Terry Peloton

Author: tpbWPadmin

  • It’s Not About the Wheels

    Recently I read a forum posting in which the writer stated she preferred 700c wheels to 650c wheels because she sat higher on the bike and felt more on a par with riders around her. She may have felt this way, but it had nothing to do with wheel size. Something else was going on.

    On first take, you might think the larger the wheel, the higher the bike. Seems logical, but it’s not. Whether a bike is being designed around 700c, 650c, 650b, 24″ or 20″ wheels, there’s one dimension that usually doesn’t change much — the bottom bracket height. It’s the distance from the ground to the center of the bottom bracket, the “central movement” according to the Italians. It’s where the crank arms meet the bicycle.

    So why is the bottom bracket height important? Well, if it’s too low, you’ll scrape your downside pedal when you’re cornering. Not a safe situation. If you have really short crank arms on your bike, the bottom bracket height can be lower than it would be on a bike with long crank arms. If the bottom bracket height is too high, your center of gravity will be high and the bike won’t feel stable in turns. Mountain bikes used to be built with very high bottom bracket heights to clear debris on the trail.

    Back to our rider. Assuming she had the same fit on both bikes, then she was using the same crank arm length on both bikes and therefore, the distance from the pedal to the top of her saddle was the same. If the seat angle was the same, then the distance from the ground to the top of the saddle was identical on both bikes. So her hips were in the same place on both bikes.

    How about her upper body? Again, if the “cockpit” fit identically on both bikes, her reach to the handlebars was the same and the vertical distance between the seat and the handlebars was the same. So her upper body was in the same position. In other words, she was exactly the same rider in exactly the same height/position on both bikes.

    Here are two drawings showing our hypothetical rider on bikes with 650c and 700c wheels. The distance to the saddle from the pedals is identical as are the “cockpit” dimensions. Two drawings are worth six words: “it’s not about the wheel size.”

    So why does this rider feel taller on the 700c bike? Well, one reason might have to do with the seat angle on the bike. If the 700c bike has a steeper seat angle than the 650c bike, she will ride higher in the saddle. Imagine a 90 degree seat angle: she would be sitting really high! There are a lot of 700c bikes for women built with steep seat angles in order to make the top tubes shorter, so that might be one of these bikes. (Not the right way to do it, by the way…)

    Or perhaps she’s riding with different “cockpit” dimensions. If the reach to the bars is shorter, the stem is shorter and/or the stem is taller, she will sit more upright. Taller in the saddle. And back to the bottom bracket height — it may indeed be higher on the 700c bike.

    Lots to think about here. One of the most important is that wheel size is one of many tools available to bike designers so we can give our riders the best fit possible. The bike is a wonderful work of engineering and art whose pieces are remarkably intertwined — as much with each other as they are with you, the cyclist.

    Tailwinds,

  • Saga of the Stuck Seatpost

    If you followed my recent tweets, you know I was obsessed for a while trying to remove a stuck seatpost from one of my favorite rides, “Moo”, a 22 year old hybrid. Last summer, I designated this winter as the time when Moo would shed her tired 7-speed components for something a little more up-to-date. Everything was going according to plan as I tore her down — until I got to the seatpost — which wouldnt budge. What followed was an excursion into part stubborn, part “Im not going to give up on this bike after 22 years”. In the end, everything worked out. The seatpost, in pieces, came out and I experienced a moment of euphoria not unlike Lindsey Vonn’s when she won the gold.

    Googling “stuck seatpost” directed me to several good posts, in particular, Sheldon Brown‘s and Lennard Zinn‘s. I exhausted the “easy” solutions first and quickly found myself with hacksaw in hand. My blog, complete with color glossy photos, will tell you how I finally extricated the seatpost. And you should read it before you read the rest of this so things will make sense.

    Sometimes you learn as much after an experience like this as you do when you’re in the thick of it. I continued to snoop around the web and talk to some bike mechanic friends about it. Was hacksawing the only way to remove the seatpost? And how did that little 2 mm ribbon of aluminum corrosion around the base of the seatpost lock it in so tightly given that the steel seat tube was very clean, only showing some slight oxidation on its surface?

    Some of the best information I found came from Jobst Brandt. I learned that aluminum oxide (corrosion) has more volume than aluminum that has not corroded. So it was as though a larger seatpost had taken over my bike. Like cramming a slightly oversize round peg into a round hole. This explained why the CO2 cartridges didn’t have much effect. The cold temperatures caused the seatpost to contract, but it just wasn’t enough to overcome the effect of the corrosion.

