Tag Archives: bicycle

Checklist for fixing up a used bicycle

The following checklist, inspired by Cycle Jam at the Canberra Environment Centre, is to make a used bicycle safe and rideable. It is just a minimum; it does not optimise a bike.

Frame should not have cracks. Frame should not be bent.
Handlebar should not rotate in clamp.
Handlebar clamp should not rotate relative to front wheel.
Brake levers and shifters should not rotate on the handlebar.
Both brakes should be securely attached to the frame.
Brake levers should not hit the handlebar.
Brake pads should hit the rim when the brake is pulled, not the wheel or the spokes. Brake pads should be more than 1mm thick. Brake cables should slide reasonably in their housing.
Wheels should not be so bent that either the brakes rub or the brake levers hit the handlebar and prevent braking. Spokes should not be broken or loose.
Wheels should not clunk side to side on axle. Preferably wheel bearings should not grind either.
Wheels should be seated in the dropouts properly.
Quick releases of wheels should be closed properly.
Headset should not clunk, preferably not grind either.
Bottom bracket should not clunk side to side, preferably not grind either.
Crankarms and pedals should not clunk on their attachment point, ideally pedal bearings should not grind.
Seatpost clamp securely fastened, quick release closed properly. Seat securely attached to seatpost.
Chainring bolts should be tight.
Tires pumped, not too worn or cracked. Valve stem straight (pointing to the hub).
Suspension (if any) working reasonably.

Check shifting into all gears front and rear. If problems, then:
Front derailleur should be securely attached to the frame at the correct height, not bent or angled wrong.
Front derailleur limit screws should not allow the chain to come off.
Rear derailleur securely attached to frame, not too bent.
Shifter cables should slide reasonably in their housing.
Chain should be neither too worn nor too long (sagging, too many links).

Optimizing a bike for commuting

The objective is to get from point A to point B every day, minimizing some combination of time, effort and cost. The objective is not to get exercise (in that case, take a longer route, make the bike heavier) or to win a sprint. If cost is not a concern, then of course get the best bike money can buy. It is still not obvious this should be the fastest road bike.

The total time spent on bike commuting includes maintenance, locking and unlocking the bike and any other unavoidable tasks. A high-end road bike with thin tires may save some time every day, but gets flat tires more frequently than a thick-tired mountain bike. Each occasion of a flat tire costs significant time, plus some money. The time cost occurs randomly, which for most people is worse than if it were predictable and could be scheduled.

Thin wheels get bent more easily than thick ones, again requiring maintenance. Thus the fastest commute is not achieved by the lightest, thinnest bike. Reliability is what influences both time and cost the most.

Wheel and tire width affects weight, aerodynamic resistance, rolling resistance, flat tire and wheel bend frequency and ride comfort. The lowest rolling resistance occurs when the tire pressure is such that vertical tire thickness drops 15% under load (F. Berto, Bicycle Quarterly Vol 5 No 1). Tire tread pattern has such a small effect on rolling resistance that it can be ignored for commuters. The tire thickness that minimizes rolling resistance is 22-23 mm (wheelenergy.com). The thinner the wheel and tire, the lower the aerodynamic resistance, but this effect is under 1% of effort, small enough to ignore for commuters (http://www.biketechreview.com/index.php/reviews/wheels/63-wheel-performance). Wheel weight and inertia have an even smaller effect.

The thicker the wheel, the less chance of it bending (other things equal – wheels of weak material or poor construction bend no matter what). More expensive wheels are on average stronger and lighter. The thicker the tire, the lower the probability of punctures and pinch flats. For a commuter, it is optimal to choose wheels and tires heavy and thick enough to never bend or get flats on normal roads (having some potholes, broken glass etc). In my experience, this means thicker than 25 mm road tires and thinner than 50 mm mountain bike tires.

Punctures are less likely than pinch flats even with 25 mm tires. Puncture probability can be further reduced with e.g. Kevlar-lined tires, which add less than 40 dollars to cost.

It sounds like I am advocating a hybrid bike – these have intermediate thickness wheels and tires and are supposedly designed for commuting. My experience with the one hybrid I tried (Apollo Trace 10) was very bad. Both wheels bent enough to hit the brakes in less than a month of half an hour per day riding and two spokes broke on the rear wheel. Looking closely at the wheel, the substandard manufacturing was obvious. My speculation is that hybrids may be low quality because they are marketed to people who on average are not bike fans, ride little and in flat road conditions. They thus cannot distinguish quality levels and may buy a bike mainly based on its flashy paint. Road and mountain bikes, on the other hand, may be bought by more knowledgeable customers. For these to sell, they may need some minimum reliability.

