Hot answers tagged

25

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, ...


24

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. ...


24

Breaking the rules with a kind-of non-answer and personal opinion, but... 1) Mountain bikes should be heavier than a cyclocross bike. It's got a suspension fork and frame and wheels need to be beefier to handle bigger loads and impacts. 2) Don't buy a bike with a plan replace major components. Just buy the bike that meets your needs in the first place (in ...


23

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 ...


21

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 ...


21

First things first: A belt is probably slightly less efficient than a properly installed clean chain. The test you link already indicates that. Probably with the tension Gates requires you'll loose a bit more power. On to your question: The chain is 200 grams heavier than the belt, of course with the chain you get gears, which you don't get with a belt ...


21

Most important - Well done in losing weight, what you are experiencing is very normal, don't let it put you off. A word of warning - despite the common perceptions, most people do not lose weight exercising. Their appetite increases to compensate for the the increased calorie demands, this could be what's happening to you. Personally I think focusing on ...


16

Bonking occurs when your body cannot metabolise stored fat (and muscle protein) fast enough to replace the glycogen reserves, you deplete the reserves in your muscles and liver, and eventually you run out of glycogen. Fat conversion requires high levels of oxygen, and is slow, so once those reserves are gone, your blood sugar plummets. I suspect your body ...


15

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 going (...


14

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 ...


14

According to BikeCalculator, assuming you drop 10 kg while everything else remains the same (power output, etc.), you would travel 0.3 km/hr faster over a 50 km ride, on the average. In other words, at 100 kg, assuming an average power output of 150 Watts, you'd average 27.54 km/hr over a 50km ride if you weighed 100 kg; doing the same ride at the same 150 ...


14

The heavier person will present more area to the wind, but this is mitigated by two factors: The bicycle presents a fixed area to the wind and the area presented by the heavier person is not proportional because of the 2/3 power law. If you just scale up a rider by a factor in mass, the volume increases in proportion, but the frontal area scales up as the 2/...


13

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 (...


13

In context of this kind of discussion - weight and cost are the same thing - the more you spend on a bike, the lighter it is (with diminishing returns) and you cannot talk about weight without talking about how much money you have and are prepared to spend (sometimes not the same). The context of this answer is a targeted weight of a 7-8kg MTB. No weight ...


13

Bontrager's Law states parts can be light weight, durable, or inexpensive you only get to pick two characteristics. The only time it makes monetary sense to replace a part with a lighter one is if the component has failed. If you think 3kg. will make a difference between winning and losing try this experiment. Ride a timed course while carrying 2 full water ...


12

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 ...


12

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 ...


12

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 you'...


12

I have carried a laptop on my commute bike for closing in on 15 years now. Mainly in panniers (saddle bags). For a little while in a courier bag when when I was young and dumb. For what it is worth (aka the dangers of anecdotal evidence) I didn't have any laptop failures directly related to a bike trip. I even toured with a 17inch laptop across 800 km of ...


11

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: ...


10

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 ...


10

According to the Weight Weenies.com web site listed weight can differ from actual weight by as much as 10-13%. One thing you should be aware of is there is some variations between identical frames due to manufacturing tolerances. Most weights listed in advertising literature are not for large frame sizes. Looking at the listings on the site it appears that ...


9

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 ...


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 ...


9

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 ...


9

'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 ...


9

The important thing to remember is that on a modern road bike, the frame is actually a small percentage of the overall weight of the bike. This frame, including the fork, is advertised at 3 pounds, while a bike built on the frame weighs in at 16.69 pounds. The frame is only 18% of the weight of the bike. Even if the frame which was a bigger size weighed 20%...


9

The physics model of cycling power and speed has been validated in the real world. Two examples are this and this. The model embedded in Analyticcyling.com's online calculator is based on these two papers. Whether the amount of difference calculated by the validated models is worth it to Joe and Billy is a question that can't be answered by the physics.


8

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 ...


8

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 ...


Only top voted, non community-wiki answers of a minimum length are eligible