It often is surprising that high-end components cost not just a little more, but several times as much as budget components. For example, the high-end Sugino cranks (above right) cost more than three times as much as the budget model from the same maker (above left). (This already takes into account that the bottom bracket is included with the expensive crank.)
Both are good cranks. Neither is likely to fail prematurely. Both will transmit your pedaling power to the chain. The high-end crank has some advantages: It is lighter, it has a narrower tread (Q factor), it probably is a bit stronger, and the finish is prettier.
In this post, I am not concerned about whether the high-end crank is worth the extra money. Instead, I will examine why it is so expensive. Many cyclists gladly would pay an extra 20% or maybe even 50% more for a nicer product, but isn’t the upcharge for high-end products excessive? Are the makers of high-end products getting rich? If not, where does all the extra money go? Here are some answers:

Better materials: High-strength steel and aluminum alloys are more expensive than more basic versions of the same metal. The same applies to carbon fiber.
Even for the same alloy, reputable suppliers charge more, but they also guarantee the composition and temper of their metals. Discount material suppliers have been known to “substitute” a less expensive aluminum without telling the company who places the order. (That is how they can undercut the prices of the competition.) There is a reason why quality materials are marked with complete product information (above).

Better manufacturing techniques: Forging parts (above) costs more than casting, which in turn costs more than stamping. Even for the same technique, employing skilled labor and the best machinery results in more precision and strength. For example, inexpensive castings can contain air bubbles that reduce the strength. A skilled craftsperson will get better results, but at a higher price.
Closer tolerances: A lightweight, high-performance part has less margin for error, so it must be made to closer tolerances. For example, the casing layers in a high-performance tire must be placed much more accurately into the mold than those of a utility tire, which has much more overlap between layers.

More manufacturing steps: Extra steps in manufacturing can improve performance and appearance, but add cost. For example, drilling out the center of a bottom bracket spindle reduces the weight, but takes an extra step of precision machining. A dedicated crank machining fixture can improve the runout of your chainrings. And polishing components requires extensive manual labor. All these things cost money.
More research and development: The more you optimize a component, the longer it takes to develop it. You need more prototypes, you need better engineers, and they need to spend more time.
More oversight: Getting suppliers do exactly what you want is extremely time-consuming. Our engineer in Taiwan has been working almost full-time on the René Herse crank project for months now. He visits the various factories weekly (or more often) to make sure everything is according to spec.
It is much easier (and cheaper) to send a set of drawings (or even just a photo and sketch) to a supplier and just accept what they come up with.
More testing: High-end parts usually are tested both by the company, as well as independent testing labs, to make sure they are safe. For lower-end parts from small companies, the customer often does the testing. If there is a failure, the company usually recalls the parts, but sometimes people may get hurt.
Smaller production runs: A high-end product tends to sell in smaller numbers because it costs more. This in turn means that the costs of R&D, molds, dies and setup must be amortized over smaller numbers, which increases the price.
For example, a tire mold costs about $18,000. If that cost is amortized over 100,000 tires, it adds 18 cents to the price of each tire. If it is amortized over 1000 tires, then it adds 18 dollars to each tire.
Knowledge costs money: We often think of geometries and other knowledge as “free.” After all, you can buy a copy of Bicycle Quarterly and learn all about optimized geometries for front-loading city bikes. And it doesn’t cost more to rake fork blades to 55 mm offset than it does to rake them to 43 mm. So why do many makers simply strap a rack or basket to their standard hybrid frames?
I have come to realize that knowledge isn’t free. Researching a topic and evaluating the results takes time. Making prototypes and testing them takes even more money and time. Making decisions within a company takes meetings, presentations and more time. Qualified people spending time on a project adds up very quickly to a lot of money. It is much cheaper to say “We’ll just copy the specs from our competitor’s catalogue.”

Prestige: In some cases, companies charge more for a product simply because they can. The Campagnolo Super Record cranks (above left) are virtually identical to the Record model (above right), yet the “top-of-the-line” Super Record model costs $120 more. While this practice is common in the mainstream (just think about cars!), it is rare among the small makers who make products for enthusiasts.
When you add it all up, I hope you are no longer surprised that better parts cost significantly more than the cheaper offerings. The sad truth for small manufacturers of high-end parts is that the profit margins usually are lower on the more expensive parts and bikes than they are on the cheaper ones. In the end, it is up to you to decide whether the improved performance warrants the higher price.

