Cycling Myth Buster #6 Crank lengths – is longer better?

LoL don’t worry, this is not a R(A) article about length but about crank arms of what you are riding.  We came across several Bike fitting sites, books and they offer some information on Hip Angles and Knee Angles. Thanks to all the articles that cover this.

Most crank lengths are available in 170 and 175mm lengths. This is fine if your inside-leg measurements is on  the long side of average, otherwise it can reduce pedalling efficiency.

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Cranks that are too short do not allow the full leverage of the legs to be used, those that are too long force the knee, hip and ankle to bend more often resulting in slow cadence.

 Extracted from Bike Dynamics  & The Racing Guide by Haynes

Indicators your cranks are too long.

You are the first to get out of the saddle when climbing in a group.
You feel your upper body bobbing?vertically when spinning fast and lightly loaded.
Your transmission occasionally clangs?as you hit a dead spot at the top of the stroke.
Your knees / hips hurt.
Your knees come uncomfortably close to your chest when on the drops or tri bars.

Indicators your cranks are too short.

You feel strong on hills but seem to struggle on the flats.

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A good guide is to apply 20-21% of your inside-leg measurement but bear in mind your saddle height plays a role.  As a guide:

Inside leg measurement(cm)           Crank length(mm)

72-75                                                         155 – 160

76-79                                                         160-165

80-83                                                         165-170

84-87                                                         170-175

88-91                                                          175- 180

92- 95                                                         180-185

After that, adjust your saddle position and see if you can get into the “zone”. Minimum knee angles should exceed 70° to avoid any discomfort issues. It has been captured over time and measurements that  really fast, powerful people have tended to be in a range around 75°.  So anything within the “zone” 74°-77° is ideal.

So for those who want to get optimum knee angles for power, shorter cranks may be the answer to help you achieve that ideal angle but not too short or you lose the leverage on straights… Still with me?

How to Choose Crank Length? Various authorities on this:

So, what crank length is right for you? Just like everything else with bike fitting, some general guidelines exist, but they won’t work for everyone. Formulas for computing crank length (in mm) from height, inseam measurement (in cm), and femur height (in cm, measured from the floor to the top of the femur bone) include:

  • Graeme Obree method: crank length = 0.95 * height
  • “Machine” method: crank length = 1.25 * inseam + 65
  • Lennard Zinn method, upper end: crank length = 2.16 * inseam
  • Lennard Zinn method, lower end: crank length = 2.10 * inseam
  • Bill Boston method: crank length = 1.85 * femur height

 

Cycling Myth Buster #5 Gear range – how does that really work?

A gear range is a set of figures that allows you to caculate the combined effect of a given cassette cog, chainring and wheelsize. This calculation was based on the Penny Farthing bike  where one measured the length of 1 revolution of the front wheel  (see below) and provide a length called X inches of development. Mind you that the Farthing Penny Bikes were very unstable due to the short wheel base and the rider sometimes sitting at a abnormally high position and the your legs peddling forward that actually reduces leverage…hmm reminds you of the A bikes and A design frames with small wheels.

So often for the misinformed,  when they see us on our Minivelos, comments usually are said like  “are you sure you can keep up?” and “don’t you cycle like a hamster?” , “Small kids bike” then have their expression in disbelief when we overtake them with ease.

So how do we do it? In the laws of physics, it is  true, a smaller wheel means you need to peddle more and faster BUT with folding bikes that we range, a bigger chainring ( not to to point where you need tremendous leg power to drive a 75T chainring) gives you the necessary range. You can still get your speed up and peddle at a comfortable pace BUT you need the right combinations.

Let’s do a few baseline understanding.

Gear size (inches)

<40         Mountain and touring bikes

41-50      Hill Climbing

51-60      Lowest gears for flattish course

61- 70     Lowest gears for flat time trials

71-100    Normal gears

>100        Flat out gears

Some Maths formulae.

