Cost-Benefit Comparison: Folding vs. Mountain Electric Bicycles

Mike leroy

Active Member
This post explains how to apply Prospect Theory to eBike purchases. Prospect Theory explains the psychology of decision-making. People are willing to pay a certain cost to gain a particular benefit. I prefer the term "Cost-Benefit Comparison" to Prospect Theory.

Five basic decision types are illustrated as Star Plots below. The tradeoffs you make result in decisions that balance:
  1. Benefits (contains six categories)
  2. Purposes
  3. Costs
  4. Risks
  5. Biases

The six eBike benefit categories were adopted from Bosch marketing research. The categories are applicable to many other products or personal situations:
    • Economy
    • Excitement
    • Ease
    • Enjoyment
    • Elegance
    • Endurance
The six benefit categories represent bicycle features. The features are scored. The benefit category score is the averaged features score. Features often appear in long and tiresome bicycle specification sheets.

Folding bicycles do have a clear Purpose, compactness, which is rated a 5 on s scale from 1 to 5. My initial preconceptions concerning folding eBikes are diagrammed in the following Star Plot. A three rating indicates average, normal or no significant difference. The left-hand side of the Star Plot represents Benefits. The right-hand side represents psychological aspects of decision-making.

StarPlotFoldingBiasNegative.png

Prospect Theory helps me find mistakes in my decision-making process. Personal biases often interfere with good decisions. My personal bias against folding eBikes was very strong. Ford's Future Mobility project features folding eBikes, which caused me to re-consider folding eBikes.

My strong bias against folding bikes was based on misconceptions. The small size was perceived as weakness and low quality. Folding bikes are typically half the cost of most eBikes. The small wheel size appears comical to me. Small folding eBikes remind me of clowns riding unicycles at the circus.

My first mistake was stereotyping folding bicycles as having small wheels. Folding bicycles are available in any wheel size, but I lacked the motivation to uncover that fact. Three more exceptions to my generalizations are listed below:
  1. NYCE customized Dahon Formula 18. - Bionx 350W to 700W peak - very powerful. seems very similar to Ford MoDe:Me eBike.
  2. Mu Rohloff 14. - 523% gear ratio - as high a climbing ratio as possible.
  3. Full Suspension Jetstream D8. - compact mountain bike.

Ease of use depends upon wheel size. In this example, Ease is the first benefit category considered. One needs to ride bikes of different wheel sizes, to determine comfortable wheel sizes for your body size. Tires provide shock absorption, which is another Ease benefit. The surface you ride on is a factor determining tire selection. Tire width, height and low PSI levels affect tire shock absorption capability.

A sturdy rear rack is an essential Ease benefit. I want to carry 40 pounds of food from the store. A rear suspension limits rack options to seat post racks. Seat post racks do not support panniers (i.e., saddle bags). A rear suspension is a very important Ease benefit in my situation.

Traction could be considered an Ease or Endurance benefit, depending upon the conditions of your situation. The clay ground on my path becomes very slippery when wet. Tire tread is a key factor in my decision, which favors a mountain bike. A tire like Schwable Crazy Bob is needed, which is available in 20, 24, or 26 inch sizes. The Schwable Pro Core is such an important safety feature, that it constrains the minimum wheel rim width to 23mm and 26, 27.5 or 29 inch sizes. The rim must also support the UST standard for low PSI traction, which is an Endurance benefit.

Some folding mountain bike frames are available. The tradeoff is between a car rack or convenience of storing the eBike inside the car. The more frequently one uses an eBike, the greater the Ease benefit is derived from a folding bike. Also, storage constraints influence the decision.

Endurance is the second most important benefit in my situation. Motor and battery features are important Endurance benefits. Brake features also affect Endurance on long downhill stretches. Motor, battery, gears and brake features are involved, which are topics best addressed separately. Gears are perhaps the biggest constraint for a folding bicycle. The Endurance benefit is lower, due to the need to compact the bike quickly, tightly and easily.

Elegance benefits are derived from design aesthetics, internal wiring and folding implementation. The degree of computer console and battery integration affect Elegance benefits. A smooth and sleek motor profile provides greater Elegance benefits.

Motor sound may improve or detract from Enjoyment benefits. Motor power contributes to both Enjoyment and Excitement benefits.

Economic benefits can be compared to parking, fuel and maintenance costs.

I run two miles to the grocery store and carry 30+ pounds of groceries home. My motivations are part fitness and environmental. Driving a big car to carry a small bag of food seems very wasteful to me. Unfortunately, I live in very steep hills caused by the San Andreas fault. The steepest road section is an 18% grade for about 300 yards. Few public roads are above 20% grade. Switchbacks are much more common than 20% grades. A 10% grade is steep.​

I have been unable to find a satisfactory eBike to carry 40 pounds of groceries up my 18% grade. The 750 watt 8Fun BBS02 may provide enough power. I prefer to wait for a 1,000W model, which is still a street legal bike in California. The lack of torque sensor makes gear shifting very awkward on steep hills, at slow speeds. I expect this feature to appear in the next model.

An Internally Geared Hub (IGH) is the solution for smooth uphill shifting. The IGH best suited to my hill costs $1,400, which provides low benefit, relative to cost. Additional costs and constraints, such as brake adapters make the IGH less attractive. Less expensive IGH are available, but their ability to handle 120Nm of torque is uncertain.

Also, my frame options are limited to conventional bicycles with 68 or 73mm bottom brackets. Mountain bikes typically have larger bottom brackets. Since the BBS02 is a conversion kit, the Elegance benefit is low.

The most reasonable solution is to drive an eBike past the steepest section. A folding eBike is the best solution, if I ride frequently. I only expect to ride to the grocery store about 50 times annually. A car rack or pushing the eBike uphill in walk-assist mode is more economical.

The two mile section of my grocery shopping traverses a gravel fire road between 5% and 10% grades, a grass field crossing ten street curbs and suburban streets. This short trip is a great testing ground. I always assumed I needed a mountain bike with full suspension to carry 40 pounds of groceries back from my local grocery store. Because my initial assumptions were unfounded, my Bias has swung in the opposite direction, probably an over-reaction.

StarPlotFoldingBiasPositive.png

Folding eBikes seem to require more effort to pedal than ordinary eBikes. Therefore, I rate the Endurance and Enjoyment benefits low. Perhaps the electric motor can compensate for this perception. Again, my perception may be biased. They key is to adjust your rating as you learn.


StarPlotFoldingBenefitBias.png

The Economy, Elegance and Ease Benefits are best discussed on an individual eBike basis. Since I have no educated guess, I score unknowns as a 3 on the scale from 1 to 5.

My eBike is highly tailored to my particular situation. The final decision is a put a conventional mountain bike, rather than a folding bike, on a car rack. However, buying a new full-suspension mountain bike to convert with the BBS02 motor is still too risky for the benefits. I decided to wait another year for a complete solution from a major, international eBike company. Service is an important Risk factor. My situation will stress the eBike to its limits. I expect to take the bike to the shop on a regular basis for maintenance and upgrades.

My initial bias and intuitive guess was correct for reasons unclear to me. Elaborating the costs, constraints and benefits clarified a complicated decision.
 
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Mike leroy

Active Member
The Benefit categories are flexible. Create any set of categories and features to reflect your situation. The Benefit categories displayed in this post originated from Bosch Marketing material.

For illustration purposes, let's change the categories and the subordinated features for folding bicycles. Suppose we are interested in the bicycle frame differences. We create a Benefit Category named Frame. To rate the Frame category, we add features such as Bottom Bracket, Folding, etc.... Our new Star Plot appears below:

StarPlotFrameCategory.png
 
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