Does weight matter?

The basic phisycal equations for the forces on a bicycle rider show that weight has almost proportional effect on the power required for cycling. That is: the required power is greater by the same percent as the percent weight increase of the rider+bike+luggage combination. Interestingly, this fact is the basis for the conclusion that weight doesn't really matter that much: if I weigh 75 kg, my bike 15 kg and my touring luggage 20 kg (a total of 110 kg), then even if I manage to reduce my luggage by 50% (10 kg less - a very difficult task indeed), it would still mean just 9% gain in power. Why then bother with it at all? Well, there are several reasons why light weight might be prefered. I can think of the following:

- The fatigue life.
- The simplicity.
- The effort.
- The lifestyle.
- The elegance.

The fatigue life. Weight has large influence on the material of the bike and other equipment. Metals fatigue roughly with 3rd power of stress - and stress is proportional to weight. 5% decrease in weight, for example, results in 16 % increase in fatigue life of the equipment. 20 % decrease in weight = 73 % increase in fatigue life. By reducing the weight one then considerably reduces the likelyhood of equipment breakage. This is the primary benefit and the one that made me go the light way. The stories about cracked rims and broken racks are almost without exception told by 4-panniered heavy-duty tourers. By the way, it seems logical that the weight has similar effect to the body fatigue. The body can heal, of course, but it requires energy to do so.

The simplicity. Simplicity is freedom. And freedom means simplicity. They are the same thing. With each thing less you are more carefree. I remember one occasion when I bought a wooden carving in Zimbabwe. From the moment when I purchased an, otherwise outstanding sculpure, I was in a constant worry. How will I transport it on a bike? How will I protect it from the rain? What if they stole it from my tent? How will I take it on the plane trip back home? Will they accept it as hand luggage? And if not how will I package it? These worries made for some miserable nights until the return trip and a 2 kg statue on the the rear rack resulted in a couple of broken spokes (on otherwise already weakened back wheel).

The effort. As said above, you need more power to cycle with heavier setup. 9 % more power may seem negligible with respect to the comfort that you're supposedly throwing away. It is a matter of preference: is it important to you to make 10 or 15 km more each day? Or you can cycle the same distance, feel much less tired and have more time in enjoing your rest. Far more effort (in terms of percentage) is saved when you have to carry or push your bike: in this situation your body weight doesn't enter the equation and the effort is proportional just to luggage (and bike) weight. In fact, body weight should not have the same impact as luggage and bike weight. Heavier people are usualy stronger and can produce more power. It is somewhat misleading or "unfair" to compare lugguage weight of differently strong people. But if we take out the body weight from the above equations, then reducing the luggage weight by 50% makes a 29% gain in power, instead of 9%. The real percent gain is somewhere in between.

The lifestyle Cyclists like to think of themselves as ecologicaly superior to motorists. By the same line of reasoning lightweight touring is superior to loaded touring. A couple of years involved in reducing the luggage weight had changed my view on many things, unrelated to cycling. I became aware of many redundancies in our everyday procedures and behaviour.

The elegance Obviously this is a subjective thing, but a light setup on an elegant bike, preferably set in some spectacular natural environment, is a real pleasure to my eye.

The clipless myth

To start right from the middle: I don't like clipless system. The fact that I broke my arm in a low-speed fall because I failed to unclip may have to do something with this position, but it's not the only reason.

Efficiency. I heard claims that clipless system greatly improves cycling efficiency - there were numbers as high as 20%. I was skeptical, so I did my own measurements in a real-world road-cycling circumstances. I was more then disappointed. I measured average speed on two loops of fixed length (60 km and 85 km) with and without clipless system, all the other factors being the same (i.e. the same bike and clothes). The average difference (averaged over 2 and 6 rides) in average speed was less then 0,5%. On one of the sections it was in favor of clipless system, on the other section it was in favor of plain pedals and shoes. The difference was smaller than the difference in individual rides within one system. Thus, my measurements doesn't show any statistically significant advantage of any of the system.

Safety. All clipless advocates confess that falling off is part of the learning process. What they do not tell is that you will damage your bike in that process and that an injury is a real possibility. My quick search through the net revealed only 4 voluntarily reported injuries caused by clipless system. When talking to the people after my accident I got the impression that they are much more common - even my physiotherapist had broken the arm. There seems to be a high degree of self-censorship, self-guilt (e.g. "it's MY fault that I couldn't unclip") and the dread of being scoffed at by the "pro"'s.