    Brandt also mentioned that some shops will Dremel out the seatpost. I think that would require the same kind of finesse with the Dremel tool as it does with the hacksaw. I also wonder how this would work with a long seatpost, like the 300 mm variety so commonly found on bikes with sloping top tubes? In retrospect, that was one thing I did right with my seatpost. When it was new, it was 300 mm long, but I cut it down to 220 mm since I couldn’t see why I should carry around all that extra seatpost when I wasn’t using it.

    One of the more interesting concepts on removal came from a friend who spends a lot of time at Kraynick’s Bike Shop in Pittsburgh. He prefers to pull the seatpost straight out of the seat tube. To do this, he’s designed a tool that “hooks” the bottom of the seatpost. Using the top of the seat lug as a platform, he slowly winches the seatpost up:

    “I used a length of threaded rod. At one end I put two nuts and tightened them against each other. I took a deep 3/8″ drive socket and cut slits through the socket wall from the nut-engaging end and down about two-thirds of its length. Then I heated and bent the tangs slightly outward. The tangs catch the bottom rim of the seat post but don’t scar the inner surface of the seat tube when the rod is installed. I bored out the square drive hole to a loose fit over the threaded rod and slid it on. I put a pin in a hole drilled through the socket base and the threaded rod. I cut the seatpost off beneath the seatpost clamp and tapped the threaded rod and s ocket assembly into the seatpost. The tangs were bent enough so that they could spring out and get purchase on the underneath of the post. A piece of tubing was put over the the threaded rod and cushioned and rested on the seat tube lug area and a washer was added to create a platform against this tube. Screw on a coupling nut about 1″ long and begin tightening it…”

    Photos to follow, I hope!

    Okay, if you’ve read this far, you’re probably thinking to yourself, “I hope this never happens to me!” Just make sure your seatpost is greased and check it a couple of times a year to make sure it moves freely. That’s all it takes.

    Tailwinds,

  • The Tale of the Beater Bike

    Recently, I received an email from a customer inquiring about “step through” frames. Often the need arises from a physical disability, a lack of flexibility or the need to achieve that certain comfort and confidence level that only a step through provides. As we exchanged emails, I learned a lot about bike design, thanks to this customer’s curiosity and engineering nous. I thought it would be helpful to share this wealth of information.

    The Problem:

    A small rider (4’11” – 5′ tall with a 25″ inseam) wants a bike with a step through height no higher than 16.5″. Since she’s returning to cycling after a 30 year hiatus, she has to re-learn the sport. The goal is to participate in a 50k race at least once a year. But for now, she needs a bike on which she can reintroduce herself to riding.

    Unraveling The Problem:

    We could build a custom bicycle for this customer, but as she investigated her options, it seemed to her to make more sense in the short term to try to find a beater bike she could use as an intermediate step to a bespoke solution. The beauty of taking this path is that it allowed her to determine what the geometry of her ultimate bike would look like. What better place to start than the local pawn shop?! I’m sure this little Gary Fisher bike thought it had died and gone to heaven when it was rescued from a life of curb jumping.

    One of the first issues to deal with was the seat tube length and the crank arm length. She reasoned that given her 25″ inseam, a custom bicycle with a 43 cm seat tube didn’t leave much left over for the seat height and the reach to the pedals. Worst case, if she couldn’t lower the saddle enough, her hips would rock as she pedaled — not only uncomfortable, but inefficient as well. At this size, there is clearly a relationship going on between choosing the right seat tube length and the right crank arm length.

    The Fisher came with 162.5 mm cranks, but they felt too long when it came to getting re-acquainted with balancing and starting up the bike. After all, skills need to be refreshed after 30 years! The solution was crank shorteners. These aren’t hard to find and are often used on tandems to accommodate a child’s shorter legs.

    By trying different crank arm lengths, she was able to find the one that let her gradually acclimate to the feel of starting up on the bike. As she became more comfortable with this, she was able to lengthen the crank arm. Because of some physical limitations she has, the final crank arm length may end up being more a function of what works best for her rather than what the rules say about crank arm length.

    For that matter, the rules seem to be perpetually in flux, depending on whose study you’re reading at the time. One study has indicated that the optimal crank length is 20% of leg length and that most adults are fine with the ubiquitous 170 mm crank. In response to the concern that what applies to “average” adults may not apply to those with smaller legs, the same study done with 8 – 11 year old boys also supported the use of the 170 mm length.

    A July, 1982 Bicycling article by a former research engineer at Schwinn Bicycle Company matched up leg length and riding style to determine optimal crank arm length through use of a nomograph. The author focused on “pedal feel”, which depends on crank length and crank rpm. Much like wheel size, crank arm length is not hallowed on its own, but part of an integrated system.

    Dig deeper into the research and you’ll learn about pedal speed (the velocity of the pedal and your foot) and pedaling rate (the revolutions made in a certain period of time) and how these tie into muscle excitation states.

