may or may not be illegal where you live. It's pretty common for the law to require you to be able to lock up both wheels on flat dry pavement. Regardless, both brakes are important, and you shouldn't remove one for something a silly as weight reduction. The contact patch on your tires is small enough already without ...


5

Roadies are concerned about weight because they believe that lighter bicycles go uphill faster for the same effort. This is obviously true (it's simple physics: the energy required to lift a mass m a fixed distance against gravity is proportional to m), but how much difference does it actually make in practice if you're not racing up mountains? Let's ...


5

There are two problems with your assumptions: You appear to be assuming that the rider is on flat ground but neglected to mention that. The assumptions that the rider is traveling at high speed with few corners and stops doesn't reflect real world conditions. When riding hills, weight is a huge concern because of gravity, as others have mentioned. Quite ...


5

The two major "drags" on a bike, on level ground, are the rolling resistance of the tires and the wind resistance of the bike and rider. In general, up to a point, a tire with higher pressure will have lower rolling resistance, as will a tire with a smoother tread. Tire width also figures in, but mostly in terms of how it influences pressure and tread. ...


5

There is no need to have equal tires on both wheels, except for aesthetics. Just make sure that front tire has enough grip so you can remain in control. As for getting pinch flats - make sure you mount tubes correctly and they are not trapped between tire and rim. Having high pressure should help you avoid pinches. More durable tire will help with ...


5

According to Wikipedia, Gold has an "ultimate tensile strength" of 100 MPa, while steel runs from 400 to 5000. (Carbon fiber laminate is 1600.) Gold has a specific gravity of about 19, while steel has a specific gravity of about 7.8. So it would take about 4 times as much pure gold by volume, or about 9.7 times as much gold by weight. A 15 pound steel ...



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