The feel. Nothing is life is all bad or all good. I liked some aspects of clipless system, especially "the feel" and "the look". I suspect that these are the main reasons for its popularity. As for me, I am not going to risk another 2 or 3 months of rehabilitation, just to stay within the "cycling mainstream". The proper cycling technique and a positive feel that your foot is not slipping on a pedal can be trained and learned, without any disadvantages of restrained feet.

Every so often I read and hear people comlaining about some additional aspects related to the clipless system: pain in feet, ankles or knees due to restricted movement, water seeping in through the holes in the soles, cold sensation due to heat transfer through the cleats, sorenes in the feet due to pressure in the cleat area, awkward walking, the need for a second footware on a tour. The general consensus, however, is that the benefits of the clipless system override any disadvantages. But what exactly are these benefits? Have they ever been proven in an authoritative research? I know of a few reasearches regarding this issue (link here) and according to them the benefits for a non-proffesional cyclist are so slim (*), that I can only conclude that clipless system is just another market gimmic with huge turnover, exploiting people's urge to follow the fashion.

(*) What this abstract says is: Shoe-pedal interface (flat pedals vs. clippless pedals) does not influence cycling effectiveness during normal (submaximal) exercise. Only an active pulling-up action on the pedal during upstroke increases the pedalling effectiveness, while reducing overall efficiency. It is, really, pretty logical: yes, when you pull up, you will be quicker, but you will loose more energy then if you didn't pull up. So, in brief, there is no free lunch; in fact, the clipless lunch is more expensive.

Repair tips

Some of us like to have our bikes in perfect order, no ticking, skipping, squealing. Here are some things that I learned over the years, by experience or from the net.

1. Tyre wear at one spot can be the result of a bent or untrue rim. When the bent part of the rim hits the brakes, the part of the tyre which is at the contact with the ground at that instant skips. As this is
   always the same point of the tyre (unless you are rotating it regularly on the rim) it will eventually wear out and blow. The thing happened to me in Kyrgyzstan, the explanation is Sheldon Brown's.
2. Broken brake cable usualy doesn't happen unexpectedly. The individual wires in the cable break first with a warning sound that can be heard, and which usualy happens after a sudden squeeze of the brakes. Check out the cables when such warning comes.
3. When breaking the chain the pin should not be extruded completely. If this happens however, you can hammer it back by holding it with some narrow tool. Needle plies are the best, but a piece of wood with the hole in it might do as well. The stiff link is loosed simply by bending the side plates of the adjacent links.
4. If you feel a bump every wheel revolution and the rim is true, it's most probably a tyre bead that is unevenly engaged in the rim or is even pinching the tube. It may also be due to the damaged tyre sidewall.
5. If the chain stucks in the deraileur seemingly unrelated to the revolution of the cranks, check out the side plates of the chain - they may be broken.
6. Ticking in the handlebar most likely comes from a stem/stearer connection. Grease every part of this connection, including bolts, and tighten.
7. Ticking in seatpost. Check if your seat tube has a metal shim between the tube and the seatpost. Grease all the surfaces that come into contact (shim/seatpost, shim/seat tube).
8. Squeal in the rear derailleur during shifting. Oil the axis of pulley wheels.
9. Ticking in the crankset area. Could be number of things. Check out the simple things first: oil the pedals; tigten cranck bolts; see if cranck is not hitting the front derailleur cable; make sure the sound is not coming from your shoes. The sound could be comming from loose saddle or seatpost.
10. Cracking sounds unrelated with pedal or wheel revolution. When the spokes are too loose they can slip at the points where they cross each other. Happens both when seated or not, holding handlebar or not. Can't happen on radially laced wheels.
11. Squeel when turning the handlebar. Break/shifting cables are fretting in cable stops - oil the cable stops. Cables may fret one against other - tie them with tape.
12. Rattling when going over rough surface. It can be caused by anything that is attached to the bike (bags, lock, pump, water bottle, ...) or anything loose in the bags. If it happens on "naked" bike: check the headset for looseness; check that the shifting or braking cables are not hitting each other.
13. Unusual sounds. Deal with them by eliminatig possible causes one at the time. Is the sound present only while turning pedals? Only while seated? Only while riding a bike (i.e. not when turning the wheel by hand)? Only when holding the handlebar? Only when peddaling forward? Only with bags attached?
    With each crank revolution? With each wheel revolution? Sounds may not necesarily come from the bicycle - check the panniers, racks, shoes, things in your pockets.
14. Derraileur adjustment is most easily done when the bike is turned upside down. Just check visually that the pulley wheel runs in the middle of the cog.
15. Rim wear can be drastically reduced by using quality brake pads. The sand particles will embed quickly in most of the ordinary pads. This will act as sand paper, chipping off bit of rim material, which will in turn embed into the pad rubber, resulting in even more wear. Use best pads you can get:
    Kool-Stop pads are the best.
16. Brake squeal is reduced by proper toe-in of the brake pads and sand-papering the rim.
17. Cleaning the chain on the road. Find a piece of rug by the side of the road. Start by cleaning the pulley wheels. Then clean the front chainrings. Then start cleaning each chain link: shift the chain to the big front ring and clean the links as they go around the front ring teeth. The chain is not flexing there so you can clean it using one hand only. (This is one operation where I would not agree with Jobst Brandt
    and prefer to do it with the bike upside-down.) Then oil the chain: dip the end of a toothpick into oil and put one drop of oil in the roller/sideplate gap of each chain link. Wipe excessive oil.
18. Carbon forks have a bad reputation for touring. I don't know why. I cover mine with electric tape or with bubble wrap as a protection from scratches. So far, it worked rather good.
19. Low pressure is bad. Among other things it can result in cracked tyre sidewall.
20. Tips about reducing probability of punctures are given elsewhere.
21. If you don't have the appropriate tool try to improvise. Imagine what the procedure would be like if you had the tool. Think about the principle of that tool. You may find a simple substitute that has the same principle.