    Also of interest is the bottom bracket height on the beater bike — at about 10.8″, it’s on the high side when compared to sports bicycles, which are typically around 10.2″ or 10.3″. (The bb height is the distance from the ground to the center of the bottom bracket — the “central movement”, where the crank arms are attached to the bicycle.) That additional 1/2″ or so that she will gain in a reduced step through height will be very beneficial on her custom bike.

    Now that the lower body was squared away, it was time to address the upper body. As it came equipped from the pawn shop, the Fisher felt very cramped, causing the rider to push back on the saddle in search of a more natural position. Without knowing this rider’s “geometry”, I would guess that this is a result of trying to get the knee in the correct position over the pedal. A lot of women find themselves doing this! Her solution was to put a very set-back seat post on the bike. Other adjustments involved raising the handlebars to get them in the right position relative to the saddle. Here’s the “new” bike:

    You may be looking at this and thinking it still looks like a pawn shop bike. Yes, but, to turn the phrase, beauty is only skin deep. What this is becoming is a blueprint to a bike that fits and does what its owner wants it to do. Once the crucial measurements are dialed in, like the reach, the crank arm length, the effective seat angle, etc., the blueprint is complete.

    Wow! Have we learned a lot, or what?! As this rider renews her cycling skills, she will undoubtedly tweak the bike even more. The search for the proper riding position is always ongoing. I think the term “evergreen” applies perfectly to this situation.

    Many thanks to her for sharing the journey so I could share it with you!

    Tailwinds,



    Resources:

    • Crank Shorteners
    • Adjustable length cranks
    • Customizing crank length
    • Studies on crank arm length:
    • Adults
    • Children
    • Buttars, Kent R. “Crank Length and Gearing.” Bicycling July 1982: 26-37.
    • Make your own bike “blueprint”

  • Will my tires explode?

    The fodder for this eLetter came from this blog post:

    “I won a new bike at my company picnic and I’d love to ride it, but I’m extremely afraid of popping all the tires at my weight!!!”

    Here’s the quick answer — the tires will be fine. Food for thought: a 4000 pound car is supported by four tires, each with typical inflation pressures of 30 -35 psi.

    But getting to this answer led me through a neat maze, full of twists and turns. Logically, I started with the sidewall markings on tires. Auto tires have a plethora of information and, in North America, are required to state the maximum load the tire can handle. But I have yet to see a bicycle tire with a load marking on it. Tire pressure range, size, yes — but no maximum load.

    That doesn’t mean it hasn’t been calculated for bike tires, though. Many manufacturers have done this, but only publish it in their literature or on their website. Since we spec Schwalbe tires on most of our bikes, they seemed to be the logical company to contact for more information. Schwalbe calculates loads, but the data is currently only published for off-road tires. In the future, it may be published for road tires as well, but Schwalbe has no plans to mark the load data on the tire itself. Here’s a look at the data for one of Schawlbe’s off-road tires.

    This [b]single[/b] tire can withstand a load of 140 kg (308 lbs). Pretty amazing, huh? I asked Carsten Zahn from Schwalbe for a little more information about how this was calculated. A load is applied to the wheel. The maximum load is the load that will cause the tire to deflect by 20% (that is, when the tire “drops” by 20% from its unloaded height). The test is always done with the tire at the maximum recommended inflation pressure. Remember, this is a static load. Things are very different when jumping off cliffs….

    The choice of 20% as the maximum allowable deflection begged for more explanation. Schwalbe says this comes about from their experience and from a standard in the ETRTO (European Tyre and Rim Technical Organization) norm. If the tires are ridden for a long period of time at a higher defection, the sidewalls will eventually collapse.

    Interesting. I wondered what the Consumer Product Safety Commission had to say about load requirements for bicycle tires. Not a lot. The only reference to loads refers to “side loads” — the wheel is turned on its side and supported around the circumference of the tire sidewall while a 450 pound force is applied to the axle for 30 seconds. During this time, the tire must stay on the rim when the tire is inflated to 110% of the recommended pressure.

    But that wasn’t the end of it. The deflection issue would come back in a different context. I’m the kind of person who runs my tires at the maximum recommended pressure. I figure they’re going to lose pressure as I ride them, even if it’s only a tiny amount, so I might as well start at the top and work my way down until I re-air in seven days. (Schwalbe says to check your tire pressure monthly, which is way too long for my taste.) Besides, there’s something nice about the swish and hum of hard tires on the road. Or is there…..???