It would be good to have bicycle reliability statistics like there exist for cars. Then this would be the best source to base bike choice on, not recommendations from friends, forums or bike shops.

What matters for speed and ease of riding is first the fit of the bike to the rider and second the maintenance of the wheels and drive train. The weight and general flashiness of the bike are far less important.

I think that the best used bike for a given price is better than the best new for that price, because clueless customers go for new, and some people want to demonstrate their wealth by replacing their high quality used bike with new at short intervals. They sell a high quality used bike for cheap to make room in the garage. I got a great on a used bike: a like-new 2008 Giant OCR 1 for 350 AUD. But this is just one data point.

A residential bike shop business model

There is an empty market niche for a neighbourhood mechanic who accepts a bike in the evening and returns it in the morning. The demand is concentrated almost entirely outside business hours – evening, early morning, weekend. Opening the residential neighbourhood shop at those times would target cyclists whose bike breaks down on the commute from work to home. An overnight fix means they would not miss their next morning’s ride and would not have to haul the bike to a city shop by some other transportation.

Currently the neighbourhood shops I have seen are open during regular business hours, perhaps close a little later and open also on the weekend. I have not checked, but they must be almost customerless in the daytime on weekdays. People go to work or school. I doubt there are enough stay-at-homes who bike enough to require a mechanic’s services frequently. People in the city may visit a city bike shop at lunch, but not a residential neighbourhood one. The local shops seem to be open exactly when the customers are not there.

Fixing a bike takes time, so cyclists leave it in the shop and come back later. It is important which time of the day the bike spends at the mechanic’s. Customers who use their bike a lot and thus need frequent service want the bike available and working mainly during rush hours, because many of them commute with it. A city bike shop open during business hours can accept a bike in the morning, fix it and give it back by the end of the workday. For the commuter, the bike is available both morning and evening. The shop does not need to store the bike overnight, so does not need to rent a large space, saving costs. In a suburban shop, customers could leave their bike one evening and pick it up the next evening, but they could not use their bike for one day’s commute then.

Load sharing between city and suburban bike shops is possible. Mechanics can work in several shops at different times. They can shift to accommodate peak demand, the timing of which differs by shop. The residential neighbourhood shop would get the most customers on the weekend or outside business hours. The city centre would get more on weekdays in the daytime (the cyclists whose bike breaks down on the way to work).

On electric bikes and science news

There is some debate on whether electric-assist bikes are good or bad. The argument on the negative side is that people will stop cycling and bike roads will be taken over by these (electric-)motorized vehicles. On the positive side, the claim is that electric bikes replace motor scooters, cars and public transit, which is good for the environment and perhaps health if people actually pedal their electric bike a bit. To summarize: electric bikes good if replace motor vehicles, electric bikes bad if replace bicycles or walking. It is an empirical question what the substitution sizes are.

There are many calls for scientists to communicate better, engage the public, present their results simply and interestingly etc. Whether more science news and popular science is good or bad depends on what it replaces, just like for electric bikes. If dumbed down entertainment science replaces the rigorous variety, this is bad. If science news replaces brainless news (celebrity gossip, funny animals, speculation on future events), it is good. It is an empirical question to what extent scientists switch to popular topics and crafting press releases if their evaluations rely more on outreach or policy impact. Also a question for the data is which news are left out of print to make room for more science news.

To maximize education of the public, there is a tradeoff between the seriousness of the science presented and the size of the audience. Research article level complexity is accessible to only a few experts. Entertainment is watched by many, but does not educate. The optimum must be somewhere in the middle.

Similarly, difficult courses in a university have few students taking them, but teach those few more than fun and easy subjects. The best complexity level is somewhere between standup comedy and a research seminar.

Of bicycle bells

In Australia, it is compulsory to have a bell or horn on a bike to warn other road users. This seems strange, because when cycling, hands are in use, but the mouth is not. So it would make sense to use the mouth to produce sounds, leaving the hands for steering. Perhaps a better law would require cyclists to be able to produce the bell or horn sound, giving them the choice of whether to use their mouth or a device for this.