The two “randonneur” bikes above look roughly similar. Both have a front rack and both have gears. Yet the one on the right would cost more than five times as much as the one on the left, if you ordered one today.
Of course, there are obvious differences: One already is equipped with lighting and fenders, the other isn’t. But even if we add $500 for those parts to the bike on the left, we still have a remarkable difference in price. Why is the bike on the right so much more expensive?
The bike on the left is a mass-produced machine, whereas the bike on the right was hand-made by a small constructeur. The “cachet” of a handmade product is nice and well, but what do you get with the hand-made machine that the mass-produced bike does not offer?
The production bike is a fine machine that will make many cyclists happy. So what does the hand-made high-end bike offer that justifies its price? From my experience, the extra money buys you improvements in three areas:

1. Performance: The high-end bike has a geometry carefully conceived for its intended purpose. (The production bike typically is a standard “road” bike, to which a rack has been added.) For the custom bike, the tubing was chosen to offer the ultimate performance for its rider. The fork blades are thin and absorb shock better. The rack sits lower and is stiffer, so the load works in unison with the steering. The fenders attach to precisely located bridges without spacers, so they are less likely to rattle or resonate.
The high-end components work flawlessly. The cranks offer narrow tread and exactly the chainring choices the rider needs. The end result is a bike that handles better, climbs better, descends better and is less fatiguing to ride.

2. Durability: The hand-made bike has each tube carefully mitered. The best hand-made bikes are brazed by master craftsmen who knows their craft. You can be sure that there is braze in every joint, and that the frame will not fail prematurely. The bearings of the components are precision-ground, so they will last multiple times as long as those of a less expensive bike. The cranks are forged and thus stronger and more durable. Even the paint is more durable, because it has been applied over a primer coat, and then been baked and cured.
On the inexpensive production bike, the quality of construction simply is not the same. Every part of the bike is spec’d to the lowest cost, rather than the highest quality. This starts with the tubing, and continues to even the smallest screw. Depending on how much you ride, the production bike can be adequate, or it can be frustrating as parts wear out and have to be replaced.

3. Aesthetics: The careful construction of the handmade bike also shows in its appearance. The fork has a gentle curve rather than a dog-leg bend in the middle. The lugs are crisply filed. The rack sits in exactly the right place on top of the front wheel. The fenders follow the curve of the wheels. The components are polished rather than powdercoated. A bike like this is a joy to behold, and it will age well.

Do you deserve a better bike?
The question for most riders is whether all this makes enough of a difference to warrant the extra expense. I believe this depends on how much you plan to ride the bike. If the bike is to serve for occasional rides, then the production bike may be all you need. But if you plan to ride more often and longer distances, you soon will appreciate the performance and durability of an excellent bicycle. Even the appearance is important: A beautiful bike will beckon you to ride more often.
The initial investment may seem high, but the better bike will be less expensive in the long run. Not only will its quality components last longer and require less maintenance, but you also will be less tempted to upgrade to a “better” bike.
In the end, every cyclist chooses for him/herself where they are willing to make compromises. Some don’t care much about aesthetics, others don’t need speed. Knowing what the trade-offs are allows you to make an informed choice.

Good bike tests provide information that allow you to choose a bike that is right for you. Your bike need not look like the one that was tested, because it often can be customized to your personal tastes.
When we test a production bike, the bike we test is the bike that you would buy. If you don’t like the components, you’ll have to buy another set and replace them, which significantly increases the price of your bike. Thus, it makes sense to comment on each part and how it affects the feel and performance of the bike.
Testing custom bikes is different, as they are built to suit the customer’s preferences. That means if you don’t like the handlebar shape or derailleurs on a test bike, you can order your bike with different components. Or if you want a different geometry, the builder may be able to accommodate it. To reflect this, our tests of custom bikes convey two levels of information:

1. How well the test bike performed for us. This is useful for readers who plan to order a similar bike, no matter which builder they choose. Here we discuss geometry, tubing choices, components, etc., and how everything works together.
2. How well the builder crafted the bike. This is useful for readers who consider ordering a bike from this builder, even if their bike would be somewhat different from the one we tested. Here we look at the quality of the construction, the design and how well the various components and other parts (fenders, racks, lights) were integrated into the complete bike.

