[Note: this is #1 in a series of 4 about bearings]

Hidden from sight in greasy, gritty recesses, bearings have the power to transform a bicycle’s performance. No wonder engineers pay attention. Nothing affects wheels and our quest to make great ones like bearings. Wheel building is faster and more informed the more you know about bearings. As we seek highest trueness and lowest rolling resistance, bearing design, function, and fitting becomes a major factor.

Overlooked for decades, bearings are one of the simplest yet most important parts of the bicycle. They transfer power, absorb nasty side loads, reduce friction, and help an otherwise unstable machine balance; all this with little weight, cost, or recognition. These dynamic elements have been around as long as the wheel and have played a central role in some of man’s greatest achievements.

STONE AGE ROOTS
When Neanderthals spun sticks above a central contact point, generating enough heat to start a fire, they had essentially harnessed the concept of rotation about a fixed center. That combination of load and motion would lead to the development of the wheel. It is also why the wheel center experiences concentrated wear. To reduce that wear, man used hard woods and animal fat. Those bearings were crude, but still, the burden was off our backs and into the wagon.

By the time the Stone Age finished, materials with lower friction and greater wear resistance were available. Metallurgy offered options with lower friction than wood and longer life, but it was only the perfection of rolling elements that reduced bearing friction to negligible levels. That creation had to wait until the 19th century and with it came the bicycle’s meteoric development.

Cup and cone bearings on the early bicycle.

Rolling elements (initially balls) must be extremely round, smooth, and uniform in size. Making these is a mechanical marvel and required most of the advances of the industrial revolution. The biggest lynch pin was hard materials. Alloying iron with carbon created steel hard enough to survive the concentration of load in a small bearing. This discovery and further refinements make ball bearings possible. For a glimpse at these dazzling processes, check here. Note particularly after 2min, the making of the balls.

Not holiday ornaments, but humble ball bearings.

BYE, BYE FRICTION
Reduction in friction is miraculous. Archibald Sharp in his 1896 masterpiece, Bicycles and Tricycles, asserted that the rolling friction of ball bearings is 1/1,000 the weight of the rider. In other words, thanks to ball bearings, it takes a thousand times more force to lift your body than to push it forward (the same distance). By that measure, less than 1 per cent of riding energy is absorbed by bearing friction.

One-percent is a pretty sweet number considering the size of human motors. Great competitors are reputed to sustain 500 watts of power for 40 minutes. Impressive but, nothing personal, that’s less than 3/4 horsepower. A pretty feeble lawnmower. Me, I probably generate less power than a fruit juicer. We need ball bearings.

So why are they often overlooked? Because they are tiny and their friction has been considered negligible for more than a century. More ball-bearing-related patents were filed for bicycle use than for any other purpose. Today, the proliferation of electric motors fuels an industry making low friction ball bearings that fit nicely into bikes. The bike industry concentrates on comfort, cost, weight, and efficiency. Bearing are available off the shelf and friction remains negligible.

Annular (radial) contact cartridge bearing. Made by the millions for electric motors and work well in bicycles.

How are bearings so efficient? Simple: they concentrate loads onto tiny contact points with very hard materials. The entire weight of bicycle and rider is transferred to the ground through the bearing mechanism. Within the bearing, each ball rests on a steel raceway at a spot that is microscopic. With super hard (undeformable) metals for both surfaces, friction is microscopic too.

ALL SHAPES AND SIZES
There are several types of bearings used in bicycles. First are bearings with rolling elements, what we’ve discussed so far. Second are plain bearings, which consist of close fitting, smooth surfaces. Bushings are plain bearings. Hubs use rolling bearings with tiny balls. Derailleur pulleys, brake pivots and rear-suspension links often use bushings.

Rolling bearings can be categorized in at least two primary ways: the shape of the rolling element and the angle of contact. The rolling element can be a sphere (ball), a cylinder, or a shape that resembles a cone or barrel (toroidal). Bearings with balls offer the lowest friction because their contact point is so small, but those with other shapes can support greater loads because they have larger contact area. Since bicycles see relatively low loads compared to many other machines, there is little need for non-ball rolling elements.

