Tongsheng TSDZ2 review

I ticked over 500km 1000km 1300km1it took me a little while to get round to publishing this, ok? on my Tongsheng TSDZ2 ebike conversion a few weeks ago, so it’s high time to get some thoughts down on (virtual) paper.

Given I’ve done a series of posts on the motor and fitting it to the bike (see here), I won’t go into too much detail on the nuts and bolts in this review. As a quick recap though:

  • The Tongsheng TSDZ2 is a retrofit ebike motor that will fit the vast majority of cycle frames with a threaded bottom bracket.
  • You pair it with a battery and an unassisted bike, do some intermediate-complexity bike-spannering, and you have a ebike.
  • Unlike kits where you swap out a wheel (BionX, Swytch, etc), the TSDZ2 is a mid-drive kit that replaces your existing bottom bracket and crankset. This is more complex to install, but once fitted is more efficient.
  • The TSDZ2 is “torque-sensing” – if you pedal gently, you get a gentle assist; if you pedal hard, the motor works harder. This differs from the other common mid-drive kit (Bafang) which is cadence sensing – you set the assistance you want, and so long as the pedals are turning, the motor gives that flat level of assist.

Finally, I’ve fitted the 48V, 250W version of the TSDZ2 (ie EU-legal), with the factory firmware. It’s paired with a 12Ah battery.

Is the TSDZ2 as good as a dedicated ebike?

Let’s start off with the key question – is a bike with a retrofitted Tongsheng TSDZ2 motor going to be as good as a dedicated ebike?

Answer: It’s Complicated.

As a motor considered in isolation, no; the TSDZ2 is not as good as an offering from Bosch, Shimano, or any of the other big players. It’s not as well made, generally not as powerful, you’ll be lucky to get a warranty unless a reseller offers it, and the interface and controls aren’t as polished.

However, is it possible to use the TSDZ2 to make yourself an ebike that is better for your specific needs than anything else on the market, and save a bunch of cash? Absolutely.

My electric Sutra is an excellent example. I wanted a 622-wheeled ebike2ie “conventional” road-bike wheel that could take front and rear racks, mudguards and spiked winter tyres, whilst being no longer than “normal” bike (so I could use trains without difficulty). I also prefer steel frames for comfort and longevity. That’s a relatively niche set of requirements, and not something offered by any manufacturer I could find. I’d have had to compromise with either smaller wheels or a longer length overall, and obviously a brand new ebike is not exactly cheap.

With the TSDZ2 I was able to take a bike I already owned and craft something that was exactly what I wanted. I also included a bunch of upgrades (hydraulic brakes, Surly Moloko handlebars), and still had change from £800. And (in my humble opinion), it doesn’t look half bad.

Hopefully as ebikes become more popular there’ll be a broader choice of off-the-peg offerings, but for now if your needs are at all “specialised”, you might find an easier route to happiness by finding the perfect bike first, and then electrifying it.

Bonus point: part of the reason it took me a while to publish this is that over the last month I’ve swapped the motor from the Kona Sutra to a brand new Kona Ute longtail3I decided that now I wasn’t using trains because of lockdown, actually, I did want a longer bike that could carry more stuff. It took about three hours to transfer the kit over, and it works just as well on the Ute as the Sutra. Something you just can’t do with a factory assist.

Good points and bad points about the TSDZ2

Let’s pick out the three best and worst bits.

Bad – manufacturing tolerances

The TSDZ2 is not as well made as anything from Bosch or Shimano. This is kind of inevitable given it’s much cheaper, but if you get an unlucky combination of part sizes you might find yourself with real problems. Things are nowhere near as bad as when the motors first came out (for tales of woe see this 321-page thread on Endless Sphere), but mine has a tendency for the bottom-bracket securing nut and crank bolts to work loose over time.

I deal with this by carrying the spanner around with me; if you have a more organised maintenance routine you could instead just snug it back up once a month, or use threadlock. And don’t bother with the spanner that comes with the kit: it’s too short and can’t be used without taking the crank off. Get yourself a lockring hook spanner.

Bad – battery indicator

The display that comes with most TSDZ2 kits is the catchily-named VLCD5. This is perfectly adequate, except for the battery remaining indicator, where it seems to try and estimate range remaining based on how hard you’re working the motor at the current moment. That sounds like a helpful thing, until you go up a hill and the “bar remaining” drops from four to two. Coast down the other side, and it’ll jump back up to five bars. Given there’s only six bars when full, the indicator is really only reliable to indicate “full”, “not full”, and “OMG flashing empty hope you’re nearly home”.

