Bosch cx vs Bosch sx.

[egroover]

I stumbled across this article earlier comparing lightweight eMTBs, might be useful

The end of the light eMTB era? – 9 lightweight e-mountainbikes in direct comparison

Wir haben in einem knallharten Vergleichstest mit 9 spannenden Light-E-MTBs herausgefunden, was die besten (Light-)E-MTBs aktuell können und welches Rad das richtige für euch ist.

ebike-mtb.com

 

[Johnecybrid]

I stumbled across this article earlier comparing lightweight eMTBs, might be useful

The end of the light eMTB era? – 9 lightweight e-mountainbikes in direct comparison

Wir haben in einem knallharten Vergleichstest mit 9 spannenden Light-E-MTBs herausgefunden, was die besten (Light-)E-MTBs aktuell können und welches Rad das richtige für euch ist.

ebike-mtb.com

Interesting reading but I am looking for a hard tail. Thanks anyway, much appreciated.

 

[egroover]

This is 22kg so no lightweight but has probably the most powerful legal motor 108Nm and a big 720wh battery (480wh on small frame size) and now reduced to £1999 so huge saving

Rocky Mountain Fusion PowerPlay 30 Electric Mountain Bike Black/Red

From busy commutes, to gravel exploring to singletrack cruising, the Rocky Mountain Fusion Powerplay is your hardtail multi-tool.

www.paulscycles.co.uk

 

[Johnecybrid]

This is 22kg so no lightweight but has probably the most powerful legal motor 108Nm and a big 720wh battery (480wh on small frame size) and now reduced to £1999 so huge saving

Rocky Mountain Fusion PowerPlay 30 Electric Mountain Bike Black/Red

From busy commutes, to gravel exploring to singletrack cruising, the Rocky Mountain Fusion Powerplay is your hardtail multi-tool.

www.paulscycles.co.uk

Wow, pretty impressive figures...108nm torque, phew

 

[Az.]

You don't need eMTB to ride on roads.

At your age I will prioritize power (as mentioned above) and comfort (step through frame and relaxed up right riding position, good saddle and good suspension).

Till end of my days I will avoid proprietary systems like plague, so no Bosch motors for me unless they will rethink what they are doing.

 

[Sturmey]

Wow, pretty impressive figures...108nm torque, phew

Re the bike above (Rocky Mountain fusion at £2000), I am presuming when torque is quoted, this refers to torque at the back wheel. If this is the case above, the 108nm comes from a 34t front chain ring and a 51t rear cassette, so this gives a maximum motor torque figure at the chain ring of 108 X 34/51 = 72nm which (for the case of comparison) is similar to what torque can be got or exceeded from a cheap mid drive conversion with suitable gearing.
I wonder am I right in my thinking above?

 

[matthewslack]

Re the bike above (Rocky Mountain fusion at £2000), I am presuming when torque is quoted, this refers to torque at the back wheel. If this is the case above, the 108nm comes from a 34t front chain ring and a 51t rear cassette, so this gives a motor torque figure at the chain ring of 108 X 34/51 = 72nm which (for the case of comparison) is similar to what torque can easily be got from a cheap mid drive conversion with suitable gearing (e.g 34front/34rear).
I wonder am I right in my thinking above?

No, mid-drive motor torque is quoted at the pedals.

But BBS01 is not too far off in max torque, so the cheap conversion bit holds good!

 

[Johnecybrid]

You don't need eMTB to ride on roads.

At your age I will prioritize power (as mentioned above) and comfort (step through frame and relaxed up right riding position, good saddle and good suspension).

Till end of my days I will avoid proprietary systems like plague, so no Bosch motors for me unless they will rethink what they are doing.

Well that of course is your choice. I find my bike comfortable to ride, but rather it was lighter.

 

[Sturmey]

No, mid-drive motor torque is quoted at the pedals.

So in the example above, the figure of 108 when driving thru the 34 front and 51 rear delivers 162nm of torque at the wheel? That is impressive. Or is it limited in some way by the controller. (I am trying to make sense of the figures).

 

[AndyBike]

I've 2. A 23.5kg full susser and a 20kg city bike and TBH I dont really feel any difference when riding, and the extra when manhandling it isnt that noticeable either. They are indeed both heavy bikes, but my last analogue city bike probably weighed 35+lbs so I think I'm just more used to lugging a heavy bike.

Another option would be a carbon road bike. Probably looking about 7kg for a good quality one.

 

[matthewslack]

So in the example above, the figure of 108 when driving thru the 34 front and 51 rear delivers 162nm of torque at the wheel? That is impressive. Or is it limited in some way by the controller. (I am trying to make sense of the figures).

Minus efficiency losses, in theory yes, but with one big caveat.

I don't know that motor, but the Shimano, Bosch and Yamaha with which I am familiar are torque sensor systems. They work by measuring the torque applied by the rider and adding a percentage of that as assistance from the motor.

However, there is an upper limit to the percentage, and I have yet to see one higher than 400%. Often it is nearer 300%.

With a 400% maximum assistance, the rider would need to contribute 27Nm for the motor to give 108Nm. And these motors demand cadence typically above 60rpm.

