TSDZ2, mini 750W mid-drive with torque sensing

The TS in TSDZ2 stands for Tong Sheng, and that company decided a few years ago to make a mid drive kit that was as small as possible, but it would still be able to meet the 500W power restrictions of Canada, Austria, and Switzerland. Electric bike experimenters have figured out that it can actually put out an occasional peak of 750W, and it’s growing popularity has caught my attention. Here’s what I could find out about it…

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The tiny mid drive with torque sensing

How small is this small mid drive? take a look at the pics below. From the right side it is almost completely hidden behind the large chainring (and trust me you will want a largish chainring). And from the left side you can see that the only place to put it is below the bottom bracket (BB, the pedal-spindle assembly).

 

 

 

Europe really likes what’s called “pedal assist”, meaning an electric bike over there is typically NOT set up to use a hand throttle. When you pedal, the power is applied. And when you stop pedaling, the power stops. They have a “street legal”  speed limit on ebikes of about 16-MPH (25 km/h). You can go faster if you want, but…over 16-MPH, you can’t add any electric power.

The USA has a 20-MPH speed limit for ebikes on streets, and the power limit is 750W (one horse-power). I don’t want to get off on a rant, but it’s illegal in the USA to ride on the sidewalks, and the slowest side-street speed limit is 25-MPH, so…if an ebike commuter wants to share the road with 4,000-lb steel death-machines that are operated by texting zombie-drivers, we have to back-up the traffic with our puny 20-MPH legal ebikes.

To be fair, as long as you keep it under 100-lb, you can get your ebike licensed and insured as a 45-MPH moped, which grants you the right to ride in traffic with tons of horsepower. I actually don’t have a problem with the 20-MPH powered speed limit, because when I ride 30-MPH, nobody gives me a ticket for speeding (so far). But I have  a big issue with the power limit. Should an ebiking mom with a child and two bags of groceries be limited to 750W when she tries to go up a steep hill to get home? Should she walk, or just take a car? [rant over]

Getting back to Pedal Assist Sensors (PAS)…there are two main types. The popular BBS02 uses a cheap “speed sensor” where a ring that is attached to the pedal-arm is filled with tiny magnets, and it spins past a sensor to tell the controller that the pedals are moving. It’s popular because it works “well enough”, and it helps to keep the price down.

The other style (the more expensive one) is called a “torque sensor” (TS). There is one TS style that is built into a bottom-bracket spindle to activate a hubmotor. And there is even a TS style that monitors the tension on the chain.

 

One of the things that experimenters like about the TSDZ2 is that it has both, a torque sensor and speed sensing. A “strain gauge” is a tiny but sophisticated device that measures the strain that occurs in a metal object, as force is applied to it. An ebike torque-sensor is a specialized type of strain gauge.

I’m mentioning a lot about torque-sensors because many ebikers like it…and some like it a LOT. I have ridden many factory ebikes with TS, and I appreciate its virtues. The power application is instantly on, and when you stop pedaling, it is instantly off. One key feature is that the harder you pedal, the more power it applies, with a very smooth transition.

PAS power levels are adjustable, regardless of the type. TS enthusiasts often mention that it is a more natural and intuitive cycling experience to use a TS type of PAS. The expensive factory drives from Bosch, Yamaha, and Continental use this. But those companies won’t sell it in a kit that can be added to a frame that you already own. There are only a few companies that will sell a TS kit (Lingbei, Xofo, etc), and the TSDZ2 is not only the most available, it is also the most popular.

If you are annoyed by a speed-sensing ebike with it’s “delayed power on, and delayed off”, the time interval can be adjusted, but…like most people, I am not concerned about it. My favorite ebike has a 1500W BBSHD. It takes a 1/4 turn of the pedals to start power (or I can start with the hand-throttle), and after I stop pedaling, it takes a second for power to stop.

I spoke to some people from Bafang, and they actually feel that the delay is a safety feature. If power is instantly on from a slight pedal movement, the bike could jump when you don’t want it to, or someone simply bumps into the pedals when you are at a standstill.

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36V, or 48V?