You can go by gut feel instead (with the kind of riding I do I can get about 80km from a full charge), and if you’re doing regular commutes you’ll quickly work out how often you need to charge, but it’s not ideal for maximising the life of your battery (where ideally you’d normally keep it between something like 30-80% charged).

Bad – max power output

I’ve already said that, even within the 250W constraints set by EU legislation, the TSDZ2 is not as powerful as some other offerings from Bosch and Shimano. That’s not a disaster as a more frugal motor will give you a longer range, but it would be nice to have a bit more oomph at the top end.

I suspect some of this is a necessary evil from the mounting system. It must be much more straightforward to deliver torque against the angular mount for a factory-fitted motor than against the smooth shell of a bottom bracket, where the only thing to lever against is the anti-torque bar above the chainstays. There’s presumably a desire to keep a healthy safety margin below whatever force is needed to damage those same chainstays.

I’ll also mentioned that Tongsheng’s firmware (ie the code that tells the motor how to behave) is a little weird. In particular, you get maximum assist at an oddly low cadence – about 60. It then tails off until at about 100 RPM you get very little help at all. This is not intuitive if you’ve mentally programmed yourself to spin up hills to stop your knees exploding; I sometimes need to change up to a harder gear if I want more help on a hill (this only works if you’re not already getting the max available power from the motor. If you are, then you need to change down to keep going. You’ll get the hang of it after a few weeks, honest).

However, see next point…

Good – it’s almost certainly powerful enough to change how you use your bike for the better

I said the TSDZ2 max power was a touch low, but it still does the job. My electrified Sutra weighs 36kg, I weight about 85kg, and even carrying about five kilos of shopping it’ll still trundle up a 12% hill at 20kph-ish. Add more weight (say my four-year-old), and you’ll need to change down another gear, and will be going up the same hill at maybe 15kph. On the flat it’ll happily get you up to 25kph (where the assist fades away; again, a legislation thing).

Plus, your bike is almost certainly going to weigh less than 36 kilos (even with the motor adding about 4kg, and call it another 3 for the battery). I have a thing for adding heavy accessories to bikes…

So yes, it might not be the magic “thou shalt never go below 25kph” that the Nihola Trekking was with its Shimano Steps system, but it will still make the world of difference if you want to reduce your reliance on a car or public transport. Also (and to my slight horror), there’s a range of cargobikes that you could electrify and still come under my Sutra’s total weight (eg the Yuba Mundo V5 is 26kg stock, albeit would pork up a bit if you add on child-wrangling accessories).

Good – so cheap!

OK, nothing related to ebikes is cheap, but the TSDZ2 is cracking value. Even buying from UK reseller Woosh Bikes (who, coincidentally, take Cycle to Work vouchers and offer a year warranty), a TSDZ2 kit including a 12AH battery was £660. You can’t buy Bosch or Shimano motors by themselves, but we can compare the price difference between electrified and non-electrified versions of the same bike to get a feel for the electric uplift:

  • Yuba Mundo (Shimano E8000 Steps): +£2,420
  • Bicicapace Justlong (Shimano E6100 Steps): +£1,870
  • Kona Ute (Bosch Performance CX 25kph): +£2,300
  • Surly Big Dummy/Easy (Bosch Performance CX, which isn’t EU-legal): +£2,200

(I’ve roughly converted euros and dollars to sterling, and this was done before we crash out with a no-deal Brexit. And again; those prices above are the difference between the electric model and the non-electric model; not the whole ebike.)

The TSDZ2 might not be as good, but you can buy a whole load of other upgrades for that price difference. Or, maybe, the TSDZ2 allows you to dip a toe in the electric bike world that was previously just unaffordable.

Good – user serviceable and upgradeable

At the moment, Bosch and Shimano motors have a two-year warranty from new. After that, if you get a fault, you either live with it or get a dealer to buy and fit a replacement motor (and from what I can tell it has to be exactly the same motor model – no upgrading). It’s not entirely clear how that process works, or whether dealers can get hold of spare parts, or just entire motors.

With the Tongsheng, spare parts are available even to amateur mechanics, and there’s a good amount of stuff online on how to replace parts.

(Big flip-side to this: at least Bosch/Shimano stuff does come with a manufacturer’s warranty, and is better built and far less likely to break in the first place. This isn’t much comfort if you’re having motor problems, but let’s not pretend that it’s all roses with Tongsheng.)