Curtis Odom uses magneto type bearings on some of his hubs. These are cartridge but disassemblable, much like cup and cone. More costly but magnificent low friction. © Curtis Odom

Thanks to its single-track nature, bicycles and their bearings see few side forces. By single track, I mean one wheel following the other. When cornering, bike and rider lean into a turn. G-forces generated by the turn are in the plane of the frame, right down to the tire-ground contact. From a wheel’s point of view, these are radial loads. So, radial-contact (annular) ball bearings suit the job.

One area where non-radial loads exist is steering. In a headset, loads are huge and sideways to the bearing. But at the same time, a single-track vehicle requires low steering friction. Why? How?

That’s where we’ll explore in the second of four Dirty Secrets installments about bearings. Our point: for wheel builders to know about bearings to build better, faster wheels, by understanding the role they play as we center the hub in the rim with high, uniform tension. Otherwise, you might think the wheel was actually interfering with your build!

We carried P&K Lie truing stands for 14yrs, ending that representation in 2021. Now, please contact them directly for stands.

A shipment of P&K Lie stands is on the way. Anticipating the arrival produces a childlike excitement in me that I’m sure is familiar to many of you. Some items have a beauty and uniqueness that never fails to dazzle.

Wish I could have seen the crowd at the P&K booth at Eurobike 2014. There was no hope of my attending but I can imagine the stunned expressions of amazement, appreciation, and lust. A frame as beautiful as exquisite wheels is no surprise. Bike design benefits from a balance of quality. Truing stands to match (and exceed) the beauty of fine wheels are rare.

P&K stands have owned the “Most Beautiful and Effective” title for years now but it still comes as a visual shock to those seeing them for the first time. This year they jazzed up their display at Eurobike. When Kerstin was in the fashion trade, Peter built futuristic furniture for her studio. Wow, right off a film set.

Snazzy furniture at the P&K workshop.

Against these arresting pieces was a colorful array of stands. When our shipment arrives, we will have blue, red, green, and black!

On display at Eurobike.

The best news for many is the return of P&K’s famous spoke wrench. We’ve been without for a full year. The new production includes five colors (green, black, blue, silver and red). Welcome back, trusty 3.25mm model.

Headed our way.

I have recently corresponded with Mike Tierney, a wheel builder and writer from Ontario. He epitomizes one of cycling’s healthiest habits: avoiding high tech glitz. This runs deep in our industry and sport. Bicycles at very modest cost can deliver such joy and function. And wheel builders are among the most rightfully proud as it requires next to no tooling investment to make great wheels. From Mike’s mouth:

I’ve always been the champion of motivating people to build wheels by using the least amount of equipment (less initial investment = more potential Newby wheelbuilders). So I practise what I preach!  Heck it wasn’t until about 3 years ago that I owned a wheel stand!  I used frame and fork for 48 years! 

Mike’s practical view powers cycling across the globe, nearly irrespective of economic conditions. While we dearly hope that never changes, there are good excuses to own fine tools. Wheel building tends to short itself in this department.

In the US, most $2000 wheel sets are built on $200 stands. Nothing wrong,  but for many working hard on their skills and careers, a stand like P&K is justifiable. Perfectly executed as the highest level cycling components, genuinely effective for speeding and improving building, and fabulously good looking.

Builders can’t stay away.

Eurobike 2014 saw Vittoria debut a high end wheel line . Check this artistic video of their service center. Vittoria values both beauty and function.

Let’s finish with a shout out for one of USA Cycling’s oldest and best programs, the annual Bill Woodul Race Mechanics Clinic. The 2014 session was a big success, graduating 64 mechanics. Next years (usually late November/early December) fills up fast, so stay tuned.

I was proud to bring a P&K Special250 stand. Here it provides background to one of the Clinic sessions.

Students learning from the best.

I hope some of you have the opportunity to attend a Clinic or try a P&K stand. Or both!