    “Inflating your tires to achieve 15% tire drop will optimize your bicycle’s performance, comfort and handling.” This is the first sentence in an article by Jan Heine (see full citation below). The logic here is that even though rolling resistance is lower at higher pressures, comfort is lessened because of vibration and bouncing of the bike. By lowering the pressure, comfort improves. The trick is to find the “sweet spot” where the most comfort is achieved at the least performance cost. Download the full article here.

    As you’ll see, the article contains a chart which tells the reader what inflation pressure to use given the width of the tire and the weight it bears. I tired this using my own weight and tire size, but I was off the chart! Extrapolating, I shouldn’t be riding a bike at all. (The perils of the rider with a slight build…the same thing happens to me with those BMI charts.)

    Nonetheless, I lowered my tire pressure about 10% just to see what the ride was like. Hardly scientific, but the bike just didn’t seem to have its usual zing. Which made me start thinking about the “comfort” aspect of this and how dependent it is on a variety of things, like frame material, frame geometry, road surfaces, wheel construction, ambient temperatures, to name just a few. Tire resistance can be measured with a lot more accuracy than comfort. There’s nothing better than a fine ride on a fall day spent mulling over things like this.

    But, coming back to our cyclist who won the bike — even though this chart was designed around a 15% deflection, she can see that she’ll be better off with a wider tire she can inflate within the recommended inflation range. A very narrow tire will have to be quite a bit overinflated to do the job. The widest tire on this chart is 37 mm (about 1.5″). Think back to the Schwalbe tire, 2.1″ wide, with a maximum inflation pressure of 55 psi and able to sustain a load of about 300 pounds. Ride yer bike and enjoy it!

    Tailwinds,

  • Bicycling for Ladies

    This Cycling Savvy eLetter is a little bit of a departure for me. I usually focus on technical aspects of cycling, but when a customer was kind enough to send me this book, I thought this would be an appropriate place to present it.

    The book is Bicycling for Ladies (The Common Sense of Bicycling). Ms. Ward penned this 200 page book in 1896. 113 years ago! So much has changed, but so much has stayed the same.

    When I first saw this book, I assumed it would be kind of lightweight. I mean, how serious could a 1896 book about cycling for women be? As out it turns out, very serious. Ms. Ward must have been a mechanical engineer with a flair for poetry.

    Here’s the poet: “A bright, sunny morning, fresh and cool; good roads and a dry atmosphere; a beautiful country before you, all your own to see and to enjoy; a properly adjusted wheel awaiting you — what more delightful than to mount and speed away, the whirr of the wheels, the soft grit of the tire, an occasional chain-clank the only sounds added to the chorus of the morning, as, the pace attained, the road stretches away before you!”

    And here’s the engineer: “The bicycle has one weight-carrying wheel and a frame and a pivoted wheel. The driving power is applied to the weight-carrying wheel and the steering is done with the pivoted wheel. The bicycle remains upright because several forces co-operate to enable it maintain its plane, change direction, and overcome certain resisting and opposing forces.”

    Following are some of my comments with excerpts from this neat volume.

    I would be the first to say I feel at one with my machine, but in 1896, cyclists were a lot closer to their bikes in some respects. Like straightening the frame if need be: “…to straighten a bent frame is an easy matter. Take out wheels, saddle, and handlebars, and use a piece of broom-handle to spring the frame into true; or take a stout cord, fasten it to either end of the part to be straightened, insert a stick, and wind up the cord tight.” Try that on your carbon fiber frame!

    Forget about kickstands on a bike. Here’s a clever way of “standing” the bike. “A bicycle will balance in this way: The front wheel kept from moving at either the tire or the centre of the frame; the pedal resting against some firm object.” I often use a curb in this manner, but with the pedal on the back of the stroke, rather than the front as shown here.

    One of my favorite lunches to carry on the bike is Fig Newtons, grapes and an energy bar. Not so different with Ms. Ward: “…if you carry luncheon, a couple of bread-and-butter sandwiches well wrapped in waterproof paper, and thin slices of cheese in a separate paper, or hard chocolate and water-biscuit, are as good as anything…”

    We’ve all been in this situation! “Each hill has its peculiarities, which must be studied and conquered. The actual mounting to the top is not all you have to do; you should mount in proper trim, arriving at the summit fresh and fit. It is most saddening to see s ome one else mount a hill easily, leaving you, puffing and pushing, half way up, and to know that, when you reach the top, speechless and exhausted, that exasperating person will be seated there, cool, contemplative and comfortable.”

    Ward’s 1896 woman was no stranger to working on her own bike. “I hold that any woman who is able to use a needle or scissors can use other tools equally well.” “Tools are but the continuation of the individual brain and will power.” “On returning from a ride the wheel should have a thorough going over, the enamel dusted, and any mud washed off with a wet sponge. The chain…should be taken off every two or three hundred miles of dusty road, and soaked in kerosene over night; the nickel or metal well dusted, rubbed with a chamois, and polished; and all the bearings, axles, and gear carefully wiped, and dust and grit removed. Then the chain should be replaced, oiled, graphited, and the bearings oiled.”