Chainring size (no of teeth) xwheel diameter(inches)/cassette cog x tread to tread

e.g. (52×26.4 inches) (aka 700C)/14 = 98 inches

So for a Dahon MuEX where they use the top of the  line SRAM Red cassettes, the max range is 55Tx20 inch/11 = 100 inches so now you understand why the MuEX can attain such high velocities.

Even if you take a standard Vitesse D7 or Boardwalk D7 52X20/13 = 80 inches. Most entry level MTBs are using 44T , (44X26/13=88 inches). So you NOW understand why most D7 series bikes actually overtake these MTBs without seeing the rider huffing and puffing away.

Depending on the terrain, but for Singapore where there are  gradual hills and Beginners/Training is usually the initial goal, a gear range from 45 – 114 inches is what you need. ( 52/39 x 12-23). So when you do the specs, you understand why these Flamingos HSF1 and MuP24s can really give you  that mileage.

OK with the ideal gear range…you still need TWO Ls – strong LUNGS and LEGS or all the gear ranges in the world mean nothing.

Cycling Myth Buster #4 Chainring size – is bigger better?

Basics about Chain Rings

Ranges are measured in the number of teeth. For road bikes, the larger sizes are around 52T/53T, going as small as 39T for hilly rides or a 42T in flatter terrains.If you’re riding a mountain bike, you’ll want a slightly different range, of 24T-28T teeth for hill climbing and a larger ring of 46T-50T teeth for use on faster courses. Mountain bikes nearly always have a triple set of chain rings up front; road riders can consider this, too, if their rides tend to be hilly.

Mini Velos or Folding bikes by virtue of the smaller tires compensate gearing range by the use of bigger chainrings so it is no surprise that you will find 53T or 55T chainrings configured on folding bikes.  The bigger chainring actually helps small wheeled bikes attain the same speed without the need to peddle like a “hamster” or “lab mice”. On the contrary,  smaller wheels have the advantage of faster pick up.

Some of the stronger riders have actually configured a 57T or 60T chainring but this is where bigger does not mean better as we are relying on muscle and stamina to drive the transmission, NOT a foot pedal  that feeds fuel to a engine in a car.  You really got have the legs to power such a large chainring.

For those who can settle for a 53T 130 BCD, we have Ovalised Chainrings. Oval-shaped chainrings may not be a new invention, but these days they’re proving more effective than they ever did in the past. Advocates include the 2008 Tour de France winner Carlos Sastre, and the UK’s Bradley Wiggins who finished fourth in 2009. They’re designed to eliminate something known as the dead spot when you pedal.

BMC UK Racing Team’s training bikes are already being equipped with Rotor’s Q Rings to enable team riders to gain the benefit of the rings when training.

General rule

Long rides  and hills – smaller chainring

Acceleration on flats – bigger chainring

Transmission efficiency is also affected by the wheel hubs and BB.

Buying chainrings

Before you go rush out and buy that 55T or 60T chainring. Make sure you check the BCD – bolt-circle diameter It si the Diameter of the bolts that hold the chainring to our crank. It is typically 130 mm or 110 mm

Cycling Myth Busters #3 – Balls of ceramic are better than balls of steel?

This blog is really about Steel ball bearings versus Ceramic ball bearings. Enough has written about this subject but I thought I put together the topics the guys are pre-occupied with. But for those who already burn their wallets swapping out all their existing ball bearings to ceramic based ones – the answer is Yes.

First principles:

Metal balls are rolling, spherical elements that are used in check and ball valves, bearings, and other mechanical devices that provide rotary or linear motion.  For us bikers, it means Headsets, Bottom Bracket, Hubs and Cranks .  Surface Roughness measures the irregularities that form on the surface, but are not significant deviations. Basic diameter Tolerance is the maximum allowable deviation average diameter from the diameter specified.   

