Tag Archives: Pedal Assist

Surl-E Disc Trucker Test Rides

A previous post of mine was regarding the installation of a Tongsheng TSDZ2 mid-drive pedal assist kit to my Surly Disc Trucker touring bike (now named “Surl-E Disc Trucker”). Since then I’ve had several opportunities to take the bike out both loaded and unloaded.
Unloaded rides were more or less to test the shifting and gearing together with getting used to the pedal assist motor with it’s four levels of assist – Eco, Standard, Tour and Turbo, with Eco being the lowest level of assist.
An important issue that I had learned, was to not have any pedal movement when turning the power on at the display – turn on at standstill is to allow the controller to calibrate itself. So once I switched the power on I pedalled off in Eco mode and immediately noticed the torque sensor adding to my power as I put more pressure on the pedals. Basically, this feels as if my legs were somewhat younger than they are! Riding through the local streets, I tried out the other levels and to be honest I found the higher levels unnecessary for the unloaded ride mostly due to my still shifting to lower gears as I would without the assist of the motor. And I’m still a fairly strong cyclist adding a fair bit of effort to the power needed.

Surl-E Gear Chart
Gear Chart in Gear Inches

After a couple of runs unloaded, I noticed that my gearing was somewhat duplicated between the 34 & 42 chainrings, so I installed a 44 chainring. My present gearing in gear inches is displayed on the left showing a usable spacing between the gears. The only issue that I had with this set-up was that the chain was too short to reach from the 44 chainring to the 42 cog on the rear cassette. Lengthening the chain would be easy, but normally I would never run “big-big” anyway due to chainline issues, which was even more pronounced with the drive being off centre somewhat. Chainline when in the 34 chainring is very good and I can shift through the whole range of the cassette no problem. Whereas shifting (and chainline) when in the 44 chainring is best when using the 11 through 30 cogs on the cassette.

I got a window in the January weather (not many during January here in the Pacific Northwest!) and decided to load the bike up with four panniers full of ??? Not wanting to drag all my touring/camping gear out, I decided to fill up some water containers to at least mimic a decent touring load. The whole point of this exercise was to determine some range and life of the battery through similar load and terrain to my regional camping venues, therefore a similar load was necessary to achieve this.

Surl-E Loaded
Surl-E Loaded

The above photo shows the bike loaded, somewhat evidently with water bottles sagging in the panniers! But it worked for my purpose.

I have some local routes that I ride regularly on my recreational bike of approximately 50 – 60 km and I decided that two runs on the same route were required for my tests. For the first ride I would ride only in the lowest Eco setting and see how things panned out.
The route ended up being 52 km with about 260 metres (850 feet) of total elevation. I started the ride with my fully charged 48V battery reading of 54.2V. My VLCD6 display only has four bars for battery level (I assume the bars represent 25% each?) so I was using a multimeter to check the actual voltages. At the halfway point of my ride, which was after the hilliest sections of the route, I checked the voltage to be 51.5V and still four bars showing on the display. I continued on, then when I arrived home I checked the voltage again to be 50.3V with still four bars showing! The bike performed very well and with all the weight well distributed handled just about the same as previous loaded touring ventures without the pedal assist drive. All in all, the ride went very well and I did get a good workout even with pedal assist, but having the assist and low gearing made any grades definitely easier. Next test would be to boost up to level two of the assist on the hills to make those even easier.
I recharged the battery with the 2 amp charger that it was supplied with and that took 1 3/4 hours to bring it up to full charge again.

Due to the rain squalls starting after I returned home, I would have to cool my heels for another test ride until the weather improved.
At this point I decided to actually weigh my load and bike etc. to see what I was actually hauling around. I surprised myself as the load of the four panniers (including the panniers) and a couple of water bottles in racks was 57.4 pounds – quite a bit more than I normally take when bike camping/touring! To add to this, the bike with all its racks, bottle mounts, mirror, kick stand, frame lock, tire pump, fenders, a frame pack with essential tools and the drive with battery weighed in at 57.2 pounds; surprising how all these items add up! The drive, wiring and battery comprised 16 pounds of that weight. Add me in at 161 pounds with clothing for a total of 275 pounds – ouch! Good job that I have good wheels and tires!

A few days later the weather window opened once again, so off I rode with the same load on the same route. At each grade or hill I boosted the drive to the Standard mode of Level 2 and there was a very noticeable increase in assist from the drive. On the flats, I still maintained the very comfortable Eco mode of Level 1. This time at the halfway point, the battery measured 51V with four bars showing, and at the finish line of 52 km it measured 50V with, surprisingly, four bars still showing.

Surl-E Mudflap
Surl-E Mudflap

For the last half-hour of this ride, the skies opened up and I was hit with some rain together with some light hail. I soldiered on the wet roads and was glad that I have a large mudflap on my front fender, otherwise all the road spray and grit would have covered the motor housing. I’m not sure how well the unit is waterproofed but feel that the drier the better!

I also tested the throttle by stopping on a steep hill and instead of just pedalling away for a restart, I used the throttle to just get me in motion then carried on pedalling – worked very well. As far as shifting, I had no issues with either the rear or front derailleurs.
This time the battery took 2 1/2 hours to recharge to full.

What surprised me was how the battery still showed four bars; I’ve tried to research what voltage each bar represents to no avail. I guess that further test rides where I can associate each bar with an actual voltage may answer that issue. I do know that the motor controller and/or the battery maintenance system (BMS) will cut off power at around 42V, so knowing when I am close to that figure would be advantageous on longer rides.

To summarise… For loaded touring I feel that the 34 chainring is a must and one could easily manage with just that chainring and a cassette such as mine for that purpose if top speed was not a concern – let’s face it, loaded touring and speed do not often go hand in hand, not for me anyway! The higher gears of the 44 chainring were useful for downhill grades, flat terrain etc., and also for achieving a comfortable cadence in between the gears when in the smaller 34 chainring. The drive will assist very well even with only the standard 42 chainring that came with the unit, but the trade off is having to use a higher level of assist – read, less battery range.
What’s missing? A reliable/accurate voltmeter on the display instead of just the bar readout would be really nice. There are different displays for the TSDZ2 that do have better visuals, so I may research that at a later date.
I’m very pleased with the results so far and glad that I installed the pedal assist system, it will be a huge help on those sections that are getting a bit tougher nowadays. And it makes the bike a lot of fun to ride in addition to making my legs and lungs feel a lot younger!
I feel that with judicious use of the levels of assist and use of my gearing, I feel that I can tackle longer rides fully loaded without any issues. For longer distances I would probably consider carrying a spare battery to for peace of mind – but of course, that is more weight, isn’t it!