    Weight, not of the rider, but of the bike: “A certain weight of material has been taken from the bicycle to make it light; the machine begins to lose its rigidity and consequently its accuracy, and cannot maintain its direction, but wavers, and really travels further to attain a given distance.” My how different materials and material shapes have changed this point of view!

    Nutrition is always a large part of the active cyclist’s lifestyle and it was then, as well. “A mixed diet, with plenty of variety, is the best to work on, everything to be thoroughly cooked. Beef and mutton are always good food; and fresh vegetables, fruit, milk and eggs, and cereals either with cream and sugar or milk and sugar. Simple desserts are not harmful, neither are they necessary.”

    I could go on forever with this, but by now you have the idea that this is a gem of a read. I imagine it’s virtually impossible to find in hard cover, but luckily, you can download this book from Google Books. Enjoy!

    Tailwinds,

    __________________________________________________________________________________________________________________
    References:
    Maria P. Ward Bicycling for Ladies (The Common Sense of Bicycling) New York: Brentano’s, 1896

  • 650 Wheels: Pro and Con

    With the season upon us, I’ve been hearing from a lot of you who are thinking about purchasing a new bike and wondering about 650 wheels. Like Terry, many other WSDs use this size, front and rear, on their smaller models.

    In a nutshell: “If the shoe fits, wear it!”. Don’t shun a properly fitting bike because it has 650 wheels.

    What are the main objections to 650 wheels? I can think of a few: they don’t go as fast, small wheels have more rolling resistance than larger ones, tires are harder to find, and 650s are not supported in road races. Let’s see which of these have any merit.

    650 wheels don’t go as fast as 700c wheels.
    Absolutely true. If you’re on a 700c wheel riding in the same gear and pedaling at the same rate as a friend on 650s, you will go faster than your friend. But that’s not the whole story. Just how fast do you usually ride? 15 mph, 18 mph, 20 mph? At 90 rpm, in a 50 x 25 gear, the 700c rider will go 29 mph; the 650c rider will go 27 mph. Moral of the story: if you consistently ride faster than 27 mph, you might find 650c wheels to be a hindrance. The solution: fit a larger chainring or a smaller rear cog.

    Small wheels have more rolling resistance.
    What is rolling resistance? It’s one of the things that can slow a bike down. It’s caused when the tire deforms, which it does as it revolves. This happens where the tire is in contact with the ground. If you could put the bike on a sheet of glass and look up at it from below, you’d see the oval contact patch — where the rubber meets the road, so to speak. If you inflate a 650c and 700c tire to equal pressure, the contact patches will have the same area for the same rider weight. But more of the “roundness” of the smaller diameter tire is lost during deflection. This deformation ultimately causes more rolling resistance.

    So, in the big picture, is this rolling resistance important? The accompanying chart shows the resistance forces on a bicycle at different speeds (km/hr). Note that rolling resistance isn’t much of a contributor. It’s the air resistance that gets you!

    Tire Availability
    Just about everyone has a 650c tire – Schwalbe, Continental, Michelin, Panaracer, Vittoria and Terry, to name a few. With so many WSDs and tri bikes using this size, there’s no shortage of supply. According to Schwalbe tires, demand for the 650c size is increasing.

    No Race Support
    Yes, this is correct. According to our team riders, the 650 size is rarely supported and, when it is, you really have to dig around in the wheel van to find it!

    Thanks to Schwalbe Tires for the use of their graphics!

    Tailwinds,

  • Tips for Buying a Bike

    Are you thinking about buying a new bike? I frequently get calls from customers who are a little intimidated about going into a bike shop. Here are some tips that will help you.

    Which shop?

    • First, find a shop that specializes in the kind of bike you’re looking for. Some shops sell lots of road bikes, but not mountain bikes, and vice versa. You want the shop that sells the type of bike you’re planning to buy.
    • Take some time to browse as many shops as you can. Are you comfortable with the shop environment, the employees, the “feel” of the store?
    • Some women feel more comfortable working with a female salesperson. Other women have no preference. Which are you?
    • Talk to your biking friends. Which shops do they like?

    Once you’re in the shop.

