Bosch CX - is it possible to reduce pedeling resistance with aftermarket mods

bikey850

Pedelecer
Aug 22, 2016
97
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UK
Hi,

For those who have been inside the Bosch CX motors or know about how they work in a bit of detail...

Is it technically possible to reduce the pedeling resistance from the system by replacing any of ther internal components (gears, bearings, etc) to reduce the losses in the system? Is that where the pedeling resistance comes from?

Are there any aftermarket companies who would overhaul the motor but also be able to reduce the pedeling resistance at power cut-off? Is this possible with "better" components or is it simply not possible to modify the system to reduce these without a complete re-design?

I am asking as it would be good to send off a motor for overhaul/service and get it back with these improvements. I apprecaite that the waranty would be out the window at this point however a strong third party support network is available for Bosch motors.

Many thanks in advance for your thoughts.
 
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soundwave

Esteemed Pedelecer
May 23, 2015
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even if you put the best money can buy bearings in the hole motor assembly i doubt you would notice the difference as the mass of all the gears inside will still be there and still have to spin the motor gear with no power.

best option is to get a dongle and forget about it ;)
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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Basildon
The answer is no. It's the basic concept of the motor that causes the drag, where it has the drive sprocket not turned directly by the pedals.
 

Darren Hayward

Finding my (electric) wheels
Mar 25, 2015
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2
56
It's not frustrating, its engineering. The CX motor gives 50% more torque than the ALP because its internally geared. You have to overcome the gearing to pedal unpowered. You can't have the extra power without the gearing. For anyone who expects to pedal unpowered the ALP is the better choice.


Darren
 

MarcusT

Pedelecer
May 5, 2019
32
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NE Italy
Engineering can still be frustrating, can it not?
I use my EMTB for hill climbing, so I appreciate the extra torque, but when I am on smooth flat roads and begin to feel that drag, it is...frustrating. o_O
 

Artstu

Esteemed Pedelecer
Aug 2, 2009
2,304
865
It's not frustrating, its engineering. The CX motor gives 50% more torque than the ALP because its internally geared. You have to overcome the gearing to pedal unpowered. You can't have the extra power without the gearing. For anyone who expects to pedal unpowered the ALP is the better choice.
I'm sure they could get as much from the active line style if they wanted to.
 
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Nev

Esteemed Pedelecer
May 1, 2018
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I went for a ride the other day with a mate of mine, we are same age and similar levels of fitness. I was on an APL powered racing type bike he was on a CX powered mountain bike. On the flat, down hill or slight up hill gradients I was much faster than him. On steep hills however I could not live with him. That extra 50% of Torque makes a big difference when the going gets very steep.
 

bikey850

Pedelecer
Aug 22, 2016
97
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119
UK
Hello, looks like there is a 2020 update planned for the CX motor that will reduce friction at cut-off (using a freewheel to decouple the motor from the gearbox). It also appears to use a "normal" size front chainring.

Obviously nobody (other than press) have tried it yet so it's hard to say if it's the solution we were hoping for.

It would be good if Bosch allowed a trade-in to replace the current CX with the new model (assuming mounting bolts are similarly spaced). I'm guessing there would be no incentive for the bike companies if they were to do this but it would be good to see Bosch continue with their backward compatility and support programmes.

The hard thing will be getting hold of the motor and updates necessary if they choose not to do that.
 

Artstu

Esteemed Pedelecer
Aug 2, 2009
2,304
865
Either way it's not due until 2020 plus bikes will take a while to filter through the channels.
Hopefully my Bosch Classic will soldier on for another couple of years until next years models are a year old and discounted.

It is a shame that Bosch's focus seems to be on improving performance with no mention so far on improving the longevity and crucily the sealing of their motors.
 
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Gringo

Esteemed Pedelecer
Jun 18, 2013
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It would be good if Bosch allowed a trade-in to replace the current CX with the new model
That makes good business sense, I wonder if Kia will do that with my car, this years model has more horse power than the one I brought last year :p
 
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Dizer

Finding my (electric) wheels
Feb 7, 2019
16
0
I went for a ride the other day with a mate of mine, we are same age and similar levels of fitness. I was on an APL powered racing type bike he was on a CX powered mountain bike. On the flat, down hill or slight up hill gradients I was much faster than him. On steep hills however I could not live with him. That extra 50% of Torque makes a big difference when the going gets very steep.
Are your bikes tuned? Or where you simply cycling till the 25km/h limit?
Because then it makes sense that on flat gradients you are much faster, because above the 25km/h you don't have any pedal resistance.
 

Andy McNish

Pedelecer
Nov 28, 2018
232
123
I think Nev has a Cannondale Neo Synapse.
The whole point of bikes like it and the Orbea Gain is that they can cruise at speeds well above the cut off, and only call on the battery assist when it's really needed.
 

Dizer

Finding my (electric) wheels
Feb 7, 2019
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0
Then the comparison is not fair, because of the pedal resistance.
 

Andy McNish

Pedelecer
Nov 28, 2018
232
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Then the comparison is not fair, because of the pedal resistance.
What comparison isn't 'fair'?

We all understand that, if your ebike is easier to pedal over 25kph (because it is lighter, has less rolling resistance and is zero resist) and is road legal with a 25kph cut off, it will use less battery on just about any given route than a heavier/non-zero resist bike going at similar speeds for the same amount of rider effort.

That isn't 'cheating' a fair comparison in some way, it's the whole design philosophy of such a bike.
 

BazP

Pedelecer
Oct 8, 2017
81
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Sheffield
What comparison isn't 'fair'?

We all understand that, if your ebike is easier to pedal over 25kph (because it is lighter, has less rolling resistance and is zero resist) and is road legal with a 25kph cut off, it will use less battery on just about any given route than a heavier/non-zero resist bike going at similar speeds for the same amount of rider effort.

That isn't 'cheating' a fair comparison in some way, it's the whole design philosophy of such a bike.
I thought that Nev's comparison was about speed and nothing to do with battery longevity. He was just pointing out the advantages and disadvantages of both bikes. It's fairly obvious why the "racing bike" was superior over certain terrain.
Personally I'm not bothered about speed, especially on a hill. 1 mph will do if I can pedal comfortably without falling over sideways.
 

Andy McNish

Pedelecer
Nov 28, 2018
232
123
I thought that Nev's comparison was about speed and nothing to do with battery longevity. He was just pointing out the advantages and disadvantages of both bikes. It's fairly obvious why the "racing bike" was superior over certain terrain.
Personally I'm not bothered about speed, especially on a hill. 1 mph will do if I can pedal comfortably without falling over sideways.
That might be tricky at 1mph!

I recently went up some hills with a rider who was bonked and had to push their non-ebike up them at walking pace.

I had no issue doing this in Eco in 2nd gear even on my monstrously heavy Cube Tourer but even then it must have been at 3mph+. Once you go under that you really are are liable to 'fall off sideways' :)

For even the slowest climbs, when I'm going for minimum HR increase, I tend to be doing 5mph +