However, another big opportunity with the TSDZ2 is there’s a very active open-source firmware build available. This allows you to tweak a whole range of values (and sorts the diminishing-assist-with-increasing-cadence issue I mentioned earlier), add in a walk-assist mode, and apparently makes it feel like a completely different motor (in a good way).

A word of caution; if you’ve got a warranty from the place you bought the motor from, flashing a new firmware onto it would obviously void that. Plus I believe it’s possible to tweak the firmware to make the motor non-EU-legal, which would leave you riding an uninsured, un-registered motorbike (not a good situation to be in should you ever find yourself in a collision, regardless of fault).

Conclusion – would I buy it again?

Absolutely. I’ve already recommended it to a couple of people. In fact, I’d go so far as to say the only reasons not to go for a retrofit kit would be:

  • If you just want an off-the-shelf, buy-it-and-ride-away, no-maintenance-needed ebike. Nothing wrong with that; it’s not as if you would be asked to fit the engine to your car after buying.
  • If you wouldn’t be happy changing the bottom bracket on a normal bike. You could always get a shop to install it for you, but I imagine most would be a little hesitant around liability if the motor or battery fails.
  • If you need something with real oomph (because you’re towing a heavy trailer up a 15% hill twice a day and want to do it at 25kph, or something). At that point you really need a frame dedicated around a motor to handle the torque, and (as far as I’m aware), you can’t buy frames like that without the motor coming with it.

If you want an analogy, it’s a bit like the early days of smartphones with Android and Apple. If you wanted something to just work, didn’t mind Apple setting the rules on how it worked, and were willing to pay a premium; you bought an Apple phone. If, instead, you wanted something to work exactly the way you wanted it to, and didn’t mind a bit of effort to get it that way, you bought a cheaper Android handset.

If you’re thinking about it, just buy it. It’s excellent.

PS: as a sneaky preview its current incarnation:

About which, more later…


Add Yours →

The Shimano Steps we have is almost as terrible at range remaining. Because we tow a trailer much of the time, it’s obviously broken the curve it uses to estimate range. If I pick up at nursery with less than 10 miles range, I know I have to ration the e assist (it’s about two miles home).

Interesting to see that Shimano isn’t much better. Wish there was an option to see voltage remaining instead of the attempt at user-friendly-ness. (Actually, I suspect there *is* an option to do that in the custom firmware for the TSDZ2. Might have to be the summer project…)

Hi – Looks a good fit for the Ute. Did you use a different mounting method for the battery on it? I’ve gone for a 17.5ah battery on my bike which is pretty weighty, and not yet found a solution for mounting on the down tube I’m entirely happy with at the moment it’s a combo of the bottle bosses and gizmos. – I also don’t want to be drilling holes to install rivnuts!


The battery is an…exact fit for the Ute! It fits perfectly, to my relief. For mounting, I’m now using two GRIN Bottle Bob’s, which are like the Gizmos but a bit chunkier. Plus one of the frame bottom bosses that just happened to be in the right place.

Like you, I didn’t fancy drilling holes in the frame…

Good article, the benefits you describe of converting a specialty bike like a cargo bike bring prices down to a more realistic level for parents. I get asked lots of questions about my BBS01 conversion when I bring my 5yo to playschool on a towed trailer-cycle.

Thanks. And agree; that initial investment is going to be a challenge for a lot of people, so anything to being it down a bit is good news.

I have just fitted a TSDZ2 motor to my Claus Butler road bike which now weighs in at 21kg. I fitted a r8v 750w version, 6 pin (without the facility to fit a thumb throttle)
I am 73yrs and bought the Tong Send unit to give me a bit of umph up the hills. Sadly my first trip along the British country lanes didn’t go to plan as at every hill, in spite of having 7 gears to choose from I failed to find the sweet spot that would bring the torque controlled motor to my rescue. Like yourself, changing to a harder gear seemed to help a bit but, sadly, when I reached the top of the hill I was knackered. I am now thinking of swapping out the 6 pin control board to an 8 pin to allow me to fit a thumb throttle. What do you guys think? Should I persevere, and practice harmonising my gear changing with my mode selection, Eco to Turbo, or should I throw the towel in?

20km/h @ 12% slope seems unrealistic on my 36V version especially during long climbs. I can get only about 12km/h @9% slope using 42t chainring and 32t or 36t granny gear.

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