I had stumbled across the TSDZ2 a few years ago, but at 36V and being adjustable to 250W-500W, I wasn’t interested in it, and there was always something more interesting to write about at the time. Well, one of the quirks of the TSDZ2 is that the controller is a  mass-produced unit by Kunteng/KT, and it uses a programmable master chip that is unpotted (not sealed under a thick coating of water-proofing goop). That makes the programming easy to hack (more on that below).

When I was un-impressed by the TSDZ2 years ago, it was a 36V unit that had a max adjustability of 500W, which means it was clearly designed for all the nations outside of the USA (admittedly a huge market), but if you start using this unit at 48V, I’m told it really wakes up (33% more watts, without a significant increase of heat).

Now, it’s finally time to address the elephant in the room, which is the TSDZ2’s biggest competition. The Bafang BBS02 (the BBS01 uses 36V, the BBS02 uses 48V/52V).

Both of these mid drives have a poor heat-shedding path from the hot stator to the outer aluminum shell, so it is typically better to hot rod them by increasing the volts instead of the “heat producing” amps. That being said, the “750W” BBS02 has a better heat-shedding path, and also it starts out with more copper mass in the motor.

If you add a temperature sensor and follow the rules of wise mid-drive operations (always shift to the proper gear, don’t start out in high gear), the BBS02 is regularly run at (52V X 20A =) 1100W. To be clear, the TSDZ2 is maxed-out at 48V X 18A = 860W (I recommend 52V X 16A, plus a temp sensor). If you are one of those people who wants to obey the law, even though you live in a land where the police don’t know how to read a multimeter, I recommend 52V X 14A for a true 750W. The fewer amps you use, the cooler it will run. If you rarely end up using the highest power settings, you should lower the max amps to reduce the motor heat.

For people in Europe, part of the appeal is that Tong Sheng actually makes a street-legal 250W drive using the same body, so this tiny 750W motor looks legal. Did I mention that it’s tiny? I’ve seen coffee cups that were larger (and daddy likes his coffee).

The controller will likely overheat at any amp level above 18A, so the path to the max power is using more volts. Plus, a 48V battery can power an inverter to provide 120V AC to your home during a power outage. A 36V battery cannot. Most home back-up inverters will accept 48V/52V (13S/14S), so…the 48V/52V batteries are my favorite.

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Let’s open it up!

I have occasionally wanted to write a certain article, but if I couldn’t find any pics, there would be no article. By the time I finally became somewhat curious about the TSDZ2, there are now plenty of user-posted pics to add.

Here is a 23-minute video of tearing down a TSDZ2 (click here).

 

 

The infamous TSDZ2 side-cover

The Tong Sheng TSDZ2 has a water-proof rating of IP54, which is pretty good. Notice that the side-cover above has a rubber O-ring around its’ edge. I would also recommend spraying the controller with a conformal coating, and then drilling a tiny 1/8th inch diameter hole at the center-bottom of the cover to allow any condensed humidity to drip out (instead of building up inside).

 

 

The three larger 16-ga Blue/Green/Yellow (BGY) wires above are the motor phase wires (18A max). The five smaller wires that are attached to the white plug, they are for the Hall sensors. The red and black Hall wires are the positive and negative for all three Hall sensors (5V), and the thin BGY wires are for the on/off signal from the three Hall sensors to the controller.

As you can ALSO see…there are many layers between the hot stator and the aluminum shell, and not enough contact between them to help absorb the peak heat, and then shed it to the outside air. This runs fine on 500W, but 750W requires caution.

 

 

The helical gears shown above (spirally shaped teeth), are more expensive than straight-cut “spur” teeth, but…they run quieter at high RPMs. The blue plastic reduction gear also acts a a “mechanical fuse” so that…if someone applies too much power? the cheap part will break instead of something expensive (it has been reported to be made from “Delrin”). Also be aware that it is not just the “applied power” that is a concern, the heat that you cause can make the blue plastic gear softer, which lowers it’s power rating.

The blue gear has 36T, and the metal drive gear has 8T, for a 4.5:1 reduction in RPM’s, and a 4.5:1 increase of torque at the output of the blue gear.

 

 

The TSDZ2 uses a 3-phase Permanent Magnet/PM in-runner motor, 18 poles on the stator (3-phase, so 6 poles per phase), 16 poles on the rotor (8 pole-pairs). You can read our article on the how and why of motor design by clicking here

 

 

Now…let’s move on the the chain side

 

 

With the clutch-bearing types found on a bicycle, the shaft can spin freely in one direction, but…then when it spins the other way, the shaft “grabs” the outer bearing-shell, and they both spin together. The three most common styles are a sprag, ramped-roller, and pawl.