    • Forget about your price point. Try bikes that are more expensive and less expensive just to see what they’re like and why they cost what they cost. If the person waiting on you doesn’t have the patience for this, try another store.
    • Make sure the test ride is enough of a ride to give you an opportunity to really assess the bike.
    • The test ride is critical! Just sitting on a bike while someone holds it up for you tells you next to nothing.
    • If you can, on the test ride, wear the shoes and clothes you usually wear when you ride. Think of it as Linus and his blanket. Eliminating as many unknown variables as possible will help you better evaluate the test ride.
    • If the shop employee who’s waiting on you is good, he/she will make sure the bike is adjusted properly before you test it. This means adjusting the saddle height/tilt/fore-aft position and the height of the handlebars. If the shop is really accommodating, they’ll swap out stems if necessary to really dial in your reach. If the bike’s not adjusted for you, it may feel uncomfortable and you may pass up on the perfect bike and never know it.
    • Let comfort be your guide. If you don’t feel comfortable on the bike and the shop can’t adjust it to make it feel comfortable, try another bike. And remember — you define comfort. It doesn’t matter how good someone says you look on the bike. If you don’t like it, it’s not for you.

    Where are you coming from?

    All the things you like and dislike about your current bike are clues you can use to make sure your new bike is indeed your dream bike. Take measurements of your current bike so you can compare it to the new bikes. For instance, if you feel too “stretched out” on your existing bike, look for a bike with a shorter reach to the handlebars. This chart will help you do that.

    Do your homework.

    • Read up on different frame materials and component groups. Check out reviews of the bikes you’re considering. Talk to other riders.
    • Don’t overload on information. Information is good, but it can have the effect of paralyzing you if you get too caught up in it.
    • Watch my video series on bicycle design.

    Good luck on your search. Find that perfect bike and ride a few miles for me!

    Tailwinds,

  • Fixing a Flat Tire

    First, here’s some general information about tires:

    Since tires are your only contact with the road, it’s important to make sure they’re in good working order. Inspect them regularly for cuts on the tread or sidewall. Small cuts can hold shards of glass or thorns, which can eventually cause a flat tire. Big gashes can allow an inner tube to ooze through. Nothing’s as frightening as having a front tire blow out while you’re blasting downhill. The rear tire will wear faster than the front tire, since it bears more weight and is the driving wheel, so watch it carefully.

    Inflation pressure is also important. Proper pressure keeps the rolling resistance of the tire low and helps avoid flat tires caused from rolling over uneven surfaces. The recommended inflation pressure is printed on the sidewall of the tire.

    Use a hand bicycle pump or a floor pump to inflate your tires. Most floor pumps have gauges built into them. If you use a hand pump, use a gauge to verify the pressure. Check your tires before each ride.

    Tires that have never been used can still go bad. They dry out and lose their elasticity, so they crack and puncture easily. Replace your tires annually. It’s a cheap investment.

    Fixing the flat:

    To fix a flat, you’ll need a few tools: tire irons, a patch kit, a pump, and some arm muscles. (See, cycling [b]is[/b] good for upper body strength.)

    The first thing to do is to remove the wheel from the bicycle. If it’s the front wheel, it’s a cinch – release the quick release and remove the wheel. The rear wheel is ornery because you have to contend with the chain and the rear derailleur. Before removing the wheel, shift the chain until it’s on the small sprocket on the back and the small chainring on the front. Then loosen the quick release and slide the wheel out. If the rear derailleur cage holds things back, just pull the cage gently downward and rearward to get it out of the way.

    The next big project is to remove the tire from the rim of the bicycle wheel. You’ll probably need a set of tire irons to do this. Sometimes, if the fit is loose enough, you can work the tire off with your hands, but you’ll usually need tire irons. Start on one side of the tire and work it off the rim, using the tire irons to gently pry it over the rim. Be very careful not to crimp the inner tube in the process. Once this side is off, you can reach in and remove the inner tube. Make sure you take off the plastic valve cap and the small nut on the inner tube valve before removing the tube. Now, remove the other half of the tire.

    If you watch others fix a flat, you may notice they don’t take things apart as completely as you are. You can get away with less, like just pulling out the tube where it’s punctured if you want to repair it and you know where the puncture is. The point of this exercise is to learn about the makeup of a wheel, so that’s why you’re now holding an inner tube (punctured), a tire (punctured or possibly worse), a wheel, and maybe a rim strip (wondering what the heck it is and where it came from).

    The rim strip is a strip of plain rubber or adhesive backed cotton that wraps around the rim to protect the inner tube from the sharp edges of the rim where it’s drilled for the spokes. Adhesive backed cotton strips are preferable because they don’t migrate and they have a very long life. Rubber strips can move around and eventually dry out. Make sure the rim strips fully cover all of the spoke holes, or this could cause future flats.

