Category Archives: gearing

Some observations about bike-share bikes

I recently spent several hours riding in Montreal with a companion who was using the Bixi bike-share bicycles. These are similar if not identical to others being deployed in North American cities. I have some experience riding a Hubway bicycle in Boston, too.

These bicycles are designed to meet different requirements, compared with a rider-owned bicycle. A few observations:

  • The user is relieved of the burden of servicing the bicycles. That is advantageous– there are no worries about flat tires or other mechanical problems. If a bicycle becomes unrideable, you walk it to the nearest rental stand and trade it for another. A related advantage, especially for city dwellers, is that there is no need to store or secure one’s own bicycle.
  • The bicycles are rugged, and so they are heavy.
  • The three-speed hubs are not overgeared, like those on classic three-speed bicycles. The top gear is about right for level-ground cruising. These bicycles climb better than the classic three-speed in the lower gears, but still, the limited gear range and weight of the bicycle make it unsuitable for steep climbs except when using the “two-foot gear” (that is: get off and walk). My companion found one Bixi bicycle with a Shimano 7-speed hub, which he used for part of our ride, but never found another despite looking for one among several dozens waiting at rental stands.
  • The bicycles have fenders, integral lights powered by a generator in the front hub, and a (front) baggage rack, all features necessary for practical transportation use. Additional baggage capacity would be nice but would require a rear rack.
  • The very low step-through frames and skirt guards either side of the rear wheel allow a person to straddle one of these bicycles even if hardly able to left a foot off the ground, and to ride in an ankle-length skirt.
  • The skirt guards carry advertising logos — a reminder that the bike-share (actually, bike-rental) program doesn’t pay for itself.
  • Many features of the bicycles are designed specifically to prevent vandalism and theft. Wheels are not removable using conventional tools, tire valves are not accessible, the seatpost cannot be pulled all the way out etc. Some of the anti-theft features come at the expense of performance…
  • My companion found that the seatposts on most of these bicycles could not be extended far enough for full leg extension, though he is a full 5’7″ (170
    cm) tall.
  • All the bicycles have flat pedals. If you prefer clip-in pedals or toe clips and straps, you’ll have to ride your own bicycle.
  • The street-tread MTB tires are inflated rock-hard. Evidently, protecting the rims rates higher than rider comfort.
  • Hub brakes — Shimano Rollerbrakes front and rear — allow rims to be out of alignment without affecting braking, but these brakes are weak. The front brake appears to have a power limiter, or else it is mismatched to the brake lever. Braking appears to reach a limit which does not increase, no matter how hard the lever is pulled. (I hope to do a braking distance test soon).
  • The black, padded saddles get uncomfortably hot sitting in the sun on a summer day.
  • The system recommends helmet use but doesn’t supply helmets. Boston is, as I understand, working on an automated helmet dispenser.
  • In both Boston and Montreal, rental stands are consistently placed in the street with the rear of the bicycle facing out into the street. Some are on busy streets. You must walk in the street and back the bicycle out into the street to disengage it from its dock. In many cases, the rental stand is on a one-way street or a street with a median, so the user must walk in the street or ride opposite the legal direction of traffic to get to the through street or bikeway which it services. Usually, one-way streets lead away from the serviced street, and so the travel opposite traffic is almost always at the start of the trip.
  • A user has to to walk to and from rental stands, same as bus stops. The bicycles don’t come with locks except to lock them to the rental stands. If you stop in mid-trip to have lunch or so shopping, you must bring your own lock, and the rental clock keeps running.
  • The Montreal system offers a 24-hour pass, but extra charges accrue for any bicycle that is kept in use for more than 1/2 hour. At cycle-track speeds while obeying traffic signals, that was good for 4 miles (6 km) or less. My companion would note where a rental stand was at the right distance to switch bicycles just short of the half-hour limit. The system made him wait two minutes before he could release another bicycle at the same rental stand. Even one minute over the 1/2 hour adds a charge of $1.75 for the next half-hour. The payment plan, then, provides a strong economic disincentive against longer trips.
  • Walk time seriously increases trip time beyond what it would be with the user’s own bicycle. On average, depending on distance of the start and end of the trip from the rental stand, the time overhead for a ride on one’s own bicycle is less even if it involves donning/removing special bicycling shoes, bicycle gloves and a helmet. There also is some uncertainty whether a bicycle will be available to start a trip, and whether there will be an empty space for docking at the end of a trip. Nonetheless, the program is popular.

I note that the on-street separated bikeways in Montreal have a speed limit of 20 km/h (12 mph). That is more or less what these bicycles are designed for. People riding their own bicycles commonly go faster. The design of the bike-share bicycles goes very much in the opposite direction from the racing spec hype that dominates the recreational cycling market.

All in all: when you ride one of these bicycles, you have been recruited into the bike mode share increase army. It’s like eating army food, which will fill your stomach but which is missing some of the nicer qualities of fancy cuisine or good home cooking. Or like sleeping in an army cot, which doesn’t quite compare with a bed in a fancy hotel, or your own bed at home. But then, an army provides for its soldiers, with a couple of tradeoffs, to be sure — the cost borne by the public at large, and the risk factor for soldiers.