For a 10-minute video on how to swap-out the sprag clutch, click here.

 

 

 

The secondary has a 93T gear being driven by an 10T, so it is an 9.3:1 reduction (the primary “blue gear” was 4.5:1), for a total of 4.5 X 9.3 = 41.8:1 reduction between the 4,000-RPM motor and the pedals. Having a very high reduction like this allows a fairly modest motor to put out a decent amount of torque.

 

 

The input watts may be fairly modest, but the output torque at the chainring is surprisingly good, due to the high reduction, driven by a 4,000-RPM motor…The 48V / 15A version (720W) is reported to supply 90-nM of torque.

 

 

If you hot rod a TSDZ2, there are many parts that could be damaged by the added heat, but…as far as the mechanical limits, the three main culprits are shown in the pic above. If the blue plastic gear is damaged, you can replace it with a readily available brass gear, however…the drive WILL be noticeably louder after that.

Inside that primary reduction gear is a roller-clutch bearing (shown in the middle of the pic above). The stock 500W unit is made from “Chinesium”, which is a blend of recycled Chinese scrap steel and expired South-Korean cheese. If it dies, replace them with very affordable units from Japan or Germany…

Here is a video from an Italian website that shows how to replace the blue nylon reduction gear with a brass upgrade gear.

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110-BCD and two chainrings

The TSDZ2 comes with one 42T chainring, which uses a fairly common 110-BCD mounting pattern (110mm, Bolt Center Diameter ). However, due to its’ modest power level, some builders are been very appreciative that this style is easily adaptable to using two chainrings and a derailleur.

I honestly believe that anyone who uses 750W (or more) will eventually realize that they can be happy with the simplicity of a single chainring with no bottom bracket derailleur, but…some builders still want this, and the TSDZ2 is one of the few mid drives that allow that.

 

 

If you don’t want to hack the controller firmware (which voids the warranty, see below), the stock unit comes with a 90-RPM power cutoff. This is why I mentioned earlier that you may actually want a large chainring. When the pedals reach 90-RPM, the power stops, so a larger chainring raises the road-speed where the motor-power will still be applied.

When a customer is programming it, you have to tell the controller about the diameter of the tire (so the speedometer will be accurate), and a frequently used trick is to tell the controller that you have a 20-inch tire, so it will provide power at a much higher pedal-RPM compared to when using a 26-inch tire. Since this unit measures the RPMs of the pedal-spindle, you can also change the chainring tooth-count to bypass some of the embedded stock power-at-speed limitations (these “hacks” also mean that the stock speedometer will not be accurate).

The stock single chainring has 42T. Using a 42T on the front will provide about 28-MPH when using an 11T rear sprocket on a 27.5-inch tire, when using an unrestricted controller. I am firmly against ANY power limits, but I do believe that the current 28-MPH (45 km/h) federal speed limit for ebikes in the USA is actually very reasonable.

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Here’s a Review…

“…I prefer the Tongsheng and here’s why: It’s much smoother and blends into the normal bike riding experience, but still giving a nice boost. Although the Bafang is more powerful, it’s more like riding a moped and not as intuitive. With the BBS02, you just spin the pedals and go. With the TDSZ2 you have to apply pressure to the pedals and so it feels more natural. That said, I highly recommend both, but I prefer the TSDZ2. 

Power: The BBS02 delivers 100% power as soon as you start rotating the pedals. It can be too much power if you have it on a high setting. The BBS02 can be set on levels 1-to-9. I typically kept mine on 4. It’s only when I wanted turbo speed that I increased it to 9. I found that I frequently adjusted the power levels, like gears, so I could keep it in control. If I had it on a high level, it could lurch unexpectedly.

The TSDZ2, on the other hand, is torque-sensitive, so it detects how much pressure is put on the pedals and delivers more power the harder you pedal. The TSDZ2 delivers the power more smoothly, so I never feel the need to adjust the levels. The second I reduce pressure on the pedals, the motor slows down. The TSDZ2 has 4 levels. I usually leave mine on 3 and just forget about it.