    You have two options now: you can repair the damaged tube (see the instructions that came with your patch kit), or you can use the spare inner tube you always carry with you. Regardless, make sure the culprit that caused this flat isn’t still with you. Start with the tire. Check it inside and out for a tack, shard of glass, whatever. If something’s still embedded in the tire or floating around in the casing, you may have another flat in avery short time. Try to find the damaged area. If it’s small, you can usually ignore it. But if it’s large enough for more debris to enter, you should patch the inside of the tire.

    It’s a good idea to look at the tube, too. It can give you a lot of information. Flats aren’t always caused by events on the outside. They can be caused by aliens on the inside. For instance, if the rim strip has moved out of place, a rough spot on the rim may rub against the inner tube and eventually puncture it. If the puncture is on the outer circumference of the inner tube, the culprit came from the outside; if the puncture is on the inner circumference, it came from within the rim. In any event, make sure you know what the cause is so you can finish your ride without more problems.

    Reassembly can be a breeze or a bear. Start by making sure the rim strip is on and straight. Then put one side of the tire back on the rim. Put the inner tube back in, starting with the valve and then work the entire tube back in place. (Sometimes it helps to keep the tube slightly inflated, but let all of the air out after the tube is in place.) Keep it straight and untangled. Here comes the breeze or bear part: starting at the valve, using your thumbs, begin working the last side of the tire onto the rim. Check the valve occasionally to make sure it points straight toward the center of the hub. Also make sure the tire bead is seated in the rim at the valve. If you push the valve back into the tire, it will make room for the tire to “seat” itself properly.

    By the time you get about half way around the rim, it’s going to get harder to slip the tire on the rim. Make sure the tube is completely deflated and work the tire opposite the hard spot down into the channel of the rim to give you as much “slack” as possible.

    It will be very tempting to use a tire iron to pry the tire back on, but you really shouldn’t because this will inevitably pinch and puncture the tube. If you must use a tool, use one like the Crank Brothers Speed Lever. With this tool, you can pry the tire onto the rim without hurting the tube. The best situation is to use your hands, but sometimes you can encounter a very difficult fit–the rim is just a little too large and the tire is just a little too small and the result is misery and frustration. Be patient. People have been known to flag down passersby on the theory that two pairs of thumbs are better than one.

    Don’t use a gas station air hose to inflate your bicycle tires–the air goes into the tube so quickly that it can blow out the inner tube–car tires have much more volume than bicycle tires. Ever try to inflate a car tire with a bicycle pump?

    No pump? Take out the inner tube and stuff the tire casing with leaves, grass, or newspaper. Ride very slowly and walk all your turns! Hole in the tube too big and you have no spare? Cut the tube in two, tie a knot at each end, reinstall and inflate at a low pressure. Tire casing gashed? Use a dollar bill, duct tape, or an old tire casing to make a boot.

    Practice makes perfect, so you may want to try taking the tire and tube off your wheel and reassembling it. Better to learn about the snags in the privacy of your own home than under duress in a rainstorm!

    Tailwinds,

  • Bicycle Frame Geometry

    Frame geometry, loosely defined, is all about the lengths and angles of a bicycle frame. It’s important because it determines how the bicycle will perform as well as how it will fit you. Sometimes it’s easy to look at the most obvious aspects of frame geometry (how long is the top tube and what is the standover height) and forget about the rest. Understandable, because we (the manufacturers) don’t always do a good job of explaining the rest to you and what it means. This gets a little dry, but bear with me.

    So let’s start with frame angles: the seat angle and the head angle. The seat angle is the angle between the top tube and the seat tube. The head angle is the angle between the top tube and the head tube. For typical road bicycles, the head angle is between 71 and 74 degrees. The head angle, in combination with the rake, determines how the bicycle handles. Steeper head angles, like 74 degrees, are usually reserved for bikes that are very manuverable, like criterium bikes. On the opposite end, shallower head angles are found on touring bikes where, in combination with a long rake, they provide stable handling.

    The seat angle isn’t quite as sacred as the head tube angle, but it sure has important implications for fit because it determines whether or not you’re going to be able to get in the right position relative to the pedals. Seat angles range from 72 to 74 degrees with 73 degrees being the most typical. Note that by moving the saddle back and forth on the rails, you can effectively change the seat tube angle a couple of degres. Once the seat angle is greater than 74 degrees, the geometry really puts the rider in an awkward position relative to the pedals. Unfortunately, some designers manipulate the seat angle to make the top tube shorter. To easily visualize this, imagine a bike with a 90 degree seat angle (i.e., the seat tube is vertical). Yes, the top tube is really short, but at the expense of a good fit. Steep seat angles also tend to give a rougher ride: imagine sitting on a pile driver.

