# What E-mtb Mode Provides Equal Assistance To Standard Mtb?



## BobBracket (Jun 6, 2018)

I hope I can convey what I want to know well enough. I have never ridden an e-mtb (or any e-bike). But to those who have, I'd like to get a general idea of how much assistance is required on an e-mtb to achieve the same speed as a standard unassisted mtb.

Regarding the type of e-mtb, I think I'm talking about Class-1 mid-drive e-mtbs such as the Trek Power Fly.

I believe the Power Fly has a 250W Bosche motor with 4 modes. Econ mode provides 50% assistance, Tour mode provides 120% assistance, Sport mode provides 210% assistance, and Turbo mode provides 300% assistance. What I'd like to get a general idea of is the percentage of assistance you'd need on an e-mtb to make it as fast as a standard mtb. For example, would 20% assistance make it equal to a standard mtb, or 50%, or 80 or 150%...?


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## Le Duke (Mar 23, 2009)

That’s going to depend on how much you weigh, how much a non-e-bike weighs, and how much power you produce for a given length of time. 




Sent from my iPhone using Tapatalk


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## BobBracket (Jun 6, 2018)

Le Duke said:


> That's going to depend on how much you weigh, how much a non-e-bike weighs, and how much power you produce for a given length of time.
> 
> Sent from my iPhone using Tapatalk


Regarding rider weight, maybe I'm wrong but I thought it wouldn't matter as the rider is the same weight on the e-mtb as on the standard. If it does matter, just say an average weight of 80 kg. With rider power output, we're assuming same rider is producing the same power output/watts on each bike, 200 W for example.

Regarding how much the bikes weight, just go on general averages such as two trail bikes with a 50lb e-mtb and 14 lb mtb (EDIT: I meant 31 lb mtb/14 kg), both bikes being of similar type such as two FS trail bikes with similar spec. and suspension travel.


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## Le Duke (Mar 23, 2009)

BobBracket said:


> Regarding rider weight, maybe I'm wrong but I thought it wouldn't matter as the rider is the same weight on the e-mtb as on the standard. If it does matter, just say an average weight of 80 kg. I would also have thought the same principle applies with power output, same rider power output/watts on each bike.
> 
> Regarding how much the bikes weight, just go on general averages such as 50lb e-mtb and 14 lb mtb, with both bikes being of similar type such as two FS trail bikes with similar spec. and suspension travel.


Well, no.

The basic math works out such that climbing speed on a bicycle has a nearly linear relationship to watts per kilogram of mass (rider + bike). Particularly at typical mountain bike speeds.

Meaning, if you are producing 2.5w/kg and going 5mph on a certain grade, doubling your power output to 5w/kg will result in you going 10mph up that same climb.

So, using your example of an 80kg rider, 22.7kg e-bike (50lbs =22.7kg) and 6.3kg mountain bike (14lbs = 6.3kg), let's do some math, using some additional inputs. Say, 200w of human propulsion.

The easy one first. 200w/(80kg+6.3kg) = 2.31w/kg.

Now, the e-bike on econ (50%) and turbo (300%) modes, respectively.

(200w+(200w*0.5))/(80kg+22.7kg) = 2.92w/kg

(200w+(200w*300))/(80kg+22.7kg) = 7.78w/kg

With an e-bike in turbo mode, you'd be climbing 3.3 times faster than a much lighter bicycle with the same human powered effort.


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## BobBracket (Jun 6, 2018)

Le Duke said:


> Well, no.
> 
> The basic math works out such that climbing speed on a bicycle has a nearly linear relationship to watts per kilogram of mass (rider + bike). Particularly at typical mountain bike speeds.
> 
> ...


Hang on sorry, I said 14 lb mtb? I meant kgs, 14 kg trail mtb. There are no 14 lb fs trail bikes. I'm Australian and am trying to convert between kg and lbs as I know most on here are from the US, but I'm getting it twisted. Well that throws that throws your math off by a long way I suppose.


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## BobBracket (Jun 6, 2018)

Actually it's not that much different with the adjusted bike weight. So adjusting the math of the first equation for the standard mtb, it's 2.13 instead of 2.31.

Using the other equation for the e-mtb, I figure that for the e-mtb to be going at the same speed as the standard mtb with the same rider power output, the e-mtb needs to be using 10% assistance. Really, that's very little until the e-mtb is equal with a standard one.

What I also figured using your methods, is that in the econ mode the e-mtb is 1.37 times faster than the standard mtb. And 3.65 times faster in turbo mode. Interestingly, the increase doesn't seem to be linear with this one.


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## BobBracket (Jun 6, 2018)

So do these equations apply to the flat as well, or just to climbing? Which way would riding on the flat push the results?


