Anyone one else have a big issue with serious drag back from the hub with this bike? If doing about 16.5 /17.8mph on the flat I get a real drag/hub brake engagement. The harder I pedal the worse it gets. If I can get past this speed downhill, its fine. On a flat I'm stuffed. Why would it have such drag at this speed? I know they are limited but would expect the electric to cut out but not put the hub/brake/drag on to the extent that it I have to stop peddling and than wait to drop under 15mph before starting peddling again. Really getting on my nerves!
Carrera Crossfire-E bike Hub drag
- Thread starter Sprog
- Start date
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Deleted member 4366
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It's an illusion. At 14 mph, you have full motor power helping you so pedalling is easy. The power then ramps down and cut's off at 15.5 mph, so you'd need to pedal about 5 times as hard above that speed to go with the same power. If you can go OK downhill, there's nothing wrong with the motor and no drag.
No issues in that respect with either mine or my partner's crossfire-e.
I would check for binding brakes (although with hydraulic discs I think that is unlikely).
I would check for binding brakes (although with hydraulic discs I think that is unlikely).
Not familiar with this type of bike. If it has a hub motor, the clutch of your planetary gears may be stuck at may need to be replaced. Daveh is also correct about the field of mud effect when the power goes away. This is made worse if your tyre pressure is low as well.
Thank you for the comment. As a very experienced cyclist and have given bike mantiance classes I do appricate the field of mud concept and would expect that. But it's not that! Thank you for info on of the planetary gears. This is a new area for me with the electric hubs. Someting to go on.
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Deleted member 4366
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The motor cannot behave differently going uphill or downwill. in that case, the only effect on you and the bike is gravity. The speed at which you feel the problem is significant, as it's the speed at which the motor cuts off.
If you said that your bike wouldn't roll down hills properly, then there could be a mechanical problem, like brakes binding or clutch stuck. There's nothing that can happen in the motor that suddenly increases drag at a given speed. The drag you're feeling is wind resistance, which is overcome by the motor at speeds below 17 mph. You'd have to be pretty fit to pedal a heavy MTB-type bike faster than 17 mph. It takes about 250w to go past 15 mph and increases rapidly after that.
If you said that your bike wouldn't roll down hills properly, then there could be a mechanical problem, like brakes binding or clutch stuck. There's nothing that can happen in the motor that suddenly increases drag at a given speed. The drag you're feeling is wind resistance, which is overcome by the motor at speeds below 17 mph. You'd have to be pretty fit to pedal a heavy MTB-type bike faster than 17 mph. It takes about 250w to go past 15 mph and increases rapidly after that.
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Deleted member 4366
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.. is this with the motor and controller energised or with the power switched off.?
The internals should be , a big cog on the inside of the hub housing mated with three planetary gears. These all rotate when the wheel is rotating. There should be a clutch or pawls connecting the actual drive motor to the planetary gears. If the wheel is rotating faster than the motor drive then there should be effectively a freewheeling effect, limited only by the friction of the planetary gears and the clutch.. if the clutch is not disengaging , then the reluctance of the motor comes into play , and it will try very inefficiently to drive current back into the electronics .
I had experienced this same effect on my UrbanMover,with a hub motor of cycling through treacle, when the battery ran down. .. and I was not anyway near 15 mph, more like 5mph on the flat. If I turn the bike upside down, I can spin the wheel with minimal drag, showing that the clutch is working, but cycling it without power I get the drag. Perhaps the clutch is not disengaging dependent on position.and speed ..
Contrasting that with my Bosch central drive bike, the clutch works very well and there is no drag.
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Deleted member 4366
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Some hub motors have the clutch outboard of the gears, so only the hub rotates when freewheeling, just like a normal bike wheel. Even when the clutch is between the motor and the gears, the gears turn so slowly when freewheeling that there's no significant drag. In case you didn't know, the gears spin at five times the speed of the hub when driving it, but they turn at one fifth of the speed of the hub when driven by it.
I don't think it's very unlikely that a clutch can stick consistently above a certain speed when it works perfectly below that speed. Besides, OP said that the bike freewheels OK at all speeds downhill. How would the clutch only stick when the road is flat? The motor spins, so it can't know whether it's going up or down.
The power to the motor is cut when you go over 25 km/h, so he can't put the power on above that speed.
.. I don't follow the logic of the 5 to 1 reduction when the hub drives, if the planetary gears are in contact with the hub ringgear.
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Deleted member 4366
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Look and learn. Notice the difference in speed of the planetary gears between going forwards and backwards:
... And wanting as usual to have the last word, there is a minor error in your previous explanation which is what set up my confusion.
When the clutch is disengaged, and power flowing from the motor via the sun gear, it spins at say 5 times the hub speed and the planatery gears spin at approx the same speed .The actual speeds being dependent on their respective diameters.
When the clutch is engaged, the hub rotates at the wheel speed, the planatery gears do not rotate on their own axes and they drag the sun gear around at the hub speed. It is the sun gear which rotates at 1/5 the speed it would have previously , when powered.
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Deleted member 4366
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We gave you friendly factual help, but you didn't want to accept it. I am sad, but not in the way you say. I'm sad that I completely wasted my effort trying to help someone who asks a question when he's already made up his mind what the answer is, or maybe you're just a troll trying to stir up trouble on our friendly forum.