All you never wanted to know about punctures

To unacquainted rider punctures come as incomprehensible random events which generally follow Murphy law of happening at the worst possible moment. We will however try to put a trifle of rationality in it, hoping at the same time that vicious Puncture God doesn't take this as a heresy.

First of all - as heretical as it may sound - every puncture has its cause. This is the founding axiom of puncture science and the most important concept for puncture-free experience. If you have a puncture for which you don't know the cause, you will have lots more of them - and rightly so, since you didn't make an effort to understand it.

The causes of punctures can be separated into two types:

1. external puncture is caused by an external object first protruding through the tyre and then puncturing the tube.
2. internal puncture is one that is not external.

Within these types there are variations. We further subdivide punctures as to get a list of every possible puncture cause known to man, woman or child. The following causes are ordered from most likely to least likely cause, based on my experience.

1. external punctures
1. external object embeds into the tyre and punctures the tube after several wheel revolutions.
2. external object protrudes through the badly worn tyre, punctures the tube
3. external object is pushed through tyre and the tube deliberately.
4. external object protrudes through tyre and the tube within one wheel revolution.
2. internal punctures
1. "pinch flat" or "snake bites" when a tyre presses against the tube, mostly when hitting a rock or a pothole.
2. tube punctures near the valve facing the rim.
3. tube protrudes through the valve hole and blows out.
4. tube rubs against an object caught between the tube and the tyre (eg. piece sand, shreds of rim tape, etc.).
5. tube punctured with a tool when installing it on a rim
6. tube protrudes through the fault in the tyre and blows out.
7. tube is pinched between the tyre bead and the rim and blows out or punctures.
8. deliberately deflated tube (this is not a puncture, but looks like one).
9. tube patch peels off
10. tube patch cracked
11. spoke is too long and punctures the tube from the inside
12. tube rubs against a fault inside the rim, or against the rim tape.
13. tube rubs against a fault on the inside of the tyre.

More often then not you can tell if the puncure is external or internal, or even its subcategory, by a
little forensic study. Use the following procedure:

1. Before removing the tube from the wheel mark one matching point on both the tyre and the tube. This step is not necessary if you've installed the tyre and the tube correctly (see points 13, 14 and 15 below for installation).
2. Before removing the tyre look if there are pieces of sand, etc. inside it.
3. Look if the puncture is at the inside of the tube (the surface facing the rim). If it is, it's an internal puncture.
4. Examine the rim and/or the tyre at the point that matches with the point of the puncture in the tube. You are likely to find the cause of the puncture at this point. If you don't find it there, go all around the tyre and/or the rim looking for one.
5. Some punctures (a.2, a.3, b.1, b.2, b.3, b.6, b.7) have no physical evidence of the cause, but some
   can be identified by the position or appearance.
6. Type a.2 punctures usualy occur on a very worn tyre thread (eg. so that tyre fabric beneath is showing or if there are a lot of cuts and cracks in the thread). The thread is so thin that the item that punctured the tube (a sharp piece of stone, glass) will not embed in the tyre and will fall off. Changing the tyre is the best remedy.
7. Snake bites (b.1) are often in a form of double holes about 4 mm apart.
8. b.2 and b.3 type punctures are at the base of the valve. b.2 punctures are frequently caused by high-pressured tube pressing against the nipple head on single walled rims. (See the solution below).
9. Some punctures (b.2, b.3, b.6, maybe b.7) can happen when the bike is not in use (e.g. overnight).
10. A minuscule, slow leaking puncture on the side of the tube is representative of a needle pinch (a.3)
11. Blowout type of punctures (b.2, b.3, b.6) deflate the tube immediately. b.3 and b.8 leave large holes.
12. External punctures of type a.1 are often slow leaking.
13. Rubbing-type punctures (b.4, b.12, b.13) are also slow leaking, at least in the first stage when the tube develops small sracks in the rubbing area. Eventualy these cracks join into a bigger hole.
14. If you can't identify the cause, record the circumstances for further analysis. If a puncture is particularly mysterious, send the details to me, I am collecting such data.

The good news about the punctures is that most of the type b punctures are avoidable. With little care, most of the type (a.1) punctures are avoidable too. Replacing the excessively worn tyre usualy gets rid of the (a.2) punctures. So only with the type (a.3) are we in the mercy of Puncture God, which in this case frequently takes the form of a common man. My advice to puncture-free experience is the following:

1. Pump your tyres to high pressure. Check and keep the pressure high at all times. Recommended pressure on the tyre sidewall is high enough. If pressure range is indicated, go closer to the higher value. I don't believe in benefits of reduced pressure (e.g. higher traction, softer ride).
2. Always find out the cause of the puncture and remove it.
3. Check both tyres regularly for embedded bits of glass, wire, etc. Do this before or after every ride at home and at the start/end of the day on a tour. I always keep a safety pin on my jersey to pick out the bits from the tyre.
4. Do the above check immediately if you ride through pile of glass, etc.
5. Do the above check immediately if you hear the sound comming from the wheel at each wheel revolution.
6. Do the above check always after a puncture unless you are absolutely certain it's an internal puncture.
7. Don't use any tapes between the tyre and the tube - at least not as a permanent solution.
8. Use rim tape.
9. Change the tyre when its sidewall is cracked. As a temporary solution make a tyre boot (duck-tape worked for me).
10. Change the tyre when its thread wears so much that the tyre fabric beneath is showing. As a temporary measure put a piece of duct tape over these parts.
11. Few things are important when patching tubes: clean the tube with sand paper before applying rubber cement; let the cement dry before applying the patch!!; press on the patch for 3 minutes; remove the plastic cover from the patch after few hours.
12. Inflate the tube slightly before puting it inside the tyre.
13. As a protection against b.2 and b.3 punctures, cut a patch of an old tube and slide it down the valve, so that it covers the valve base (about 2 cm of tube left and right from the valve). Cut a notch on one side of this patch, let's say on the left side.
14. Most tyres are marked by the manufacturer and brand names only on one side. Install your tyre so that the valve hole is at the middle of this mark and that the mark is on the QR side of the wheel (or on the opposite side, according to the drive direction marked on the tyre).
15. Put the tube inside the tyre so that the notch mentioned in #13 is to the left when you are facing the tyre mark mentioned in #14. This fixes the relative positions of the rim/tube/tyre combination and hepls in finding the cause of the puncture.
16. Refrain from using any tools for mounting the tyre on the rim. If this can't be done, it's time to think about different tyre.
17. With the tube partially inflated go around the tyre and check that the tyre bead doesn't pinch the tube against the rim.

Calibrating the bicycle calculator

I noticed that my bicycle computer is rarely as accurate as are road markers - usualy it shows few percents more. I was pretty sure this is caused by a wavy bicycle path - until I did some calculations. Let's look at this more closely.