Ceramic balls are made from inorganic, nonmetallic materials that are processed at high temperatures. Many ceramic balls are capable of achieving an extremely smooth surface finish to a high degree of tolerance. As a result Ceramic Balls have an extremely low coefficient of friction as compared to Metal Balls. Grinding removes cuts, scratches, scuffs, and other irregularities. Many ceramic balls exhibit much greater hardness than steel balls, resulting in longer life and improved reliability. Ceramic balls can also provide high stiffness, low thermal expansion, light weight, increased corrosion resistance, and electrical resistance. A wide assortment of Silicon Nitride Ceramic Balls, Alumina Oxide Ceramic Balls and Zirconia Ceramic Balls are now available.

Ceramic bearings benefits

35% less Thermal Expansion:
Think of putting a coke in the freezer. You have to allow for its expansion or you’ll blow the tin. Steel bearings are like the tin of pop. Ceramics on the other hand change size significantly less then steel with a given shift in temperature, thus raceways, rings and seals from a typical bearing can be made to much greater tolerances. They can even be fabricated with a smoother finish so vibration goes down and stability goes up.

50% less Conductivity:
Ceramics are electrically NON-conductive, and chemically inert, thus do not suffer from oxidation and the rust that degrades the surface of a traditional steel ball bearing. They suffer less heat damage since they don’t heat up as easily. This helps to maintain the spherical geometry of the ball bearings and significantly reduces your repair time.

60% less Weight:
Since silicon nitride is only about 40% of the weight of bearing steel the savings are obvious. Think about tying a heavy rock to the end of a rope. Its hard to get in motion and hard to stop. The lighter the rock the easier it is.

The issue of bearing weight is the same story. The heavier they are the more effort it takes to get them rolling and stopping. Thus ceramic bearings, with less then half the weight, and thus less rotating mass, will be much more responsive in acceleration and deceleration, with much less effort.

50% Higher Modulus of Elasticity:
that’s just a fancy way to test how easy it is to deform something. Ceramic has a 50% higher modulus of elasticity, so it takes a lot of work to alter its original shape. That gives you a much longer life expectancy in a hard wear zone like a bicycle’s bottom bracket.

Cold Welding:
Steel on steel has a nasty habit of welding itself together, that’s why you use anti-seize on some fittings. In a bearing the lubricate helps to prevent this but when bearings sit over the winter this can happen. Ceramic is NOT able to weld itself to steel. Steel and Ceramic are incompatible in that respect so cold welding is another difficulty you can avoid with ceramic ball bearings.

Research suggests that Bottom brackets equipped with ceramic bearings have a 5-10 times longer life. Industrial literature might suggest ceramics add 3-5 times the life expectancy. Either way we know they’ll be there longer than their carbon steel cousin.

Equally exciting, in tests with Olympic and professional racers and in controlled lab tests with wheels, ceramic bearings repeatedly show significantly less friction, making for faster speeds, acceleration and deceleration with less force.

So whats not to like? Only the price. Ceramic Bearings are easy to justify with longer life, less vibration, more speed but at maybe 5 times the price of traditional bearings the questions still remains as to whether you can justify the added cost?

Approximate values: Silicon Nitride Zirconium Oxide Steel
Density .11 lb/in3 .21 lb/in3 .28 lb/in3
Hardness (Vickers Hardness Scale) 1580 kg/mm2 1300 kg/mm2 700 kg/mm2
Maximum Use Temperature 1000C 1500 C 300F
Corrosion Resistance Excellent
-Chemically inert
  Poor

 

Adapted from various articles from ezinesarticles.com and mywheelsandmore.com

Cycling Myth Busters #2 – Materials for bike frames

Titanium, Carbon Fiber, Aluminum 6061T, 7005, Chromoly Steel, Reynolds Steel. The material of your bicycle frame has a large effect on ride quality and ride feel. The type and quality of material also make up a large portion of the bicycle’s price. The most common frame materials today are aluminum alloys and carbon fiber. Steel and titanium frames are highly popular, as well, but they enjoy more of a cult status with extremely dedicated followers. All frame materials have different levels of quality, and each material has its advantages and disadvantages.

