Saturday, June 13, 2009

What is a touring bicycle?

One of the things that I find interesting about being a bicycle tourist is that so few cyclist really know what a touring bicycle is. Perhaps this is because many bikes can be pressed into service as touring bike but many will not do it well.

Many think that a MTB with slick tires is a touring bike or the same thing as a cyclo-cross bike or a hybrid of some kind. A few think those bicycle tourists are guys who simply ride cheap bikes with racks. None of these assumptions are correct though some are less wrong than others.

First off, there are people who tour off road. In that case some of what I'm going to say is not technically correct. So you should realize when I say "This is a touring bicycle" I am speaking of a very special type of machine that looks, at least at first glance, like a road bike.

There are several characteristics that set a touring bike apart from a normal road bike racing frame.

These are wheelbase, frame geometry, bottom bracket height, braze on fittings, tire clearance, frame weight and versatility. I will look at these characteristics separately.

A touring bicycle has a very long wheelbase, much longer than a racing or even sport road bike frame. How long? About 1.15 meters as opposed to the .95 meter wheelbase of a standard stage racer. While this is not a figure that is set in stone and can vary some with wheel size a touring bicycle will always have a much longer wheel base than a normal road bike, cyclo-cross bike or mountain bike. Most of the additional wheel base will come from longer chain stays. This allow panniers to be mounted on the rear of the bike but still gives ample room for the riders heels to not bang into the bags. The longer chain stays also change the center of balance on the bike, they move it rearward which makes the bike easier to handle when loaded. After riding a touring bike a racer, any racer will feel like a squirrel.

Frame Geometry
This is a tricky area because geometry, especially the angle of the seat tube has changed over the years. Back about 1980 or so most racing bikes had a seat tube angle of about 73 degrees. Most touring bikes had 72.5 degree angels. But as the years have passed road bike angles have become increasingly steeper. Touring bikes still have the slacker angles.

But it isn't just the angles of the tubes. Most road bikes now have much smaller, "compact" geometry and need significantly longer seat tubes. This has been done to make the frame stiffer and more responsive. While some touring bikes made by companies like Cannondale have a somewhat compact frame many do not. However, the real issue with the compact frame is the height of the handlebars. Look at almost any road bike and you see that the handle bars are 8 to 10 cm below the level of the saddle. Look at a touring bike and you'll see the handle bars are about level with the saddle. This is an almost impossible place to get handlebars to with a normal road bike. The frame just won't accommodate bars that high. This means that a touring bike does not benefit from aero bars but also that the rider does not spend hours looking at their front tire.

To further facilitate higher handle bars a touring frame often has an up sloping top tube or if it is older uses a quill type stem with a long quill such as a Nitto Technomic.

Bottom Bracket Height
This is a rather esoteric measurement in that it is not one that most cyclist ask about. It is also called "Drop." You can measure this on your bike by tying a string to the front dropout for the front wheel and pulling it tight so that it is level with the rear dropout. Then measure the distance between the string and the center of the bottom bracket spindle. That is your bike's drop. A standard road bike has a drop of about 6.5 to 6.8 centimeters if it has 700 CM wheels. A touring bike will generally have a drop of at least 7.5 to 8.0 CM that is a big difference. What does that mean? Simple, the higher the drop the more stable the bike is at low speed and if it is heavily loaded (a lower number is a higher drop so a 6.8 is higher than a 7.5) More drop lowers the center of gravity which makes descending safer. It also lowers the stand over height so you can ride a bigger frame and makes the bike easier to control if heavily loaded.

However, a lower drop also will make the bike feel like it turns a little slower. You need to use a shorter crank arm on a bike with lots of drop because it will be easier to strike a pedal in a turn. This is why a tourist doesn’t pedal through corners.

Braze On Fittings
Most road bikes, especially those made of carbon fiber and aluminum have brazed on (though that term is now obsolete on a carbon frame) fittings that would include integrated shifters, front and rear derailleur’s and rear brake cable as well as one or two water bottles. A touring frame will have fittings for racks, eyelets at the dropouts, possibly a lighting system, cantilever brakes, 3 three water bottles and often for down tube shifters. One fitting often left off of a touring frame is the braze-on front derailleur mount because it limits the size chain wheel that can be used on the bike. Tourist come in a wide range of flavors. Some need really low gears to carry 80lbs of luggage up a mountain and other travel light and use a credit card to sleeping a hotel. They'd have very different front gearing for those bikes and a brazed on fitting will not accommodate a wide enough choice of chain wheels.

Tire Clearance
No much to say here. A touring bike will normally handle tires up to at least 36 MM wide with fenders. You'll be lucky to get 28 MM wide tires on most road bikes without fenders. This is important when carrying heavy loads. Wider tires not only carry more load but are more comfortable.

Frame Weight
A tour bike frame will weigh about 1.5 to 2 pounds more (in steel) than a comparable sized steel racing bike. But that weight is need to carry gear reliably.

A racing frame does one thing well. This is not a bad thing if you race. However, a touring frame does more things that the average person needs. Think of it as a SUV or mini-van type of bicycle. You can commute on it tour on it, ride it for pleasure, haul groceries on it, even race on it. While the racer will beat it racing, on smooth pavement the touring bike is a much more versatile machine.

Lets put all the parts together. A touring bike is a bicycle with a long wheel base, slack angles low bottom bracket, that accepts wide (by road bike standards) tires, made of heavier gage tubes and that is designed to be comfortable, versatile and reliable.

Until Next Time
Fai Mao

1 comment:

  1. Also - would there be any chance of tire rub at full travel with these larger wheels on this "demo" set up?

    Velocity Wheels Vw830