AIDSRIDEDC FAQ Section 4: Bike Selection and Fit

This section contains these subjects:

• 4.1 What Kind of Bike Do I Need?
• 4.2 Bike and Tire Sizing
• 4.3 How to Get a Bike that Fits
• 4.4 Other Resources on Bike Fit
• 4.5 What about Frame Materials?

One of the most common questions asked by new Riders is, "What kind of bike do I need to do the Ride?"

There is no single right answer to this question. Riders have completed AIDS Rides using just about every kind of bicycle that exists. On the TdF, you will see road bikes, mountain bikes, hybrids, recumbents, tandems, even the occasional "English 3-speed". [Your FAQ editor admits he's never seen a "Penny-Farthing" (an old high-wheeler), or a unicycle, but nothing would surprise me. RG]

So the first observation is that you do not need a particular type of bike to do the Ride. If you have a bike that fits (and fit is crucial), and that you are comfortable riding, it will probably be just fine for the Ride. If you have questions about bike fit, talk to a knowledgeable friend (perhaps one of our friendly training ride leaders and sweeps), look at Section 4.3 on bike fit, and perhaps have your fit checked out at a good local bike shop [LBS]. Having a bike that fits properly can make all the difference in comfort and injury prevention. Another general principle to keep in mind is that, if you are going to buy a bike, you should get one that will be suited to the kind of riding you'll be doing overall -- not just on the Tour de Friends. With that in mind, here are some general thoughts about the pros and cons of different types of bikes (we omit tandems, since these are so specialized):

Mountain Bikes

• Most popular type of bike, in terms of sales.
• Upright riding position is comfortable for most riders. (This may be especially true for larger/heavier riders.)
• Typically wide range of gearing, making it easier to cope with hills.
• Generally stable at low speeds due to frame geometry.
• Basic models can be bought at reasonable cost
• Rugged!

• Tend to be heavy compared to hybrids or, especially, road bikes. (This is particularly true of low-end models, ot those with suspension.)
• Knobby tires are inefficient and do not improve traction on pavement. (These can be replaced with narrower smooth tires.)
• Limited hand positions may cause discomfort on long rides. (Bar ends can help.)
• Upright riding position is less efficient aerodynamically.
• Handling can be questionable at high speeds, due to frame geometry.

Hybrid Bikes

• Suitable for both road and basic off-road use
• Upright riding position is comfortable for most riders
• Lighter than a typical mountain bike
• Fairly wide range of gearing.
• Generally stable at low speeds due to frame geometry.
• Probably the best all around bike for beginning riders.
• Good for "around town" riding, errands, and so on. (Hybrids are, in some sense, the current incarnation of the classic "English 3-speed".)
• Some are available with internally-geared rear hubs, minimizing maintenance.
• Generally easy to add racks, fenders, etc.
• Can be bought at reasonable cost

• Heavier than a road bike
• Limited hand positions may cause discomfort on long rides. (Bar ends can help.)
• Upright riding position is less efficient aerodynamically.
• Handling can be questionable at high speeds, due to frame geometry.
• Typically, made to sell at reasonable cost, so components are not "top drawer".
• Jack of all trades, master of none.

Road Bikes

• Generally the lightest bikes.
• Drop handlebars give a variety of hand positions.
• "Tucked" riding position is most aerodynamically efficient.
• Narrow, high-pressure tires provide minimal rolling resistance.
• Most stable and predictable handling at high speed.
• Most efficient for long road rides -- that's what they're designed for. Many riders also find them most comfortable on long rides.

• Tend to be pricey.
• "Tucked" riding position may be uncomfortable for some.
• Handling can be "squirrelly" at low speeds.
• Light-weight tires can be more vulnerable to punctures.
• Not really suited (except for cyclo-cross models) for serious off-road riding.

Recumbents

• The "easy chair" of the bicycling world.
• Very good for those with serious weight or back problems, or other medical conditions which may prevent comfortable usage of other style bikes.
• Very efficient aerodynamically. (Recumbents are not allowed in UCI-sanctioned races, because they'd beat the pants off everything else.)
• High "whoa...cool!" factor (which may make you more noticable to other vehicles).

• Can be unstable at low speed.
• Can be hard to find, and relatively expensive.
• Requires practice at getting started and steering.
• Usually not too good at climbing hills.

