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is torque a good predictor of how easy it will feel to go uphill?

Posted: May 09 2021 2:20pm
by cgokey
I'd love some opinions on this article:
https://bicycles.stackexchange.com/ques ... -go-uphill

I'm considering buying an Ebike that uses a Shimano e5000 mid drive motor (it is couple years old). It is rated at 250W with max torque of 40 Nm but is all integrated with a torque sensor into the bike. There is also a firmware upgrade boosting a little more power it seems:
Upgraded:
https://www.bikeradar.com/news/2020-ste ... re-update/

The problem is that I live where there is a lot of decent size hills, so I'm concerned maybe max torque of 40 Nm might not be enough. I know the Bafang's mid drives sport a much higher torque #'s. But the article above alludes to that basically as long as it is in a low enough gear set I might be fine and the torque ratings are sort of overrated.

What appeals to me about the Shimano is the torque sensor, from what I understand it feels more natural and more like a bike, than the Bafang middrive which are more cadence sensored. The Ebike I'm looking at is in the $1800 price range and is here:
https://bikeshopwarehouse.com/cgi-bin/B ... rodID=2594

Thanks,
Chris

Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: May 09 2021 5:41pm
by MadRhino
Those BB drives are slow climbers but yes, gear ratio does make them climb easily.

Torque does make acceleration, and/or climbing ability of course. Yet it is the total watts that are making the true power, thus a better measure of the speed that a motor can attain up a hill. Low power with proper gearing can climb steep, but slow.

Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: May 10 2021 4:24am
by dogman dan
I demoed the shimano mid drive about 5 years ago at interbike, on a very steep trail. No problem getting up the hill. But it was not riding up it like a motorcycle, it was like riding a bike up a hill. Slow, but little effort needed in the lowest gear. 250w is plenty to go 15 mph, but 20 mph takes 400w, 600w into any wind.

So its going to have plenty of hill climbing ability, but its not going to climb at 15 mph up steep hills as a 1000w hub can, more like 5 mph. The problem I have always had with lower power setups is not the hills, but the wind. At 250 w, if you are going up the hill into 40 mph wind, you are going to really be riding slow. So what? Well, in my case I was doing a 15 mile one way commute. And one fine day in the winter, the ride home would turn into 15 uphill miles home, into 40 mph wind. 50-60 min ride home now becomes 3 hours. Ouch. I found I needed 1000w for a hub motor to make a good commuter. I needed to cruise 20 mph, or better still 25 mph for a ride as long as mine, 30 miles a day.

So it depends on what you want to do with this bike. You simply won't go for a long ride in such conditions for fun. But if your commute is more than 8 miles one way, I would strongly advise getting something with more of a moped type performance, so you never have a two hour ride home.

Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: May 10 2021 12:51pm
by cgokey
Thanks! Appreciate the feedback, definitely some things worth considering.

Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: May 12 2021 6:07pm
by jamiejackherer
Yes. Hill climbing ability is directly and only related to torque. The speed you will go up is a mixture of volts and amps. But climbing really only comes down to amps which means torque.

I have built my own motor and rebuild controllers to have higher amps and literally build bikes to scramble like motorbikes.

I'm currently running 190A on a 48V battery ( peaks at over 10kW) with a custom built 20kW+ hub motor. It climbs absolutely any hill of any size with utter ease. In fact it accelerates and even wheelies up a 40% 200m long muddy hill like it's nothing.

So yeah it's all about torque for hills, and torque comes directly from amps.

Sent from my SM-G970F using Tapatalk




Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: May 12 2021 10:24pm
by MadRhino
jamiejackherer wrote:
May 12 2021 6:07pm

So yeah it's all about torque for hills, and torque comes directly from amps.
Well, we are talking about torque at the wheel.
Torque can be produced by gearing down too. So lower Amps are required for equal torque, only slower. That is why climbing speed is also related to motor power produced, for higher motor hp does not require gearing down as much, or at all.

Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: Jul 22 2021 8:58pm
by cgokey
I thought I would do a follow up. I ended up getting this bike from bikes direct and pretty happy with it.
https://bikeshopwarehouse.com/cgi-bin/B ... rodID=2594

I live in really hilly area and climbs hills greats. Sill have to work at it but it is definitely manageable. I was looking for a bike, not a scooter anyhow.. :) The thing cruises on flats and has awesome range. Really like the mid gear as all my previous ebikes where cheap heavy eBay kit hub motors.

Anyhow appreciate all the help this site has been.

Chris

Re: is torque a good predictor of how easy it will feel to go uphill?

Posted: Jul 23 2021 6:21am
by dogman dan
Again, though it was many years ago, and the first or second year the shimano mid drive system came out, when I demo'ed one at interbike, I was really impressed with the shimano and bosch setups.

Didn't like some of the other mid drives as much, but the software for the PAS on the shimano was sweet.

Glad we could help you understand what you were looking to buy.