Benelli E-M23 2.0 EXP no pedal resistance after derailleur and chain swap — how to fix?

[Illmas]

I ride a Benelli E-M23 2.0 EXP CARB 29 720.

The bike is not giving anybresistence while pedalling after the derailluer and chain was swapped after an accident. How can I increase the resistence on the pedals to make riding more enjoyable again.

@Greg Watts

 

[Greg Watts]

Hello Illmas, Greg here.

Right, let's untangle this. "No resistance while pedalling" after a derailleur and chain swap is almost never about the drivetrain itself — the drivetrain doesn't provide resistance, it transmits it. So something else is going on. A few possibilities, in order of likelihood:

1. The motor is freewheeling / not engaging
By far the most common cause. If you're spinning the cranks and feeling nothing — no assistance, no flywheel feel, just air — the motor isn't picking up your pedalling input. After a crash this could be:
• Speed sensor magnet knocked out of alignment (or missing entirely — they live on a spoke or inside the rear hub)
• Torque/cadence sensor cable unplugged or damaged at the motor
• Motor in walk mode, or assistance set to zero/off on the display
• Battery not seated properly or display showing an error code

Check the display first. Any error code? What assist mode is it in? Does the motor make its usual startup chime?

2. Chain is on the wrong cog or skipping
If the new chain is the wrong length, or the derailleur B-tension is off, the chain can sit slack or skip under load — feeling like "no resistance" because your pedals just spin through. As @steve_sordy and others on here regularly point out, you need to check chain length with the suspension fully compressed, and B-tension set with proper sag.

3. Cassette lockring loose
If the shop didn't torque the cassette properly (40Nm Shimano, 40Nm SRAM), the whole cassette can spin on the freehub body — pedals turn, wheel doesn't. Easy to check: pedal forward firmly in a low gear with the rear brake on. If the cranks move but the wheel doesn't fight back, that's your culprit.

4. Freehub pawls failed
Crash damage can knacker the freehub internals. Same symptom as a loose cassette — cranks spin freely with no drive.

What to do
Tell me:
• What bike and motor system (Bosch, Shimano, Specialized, Bafang, etc.)?
• Does the motor engage at all, or is it purely a mechanical pedalling issue with no assist either?
• Any error codes on the display?
• Does the rear wheel drive forward when you pedal on a stand?

That'll narrow it down in about thirty seconds. Drop those details and I'll point you at the fix.

 

[Illmas]

Hello Illmas, Greg here.

Right, let's untangle this. "No resistance while pedalling" after a derailleur and chain swap is almost never about the drivetrain itself — the drivetrain doesn't provide resistance, it transmits it. So something else is going on. A few possibilities, in order of likelihood:

1. The motor is freewheeling / not engaging
By far the most common cause. If you're spinning the cranks and feeling nothing — no assistance, no flywheel feel, just air — the motor isn't picking up your pedalling input. After a crash this could be:
• Speed sensor magnet knocked out of alignment (or missing entirely — they live on a spoke or inside the rear hub)
• Torque/cadence sensor cable unplugged or damaged at the motor
• Motor in walk mode, or assistance set to zero/off on the display
• Battery not seated properly or display showing an error code

Check the display first. Any error code? What assist mode is it in? Does the motor make its usual startup chime?

2. Chain is on the wrong cog or skipping
If the new chain is the wrong length, or the derailleur B-tension is off, the chain can sit slack or skip under load — feeling like "no resistance" because your pedals just spin through. As @steve_sordy and others on here regularly point out, you need to check chain length with the suspension fully compressed, and B-tension set with proper sag.

3. Cassette lockring loose
If the shop didn't torque the cassette properly (40Nm Shimano, 40Nm SRAM), the whole cassette can spin on the freehub body — pedals turn, wheel doesn't. Easy to check: pedal forward firmly in a low gear with the rear brake on. If the cranks move but the wheel doesn't fight back, that's your culprit.

4. Freehub pawls failed
Crash damage can knacker the freehub internals. Same symptom as a loose cassette — cranks spin freely with no drive.

What to do
Tell me:
• What bike and motor system (Bosch, Shimano, Specialized, Bafang, etc.)?
• Does the motor engage at all, or is it purely a mechanical pedalling issue with no assist either?
• Any error codes on the display?
• Does the rear wheel drive forward when you pedal on a stand?

That'll narrow it down in about thirty seconds. Drop those details and I'll point you at the fix.

Everything works the wheels turn normally when oedalled and all gear changes and can ride Un assisted.

As soon as I turn on the pedal assist I can only feel some resistence on the highest 2 gears. Earlier before the accident it was fun to ride in the middle gears. The cassette has around 10 gears.

 

[Greg Watts]

Everything works the wheels turn normally when oedalled and all gear changes and can ride Un assisted. As soon as I turn on the pedal assist I can only feel some resistence on the highest 2 gears. Earlier before the accident it was fun to ride in the middle gears. The cassette has around 10 gears.

Right, this clears things up considerably. @Illmas - welcome to the forum, and good news: this is almost certainly not a mechanical failure. Let me explain what's actually happening.

What you're describing is normal eMTB behaviour - but it's changed because your gearing has changed.

Here's the thing: on an eMTB with pedal assist, the motor is doing most of the work. In the lower gears (easier, smaller numbers), you're spinning fast but with very little load - the motor handles it effortlessly and you feel almost nothing through your legs. The resistance you feel comes from the actual workload on the drivetrain, and in easy gears with assist on, there's barely any.

Before the accident, your old chain and derailleur may have been set up with slightly different indexing, cable tension, or even a different cassette - meaning your "middle gears" happened to be in a sweet spot of gear ratio vs. motor output that felt engaging. Now, with the new components, that balance has shifted.

Things to check and adjust: • Derailleur cable tension - if the indexing is slightly off, you might be sitting between gears without realising it, causing the chain to float rather than bite properly. A proper index adjustment takes five minutes.