First of all, weight is important. If it weren’t, we would just buy the standard 15-18kg bicycle from ours and Giants of today.

UCI regulations limit a racing bike to about 8kg. But how does this weight difference affect performance? Does removing these few grams make the bike fly? Is a lighter bike the fountain of youth? Some swear by it. But a study done has shown that a lighter bike gives the rider biggest leverage only when climbing slopes! Even when we narrow down to only climbing hills, we are talking about mere 6 seconds per every 500g.

The performance advantage of a lighter bike is greatest when the hill is steepest. What happens as things flatten out? Then, as the speed of the bike increases, the resistance comes from the wind, tire rolling resistance, bearing drag, etc. Those 6 seconds  grow ever smaller. Of course the rider weight plus the bike makes ALL the difference!

The material of your bicycle frame has a large effect on ride quality and ride feel. The type and quality of material also make up a large portion of the bicycle’s price. The most common frame materials today are aluminum alloys and carbon fiber. Steel and titanium frames are highly popular, as well, but they enjoy more of a cult status with extremely dedicated followers. All frame materials have different levels of quality, and each material has its advantages and disadvantages. Before we get into each material, it will help to go over some basic terms:

Aluminum frames
Most of the larger companies use proprietary alloys (mixture of aluminum and other metals) to build their bike frames, and each manufacturer touts their specific brand and the way they use it. Aluminum frames can be more affordable than their counterparts because high quality alloys are easier to procure and manipulate into a quality bike frame.

The main advantage of Aluminum as a frame material is density, meaning for the same volume of material, aluminum weighs less than steel or titanium. This allows bike frame manufacturers to build fatter and, therefore, stiffer tubes that weigh the same or less than their steel counterparts. Another big advantage of aluminum over steel is corrosion resistance. You can ride aluminum in rain and snow and forget about it when you get home, while steel bikes take a bit more nurturing. The disadvantage? Fatigue life. As aluminum flexes and shifts, it fatigues and eventually hits its limit.

Steel frames
“Steel is real” is the mantra of every boutique bike builder and hardcore vintage and classic bike enthusiast in America. While some incredible racing bikes are still built out of steel today, it has lost a lot of popularity in that mainstream venue since the surge of aluminum and, more recently, carbon fiber. Steel has been used in the manufacturing of bicycles longer than any other material.  Steel was originally used in bike frames, no doubt, because of its widespread availability and its long history of use in industry.

The big advantage of steel today is its strength and comfort. The disadvantage in the racing world that goes along with the comfort of steel is its lack of stiffness. Being denser than aluminum, steel frame tubes are generally smaller in diameter than aluminum. Using steel tubes that are as fat as many aluminum tubes used on bicycles would be too heavy for practical use. The thinner tubes flex more and are more comfortable to ride, but they are less responsive in race situations. Fatigue life of a steel tube is nearly twice that of aluminum, so steel bikes can last much longer under heavy use. As with aluminum, steel comes in varied qualities, from heavy core steel that has no place in the bike world (but is used in many big box store brands) to high-quality steel tubing designed for high-end bicycles. Price tags vary greatly throughout the range.

Titanium frames
Titanium frames have enjoyed an even smaller cult following than steel. Titanium offers big advantages over steel in many ways, but it also has its disadvantages. Titanium is twice as dense as aluminum but nearly half as dense as steel. Fatigue life and tensile strength are Ti’s big strong points.

Titanium can be extruded into long, thin tubes that are lighter, more comfortable and stronger than steel. Butted and swaged tubes offer a lot of customization in ride quality and responsiveness, making Ti an optimal choice for a custom-built bicycle frame. Cost is the main disadvantage of titanium. The process of extracting the metal is costly and energy intensive. Ti as a bicycle material is also more labor intensive. It requires more care and more time to cut and weld Ti tubing in a safe, lasting manor. There is virtually no way to build a budget Ti bike. You won’t see these on the floor of your local department store.