Question: What distance will be recorded on a bicycle computer on a straight, flat 1 km path if you cycled in a zig-zag fashion, swerving away from the middle line for 10%, lets say a=1 m every L=10 m (i.e. 1 m to the left after 10 m, 0 m after 20 m, 1 m to the right after 30 m, etc)?

Lets denote a pecent of off-center deviation as f=a/L. Then, instead of every straight L meters you are doing L1=SQRT(L^2+a^2)=SQRT(L^2+f^2L^2)=L*SQRT(1+f^2) meters. Your path is longer for k=L1/L=SQRT(1+f^2) (in percents). So, for f=10% off-center deviation your path is longer for k=0.499 %. In 1 straight km you are doing 1.00499 km or 4.99 meters more.

The point of this is to show that inaccuracy of the calculator due to the oscilating path of the wheel is negligible (0.5 % for off-center deviations as high as 10%). Manual instructions for calculator set-up are typically innacurate up to +3%.

Steel frame is softer than aluminium one?

Modulus of elasticty, brittleness, strength, stiffness, elastic limit, are standard terms of the theory of elasticity. They are, however, more often than not misinterpreted when used in "technical" debates about bicycles. Many times they are abused as a "scientific evidence" of some natural feel like: "steel is softer then aluminium". Softness, by the way, is not a standard quantity in the theory of elasticity. It can be interpreted as a reciprocal quantity to stiffness. The measure of stiffnes of a material is its modulus of elasticity, or Young modulus, E, which is defined as a ratio of stress vs. strain. In that sense the common bicycle myth that steel is softer than aluminium is a total nonsense. It is not true that steel has relatively low modulus of elasticity, i.e. is a "soft material". In fact its modulus of elasticity (Young modulus) is the highest of all commonly used engineering materials: it is 210 GPa, which is 3 times greater than aluminium (with 69 GPa), 1.75 times greater than titanium (120 Gpa) and at least 1.4 greater than carbon fiber (150 GPa). You can find these figures in a table on Wikipedia page: http://en.wikipedia.org/wiki/Young%27s_modulus. Steel is the stiffest material to make a frame of, unless you are considering a tungsten or a diamond one.

It is perfectly OK with me if someone feels a steel frame to be softer than aluminium. But please don't try to prove this by misinterpretation of some half-understood theory.

P.S. I am not a "steel-hater". Steel is the best engineering material for most applications because of its strength, stiffness, ductility, fatigue strength, weldability and price - but certainly not because of it's softness.

Why is riding in mountains slower than on flat ground?

It may be obvious to most of you, but it wasn't to me. After all, there are always two sides of a mountain. While you are slower going up, you are much faster going down. The average should be equal to riding on flat. Hmmm, this calls to some math.

Let's say we are riding up and down a symetrical hill of road length 2S. We cycle up with average velocity v1 and go down with average velocity v2. The up and down parts have equal length S. What is our overall average speed v?

The enticing answer is v=(v1+v2)/2, but, as you may presume, the world is not that simple. Combining the formulae: v1=S/t1, v2=S/t2, t=t1+t2, v=2S/t, we have: v=2S/t=2S/(t1+t2)=2S/(S/v1+S/v2)=2/(v2/v1v2+v1/v1v2)=2v1v2/(v1+v2).

So the answer is: v=2v1v2/(v1+v2) and it's independant on length S. For example, if you climb with 10 km/h and descend with neck breaking 70 km/h, your overall speed is not 40 km/h as you might have wished, but only 17,5 km/h, as you will find out looking incredibly at your computer at the end of the downhill. The only reasonable way to increase the overall speed is to climb faster. If you climbed just 50% faster, with 15 km/h instead of 10 km/h, then the overall speed increases to respectable 24,7 km/h. If, instead of climbing half faster you descended twice faster, i.e. 100% faster, at the world record breaking 140 km/h, your overall speed would still be miserable 18,7 km/h.

The point of this story: instead of risking your neck at speeds where there is no margin of error, beter have an ultralight pack which will enable you to climb a little faster.

We'll make some more use of mathemathics. We first express climbing speed as a percentage f of descending speed, v1=f v2. The average overall speed is then v=v2 2f/(1+f), as compared to intuitive (and wrong) average speed (v1+v2)/2=v2(1+f)/2. The difference, together with the ratios of climbing/descending speeds from the above example (10/70, 15/70 and 10/140), is indicated in the graph.