    Another dimension most geometry charts mention is the bottom bracket height. This is the distance from the ground to the center of the bottom bracket. You’ll find higher heights on bikes where pedaling through corners is important (like bikes used in criterium races) and lower heights on bikes where a low center of gravity is important for maintaining stability (like touring bikes). Because the bb height can vary a little depending on the tires, some manufacturers also publish the “drop”. This is the vertical distance from the wheel axle to the center of the bottom bracket. It’s a fixed number, so in manufacturing, bicycle frames are built to drop, not to bottom bracket height.

    No geometry chart would be complete without rake, which describes how much the end of the fork blades deviates from a straight line drawn through the head tube. Rake is usually in the 2 to 6 cm range. Rake doesn’t mean a lot by itself, but when manipulated in a trigonometric relationship with the head angle and the circumference of the front rail, you can derive the trail and the caster angle of the bike. When all bikes had 700c front wheels, trail used to be a hallowed indicator of how the bike would handle, but with the advent of 650c and 24″ wheels, it’s lost its luster. Caster angle is probably a better measure; caster angles in the 80 to 82 degree range give neutral steering regardless of the wheel size.

    Finally, there’s the chainstay length. You’ll find them in the 39 – 40 cm range on racing bikes, since this makes for a stiffer rear end that won’t twist under explosive acceleration. Bikes made for touring usually have the longest chainstays (43 cm +) for better shifting with wide range gearing and heel clearance for panniers.

    Hopefully this has given you a little more cycle savvy about frame geometry!

    Tailwinds,

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  • Correct Bicycle Fit for your Upper Body

    One of the perks of my job is being able to escape to the Eastern Shore of Maryland for some sunny riding around Blackwater National Wildlife Refuge.

    On a recent trip, I found myself thinking about the “cockpit” of the bicycle, the area that encompasses everything from the saddle to the handlebars. Knowing when a bicycle fits your legs is straightforward. If you can clear the top tube by a reasonable distance, then you’re set. (Well, almost; that’s the topic of my next eLetter.) But it’s not so obvious with your upper body. And when you do try to tweak the cockpit to fit your upper body, just what do you tweak? The handlebars, the stem, the saddle? One of them? All of them?

    Dominoes. That’s what cockpit adjustments are like. You get something just right at one place, only to find out you’ve lost a once good position somewhere else. Just warning you!

    Let’s start with the saddle fore-to-aft position. You probably know you can move the saddle back and forth on its rails. You want to do this to get your knee in the proper relationship to the pedal. Commonly accepted wisdom says that when you are seated on the bike, with your feet in the clips and the crankarms horizontal, a plumb line dropped from the front of the knee of the forward-most leg should intersect the center of the pedal. Move the saddle back or forth until you’re in the right position.

    We may have just run into a bit of rough. It’s not unusual for women to find they can’t move the saddle back far enough. This is because women typically have long femurs. A saddle with unusually short rails can hinder a good adjustment as can a steep seat angle (greater than 74°) on small bicycles. Ever feel as though you’re always “pushing back” on the saddle? Setback seatposts are available with varying amounts of offset which may overcome this sensation.

    Now we’re ready to work on the handlebar end of the cockpit. When is the fit right there? When you can ride comfortably with your hands on the brake hoods. This means having control of the bicycle and experiencing no neck or shoulder pain. For many women we’ve fit, 50° seems to be the magic comfort number. This is the angle between your upper body and a horizontal line. More aggressive riders will prefer to lean forward more; really casual riders will prefer to sit up more.

    The stem: styles of stems vary from bike to bike, but most stems now have spacers which can be moved above or below the stem to change its height. The stem height is right when the handlebar is level with the seat. Again, there are exceptions: more aggressive riders like the stem lower; very casual riders like it higher. If the height is right, but you feel like you’re leaning too far forward, you may be able to shorten the stem to bring the handlebars closer. Likewise, if you feel “scrunched up”, you can put on a longer stem to move the handlebars away from you.

    The handlebar: often neglected because it doesn’t look like you can do much with it. We’ve found that most bike shops set up handlebars with the brake levers a tad low on the bar. This means you have an uncomfortable bend to your wrist while on the hoods. The handlebars can be rotated in the stem. If you rotate them up slightly, it can make a world of difference in the way the bike feels. Not too far, though, or it’s awkward getting at the brake levers from the drops. To learn more, check out my video on How to Adjust Your Handlebars.

    I left out one factor in this discussion: your physical flexibility and your core and lower back strength. I didn’t pay much attention to it myself until a few months ago, but now I’m sold. The more flexible you are and the more strength you have in your core and lower back, the easier it is to maintain a variety of positions. That’s a subject unto itself!

    I hope you’ve found these ideas helpful, whether you’re trying to get a new bike to fit well or just polishing up your position on your current one.

    Tailwinds,