Bike-share programs are structured as a public utility, as a form of public transit. The bicycles are requisitioned outside the usual stream of commerce of the bicycle retail industry. Whether the general sentiment in that industry is “a riding tide lifts all bikes” or that the competition is unfair, I don’t know. I did address that issue in an article I wrote for the Web site on April 1, 2012 — please take note of that date when evaluating my article.

Audible warnings

Some jurisdictions require a bicyclist to have an audible warning device, commonly a bell or horn.

My bicycle has an audible warning device. Well, actually, I have only one warning device which I move to whatever bicycle I happen to be riding: my operatically-trained voice. Though less courteous than a bell or horn to warn pedestrians, my voice can transmit messages, not only a warning — “bicycle behind you”; “passing on your left.” My voice can be modulated from a whisper to a shout, which is more likely to be audible inside motor vehicles than any bell or horn commonly sold for use on a bicycle (except an air horn, which would startle pedestrians right out of their shoes every time). Bells and little squeeze-bulb horns make the most sense on multi-use paths, but they are rather pointless when riding in the street.

My voice also operates without my having to remove a hand from a brake lever.

I live and ride in Massachusetts, USA. which requires an audible warning when overtaking a pedestrian, but doesn’t specify a device. That works for me.

Some bicyclists don’t like to install a bell on their bicycle; one claim is that there is limited “dashboard” space on drop bars.

I think that a more common objection is that these bicyclists don’t want to look geeky or add the horrifying couple of ounces of extra weight. After all, if there’s room for a bicycle computer one side of the handlebar stem, there’s room for a bell on the other side — or on the stem itself.

Bell and horn requirements could possibly be invoked by a police officer with nothing better to do, to cite bicyclists who are not committing any other offenses. If I had to defend myself against this charge in court, I’d bring little ding-ding bell, give a demonstration of it and of my voice, and ask whether the court could tell me seriously that the bell was a more effective warning device.

…and hope I didn’t have laryngitis on the trial date.

If I regularly rode where a bell is required by law, I suppose that I would install one. But I’d still use my voice most of the time.

Drive ratios of bicycle hub gears

My examination of drive ratios of the SRAM S7 hub has led to examination of other hub gears. I now have information on a very large number of hubs posted online in a Web version of a Microsoft Excel workbook — which includes a link to the source Excel file too.

The workbook gives exact (fractional) gear ratios as well as decimal approximations, and corrects a number of minor errors in manufacturers’ literature and online gear calculators. For most hubs, the information is calculated directly from gear-tooth counts and an examination of the hubs’ internals. The workbook page about each hub therefore indicates how the hub generates its ratios.

Thanks to the excellent Sturmey-Archer Heritage Web site and to documentation on the site of Tony Hadland, author of the book The Sturmey-Archer Story, I have information on Sturmey-Archer hubs all the way back to the first model sold, in 1902. I also cover most geared hubs from SRAM (and the companies it absorbed) and Shimano, and the Rohloff hub. Please see the acknowledgments page of the workbook for a list of people who have been helpful. Coverage of additional hubs will be added as the information comes to light. If you have information to contribute, please don’t be shy!

Why am I doing this? I’ll admit, I’m a bit of a math nerd. It’s been bothering me for years to see only inexact, and sometimes incorrect, decimal numbers given for the drive ratios. But also, I am writing an article for the technical journal Human Power about trends in the design of internal hub gears. My research toward the article has generated the information on drive ratios.

Very old Sturmey-Archer hub – made in USA?

I hold in my hand a piece of history. Some fortunate cyclist rode the hub shown below nearly a century ago. It turned up in the basement bike parts stash of my good friend, the late Sheldon Brown.


These hubs were made to last. Despite the rusted shell and the heavy wear to the inch-pitch sprocket, the gears and brake still engage. Clean oil seeps out — probably Sheldon’s work, and maybe he cleaned and reassembled the internals too, who knows. But even if so, the hub isn’t quite ready to lace up into a wheel and ride away — an indicator spindle and chain would need to be found or fabricated. Without them to shift the gears, the hub is a one-speed.

This looks very much like a Sturmey-Archer type F Tricoaster hub, made between 1907 and 1921 — as shown on the excellent Sturmey-Archer Heritage Web site.

However, the hub is labeled as a Type S rather than Type F, and it has 36 spoke holes rather than the 40 usual in British production. The lettering stamped onto the shell reads, in its entirety,



I inquired of Tony Hadland, author of the book The Sturmey-Archer Story, and he replied:

A 36-hole rear hub in the UK would be odd in those days – 40 was the norm. However, consulting my ‘The Sturmey-Archer Story’, I read that on 7 May 1914 Sturmey-Archer did a deal with Sears Roebuck & Co. Sears were to pay £500 for use of Sturmey-Archer’s US patents, plus a royalty on each hub. So I’m guessing the ‘S’ stands for Sears.”

If you are interested in this kind of history, I can recommend Hadland’s book highly. I found it selling at a highly-inflated price on, but Hadland pointed me to a much more reasonable source:

My Sturmey book … is still listed by the Veteran-Cycle Club at £13.75, same price its been since 1987! I suggest you email their book sales lady, Bibi Bugg, at bibibugg*at*

Don’t forget to read it in conjunction with the extensive supplement on my website.

And also, you might read Hadland’s history of Raleigh in the last quarter of the 20th Century.