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4.2 Bike and Tire Sizing

Adult bikes are conventionally sized by the length of the seat tube. (This is the frame tube that goes down from your seat to the crank axle, the longer of the two roughly vertical tubes in the frame.) There are two common ways of measuring this. A "center-to-top" (C-T) size is measured from the center of the bottom bracket shell to the top of the seat tube, while a "center-to-center" (C-C) size is measured from the center of the BB shell to the intersection of the seat tube with the centerline of the top tube. Typically, there will be a 1-2 cm difference between the two measurements for a given frame.

That's the theory, anyway; as is often the case in sizing bikes and parts, the reality is messier. In practice, there are additional small differences in the way different manufacturers measure, and they are not always even consistent with themselves. (For example, I have a Trek road bike I bought in 1995, which was sold as a 50cm C-T frame; it even has a sticker with that size attached to the frame. Nonetheless, I believe my tape measure, which says it's 50cm C-C.)

Kids' bikes have traditionally been sized by the wheel size, which is where the 24", 26", etc. sizes came from. For current adult bikes, these sizes are almost meaningless. Except for time trial and triathlon bikes, and a few bikes with small frames, current road bikes almost all use 700C wheels, which are a little less than 27" in diameter -- but not the same size as 27" wheels. (BTW, the 'C' in 700C does not stand for centimeters, millimeters, or any other conventional unit. Wheel and tire sizing is an even worse hodgepodge than frame sizing.

The ISO tire size markings are slightly more rational: a 700Cx23 road tire would be marked '23-622'. The first number is the nominal width of the tire in millimeters; the second, and more critical, number is the diameter of the bead seat, also in millimeters. (25.4 mm =1 inch, by definition.)

Mountain bikes typically use so-called 26-inch wheels. Beware, though: there are other sizes marked 26 inches that are not the same size! (Confused enough yet ?) The key dimension is the diameter of the bead seat on the rim; it is 559 mm for most (but not all!) mountain bikes. (That is, the ISO tire size, which is the most reliable measure, will be '??-559'.)

Check out Sheldon Brown's fantastic Web site for a definitive article on wheel and tire sizing.)

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4.3 How to Get a Bike that Fits

Greg Lemond, in his book on bicycling, recommends a road frame size (C-C) of 0.65 x inseam length (measured to the floor without shoes). This is probably a reasonable starting point for a person of more or less normal (male) proportions. A reasonable starting point for mountain bike frame size is probably 1-2 inches smaller. (1 inch = 2.54 centimeters, by definition.)

It's not the whole story, though. The length of the top tube is also very important, especially for women, who on average have shorter torsos than men of the same height. That means that women will often need a shorter top tube, a shorter stem, or both.

One conventional rule of thumb on top tube/stem length is based on the distance between the nose of your bike saddle and the handlebar. According to this rule, if you place your elbow up against the nose of the saddle, your fingers should just reach the handlebar.

It is important to realize that these rules of thumb are just that. The only things that count, in the end, are how well the bike fits your body, and how comfortable your riding is. (Bikes should be made to fit riders, not the other way around.)

When you make fit adjustments, it is a good idea to make them in small increments. For example, if you conclude that you should increase your saddle height by 2 inches, don't increase it all at once. Raise it in small steps of half an inch, or less, at a time. Give your body a chance to adjust to the change.

If you are experiencing more than short-term discomfort from riding your bike, poor bike fit is a prime suspect. Have it checked out.

Many quality bike shops have the Fit Kit, Size Cycle, or other systems to measure a prospective rider for the right bike size. Although the shop may charge for this service (perhaps waiving the charge if you buy a new bike), having careful fit measurements done can contribute a lot to your cycling comfort and enjoyment of your bike, and can also help prevent some common injuries.

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4.4 Other Resources on Bike Fit

If it isn't apparent from the discussion above, fitting a bike correctly is difficult, if not impossible, to reduce to an exact science. There are some good articles on sizing and fitting available on the Web, representing some different viewpoints, from Colorado Cyclist, from Sheldon Brown, and from Peter White Cycles.

For another perspective on choosing a new bike, have a look at Mike Jacoubowsky's article on How to Test Ride a Road Bike.

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4.5 Frame Materials

Coming soon.

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