Torque sensor setups. Experience and comments please!

[St. Ginger]

Hello!

I'm looking to start building my first ebike conversion. After many, many hours Pro and conning, I'll likely use a XF07 front hub kit from woosh bikes. I've never ridden an ebike for any real length of time, only an hour or two, so I want to get longer term insights from experienced users.

I'm interested in peoples experiences of the difference between cadence and torque controlled systems. I like the idea of torque control for a more natural and efficient feel, and woosh sell the XF07 with a torque sensing crank.
However, I've read that the torque sensors can be temperamental and fail under intense pedaling. I'm pretty heavy footed, so I'm concerned about their longevity. It's an expensive unit to have to replace. Also, possibly more important, I ideally want to have control over my crank and chainring choices.

Conversely, I'm very attracted to the simplicity of traditional PAS with magnets. But I don't like the idea of the jolty feel I'm imagining. When pedaling, does the sensor simply turn the motor on, and once pedaling it'll suddenly run at full power (based on assistance level on the LCD)? Or does the power output increase in line with cadence; faster feet, more power?

If anyone has mechanical experience with the torque sensors, I'd love to hear about it. I would also love to hear about the difference in feel between the two styles of assistance.

Thanks very much!

 

[Woosh]

Or does the power output increase in line with cadence; faster feet, more power?

yes, that's correct, higher cadence, more pressure, you get more power and no jolt. The torque sensor feels quite natural in use.

However, I've read that the torque sensors can be temperamental and fail under intense pedaling.

I have not seen any torque sensor damaged by pedaling.

I would also love to hear about the difference in feel between the two styles of assistance.

If you ride leisurely on a flatish road, there is very little difference between the two systems.
But if you want to go fast or climb hills, you'll have to pedal hard and fast with a torque sensor while you don't have to with a cadence sensor.

 

[St. Ginger]

Thanks woosh!

My comment here:

St. Ginger said:
Or does the power output increase in line with cadence; faster feet, more power?

...was actually asking about cadence, not torque systems. On a standard magnetic PAS, do you get relative power output based on how fast your feet move?

It's good to know about the reliability of the torque sensors. I think the threads I read where they had failed were specifically referencing TSDZ mid drives, so may not be related.

I actually sent you a long, long, rambling email today, asking a bunch of questions. Looking forwar dto discussing things more. Thanks for your super fast response

 

[Woosh]

...was actually asking about cadence, not torque systems. On a standard magnetic PAS, do you get relative power output based on how fast your feet move?

yes, you get more power on the same assist level if you pedal faster.
The power follows a pattern: ramp up then sustain. The 5 assist levels determine the current as a percentage of the maximum: 50%, 65%, 80%, 90%, 100%.
It feels pretty natural, no jolt. There is not much difference in feel between the two systems if you ride leisurely. It's only when you try to go fast or climb hills that the difference shows up.

 

[St. Ginger]

Detailed and clear. Just what I need.
Fantastic, thanks! This really helps get my head around things.

 

[sjpt]

The cadence sensor does just turn on and off according to whether you are pedalling or not, not how fast. But the on is a gentle ramp (or at least feels like it to me), not a sudden wham.

One advantage of cadence is that you can ghost pedal, turning the pedals without putting in any effort, and the motor will still work. Great if you are getting a bit lazy at the end of a ride.

One disadvantage is that cadence sensor doesn't kick in till about 1/2 turn of the pedals so it doesn't help so much on awkward hill starts.

I think I would go for the cheaper cadence sensor if we had the choice. We've got an XF07 (from Woosh) with cadence on the front of our tandem. A little underpowered for the tandem as Woosh warned us but nothing else suitable was available at the time in the right wheel size; it would be great on a solo. We've also got a 2nd hand Motus with Bosch torque sensor; it does feel a maybe tad more 'natural' but doesn't really feel a significant advantage.

 

[St. Ginger]

Good to hear from another user, thank you.

The cadence is simpler too, less to fit and faff with, which I like

 

[Woosh]

the torque sensor is slightly simpler to fit if you have standard 68mm bottom bracket and single chainring.
If you have double or triple chainring then the cadence sensor kit is simpler.
TSkit doesn't have the throttle and brake sensors.
Compared to the TSDZ2, the TSkit fits bikes with gear cables running under the bottom bracket and those Thorn Raven with eccentric bottom bracket.