My E-Bike Experiences: Comparing and Contrasting Drive Types

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by Larry Fuchtman, PCI #724T
Arizona State University Police Department

Over the past few years, I’ve had the opportunity to ride some different e-Bikes. I own one for commuting. My agency owns four; two different brands. This article isn’t about brands or what to buy. It is an evaluation of the different drive systems and what to consider when you shop. Geometry, tire size, battery power, and all those other things are individualized, so you are the best person to consider those options. I intend to compare the drive types and how they affect the equipment.

If you are reading this, you probably already know there are two drive types: mid-drive and hub-drive.

A mid-drive bike has a motor in the bottom bracket. This means the energy from the motor is transferred directly into the crank arms. That energy then pulls the chain from the top of the chain ring to the top of the cog where the chain is – all the energy pulls across the top of the drivetrain. The same thing happens to the energy you put into the pedal. The result is that an e-Bike now puts significantly more energy into the top of the drive train. In my experience, this has translated into stretched chains and worn cogs. The cogs wear more quickly when they have fewer teeth.

I started commuting on my e-Bike in 2020. After putting about 400 miles (644 km) on it, I noticed some skipping in the chain. As I inspected the bike and diagnosed the problem, I found the 11-tooth cog was worn out. I was very surprised. I have never seen a cog wear out in 400 miles – not even close. I thought I knew why but I did some online research. I found a forum and discussion specific to my bicycle. The comments on there validated my theory: because of the energy transferred into the chain, the pull on the cog is too much for the design. Well, crap. I really didn’t want to change my 11-tooth cog every 400 miles. I also didn’t want to ride more slowly. I was commuting, which meant I wanted to maximize my speed on the roadway – 28 mph (48 kph) on my Class 3 e-Bike.

As I considered solutions, I decided to buy a bigger chainring and a bigger cassette to better disperse the energy of the system across more teeth in the chainring and cogs. The bike came with a 40 tooth chainring and an 11-42t cassette. At 28 mph, I was in the 11t cog on my 40t chainring. I’m a bit particular about my cadence when riding steady speeds for considerable time. Because I live in the Phoenix metropolitan area, I rarely ride hills on the roadway. I found a cadence calculator online at https://www.bikecalc.com/archives/speeds-at-cadence.html. ; I was able to find the combination I needed: a 52t chainring and 15t cog resulted in 28 mph of travel with a cadence of 93rpm. I bought it and built it and now have ridden thousands of miles without changing a cog.

Another interesting tidbit with this story is a conversation I had with a bike mechanic. He explained that my process would not result in a change in wear because the energy would be constant. I tried to explain that the energy would also be spread across a greater distance and a greater number of teeth on the cog and chainring. He refused to believe me. I’m not sharing this to mock this stranger you’ve never met. I’m sharing it to demonstrate that we all have weaknesses and blind spots, sometimes in our area of “expertise.”

The second drive system is a hub-drive motor. It is built into the rear hub. I’ve also heard it called a rear-drive or a direct-drive. My agency purchased two e-Bikes with hub-drive motors. After about one year, we began experiencing broken spokes. We were replacing them regularly. After a significant amount of time and research, we diagnosed the problem. The energy from a hub-drive motor is produced in the rear hub. That energy is transferred directly into the spokes and then the rim of the rear wheel. We found the spokes all broke at the j-bend. Spokes are manufactured as straight rods. The j-bend is created after production. Bending the metal at this point makes it the weakest point on the spoke. In addition, that j-bend is in contact with the hub through the spoke hole, causing friction at that point but at no other point on the spoke. The result? The spokes broke – at the j-bend.

After consulting the company, we were referred to the “spoke guru” of Phoenix. I’m sure there are many opinions out there about who is a guru of what, but I really did enjoy working with Robert at Rage Cycles in Phoenix. Also, they have a dog in the store. Anyway, after talking with him, we opted to build new wheels with (1) a stronger rim, (2) heavier gauge spokes, and (3) a straighter angle from hub to rim. We have had them in place for about one year now and we haven’t had a broken spoke yet.

One of the main contributors to our problems is how our employees ride. They tend to go as fast as they can. I’ve tried education, influence, and threats of taking away the e-Bikes. Nothing has worked. I don’t understand. When I was a young, aggressive cop, I always listened to everyone and followed every safety rule. (Insert sarcasm font here.) I share this because you will likely experience some of this if you purchase e-Bikes for your agency.

As we all know (sometimes too well), new equipment will have glitches. Some problems simply won’t appear until time has had its impact. I will share one final thought. A couple months after commuting on my e-Bike, I hit something and sliced my tire. I went to the bike shop to buy a new one and the salesperson tried to sell me a tire built for e-Bikes. I asked what was different and he said it was “heavy duty” to handle the extra weight of the e-Bike.

I asked him this: “If I weigh 220 pounds (100kg) and my regular bike weighs 25 pounds (11kg), that’s 245 pounds (111kg). If my friend weighs 180 pounds (82kg) and rides an e-Bike that weighs 55 pounds (25kg), that’s 235 pounds (107kg). Should I buy e-Bike tires for all my bikes since I’m heavier?”

He smiled and acknowledged the flaw in the logic. Yep, some things aren’t really thought through. I hope I’ve helped at least one person out there with an e-Bike question.

Let my trials be your investment.

Larry is a lieutenant with the Arizona State University Police Department. He has been in law enforcement for 28 years. He has been an IPMBA instructor since 2005 and an Instructor Trainer since 2019. He can be reached at larry.fuchtman@gmail.com.

Photos courtesy QG North America/Benelli E-Bikes.

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