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## westernmtb (Dec 19, 2018)

If you want a bike that gives the same assistance as a regular bike, buy a regular bike.


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## BobBracket (Jun 6, 2018)

westernmtb said:


> If you want a bike that gives the same assistance as a regular bike, buy a regular bike.


Who let the troll in?! I own a few regular bikes already, but thanks for the genius suggestion.


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## J.B. Weld (Aug 13, 2012)

It is a confusing question because a standard mtb gives zero assistance so you can achieve the same speeds as a standard bike without any assistance at all.

Any assistance beyond what an individual can produce on their own will increase their speed. Most people probably average somewhere around 100 watts or so on a ride but results vary.


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## J.B. Weld (Aug 13, 2012)

So to have the same assistance as a standard bicycle you would only need enough power to overcome the extra weight and drag created by the motor. Maybe 30 watts or so?


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## BobBracket (Jun 6, 2018)

J.B. Weld said:


> So to have the same assistance as a standard bicycle you would only need enough power to overcome the extra weight and drag created by the motor. Maybe 30 watts or so?


Thank you, you are correct in that you need enough power to overcome the extra weight and drag of the motor. I would also add the extra weight of the frame and fork of the e-mtb which are actually built up a little more than a standard mtb to accommodate the extra weight of the motor. As well as the battery too now that I think of it.

I'm not sure if I understand this relationship of watts correctly, but I'm thinking that with the equations the other bloke gave where I figured you'd need to use 10% of a 250W motor to achieve the same as a standard mtb, that that is right in line with your 30W estimate, as 10% of 250W is 25W. If I'm figuring right, you are both basically coming to the exact same conclusion.


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## westernmtb (Dec 19, 2018)

BobBracket said:


> Who let the troll in?! I own a few regular bikes already, but thanks for the genius suggestion.


No offense, but your question is a little dumb.

1. practically speaking, no one is interested in buying an e-bike so that it offers the same performance as a standard bike.

2. even if it did, no one would use that function.

3. there are too many variables to offer a single answer. Some mid drives weigh 45 lbs. Others 80 lbs. Some mid drive systems create drag, others do not. The programming for levels of assistance varies according to manufacturer. Some allow user programming, others do not.

A simple answer would be to factor in the additional weight but as you can see, that's not a full explanation.

Add to that, e-bikes handle very differently; you need to use your upper body strength a bit more when climbing in particular.

The bottom line is that e-bike riding is a very different riding experience that can't be explained in a simple formula.


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## BobBracket (Jun 6, 2018)

westernmtb said:


> No offense, but your question is a little dumb.
> 
> 1. practically speaking, no one is interested in buying an e-bike so that it offers the same performance as a standard bike.
> 
> ...


You're being completely obtuse. I'm not after exact figures, I just want to get a general idea how powerful the e-bikes are compared to non-assisted bikes. If you think it's a dumb question why are you here? Oh that's right, you're just a bored and bitter guy with no life who's going cross-eyed-monster in front of the computer.


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## westernmtb (Dec 19, 2018)

BobBracket said:


> You're being completely obtuse. I'm not after exact figures, I just want to get a general idea how powerful the e-bikes are compared to non-assisted bikes. If you think it's a dumb question why are you here? Oh that's right, you're just a bored and bitter guy with no life who's going cross-eyed-monster in front of the computer.


LOL, you are really getting bent out of shape for no reason. Thank you for your post, it was good for a chuckle.

But like I said, there is no formula that will provide an exact answer. As far as a 'general idea,' that can't be conveyed through internet posts in any reliable fashion.

I gave you an answer but you ignored it completely. E-bikes handle very differently due to their additional mass. Even with assistance, they climb differently because they are so heavy. More upper body strength is required.

They descend differently, they corner differently, they handle differently because they are much heavier. Not only that, but when you introduce the additional power from a motor, it introduces an odd dynamic where an extremely heavy bike suddenly feels feather light by adding more boost or just by stepping on the pedals.

That's not even factoring the different types of assist from different motors. Shimano, Bosch, Brose and Yamaha motors behave very differently.

Writing that up, it seems like e-bikes are terrible to ride, big burly unpredictable beasts. But when you actually ride them, they are so fun you can't get yourself off the bike, except to try another e-bike.

It's like a virgin asking what it's like to have sex. What can you say? It's sweaty, you grimace, you swear, the parts that fit together don't look so nice, but it's amazing. Doesn't make sense? Try it for yourself and find out.


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## tom tom (Mar 3, 2007)

BobBracket said:


> Who let the troll in?! I own a few regular bikes already, but thanks for the genius suggestion.