The BBS02 can be programmed using a special cable to adjust how quickly it reacts to pedal inputs. Some people insist this improves the performance and smoothness, but I haven’t tried this.

 

 

Brakes: With the BBS02, I often used the e-brakes to cutoff the motor. I would often gently squeeze the brakes, even if I was still pedaling, if I’m going near traffic or pedestrians. Then I would release the brakes and the motor would re-engage. You don’t really need e-brakes with the TSDZ2. I would just pedal more lightly and the motor turns off. It’s more intuitive. In fact, I re-installed my regular brakes instead of using e-brakes (bonus: less wires). There is no fear of lurching. It’s just smoother. Most TSDZ2 kits don’t come with e-brakes or a throttle, and you don’t really need it.

Gear sensor: Also, I purchased and installed a gear sensor for the BBS02. Changing gears under power can cause them to grind and get damaged. The gear sensor temporarily cuts off the motor as the gears change. The TSDZ2 doesn’t have this option, but, again, it doesn’t seem to need it. The motor cuts off very quickly when you stop pedaling or reduce pressure on the pedals. It’s like how it works normally on a bike. 

Speed: The BBS02 is faster and more powerful. The speed limiter on the BBS02 can be removed (up to 99km/hr) with the C965 display. The TSDZ2 speed limit can be set up to 45km/hr (although you can set the wheel size to smaller than actual to bypass this, although the speedometer will not be accurate). 
Also, I have found it difficult to get past 40-km/h on flats with the TSDZ2. I think that is because the assist cuts out beyond a certain level of RPM. A larger front chain ring would help if speed is what you need. The default chain ring is 42T. There is also a setting for “power adjustment”, which may help if I increase it.

With the BBS02, pedaling is just for looks. You don’t put much pressure on the pedals. However, the power is great. The BBS02 has great torque and you can fly off the starting line. With the TSDZ2, you will put in slightly more effort. But let’s be clear, it’s still a powerful electric motor and with not much effort, you can get quickly up to top speed.

Throttle: A hand-throttle is available for both, but it’s unnecessary with the TSDZ2. I didn’t use my throttle either with the BBS02. I preferred to engage the pedals. I found it uncomfortable using the throttle exclusively, since you are putting 100% of your weight on your seat. That is why ebikes need softer seats, full-suspension, or seat shocks. I did use the BBS02 throttle sometimes when I didn’t have my feet in the right position and I needed to accelerate quickly.

Display: The Tongsheng VLCD5 display is big. Slightly too big. I wish it were smaller. Although it does have a USB port [editor: to power a GPS or smart phone]. I ordered the smaller XH18 display which fits on the left handle. Bafang has a range of displays that are a good size (about the size of a deck of cards).

 

 

Build Quality: The Tongsheng seems like a nicer build quality. Both drives are solid. The Tongsheng is a little lighter than the Bafang (but also less powerful). The chain ring on the BBS02 seems cheap and people often replace them. The chain ring protector on the BBS02 is plastic and the one on the TSDZ2 is metal.

Noise: The Tongsheng is quieter. While the BBS02 is quiet, there is still a humming sound. I can barely hear the TSDZ2.  [editor: noise between the TSDZ2 and BBS02 seems to be hit or miss, due to manufacturing variations]

Battery usage: I didn’t really test it scientifically, but the TSDZ2 seems to last much longer. Which makes sense, since it has a lower wattage, and it doesn’t deliver quite as much power [editor: adding your legs by pedaling always doubles the miles of the battery on any mid drive. If you swap-in a hand-throttle and only use that, you will get half the miles on the TSDZ2]

Installation: Basically, the same. However, if you don’t have to install ebrakes or a gear sensor, then that saves time. I have not done much bike maintenance before this, so it took me a while, but it was still easy to figure out. I needed to go to the bike shop to have them help me remove the bottom bracket since I didn’t have the right tools for that.

Community: The Bafang products are more popular and have been widely used, tested, and customized. There are more tutorials, information, and guides by far than for the Tongsheng products. 

Bottom line:
I recommend the TSDZ2 if you want an electric motor to assist you, but still retain the intuitive feel of riding the bike. It’s much better for a novice rider or someone who isn’t comfortable dealing with the complexity of controlling the motor. I recommend the BBS02 if you value high speed and power and don’t mind giving up the bike-like feel. Or upgrade to the BBSHD for even more power…”

Here is a 7-minute review video from a builder in Australia, after 5000-km’s (3100 miles), click here.