Of course, it often is hard to separate 1. and 2. After all, the builder sent us a bike they thought would work well, so if the geometry doesn’t offer precise handling, and if the components don’t work well together, then there is little guarantee that a customer’s bike with different parts would be much better. After all, a good builder will steer the customer toward a specification that works well, rather than leaving it up to the customer to figure out how to design the bike.
The best bikes we have tested worked together as a seamless unit. In those cases, the skills of the builder went beyond brazing the frame. The builder designed and built a complete bicycle where every part was carefully considered, and the whole was more than the sum of the parts.
This type of skill usually is transferable, rather than being limited the immediate bike we tested. For example, if somebody can build a great 650B randonneur bike, there is little doubt that their 700C version will ride just as well. (The corollary does not always apply: fitting wide 650B tires into a frame is much harder than designing a bike for narrower 700C tires.)

A good example is the Bilenky tandem we tested in Vol.  9, No. 2 (above). Our test bike was set up with multiple racks for a full camping load. It rode beautifully, but it was a bit on the heavy side. (This didn’t keep us from riding the tandem in a 400 km brevet at an average speed of 30 km/h, including stops.)
Does this mean that if you want a lightweight tandem, you should go somewhere else? Of course not; removing weight from the tandem we tested would be pretty easy.

In fact, Bilenky recently completed a similar tandem (above) that they claim to weigh 3 kg (6.6 lb) less than our test bike, simply by eliminating the extra racks and using lighter-gauge tubing.
We hope that most readers find our reviews useful and don’t get sidetracked by details that are easy to change.

Fenders, racks and other attachments can remain maintenance-free for 10,000+ miles, yet other bikes require tightening bolts on a regular basis. Why do some bolts stay tight, while others loosen quickly?
We have covered this in detail in Bicycle Quarterly’s article “Engineering a Bicycle” in Vol. 5, No. 4. The essential concept is simple: Vibrations of parts allow bolts and nuts to loosen. (At the end of the post is a link to a video that shows this in action.) The more parts you have that vibrate, the quicker your bolts loosen. Here is how to avoid this:
Do not use the same bolt to attach several things. The more “layers” you have, the more movement results, and the quicker the bolt will loosen. This is especially true for front racks that are attached to the posts of cantilever (or centerpull) brakes.

The rack above is more likely to come loose than the one below, which uses a bolt with a forward extension, onto which the rack is mounted.

Even simple metal washers increase the risk of bolts coming loose by adding another layer between bolt and the surface into which the bolt threads. Spacers are even worse, because they provide a longer lever arm for the forces that vibrate the bolt head.
Washers should be used only where they are needed, for example, to provide a smooth surface when a bolt head tightens onto paint or aluminum. Spacers should be avoided in most situations. (It is better to make your parts to fit together properly.)
All connections should be designed so that the bolts won’t tend to rotate. For example, the rack below attaches to the fork crown with straight tubes that are aligned to the vibrations of the rack (forward and backward).

If these connecting tubes were angled or even curved, then each vibration would tend to turn the bolt.

Another neat detail of this particular rack is the forked mount for the lower bolts that carry the weight of the load. This is the best possible attachment. Here is why:

With a simple mount (above), the surface underneath the bolt head and the surface underneath the nut move independently from each other. The bolts loosens as the parts vibrate.

With a forked mount (above), the two surfaces (under the bolt’s head and under the nut) no longer move against each other, so the bolt experiences much less force that could loosen it.
There is more to consider when designing good connections. And it’s true that even sub-optimal connections can work fine. The bottom line is simple: On a well-designed bike, there should be little need to re-tighten bolts.
Recently, Peter Meilstrup posted a link to video that shows how bolts loosen. I find it especially impressive to see how the nuts turn as they vibrate. And commonly used lockwashers actually make things worse! It is obvious that there is no substitute for good design. Click here to see the video.

