Bosch Gen 4 and over 25Kph problems ( motor doesn't seem to disengage )

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Waynemarlow

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My friend has an almost brand new Focus with a Gen4 motor in it. As you go through the 25kph, the motor almost feels as though it is restricting rather than disengaging. Also we ran the battery out and once it cuts out, the motor is engaged to the point that you cannot pedal it.

Is this normal as it really screws that with a flat battery, its get off and walk mode. Or do we have a defective motor ?
 
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I've got a Bosch Gen 4 bike and the feeling when you pass 25kph is very noticeable. In my case I'm sure it's not restricting but pedalling a heavy bike and a very heavy rider at 25kph+ is noticeably harder work than below. I can see how that might feel like it's restricting but it isn't. I have never run out of battery but I've been out riding with people on non ebikes and I've turned the assistance off, it's hard work but there's no restriction.

I've never ridden a different e-bike but I suspect that they all feel much the same as you pass the limit. Perhaps it's worth asking in the General part of the forum what people's experience of passing the limit is on different bikes.
 
Waynemarlow said:
My friend has an almost brand new Focus with a Gen4 motor in it. As you go through the 25kph, the motor almost feels as though it is restricting rather than disengaging. Also we ran the battery out and once it cuts out, the motor is engaged to the point that you cannot pedal it.

Is this normal as it really screws that with a flat battery, its get off and walk mode. Or do we have a defective motor ?
Click to expand...
What's it like with it just turned off ?? What's it like powered off with the backwheel off the floor and turning the pedals ?

I have a Focus Jam2 6.9 with Gen4.

Compared to other motors I find the Gen4 "hands over" from assisted to unassisted the most gracefully. Assistance slowly eases as you get to the limit rather than cutting in a sharp way. From there, because it's a smooth cut, I find I can generally keep on pedalling. Obviously this gets harder the faster you go especially with Mary's on and a 25kg bike - but I'd never say it feels like the motor is still engaged. For longer rides, say 100k+ you just ride fast, over 25 you're not using battery so your range is unlimited. Yes, it's harder, but it's not impossible by any stretch of the imagination.

Does sound like there's something weird going on.
 
I've had my Rail for a little over a year now, I always found it awful when switched off, in Eco and over the cutoff

I've recently had a new motor due to a 500 error and it's night and day. I barely notice when I go over the limit and I can actually pedal it switched off


I'm guessing my motor has always had issues from day 1
 
To get a good idea what the cut off feels like...or not.....it is best to pump your tyres up to c 30 psi and ride a level tarmac section with little or no head wind. If I do what I call an XC ride (some tarmac and mostly gravel tracks) rather than trails in the forest because of trail conditions I invariably pump my 27.5 Assegais up to 26f/28r. On the way home there is a tarmac section which is level and sheltered by tree. I can use Tour mode and pedal past the cut off which according to my Purion is 16.6 mph, and the only way I know the motor has cut out is that there is no motor noise.
If I do exactly the same thing with normal forest trail pressures of 22f/24r, even on gravel or single track leading a trailhead the difference is night and day. Rough ground and lower tyre pressures and a slight incline or undulations and it is pretty obvious when the motor cuts out.
It can be overcome simply by selecting a lower gear than I was in before the motor cut out but in general unless I am on a proper trail I stay below the cut off speed.
In other words ( assuming there is no motor malfunction) all the drag is the suspension, weight off the bike, tyres and wind resistance, not the motor ( try pushing a motorbike with no engine running!!)
 
I've not ridden the Gen 4 before and this one feels almost like the motor is resisting going above 25kph rather than cutting out. With the battery flat and off its almost get off and push, its way beyond drag as its a 25kg bike. Not sure the LBS will change the engine as we already have queried it and they are saying they are all like this. Difficult one this as the LBS is helpful, but sticking to his guns a bit.

My Bafang M600 almost totally disengages with just a bit of extra bearing drag (y)

Thanks for the tips on the tyre pressures, I'm thinking the motor should disengage fully if the battery is flat and I can't imagine there being an electrical clutch in it ?
 
On my Focus Gen 4 I don‘t notice the motor stopping assistance, just the speed stops raising so quickly. I certainly don’t get any drag from it and it rolls really easily.
 
Don't have a Gen 4 so cant really comment on that.

Surely the power level you are on will have the most affect when the assistance level is exceeded. i.e. if on echo the loss of assistance will be relatively small, if on Turbo the loss of assistance will be much more noticeable.
 
Waynemarlow said:
My friend has an almost brand new Focus with a Gen4 motor in it. As you go through the 25kph, the motor almost feels as though it is restricting rather than disengaging. Also we ran the battery out and once it cuts out, the motor is engaged to the point that you cannot pedal it.

Is this normal as it really screws that with a flat battery, its get off and walk mode. Or do we have a defective motor ?
Click to expand...
i agree with the other comments about the 25k cut out.

what you describe with the battery going flat is exactly how it was with my Powerfly 5 and the older motor. I ran it flat twice and it was almost impossible to peddle. With my new Rail and the Gen 4 motor it’s easy to pedal.

charlie
 
I forgot to charge my battery last night. Maybe I've got used to the pedal assist, but I can tell you that riding a 20+kg MTB with 2.6in tyres is exhausting! It felt like I was working against the motor, and it was like cycling in treacle!
 
I don't feel any drag from my gen 4 motor when over the limit,or switched off,or riding with a flat battery. I feel the loss of assistance (obviously) but no motor drag.

I think if you are feeling significant drag then there is a problem somewhere, either a fault with the motor or fault on the bike, maybe brakes binding or similar.
 
The amount of drag you are going to experience over the 25 kph cut out is going to vary dramatically from bike to bike and setup to setup. Just the tyres alone and their pressure, casing and rubber compound can create a huge amount of difference. A Maxxis DHRll in EXO casing, Duel Compund Rubber at 28psi will run dramatically faster than the exact same looking Maxxis DHRll in Down Hill casing, Maxx Grip rubber at 20psi.

I'm not saying there is not a problem with the motor, it's just that your initial assumption that they all feel the same over 25kph could not be further from the truth.

 
Bosch advertised the Gen 4 motor as having "less drag" than the previous motor so by definition there has to be a little drag. I've owned both versions in basically what is the same bike so I know that the Gen 4 has less drag. Having said that, when you exceed 25kph on my bike the assistance tapers off smoothly and disappears completely at around 26 - 27kph. After that it's just like riding a heavy MTB with big tyres., the drag is imperceptible.
 
IMO it's comparative, being used to having assist, then not, on a heavy bike. Change from eMTB to ECO on an incline and it will feel like ECO is dragging, but obviously it's not. Leave it in ECO for a while and you get used to it.
 
Having started from a Gen2, I can tell you what real drag is! :-D

Jokes aside the Gen3 has *way* less drag than the Gen2 because of changes they made internally. The Gen4 has even less pedaling resistance. If you're on a Gen4 drive unit and you're still noticing serious pedal resistance with the drive unit off and battery removed, something is likely wrong.

If your LBS has other bikes with Bosch drives try comparing it to another bike (again, motor off) and see if yours or better, worse, or the same.
 
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