27Nm at 60rpm is 170W from the rider, which I certainly cannot sustain for long.

 

[Johnecybrid]

I've 2. A 23.5kg full susser and a 20kg city bike and TBH I dont really feel any difference when riding, and the extra when manhandling it isnt that noticeable either. They are indeed both heavy bikes, but my last analogue city bike probably weighed 35+lbs so I think I'm just more used to lugging a heavy bike.

Another option would be a carbon road bike. Probably looking about 7kg for a good quality one.

At the risk of repeating myself, if I could ride a 7kg road bike I would, but I cant.
I am 77 with health issues and I need Bosch type power to get me up the steeper Devonshire climbs.
I currently own a Trek Powerfly 5, which I like, and find comfortable to ride, and have cycled a 75 miles there and back ride on it when the battery was new. My usual ride is between 30-40 miles.
I was considering this...

NULANE HYBRID - CITY - TREKKING - E-BIKES | CUBE Bikes

A bike that's quick, nimble, adaptable and rugged enough to take on city streets as well as gravel tracks? Welcome to the Nulane Hybrid – a blend of CUBE design excellence and lightweight Bosch power.

www.cube.eu

but not sure if 55nm of torque is enough for me...that is my question.

 

[matthewslack]

Can you give an example of the steepest climb you need to manage? That ties it to real world then.

I had to change my gearing as described earlier to manage Bealach na Ba. Before that I had to plan routes that avoided all the OS map double chevrons, and as many of the single chevrons as possible. Now almost any road is doable. I said no to Hardknott and Wrynose in September, but that is about all I have refused.

 

[Johnecybrid]

Can you give an example of the steepest climb you need to manage? That ties it to real world then.

I had to change my gearing as described earlier to manage Bealach na Ba. Before that I had to plan routes that avoided all the OS map double chevrons, and as many of the single chevrons as possible. Now almost any road is doable. I said no to Hardknott and Wrynose in September, but that is about all I have refused.

Can I assume you are young(ish) fit and well Matthew?
Let me put it this way, I call a hill steep, when I can just about to manage to get up it it turbo mode, on the 51t sprocket...You get the picture?

 

[egroover]

There's probably a theoretical equation that can work out the extra effort required by yourself when comparing the max torque of your current Trek's cx motor (85Nm) and the nax torque of the sx motor (55Nm) minus the approx 10kg weight difference in the two bikes.
Perhaps try riding up some of your local hills in Tour mode (as opposed to mx power turbo mode) on your Trek and see how you get on. That might give you an idea of the equivalent power performance of the two motors. Then load a rucksack with 5 bags of sugar on your back and see what difference it makes riding up the hill on the Trek.
I still reckon even with the extra weight the Trek at 85Nm will climb much easier and quicker than the Cube sx motor bike

 

[matthewslack]

Can I assume you are young(ish) fit and well Matthew?
Let me put it this way, I call a hill steep, when I can just about to manage to get up it it turbo mode, on the 51t sprocket...You get the picture?

Yes! And you answer another bit I had missed, you already have a 51T bottom gear.

In my touring configuration, my all up weight is around 140kg, my motor is only 40Nm, and 20% gradients are fine. Steeper I have to psych myself up for!

A lower torque motor than that you already have is not the way to go.

Edit: that is yes to I understand your hill, not yes I am particularly young or fit any more!

 

[Johnecybrid]

Yes! And you answer another bit I had missed, you already have a 51T bottom gear.

In my touring configuration, my all up weight is around 140kg, my motor is only 40Nm, and 20% gradients are fine. Steeper I have to psych myself up for!

A lower torque motor than that you already have is not the way to go.

Edit: that is yes to I understand your hill, not yes I am particularly young or fit any more!

Seven years ago I was riding my Trek Madone...life is a bitch.

 

[Johnecybrid]

There's probably a theoretical equation that can work out the extra effort required by yourself when comparing the max torque of your current Trek's cx motor (85Nm) and the nax torque of the sx motor (55Nm) minus the approx 10kg weight difference in the two bikes.
Perhaps try riding up some of your local hills in Tour mode (as opposed to mx power turbo mode) on your Trek and see how you get on. That might give you an idea of the equivalent power performance of the two motors. Then load a rucksack with 5 bags of sugar on your back and see what difference it makes riding up the hill on the Trek.
I still reckon even with the extra weight the Trek at 85Nm will climb much easier and quicker than the Cube sx motor bike

That's a great way to look at it, and no, I would never get up some hills in tour mode, so that is a good point, thank you.

 

[matthewslack]

Seven years ago I was riding my Trek Madone...life is a bitch.

Keep on keeping on, as Alan Bennett would say!

 

[AndyBike]

I currently own a Trek Powerfly 5, which I like, and find comfortable to ride, and have cycled a 75 miles there and back ride on it when the battery was new. My usual ride is between 30-40 miles.

Im 56 with some health issues(Asthma, vascular, Achilles tendonitis) and I couldnt do a usual 30-40mile stint, or a 75miler. I would be utterly done in. The occasional day out of about 20miles return trip is about my limit, and i only use turbo on Bosch performance CX 85nm

So you must be doing better than me lol