Lightweight frames, made from high-strength tubing, were thought to be stiffer than ordinary frames. They performed better for most cyclists, but the conclusion that stiffer frames were better was erroneous. Eventually, this led the makers of steel bicycles down the wrong path and may have hastened their demise.
When the plague ravaged Europe during the 14th century, people noticed that the disease arrived together with herds of cats. They concluded that the cats brought the disease and responded by killing as many cats as possible. Only much later was it discovered that the plague was transmitted by fleas that lived on rats. Cats arrived with the plague only because they preyed on the rats. So killing the cats actually made things worse, by allowing the rats to multiply.
This reminds me of bicycles and frame stiffness. For decades, riders have assumed that stiffer frames were more efficient, and thus faster. At the same time, physics tells us that a lighter bike is faster uphill and in accelerations. Stiffness and weight are conflicting goals: To make a frame stiffer, you need more material. To make it lighter, you need less material.

There was a apparent solution to this problem: high-strength steels allowed tubing makers to use less material without giving up strength. Reynolds 531 and other modern steel tubes enabled builders to craft lightweight frames. Even though these frames were light, they felt very stiff when the builders bent the tubes to align the frame. Many old builders have told me: “The lightweight Reynolds 531 was twice as stiff as ‘drainpipe’ (ordinary steel tubing). And the superlight 753 was three times stiffer than 531.”
The riders usually found that the “stiffer” bikes made from high-strength tubing performed better. This “confirmed” that stiffer bikes were faster:
1) Observation 1 (builders): high-strength tubing = stiffer frame
2) Observation 2 (riders): high-strength tubing = better performance
3) Conclusion: stiffer frame = better performance

However, Observation 1 is incorrect: The builders mistook yield strength for stiffness.
Yield strength determines how far you have to bend a frame until it no longer springs back, but “takes a set.” High-strength tubing has a higher yield strength.
Stiffness determines how much force is required to flex a frame a certain distance. All steels have roughly the same stiffness (modulus of elasticity). The only reason the high-strength frame is harder to bend is that you have to flex it further until you reach the yield point, where it does not spring back any longer.
Even though the high-strength tubing didn’t make the frames stiffer, the higher performance was no fluke. For most riders, a Reynolds 531 frame performed better than a “drainpipe” frame, and a Reynolds 753 frame performed better yet. The observation was correct, even though the explanation was incorrect.
For riders and builders, it didn’t matter that their “stiffer” frames in reality were more flexible (because the tubing walls were thinner), as long as they performed better. All was well for decades: Builders knew how to make well-performing frames, and riders loved riding them. Whether they really were stiff or not didn’t matter.
Things changed when new materials became more prominent during the 1980s: aluminum, titanium and carbon fiber. At first, most bikes made from these new materials were not very stiff, but they were very light. Many riders liked them.
How could the makers of steel bicycles counter the new competition? It was hard to compete on weight, so they focused on stiffness instead. To make a stiffer bike without a huge weight penalty, you increase the diameter of the tubes, and you get a great increase in stiffness with only a small increase in weight. That is how oversize steel tubing became popular.

Some makers also offered tubes in all kinds of shapes for improved stiffness in certain directions (above). There were even spiral-shaped reinforcements inside the tubes to increase stiffness (below).

