Finishing off, and first impressions of the Tongsheng TSDZ2

When last we spoke, I’d done the bulk of the work on installing the kit for my electric bike retrofit project, and had completed a tentative lap of the block with a single brake controlled from the wrong side of the handlebars. I was also musing on the awful job I’d done on waterproofing the connection between motor and battery.

Let’s deal with those in turn…

Hurrah for progress

I don’t know whether you’ve ever had the pleasure of bleeding a Shimano hydraulic brake, but it was always a bit of a faff. The worst bit was at the caliper, where you had to fit a fiddly 7mm spanner around the bleed nut, whilst at the same time trying to ensure the bleed tube didn’t pop off the nipple and ooze fluid all over the caliper1In truth, I may have found it particularly painful as I don’t own a 7mm spanner, so was trying to do it with the blunt instrument that is an adjustable spanner. It’s a task that is best performed with a trained octopus assistant – the more hands the better..

Imagine my delight to find that on these new Deore calipers Shimano have changed the design. Gone is that tiny spanner, and now it’s a T-shape affair where you manipulate the bleed port using an allen key in one end of the T, whilst the nipple is on another bit. Given I’ve already said “nipple” enough times to permanently bury this article in the depths of Google search results, I’m just going to show a picture:

See? Much easier.

I also highly recommend the bleed kits from Epic Bleed Solutions. They’re both cheaper and better than the official Shimano ones (particularly the open syringe replacing the tiny bucket). Their cable cutter is also very…satisfying…

I will provide a single bonus tip, which will be relevant if you need to shorten the cables. After cutting them, you need to insert a, well, insert into the end of each cable. This is a tiny piece of metal tube, and it does not want to go in that cable housing.

See? Tiny.

As the frustration builds you will become careless, which inevitably results in said tiny piece of metal springing off into the darkness of the garage.

Always have spares on hand…

There is an official Piece Of Plastic To Hold Housing With when doing this task, but I found it easier to clamp the cable in my bike stand, leaving two hands free to delicately complete the rest of the operation.

For this tip, no charge.

Improving the battery/motor connection

Remember it used to look like this?

Having taken guidance from the hive mind on the pedelec forum, the best options seemed to be:

  • doing a Proper Job with heat shrink;
  • using self-amalgamation tape;
  • soldering the join, and then doing a Proper Job with heat shrink.

You will notice that none of the options above include half a roll of electrical tape, and I’ll thank for you not pointing it out.

Soldering was too permanent – at some point I want to take a spur off the battery to power fixed lighting and a suitably subtle horn. The tape and heat shrink options sounded equally good, but I already had a load of heat shrink.

Exhibit A. A load of heat shrink.

To try and improve my previously poor record with heat shrink, I splashed out on a heat gun2I’ve always used a lighter, which is ok, but given how flame and heat works it’s hard to apply heat to the top of the join without flambeeing ones digits. . Being me, rather than a standard amateur-DIY heat gun that seemed to start at £25, I found something for £13 that I think was designed for small children doing crafts. Still, it worked…

Continuing that theme, I only have cheap heat shrink, with at best a 2:1 shrink ratio. I therefore snipped off the plastic shielding around the bullet connectors to minimise the diameter difference between the connectors and the cable at either end.

Anyway, it now looks like this, which is a bit better:

There was a final comment on the pedelec thread commenting on the Big Hole where the cables enter the battery mount, and the role that some sealant might play in the hole’s future. This will be investigated.

Some bar tape.

I added some bar tape. To reuse my comments from Twitter:


First impressions

With working brakes and a somewhat more water resistant electric system, I declare the build Done.

Not done as in finished, but done as in “good enough to use right now, whilst subject to the usual continuous improvement/tinkering approach that causes all of my bikes to gain about a kilo in weight a year”. Done is, admittedly, somewhat catchier.

High on that list of tinkering is: sorting out a kickstand replacement now my centre-mount kickstand is blocked by the motor; sealing the aforementioned hole in the battery mount; finding somewhere to stick a bottle cage; and putting the mirror in a place that doesn’t require me to adopt a gorilla pose to see past my own elbow.

However, I’ve now put about 46.93km3I love the ease of collating unnecessarily detailed statistics on VeloViewer. Also, yes, it is awkward that this is the third footnote, and the 3 makes it look like my odometer measures volume… on the Sutra in eBike mode (essential grocery/medicine collections, since you ask), and where I live is not blessed with much flatness4Ok, ok. 823m climbed in that 46.93km. Although that number is really unreliable.. Therefore, some early comments on the motor:

  • It’s good. Not just “good for some DIY effort”, but good when compared to to fully integrated off-the-shelf Bosch and Shimano assist bikes.
  • Compared to the Shimano Steps motor in the Nihola Trekking I reviewed last autumn, the Tongsheng TSDZ2 is biased with more torque at lower RPMs. There’s much more power at lower speeds (stationary starts on a bike loaded with shopping on a 13% hill? No worries, here’s a shove to get you going), but it requires more effort from you in the 20-25kph range to get to the upper limit. Not a bad thing, just different.
  • Endurance with the 12AH battery seems excellent. I’ve been riding mainly on the highest level of assist (because I don’t want to be the sort of person who has a turbo button available and doesn’t use it), and after 50km only the first bar of the five-bar battery indicator has gone. Of course it might be like my last phone in that the first bar lasts forever and the rest is gone in five minutes, but hopefully not!
  • With the motor off (either because you’ve turned the assist level to zero, or because you’re going faster than 25kph), there’s no noticeable resistance5I’d normally caveat that with “but my bike’s drivetrain is covered in crud as well”, but in this case, it’s all new!.
  • Motor noise in operation is ok. It’s there, but if you’re in traffic you won’t hear it. By yourself on a country road you will, but it’s no worse that the Shimano system. It is louder than the latest Bosch Active motors, but a) that this is eerily silent, and b) the Tongsheng is more powerful.

I’m wary of saying much more without using it for at least a month (and in some rain…), but you can hopefully tell that my initial impressions are very good.

Right! That’s enough on the ebike for a little bit. The next post may be about some raised beds, depending on whether I can tell one end of a saw from the other.


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Thanks for the write up. I’m thinking about adding one to my longtail Yuba, as it’s a bit of a slow tank when loaded with three children

Thanks for the write up.
Always good see hear about someone else’s experience.
My kit is due for delivery on Wednesday so your blig will be very helpful!

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