Carbon frames
Carbon fiber has become the frame material of choice for bike racers and many recreational riders alike. Carbon fiber is composite laminate made up of tiny fibers suspended into a resin. Carbon bike frames have many advantages and two real disadvantages.

Carbon fiber is extremely customizable. When carbon tubing is made there are many plies, or layers, of fibers that are placed in different orientations that offer different characteristics. Stiffness and flexibility can be manipulated on different planes of the same tube to offer huge advantages over all other materials. Carbon fiber is nearly half as dense as aluminum and much stronger for the weight. So a well-made carbon bike can be built stiffer, stronger and lighter than an aluminum, steel or titanium counterpart.

The biggest disadvantage with carbon fiber is flexible strength and fatigue life. The resin holding together the fibers of the laminate is a very rigid material that doesn’t like to be flexed and bent. Too much flexing causes cracks and fissures in the structure and exposes the individual fibers which aren’t so strong by themselves. This failure of the base structure can cause sudden, catastrophic failure of the bicycle frame. For these same reasons, carbon’s fatigue life is rather low, giving a much shorter lifespan to a carbon fiber bicycle.

The other disadvantage to carbon is price. Carbon is the newest addition to the bicycle industry and is the subject of much research and development. While this R&D spits out shiny new products and features, it also comes with the price tag needed to recoup those expenses.

Information adpated from various authors on bike frames. Ready set go! Let’s charge those hills!

Cycling Myth Busters #1 – Reducing wind resistance

Triathletes have been known to deploy full disk wheels to reduce wind drag. The downside is difficulties in control when you get a cross wind. Did you know that your water bottle and cage adds drag?

Look at this table published in a report – Bicycle and Aerodynamics by Rainer Pivit published in 1990.

Aero Shopping List Approx. Cost Aerodynamic Advantage Time saved over 40 km Costs per % of Aerodynamic Advantage
Part DM % seconds DM/%
Remove water bottle and cage 0 2,8 26 0
Tape over shoe laces 0 0,8 7 0
Pump under top tube instead of in front of seat tube 0 0,8 7 0
Shave the legs 0 0,6 5 0
Remove the small chain ring 0 0,3 3 0
Fill the front tire gap at the rim 2 0,2 2 10
Benotto Aero bottle with cage 30 1,6 15 19
Smooth nylon socks 8 0,4 4 20
Pearl lzumi lycra shoe covers 32 1,4 13 23
Aero helmet. ANSI approved. Bell Stratos. 140 5,2 47 27
Aero front wheel: Araya aero rim,
28 Hoshi bladed spokes,
Dura Ace hub,
Avocet 190 g tire
180 4,8 44 38
One-piece skin suit, short sleeves and legs 180 3,2 29 56
Aero rear wheel: as above, but 32 spokes 90 2,0 18 45
Aero brakes and levers, Dia Compe AGC 300 200 2,0 18 100
Gloves with Lycra backs 24 0,2 2 120
Disk wheel in front 1000 7,2 66 140
Clipless pedals 240 1,0 9 240
Disk wheel in back 1000 3,6 33 280
Cinelli aero bar 80 0,2 2 400
Edco Competition Aero crank set 250 0,6 5 420
Shimano Sante aero Schaltung 320 0,4 4 800

FACTS: Surprising, aerobars did not come out tops for wind resistance reduction but aero helmets, bladed spokes, disk wheels and the attempt to make one as smooth as possible made the biggest impact (so maybe we will start to see more guys wearing i-Fit compression undergarments since teletubbie tights are not available? i-Fit long pant/sleeve compression keeps your muscles tight and limbs smooth and cool under this hot humid weather. Our Number 1 always wears “full” gear

Looks like we will have some team MBS guys

with very smooth shaven legs and arms soon LoL