It is ironic that by making their bikes stiffer, the makers of steel bikes may have hastened their demise. (In effect, they killed the cats instead of going after the rats and their fleas.) Instead of making their bikes perform better, they actually returned to the ride characteristics and performance of stiff frames from the early days of cycling.
The makers of aluminum bikes could make their bikes even stiffer, because aluminum’s lower density makes super-large tubing diameters possible with very little weight penalty. (In the medieval analogy, the aluminum bike makers invented a more efficient way of killing cats.) Their bikes also fell by the wayside. (Even Cannondale, the pioneer of oversized aluminum tubing, now uses carbon fiber for their top-of-the-line models.)
Carbon fiber and titanium became the preferred materials for high-end bikes. Ironically, the last steel bikes ridden by top-level amateur racers were made from the superlight (and super-flexible) Reynolds 753 tubing. I remember seeing them under riders whose sponsors would have loved to give them a new bike…
In recent years, it has become clear that many riders perform better on flexible frames, apparently because it allows them to apply their power more efficiently. Many riders and builders extol the virtues of a “lively” frame made from flexible tubing. When we tested different frame tubing in a double-blind test (Bicycle Quarterly Vol. 6, No. 4), we found that two of three riders preferred the most flexible frame both for constant efforts and for all-out sprints. (The third rider could not tell the – very small – differences between the frames in our test.)
Of course, the real story is more complex. There is more to bicycle performance than overall frame stiffness. Frames can be too flexible for a given rider and application. Some riders may even prefer very stiff frames. However, it is clear that the old mantra of stiffer = more performance is not true for most riders.
The main conclusion for me is: False explanations of real phenomena may work for a while, but eventually they will lead you down the wrong path. Whether it’s trying to combat the plague or producing bicycle frames with better performance, we need to examine the real explanations beyond the current beliefs. That is why Bicycle Quarterly does fundamental research to determine what really makes a bicycle perform, rather than just try and figure out how to make bikes stiffer.

Rapha recently introduced their “Paris-Brest-Paris Jersey.” It is designed specifically for randonneuring, and as a bonus, it comes with a reflective vest. The vest has generated considerable interest among randonneurs…
Randonneuring requires riding at night. To improve rider safety, randonneuring rules not only require lights, but also reflective clothing. Reflective vests are a good idea also for all other cyclists who ride at night.
At the PBP equipment check, riders will have to show that their lights are operable, that they have spare batteries if they use battery-powered lights, and that they have an EN-approved reflective vest. This last requirement has changed recently, and most of the reflective clothing that riders have been using does not meet the new EN standard 1150. As a result, many randonneurs are looking for a new reflective vest to take to PBP.
At the check-in for PBP, the organizers will sell the “official” PBP vest that meets the requirements (right in photo above). Our club ordered these vests this spring, so I got to try it before arriving in Paris. In addition, Rapha sent me a jersey and their vest (left in photo above) for a test.
Official PBP Vest
Cost: $ 35
Size tested: Small
Weight: 183 g
Country of manufacture: not indicated
Availability: PBP check-in

The “official” vest is a substantial garment made from polyester, with numerous reflective stripes glued and sewn on. When I did not wear it, the vest took up more space in my handlebar bag than my (admittedly very small) raincoat. At 183 g, it is relatively heavy.
The sizing runs large. I usually wear Medium cycling jerseys, but a size Small vest fit me well even with two wool jerseys underneath. I wore the vest during our 600 km brevet. The night was cool, but not cold, and the vest provided a little additional insulation. The vest was well-fitted and did not flap much even during high-speed descents. The vest absorbs significant amounts of water when riding in the rain. Randonneurs from the American South have reported that the vest got soaked in sweat during hot nights on the bike, making it uncomfortable to wear.
While the “official” vests reflects well and meets the PBP rules, its bulkiness, heavy weight, and limited use in a layering system makes this vest a relatively poor choice for randonneurs.
Rapha Paris-Brest-Paris Jersey and Vest
Cost: $ 205 (registered PBP entrants get a 20% discount after they e-mail their registration confirmation)
Size tested: Medium
Weight: 293 g (jersey)/73 g (vest)
Country of manufacture: China
Availability: www.rapha.cc

Rapha recently introduced their PBP jersey, which comes with a “complimentary” reflective “gilet.” I really liked Rapha’s bib shorts (Bicycle Quarterly Vol. 9, No. 3), so I had high expectations for the jersey.
The “Paris-Brest-Paris” jersey has as many features as you’d expect from a cycling jersey for James Bond. Two of its 6 pockets are hidden, and there are multiple zippers. I carry my luggage in a handlebar bag, so these features are of  little use for me. The jersey is relatively heavy at 293 g. (A “racing” Polyester jersey weighs 143 g.)
On the road, the Medium jersey did not fit very well. I found that its cut was restrictive over my shoulders, and the fabric bunched up under my armpits. The 60% Polyester/40% Wool fabric felt clammy once I started to sweat, even though it was not very hot. The jersey features a lined pocket on the left side of the chest, which blocked the air circulating through the jersey on one side only.
Contrasting with the feature-laden jersey, Rapha’s reflective vest uses a minimalist design. It is built like a “windbreaker” vest with ample mesh panels on the sides and back. The vest folds into the space of a small apple, and it weighs just 73 g. The Rapha vest does not meet the EN standard, but some riders have suggested asking whether it could be used in PBP. (It is unfortunate that Rapha did not consult with the PBP organizers to make their PBP vest meet the new rules.)
The Rapha vest’s pink color may be less suitable for riding in rural America, but in France, it should not raise any concerns. The Medium size fit me well. In the rain, the vest does not absorb significant amounts of moisture. My only concern is the placement of the reflective material. This consists of a black and a white stripe on the front and back. The stripes on the back are placed so high that they are barely visible on a rider who is riding in the drops (see photo below). The black Rapha logo also is reflective. However, the black reflective material is not very effective (see photo at the top of this post).