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Temp sensor, and the 8-pin cable

I highly recommend using 48V (or 52V) instead of 36V. If you use the open-source firmware, you can actually unlock the controller to provide up to 30A, but plenty of  experimenters have fried their TSDZ2 by using only 18A, but…they were using it too often. To get the max possible power, I recommend the old formula of raising the volts as high as it can go, and to use just barely enough amps to accomplish your goals.

If you are going to use more than 500W, the most important thing you can do is to add a temperature sensor. Of course you can use a stand-alone unit with a digital display, but another option is to make sure you buy the TSDZ2 8-pin cable version (instead of the six pin), and that allows you (or the dealer you bought it from) to program the controller to automatically roll-back the amps when the motor starts getting hot.

If you have the 8-pin cable version, you don’t have to use the OS firmware or temp sensor, but…it is there if you ever decide to use it. Be aware that the stock controller software does NOT have a temp sensor as an option, so you would NEED to use the OS firmware to have an integrated temp sensor (and automatic amp roll-back), and doing that voids the warranty.

 

 

If the TSDZ2 turns out to be “not enough power” for you, then using a temp sensor means that you can at least sell it while it is still running, to recoup some of your investment. The worst case scenario is that you fry it while testing it [without a temp sensor], and then you can’t sell it for any price. 140F (60C) is near ideal when under load. Getting close to 200F (93C) means that you may have de-magnetized the permanent magnets, or caused some other damage.

 

 

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Open Source Firmware

The “hardware” in the controller is easy to understand, they are the the physical components that are soldered together to make up the electronics. The “firmware” is the part of the software that is NOT adjustable by the customer. The purpose of even having firmware is understandable. This drive was designed for the huge European market, and many of those governments are very involved in restricting the power of any ebike product that will be used to ride on their public streets.

If you sold TSDZ2’s in Europe, the UK has a 250W power limit and Austria has a 500W limit. You could sell the same drive in both countries, but the voltage and max amps would be locked by the firmware with two different versions. Typical “software” adjustments by the customer would be the diameter of the tire, resetting the odometer to zero at the beginning of a trip, the level of assist, etc…

In the USA (where the street-legal power limit is 750W), many powerful kits [like my 1500W BBSHD] are sold as “off road use only”. However there are many Euro countries that don’t allow that. Depending on which country you sell the TSDZ2 in, you can lock the firmware into limiting the volts to 24V, 36V, or 48V…and the max amps can be locked at any level that the dealer desires.

One of the biggest problems with mid drives is that the customers who buy them can make stupid mistakes. Even after you have warned them, they will sometimes start their ebike from a dead stop, in the top gear, on a steep uphill, while using the max possible amps. If you do this enough, the drive will overheat and die. The factory drives from Bosch, Yamaha, Brose, and Continental all have integrated safety features to protect you from yourself. The TSDZ2 gives you the freedom to destroy it with bad decisions.

The TSDZ2 controller is made by Kunteng/KT, and it uses a well-known programmable chip, and being able to “re-flash” the firmware is something that was already a known capability. But…once you make the decision to unlock the firmware, what program do you load into it?

A brilliant programmer from Portugal who calls himself “casainho” has developed an open-source firmware program for the TSDZ2. One of the benefits of unlocking the controller is to be able to use a 14S battery (sometimes called 52V). Doing that means you can get 750W from only 15A, in  order to keep the heat as low as possible. Another benefit of 52V is that it gives you the option of using a “56V” EGO lawn tool battery pack (which is actually 14S, regardless of the name).

A battery pack that has 14 lithium cells in series (14S) is often referred to as a 52V pack, but when it is fully-charged to 4.2V per cell (we recommend 4.1V, click here), the actual pack voltage would be 58.8V. The EGO company calls their 14S pack a “56V”. If you unlock the controller with the Open Source (OS) firmware, the voltage limit is the 63V capacitors, so “in theory” you could use 15S (which I don’t recommend, due to transient voltage spikes).

