Why are bottom brackets with torque sensor so rare?

Winfried

New Member
Hello,

I know someone who bought a second-hand e-bike with a Bafang/8 fun rear hub motor, and is looking for a solution to replace the very unnatural on/off cadence sensor. It feels like riding a motorcycle.

So I looked for Bafang-compatible bottom brackets with torque sensor… and found none.

So it looks like a more involved alternative would be to replace the controller with something a bit more sophisticated.

Considering the number of cheap/DIY bikes with a hub motor, and a torque sensor offers an experience closer to an acoustic bike… I'm surprised there's few bottom brackets with torque sensor. Out of curiosity, why aren't they more widespread?

Thank you.
 

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HCooke

Member
Region
USA
I cannot answer your question, but Pedego has a number of models with rear hub motors that have torque sensor pedal assist.
 

harryS

Well-Known Member
As a DIY solution, there's only one that I know of, and it could retofitted to most commercial ebikes with hub motors if they have a throttle. The kit converts pedal pressure to a throttle voltage, It adds a couple of hundred bucks and uses your existing controller.,

The alternative is to use a controller that has a more refined pedal assist system, that's less on-off. I don't think the bafang controllers worried about that., as I have a bafang mid drive that is crude because it's based on speed. . The KT controllers do a better job with cadence control. They set a current level for every PAS level. It feels much less boosted. It would be less expense to try a KT controller/display instead of a Grin torque sensor solution.





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AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
@harryS - haven't seen anything that converts the torque sensing signal to throttle input signal. That sounds interesting! Will they run in parallel (throttle and torque sensor)? Of course it wouldn't be that hard to set the up on an AB switch to allow the use of one or the other. Do you have a link? I might be willing to mess with something like that just to see how well it works.

@Marcela - Torque sensing is more than just money. It's a layer of complexity. Most controllers, including the popular KT, aren't set up for torque sensors. There's not even a place to plug one in! Not too hard to imagine that's something that could happen soon. -Al
 

harryS

Well-Known Member
Grin's Cycle Analyst converts their torque sensor signal to a throttle voltage, It doesn't have to obviate use of the throttle, if they did their electronics right, and I'm sure they did. You're looking at over a hundred bucks each for the CA and their T/S though.

The "torque simulation" pedal assist in the KT units is just marketing, but it feels OK to me, but I'm old/weak. Might still feel overboosted to a young'un.
 

Dewey

Well-Known Member
To be fair more OEM hub motor ebikes are coming out with torque PAS, as ebike sales are increasing in the EU which limits throttle use. For example I guess Bafang developed the M200 to compete with the Hydrive system.

For DIY you answered your own question, Grin Tech can supply a bottom bracket torque sensor and replacement controller for a bafang hub motor.
 
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AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
Grin's Cycle Analyst converts their torque sensor signal to a throttle voltage, It doesn't have to obviate use of the throttle, if they did their electronics right, and I'm sure they did. You're looking at over a hundred bucks each for the CA and their T/S though.

The "torque simulation" pedal assist in the KT units is just marketing, but it feels OK to me, but I'm old/weak. Might still feel overboosted to a young'un.
KT's "torque simulation" is chinglish for a "power based" cadence system, vs. the way more commonly seen "speed based".

Couldn't agree more on the "feel". I think most people, once they've ridden a power based system, will pick it over the speed based any time....

The Bafang BBSxx series mid drives offer the same option (properly labeled speed vs. power) and the power based option is just as popular there! Not REAL sure why the popularity of the speed based systems. The only difference is in the software/programming they run. Hardware is exactly the same....

Not a fan of Grin controllers. They require the use of a display that hurts my eyes....
 

Winfried

New Member
Thanks for the infos.

I'm looking for a financially reasonable solution to add to that rear hub Bafang bike shown in the picture. Since it's in Europe, it has no throttle (illegal.)

Does Grin Tech provide a bottom bracket with torque sensor that I could hook up to a Bafang hub motor?

Alternatively, what KT controller would you recommend?
 

Ken M

Well-Known Member
Hello,

I know someone who bought a second-hand e-bike with a Bafang/8 fun rear hub motor, and is looking for a solution to replace the very unnatural on/off cadence sensor. It feels like riding a motorcycle.

So I looked for Bafang-compatible bottom brackets with torque sensor… and found none.

So it looks like a more involved alternative would be to replace the controller with something a bit more sophisticated.

Considering the number of cheap/DIY bikes with a hub motor, and a torque sensor offers an experience closer to an acoustic bike… I'm surprised there's few bottom brackets with torque sensor. Out of curiosity, why aren't they more widespread?

Thank you.
In my opinion torque sensors are not a good value add on ebikes, expecially DIY kits. The programming can never really provide the level of assist any rider wants at all times while the simple throttle does. In fact I think the best kits come with a moped-like controller that doesn't have sensor wires for cadence, torque, or even speed (why complicate a bike). Sure a torque PAS system provides a more bike-like riding experience but a throttle with good resolution can actually do the same thing only better. Don't get caught up in the marketing hype about torque or cadence PAS systems as they were designed by cyclists for cyclists and that isn't always a good thing.

Note: I do understand that for technical off-road riding a torque PAS is really nice, but for urban mobility a throttle is simply a better solution. My guess is that if the bike OEMs actually provide the same model without a torque based PAS and charged for it as an upgrade over a standard throttle only assist that a small % would actually want it. It was kind of forced on the industry by the EU regulations which is another big subject of poor decision making.
 

Winfried

New Member
Throttles are illegal in Europe.

Still, how would I add it to that rear hub Bafang-powered bike? Would I need a new controller?

Also, what does "power based" cadence system (KT's "torque simulation") really does/mean?
 

mikeschn

Active Member
Region
USA
City
SE Michigan
I just finished building up a TSDZ2 this morning, which has a torque sensor. It is so sweet! The torque sensor feels more natural. It also make you feel like your legs are naturally bionic! If you already have a battery, and you only need a motor kit, consider the TSDZ2 kit. It's not "THAT" expensive! I bought it from a place in Tennessee, but seeing as the OP is in Europe, I recommend he find someone closer than TN. Ha!

@AHicks good question about the throttle. I don't use a throttle so I don't know. But the TSDZ2 kits have a throttle option if the OP is interested.

Mike...
 
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Winfried

New Member
Thanks, I did know about the TSDZ2 middrive, but replacing the controller looks like a much easier and cheaper alternative for that existing bike — after bottom brackets with a torque sensor… which seem unvailable for a Bafang rear hub.

What plug and play KT controller do you guys suggest for that hub drive that offers a user experience close to a motor with torque sensor?
 

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Ken M

Well-Known Member
Throttles are illegal in Europe.
Isn't Europe reviewing this "illegal" status on ebike assist systems? Technology provides a lot of ways to grey the line between what is a throttle-assist and a Pedal-assist solution. The problem really is the lack of brain grey matter of EU legislators to understand technology.
 
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AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
Isn't Europe reviewing this "illegal" status on ebike assist systems? Technology provides a lot of way to grey the line between what is a throttle-assist and a Pedal-assist solution. The problem really is the lack of grey matter in the brains of EU legislators to understand technology.
More likely in my mind, is motivation (what's in it for me?)