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With a 15.5mph limit on the assistance, some of the gearbox e-mtbs have a lot more torque than e-road bikes.
Question is, could I ride at 15.5mph on the MTB electric bike for similar effort to the less torque-y road electric bike. Assuming along the road, rather than trails clearly. Or does it also depend how they are programmed?
I'm thinking about commuting. My Orbea Gain (40Nm) still needs a reasonable effort to ride at 15mph up hill. Would say a 70Nm electric MTB require less effort?
I can easily ride at 30kmh on my bullitt with 70nm motor. 25kmh is slow.
Fine if the bike is loaded up, mind.
it depends. You might be a little quicker accelerating . My add on kit I turned up the sensitivity on the torque sensor so it gives more torque output for the same pedal input. Thats the key thing. Are you riding in Turbo mode? Basically the adjustment to mine means at moderate pressure on the pedals its full output from the motor. It takes about 6 turns of the pedals to reach the limiter on the flat and uphills are done at the limit for the same effort as pedaling a normal bike on the flat
The torque is immaterial when you are up to speed on whatever hill you are on - both bikes will have the same amount of power which is what gets you up the hill. The torque will help you accelerate and deal with stuff like technical climbs, I'd imagine.
On top of that the road bike will be quite easy to cruise along at 18-19mph on the flat under your own power - you'll easily breeze through the limiter since 15mph on the flat on a road bike is really quite slow. The MTB though would require a lot more work to exceed the limiter.
They only do 250W of power continuously. That’s not much power if you’re trying to do 15mph up a reasonable hill.
Just looking at my commute and I do about 14mph up a 10% road gradient on my Levo. That’s about twice as fast as on my normal MTB. Both bikes go quicker than 15.5mph on the flat unless there’s a painful headwind, despite the tyres.
Chief it depends on the sensitivity of the torque sensor.
My tongsheng kit when I first got it I only got full output from the motor if I really hammered the pedals which I could not sustain for long. By turning up the sensitivity I now get full power at an effort I can sustain indefinitely and it goes up a steeper that 10% hill on the speed limit with only a moderate effort from me.
So I can only alter the amount of assist I get for low, medium and high settings. Even in high setting with it giving me 100% assist, it's still very much an assist style bike. So up a hill I don't get a guaranteed 15.5mph or even close if I'm not putting in a reasonable effort myself. Someone said to me it matches your power output - so if I put in 200w, it will assist with 200w. Which feels about right. Is there anything that gives more assist for less rider input?
The Orbea is pretty acceptable over 15.5mph when the assist cuts out, which I agree is easy to exceed on the flat.
Do more torque-y motors make it easier to get to 15.5 going up a hill?
Most typical decent motors like a Steps E8000 peak at around 500w so yes,they would be quicker up steep hills where you are currently unable to keep at 15mph. I believe they have some limiting in the firmware to comply with the 250w rules, so you wouldn't get 500w constantly if you had a very long hill, but I've never noticed this on mine.
There's a linear relationship between power and torque:
Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488
Rearrange to:
(Power x 9.54)/Torque = speed (RPM)
250 x 9.54 / 40 = the RPM you'd need to maintain the maximum 250W power output at the max torque = 59rpm
What I don't know is whether the quoted torque figures for eBikes are at the motor or at the wheel. If it's the former then obviously gearing will have a huge difference, and you'd have to multiply my RPM by your gear ratio.
So, assuming a flat-ish torque curve, if the pedalling (or cassette?) speed is below 59rpm the MTB would be faster. But as molgrips says, once you're up to speed it's immaterial since in both instances the power is capped at 250W essentially by reducing the torque once your torque x RPM exceeds 250W.
The figure you need to know on your Orbea is the power output. If it's capable of 250W then the answer is no, a motor with a higher peak torque shouldn't help unless you run out of gears to maintain a sensible RPM.
Perhaps it isn't torque then but the way the software is programmed?
It seems it could be a sliding scale..... At one end, I am only rotating the pedals with minimal effort but yet the motor is giving me the maximum 250watts at the push of a button. That 250 watts input stays there so long as the pedals are still turning, unless I reach 15.5mph. On the other hand, the software and sensors could detect that I am only putting in ~50watts of my own effort and so the motor will only assist with a similar 50 watts. If I put in 100watts then the motor puts in a roughly comparable amount and so on. It is a latter set up like this that I perceive my Orbea to have.
Are there any that give a much bigger proportion of motor input compared to human effort?