Conclusion
The official PBP vest offers good reflectivity, but its bulk and non-technical fabric make it a less appealing choice. On the plus side, it is affordable.
The Rapha reflective vest is a lightweight performance garment with great potential. Unfortunately, it falls short on its main purpose, which is to increase the rider’s visibility. Only the white stripe offers good reflectivity, and it is attached too high for optimum visibility from behind. The black reflective material is not very effective. And you have to buy the jersey to get the vest.
I still haven’t found the ideal vest, and it’s a disadvantage to have so little time before the event to figure it out. Here are the current PBP rules. The ideal vest would use Rapha’s minimalist design with the “official” vests reflective materials. Come to think of it, I might be able to sew some of the “EN-approved” reflective material onto the Rapha vest…

A number of readers have asked where the cover photo of our blog (above) was taken. Here is the story:
An old road above Leschi in Seattle switchbacks though an Olmsted Park, with a set of  S-curves that we use for assessing a bike’s handling. It’s downhill, and with a bit of pedaling, you can build enough speed to make this truly challenging.

The first curve is an off-camber left with a decreasing radius (above). The best way around is cutting across the centerline in mid-corner once you get a clear sight line ahead. In the rare case that there is oncoming traffic, you get to test the brakes: Straighten the bike briefly while braking hard, then make a sharper turn at lower speed. Good brake modulation is key, so you can brake while the bike still is leaning into the curve.

If you rounded the left-hand curve at maximum speed, you immediately have to line up for the second curve. This right-hander is not particularly tricky, but the severe bumps make it crucial to pick a line close to the curb, where the pavement is a little smoother (above). For this, you need a bike that corners on a constant radius and can be placed on the road with precision.
Most modern racing bikes tend to drift outward once they are past the apex of the turn. In this corner, this puts you on the worst bumps. As you lose traction, you tend to run even wider and into the oncoming lane. This is a bad idea as a tunnel under an abandoned cablecar right-of-way obscures the occasional uphill traffic. In addition to precise handling,  you want wide, supple tires for optimum traction on the bumpy pavement.
For the photo, the cornering was the easy part, as the low-trail MAP test bike with its 42 mm tires went exactly where I directed it. However, the digital camera we carried on this ride had a hard time focusing. We wanted a nice lean angle, which meant approaching the camera at considerable speed. We did a good number of runs, and in the end, only one photo was in focus, more through luck than anything else. (I wished I had brought my old Nikon with manual focus, which you focus on a crack in the pavement and then hit the shutter release when the rider arrives at that spot.) Fortunately, that one useful photo, taken by Hahn Rossman, turned out to be just about perfect.
Further reading:

• Cornering on a Constant Radius. Bicycle Quarterly Vol. 8, No. 2, p. 56.
• Bike Test: MAP Project Randonneur. Bicycle Quarterly Vol. 9, No. 1, p. 36.