The controllers’ unlocked amp-limit can be set to 30A, which is just silly…since hot rodders have done the hard work for you to verify that 18A is a hard ceiling. Using 20A will just start melting things, and any more amps than that will just melt them faster. If you want to start beefing-up the weak parts inside the motor and controller, you might as well just buy a BBS02.

Video of the TSDZ2 OS firmware, part-1

Here is the video on part-2

Here is the video on part-3

And finally, the video on part-4

Here is a 13-minute video review of the Open Source firmware

If you want to download the new OS firmware, click here

Here is an OS firmware testimonial that I simply had to include…

“…Jeff is actually classified as a quadriplegic. The location of his spinal cord injury from an accident left him with 50% biceps and 35% triceps, and no use of his hands. He is a real trooper. With the TSDZ2 motor, he cycles over 100 miles a week. Sometimes 50 miles on a single ride. There are a lot of people like Jeff whose quality of life can be dramatically improved with a TSDZ2 on a hand-cycle, but it requires the open firmware project to make it work the way they need it…”

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Internally Geared Hubs/IGH’s

Instead of using the common external gears on a 7-speed freewheel with a derailleur, or an 8-to-11 speed cassette, some builders like the sleek and uncluttered option of using an Internally Geared Hub / IGH (click here).

Some of the high-powered drives we have seen would break most IGH’s, but when you are using a low-powered and efficient kit like the TSDZ2, you have the option of using any IGH that is available, such as the popular 8-speed and 11-speed Alfine, from Shimano.

 

 

Speaking of efficiency, I do  not recommend adding a hand-throttle to this kit. There is nothing wrong with a hand-throttle, but if you like that, the BBS02 has a huge global community that can help you with any issue.

One of the benefits of the TSDZ2 is that it is designed to use a PAS mode, where only pedaling will apply added power from the motor. This is the single greatest method to ensure you get a fantastic amount of miles from your battery pack, and that means you can use a very small, light, and affordable pack. Most users are reporting more than two miles per amp-hour, so the 7.5-Ah 56V EGO pack (available at Home Depot hardware stores), would provide over 15 miles.

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One TSDZ2 Quirk

“…There’s one problem that happens virtually every time it’s used by a new rider. The unit calibrates the torque sensing every time its switched on, and 95% of riders put one foot on a pedal and then turn the unit on, don’t ask me why, it’s just that the majority of riders seem to. By consequence, the calibration of the torque assist is way out of kilter and you get almost no assist…”

Keep your feet off the pedals when you turn it on.

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My Conclusion

I don’t own a TSDZ2, so take everything I say with a  fair amount of skepticism. Here are the benefits and drawbacks as I see them…

PRO’S

1. It’s an affordable 750W “USA-legal” kit, that you can add to your frame of choice
2. It’s the most available torque-sensing kit, and some riders LOVE a sweet TS
3. It is the absolute smallest 750W mid-drive kit available
4. IF…you are willing to void the warranty, there is a free firmware program that allows you to adjust every aspect of its performance and “feel”, and…many users are reporting that it works great (I don’t know, so don’t blame me).

Here are the CON’S

1. 750W is its max, and many new ebikers actually want MORE power (like me)
2. Very few dealers in the USA carry it
3. The “Q-factor” (from Quadracepts, meaning the width of the pedal placement) on the TSDZ2 is wider than average. Some riders swap-in the BBS02 crank arms, which reduces the Q from 210mm to 182mm. Some builders swap-in only the right-side crank arm to make the pedals more evenly spaced from the centerline of the bike.

 

I’ve ridden torque-sensing ebikes at Interbike, and I have to confess, I do like the feel. However, the ebike I ride the most right now is a 1500W BBSHD from Luna Cycle. When spring of 2019 arrives, my next project is boosting the BBSHD power to 2500W, so a 750W drive doesn’t interest me, no matter how smooth and seamless the power application is.

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USA dealers

 

Edit: As of January 2019, LunaCycle.com in southern California has started to carry these. Click here for the Luna price

One current USA retailer for the TSDZ2 is David in Tennessee at “eco-ebike.com”, which can be found by clicking here

Another USA dealer is Mark in SLC Utah, Electrify Bike Co, which can be found by clicking here.

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Edit: I found a well-done 26-minute video of installing a TSDZ2B onto a Yuba Mundo, click here.

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Written by Ron/spinningmagnets, December 2018