:thumbsup:.................:thumbsup:


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## ULEWZ (Dec 10, 2017)

My E-bike has 5 power settings, and on the lowest setting "1", I am still climbing better than on my 27lb Tracer. I rode with my son today, and the wind was blasting. I used setting 1 (eco) and was way in front of him (had to stop numerous times to let him catch up and only used the 50 tooth cog, to slow me down), and he normally blows my doors off. So my take is, even on the lowest setting, you will still have more boost than an analog bike. On a side note, I didn't use much battery going this slow and using the 50 tooth cog.


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## BobBracket (Jun 6, 2018)

westernmtb said:


> LOL, you are really getting bent out of shape for no reason. Thank you for your post, it was good for a chuckle.
> 
> But like I said, there is no formula that will provide an exact answer. As far as a 'general idea,' that can't be conveyed through internet posts in any reliable fashion.
> 
> ...


Cross-eyed monster go for a ride or something, we're not interested in reading your troll-books.


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## BobBracket (Jun 6, 2018)

ULEWZ said:


> My E-bike has 5 power settings, and on the lowest setting "1", I am still climbing better than on my 27lb Tracer. I rode with my son today, and the wind was blasting. I used setting 1 (eco) and was way in front of him (had to stop numerous times to let him catch up and only used the 50 tooth cog, to slow me down), and he normally blows my doors off. So my take is, even on the lowest setting, you will still have more boost than an analog bike. On a side note, I didn't use much battery going this slow and using the 50 tooth cog.


That's just incredible, these answers aren't what I expected to be honest. Quite a surprise, but a good surprise. If your e-mtb has 5 modes, I suppose your lowest "1" mode is under 50%. Do you any idea on that?


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## tahoebeau (May 11, 2014)

BobBracket said:


> I'm not sure if I understand this relationship of watts correctly, but I'm thinking that with the equations the other bloke gave where I figured you'd need to use 10% of a 250W motor to achieve the same as a standard mtb, that that is right in line with your 30W estimate, as 10% of 250W is 25W. If I'm figuring right, you are both basically coming to the exact same conclusion.


 Not sure if you are aware, but do realize that the 250w motor is just a nominal rating number and not the actual watts these bike put out. The power output is determined by the battery and controller and has nothing to do with the nominal power rating on an electric motor. You can run 1000w of power out of a 250w rated motor if you want.

I think the 2019 trek powerfly produces up to something like 600w of power. I do not believe there are any mainstream emtbs that do not put out well over 250w.


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## BobBracket (Jun 6, 2018)

tahoebeau said:


> Not sure if you are aware, but do realize that the 250w motor is just a nominal rating number and not the actual watts these bike put out. The power output is determined by the battery and controller and has nothing to do with the nominal power rating on an electric motor. You can run 1000w of power out of a 250w rated motor if you want.
> 
> I think the 2019 trek powerfly produces up to something like 600w of power. I do not believe there are any mainstream emtbs that do not put out well over 250w.


Ok no I didn't realize that, thanks very much for setting that straight, much appreciated


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## tahoebeau (May 11, 2014)

Unfortunately, myself and I am pretty sure everyone else who has read this thread is now a little dumber.


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## BobBracket (Jun 6, 2018)

tahoebeau said:


> Unfortunately, myself and I am pretty sure everyone else who has read this thread is now a little dumber.


Another troll, they're absolutely rife on this forum! If you don't want to see dumb, stop looking in the mirror.


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## westernmtb (Dec 19, 2018)

tahoebeau said:


> unfortunately, myself and i am pretty sure everyone else who has read this thread is now a little dumber.


lmao!


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## hikerdave (Mar 8, 2006)

BobBracket said:


> So do these equations apply to the flat as well, or just to climbing? Which way would riding on the flat push the results?


When wind resistance dominates and in still air, the power required goes up as the cube of the speed so 400 percent power results in 133 percent speed. So if you normally ride at 15 mph, the same effort would have you going 20 mph.

In a headwind, this simplification doesn't apply, because there's also a squared term of rider speed in the equation; the increased power in a headwind is likely to double your speed.


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## natrat (Mar 20, 2008)

basically a very low eco setting


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## leeboh (Aug 5, 2011)

BobBracket said:


> I hope I can convey what I want to know well enough. I have never ridden an e-mtb (or any e-bike). But to those who have, I'd like to get a general idea of how much assistance is required on an e-mtb to achieve the same speed as a standard unassisted mtb.
> 
> Regarding the type of e-mtb, I think I'm talking about Class-1 mid-drive e-mtbs such as the Trek Power Fly.
> 
> I believe the Power Fly has a 250W Bosche motor with 4 modes. Econ mode provides 50% assistance, Tour mode provides 120% assistance, Sport mode provides 210% assistance, and Turbo mode provides 300% assistance. What I'd like to get a general idea of is the percentage of assistance you'd need on an e-mtb to make it as fast as a standard mtb. For example, would 20% assistance make it equal to a standard mtb, or 50%, or 80 or 150%...?