New theoretical research in bicycle stability shows that many parameters interact to make a bicycle stable. No single parameter (e.g.: trail, head angle, wheel size, weight distribution) determines whether a bicycle is stable or not. When one parameter is altered, then the other parameters may need to be changed to arrive at a stable bicycle again. This matches our on-the-road experience of having to adjust a bike’s geometry for different wheel sizes, load placements, etc.
For more than a century, scientists have tried to resolve why bicycles are self-stable, that is, why they tend to stay upright even without rider input. When a bicycle starts falling over, it automatically steers into the lean, thus righting itself (see video below). In the past, it has been assumed that either the gyroscopic forces of the front wheel cause the wheel to steer into the lean, or that geometric trail and related forces re-align the front wheel.
[youtube http://www.youtube.com/watch?v=j0ilP8kb8dM?rel=0&w=640&h=390]
Bicycle Quarterly contributor Jim Papadopoulos was part of a team of researchers from the Technical University in Delft (Netherlands) and Cornell University who examined the stability of bicycles. Their paper was published in the prestigious journal Science this month, so we now can share their findings and discuss the implications.
Based on theoretical calculations, they discovered that neither trail nor gyroscopic forces are required to make a bicycle stable. To test this, they built a bicycle with negative trail and a second set of wheels that spin in the opposite direction and cancel the gyroscopic forces of the wheels (see photo on top of this post).
As predicted by their calculations, this bicycle was able to roll without falling over, as long as it remained above a certain speed. Even if it was pushed sharply sideways (see the researcher push the bike in the movie below), it would right itself and continue to roll. The authors concluded that the bike steered into the lean because the mass distribution makes the front fork fall faster than the rear frame when the bike starts to lean. If the bike falls to the left, the front wheel turns to the left. Moving the front wheel to the left steers both wheels underneath the center of gravity. The bike is upright again and goes straight.
[youtube http://www.youtube.com/watch?v=v6GUZ2aEPLM?rel=0&w=640&h=390]
The “no trail/no gyro” test bike was a final validation of the bicycle stability calculations. The researchers found that no single number could predict whether a bike was stable. There are many possible designs with and without trail, and with and without gyroscopic forces, that are unstable. Many factors are interrelated, and together, they determine the self-stability of a bicycle.
Does this mean that trail and gyroscopic forces are unimportant in determining a bicycle’s handling? Not at all. However, the research confirms that these factors should not be taken in isolation. All factors are interdependent, and if you change one, you need to change the others to retain the desired handling characteristics of your bicycle. That means that to offer similar handling, a bike with a handlebar bag should have a different geometry from a bike carrying a saddlebag. A geometry optimized for single bike will not work the same on a tandem. Simple statements like “xx mm of trail offers neutral handling” only make sense in very narrow applications (for example, racing bikes with 23 mm tires), if at all.
I hope this research will lead to a confluence of theory and practice of bicycle handling. In the past, bicycles have been designed by trial-and-error. Similarly, Bicycle Quarterly’s articles on bicycle handling came from riding different bicycles, and making observations about them, rather than trying to solve the problem of bicycle handling mathematically. Theoretical studies still have a long way to go, since they do not yet include rider inputs. That said, a better understanding of the physics of bicycle stability can only help with our understanding of these fascinating machines.
Further reading:

• More on the latest research, including a final draft of the Science paper.
• More video of the test bike.
• How to Design a Well-Handling Bicycle. Bicycle Quarterly Vol. 5, No. 3.
• Front-End Geometry for Different Speeds, Loads and Tire Sizes. Bicycle Quarterly Vol. 3, No. 3.

For an article in Adventure Cyclist, I needed a photo on braking technique, so my children and I went to a steep hill in Discovery Park. They rode up and down the hill while I snapped photos. Even though the photo above has a little speed blur, I like it so much that I want to share it with a wider audience. You really can see how braking on a bike works:

• The front tire compresses a lot as the inertia of bike and rider put most of the weight on the front wheel.
• The rear wheel is barely touching the ground.
• To counter this forward weight transfer, the rider pushes his body backward.
• He locks his arms to prevent going over the bars. (Cyclists go over the bars not because the bike rotates around the front hub, but because they fly forward when the bike slows down.)
• He picked a line on clean asphalt away from the mossy edge of the road for better traction.
• With good traction, the rider uses only the front brake. (The rear wheel is barely touching the ground, so any braking there would cause a skid.)

Add to that powerful V brakes and grippy tires, and it’s amazing how quickly a bike can stop. I am glad my children have practiced braking hard. Hopefully, it will be instinctive when they need to stop in a hurry.