 " The same speed as an unassisted mt bike"? Isn't the motor all about going faster? Hmmm. Try this. Ride a regular mt bike. Eat a good breakfast, power down some coffee. Just saved you 5-8 K. Cheers.


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## Le Duke (Mar 23, 2009)

hikerdave said:


> When wind resistance dominates and in still air, the power required goes up as the cube of the speed so 400 percent power results in 133 percent speed. So if you normally ride at 15 mph, the same effort would have you going 20 mph.
> 
> In a headwind, this simplification doesn't apply, because there's also a squared term of rider speed in the equation; the increased power in a headwind is likely to double your speed.


Sort of. On flat ground, with a relatively low starting speed (15mph), quadrupling the power input will result in a hell of a lot more than 20mph. Having used a power meter for many years, I can tell you that my power does NOT have to quadruple to go from 15mph to 20mph on flat ground, on either a road or mountain bike. Not even 50% higher, I'd guess.

Now, with a much higher starting speed, yes, that would be accurate.


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## hikerdave (Mar 8, 2006)

Le Duke said:


> Sort of. On flat ground, with a relatively low starting speed (15mph), quadrupling the power input will result in a hell of a lot more than 20mph. Having used a power meter for many years, I can tell you that my power does NOT have to quadruple to go from 15mph to 20mph on flat ground, on either a road or mountain bike. Not even 50% higher, I'd guess.
> 
> Now, with a much higher starting speed, yes, that would be accurate.


Yeah, bad example on my part. Here's a good calculator that shows 2x power from 15 to 20 mph for their initial values:

https://www.gribble.org/cycling/power_v_speed.html


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## JackWare (Aug 8, 2016)

BobBracket said:


> Cross-eyed monster go for a ride or something, we're not interested in reading your troll-books.


What was the reason for your question as WesternMTB's 'troll-book' is actually spot on with lots of info?

(These observations are based on riding a standard pedal assist class 1);
Because the motor provides practically instant assistant it's almost impossible to ride an Ebike at the speeds you would normally. On the level even without pushing hard you accelerate quicker and it takes a conscious effort to stay at a lower speed, on inclines it's the same story but even more dramatic, while downhill my personal experience is that the increased weight causes the bike to move faster even without assistance, ie coasting. 
But there are so many variables with the rider, bike and terrain the best way is to try one on the trails you know.
Personally it's not about the speed but the ability to travel further and in harder terrain than I could on my non Ebike and I'm lucky that access issues here in the UK are a lot simpler than in the US.


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## richj8990 (Apr 4, 2017)

J.B. Weld said:


> So to have the same assistance as a standard bicycle you would only need enough power to overcome the extra weight and drag created by the motor. Maybe 30 watts or so?


I'm not sure exactly what he was asking either. Let's start with how many watts he's doing on a normal bike in a normal trail loop, and say he averages 100W. If he's 250 lbs with rider, bike, gear on a normal bike, and then adds 20 lbs for the e-bike, then maybe 108W would be equivalent, at least on paper. If you add friction and other drivetrain losses, maybe 130W, like you said? But that's without pedaling at all, and class 1 doesn't have a throttle, so the question is a bit flawed to begin with, no? My throttle is way too coarse to try and get it to 100W, it shoots up to 850 watts no matter what position it's in after it is twisted more than an inch. There is only a couple of inches of throttle travel so it would be really hard to get exactly 100-130W consistently unless there was some cruise control set for that wattage.


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## tfinator (Apr 30, 2009)

richj8990 said:


> I'm not sure exactly what he was asking either. Let's start with how many watts he's doing on a normal bike in a normal trail loop, and say he averages 100W. If he's 250 lbs with rider, bike, gear on a normal bike, and then adds 20 lbs for the e-bike, then maybe 108W would be equivalent, at least on paper. If you add friction and other drivetrain losses, maybe 130W, like you said? But that's without pedaling at all, and class 1 doesn't have a throttle, so the question is a bit flawed to begin with, no? My throttle is way too coarse to try and get it to 100W, it shoots up to 850 watts no matter what position it's in after it is twisted more than an inch. There is only a couple of inches of throttle travel so it would be really hard to get exactly 100-130W consistently unless there was some cruise control set for that wattage.


I mean, a couple people already understood the question and answer it... So I don't know if this was necessary.

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## Klurejr (Oct 13, 2006)

The original question seems to have been answered.


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