You can buy them books, send them to school, but all they do is gnaw on the pages.
I admire your perseverance, but if I was a betting man, I'd wager that there is nothing you can say or do that will help them learn.
Motor Resistance, real or imagined?
- Thread starter steve_sordy
- Start date
You can buy them books, send them to school, but all they do is gnaw on the pages.
I admire your perseverance, but if I was a betting man, I'd wager that there is nothing you can say or do that will help them learn.
Absolutely not. You are spinning a magnets and internal motor parts, there is no disengaging. That is why there is excessive drag. Since there is no disengaging the motor, you are required to spin the motors internals which are geared so the motor rpm spins much faster than the peddles which factually is causing the excessive drag.
I have to put the bike on the largest cog on the cassette just to peddle level ground. The excessive drag was with the motor shut off. And the bike powered off after running out of battery. The drag is exactly the same with the bike on, but no power to motor. On electronic shifting that is your white mode. Powering the bike off changes nothing. Manual shifting has no white mode and you cannot test this unless the bike is shut off. If bike is one there is still juice going to the motor when the battery is low and almost empty.
- Thread starter
- #33
If I take the chain off the front ring, I can spin the crank freely. Therefore, there is no magnet being spun and no motor internals to spin either. My motor is a Shimano EP8. This is why it only takes 43 grams on one pedal to make it move (see my OP).
As also can I with the chain removed from the chain ring on my Bosch CX Gen 4 non-smart motor. Have a Reverse Components chain Flip-Guide for ISCG 05 so very easy and quick to do.
I think you need to get one of these mugs @steve_sordy, may come in handy for when the subject comes up again?!
ottoshape
Well-known member
My EP801 powered bike with the electronics powered off was orders of magnitude harder to pedal than my analogue bikes. I was surprised how tough it was to pedal on level pavement.
I regularly ride my ep801 with the assistance turned off on regular mountain bike trails with hill climbs. The longest I've gone is ~7 miles, I don't really buy the motor having excessive drag that you're claiming. Is it harder to pedal then my 26inch camber pro? Yes, but it's double the weight and I'm running squishy tires. It is harder but it's really not as bad as I expected it to be. I also ride with it turned off when riding with my family on gravel trails around town and it's not bad at all on hard surfaces.
I owned a Norco A-Line back in the mid noughties, a 50lb ish full suspension downhill bike with triple clamp forks.
It wasn’t an e-bike but was harder to pedal than any e-bike I’ve owned or own, motor off.
I can’t blame the motor as it didn’t have one, so why was it?
It wasn’t an e-bike but was harder to pedal than any e-bike I’ve owned or own, motor off.
I can’t blame the motor as it didn’t have one, so why was it?
- Thread starter
- #39
Where can I get one of those? (Father's Day is coming up!)
Or did you spoof it for the post?
I got it from Temu, but I think Amazon have them as well, or eBay.
Winford with his spinning magnets, gotta love it, pure quality
Redbikejohn
Member
So any engineer that understands just how motors actually work, will know the original post conclusion is flawed.
Regardless, it appears that many people (engineers included) don’t understand the kinematics with regard to e-bikes feeling like they ‘drag’ past the assist limit.
I think all Steve was trying to show is that there was comparatively little mechanical drag related directly to the motor.
I wish that we could clear this up as the forum needs to get on with discussing whether an aircraft could take off on a conveyor belt running in the opposite direction to its intended take off path.
Exactly, there is no clutch on a EP801 that disengages the motor like a Turbo Levo. I told the owner of the Shimano service center about this thread, he just laughed.
And Shimano techs are laughing right now at this debacle. I peddle thousands of miles yearly, I average 100 miles a week climbing 14,000 feet a week, for the whole last 12 months. I ride road/gravel analog and a regular mnt bike, I did a century as well analog. I would not ride my ebike anywhere without juice, because of the excessive drag. Level ground I could do your 7-10 miles, but I live on steep canyons. Its more than just a 50lb bike since its a fact these motors do not have a clutch.
TheKaiser
Active member
Hi Winford, I know I am new on this forum, but I am surprised at the level of derision and disagreement amongst the more seasoned users, despite this seemingly objective topic! Here we are, nearly 3 pages in, and I am none the wiser as to if the EP801, Turbo Levo, Bosch CX Gen 5, or DJI have some sort of fundamental differences in terms of their "power off" behavior, related to the presence of a clutch, or anything else.
From the post I'm quoting above it seems you know there to be some fundamental difference between the EP801 and the Turbo Levo in this regard. Would you care to elaborate and clarify, and, if you have similar knowledge of Bosch and DJI motors, provide similar elaboration as to their structures in terms of "power off" behavior?
Similarly, if you have any knowledge as to if the EP801 has some fundamental differences in various power modes, in terms of the free running drag, please let us know.
Worst-case scenarios and fall-back plans for the backcountry are a real concern for me, so this sort of info (while shockingly hard to come by) could be really valuable!
GodsTherapist
Member
It´s all in your mind!
So, you cycle a lot, you‘re in good company then…
If you’re saying that pedalling a 50lb bike out of a canyon is hard work without a motor, then honestly quelle surprise!
Which ‘Shimano techs‘ are laughing? Shimano e-bike motors definitely have a clutch, I know as I’ve had my E8000 motor apart and replaced it.
I have a number of e-bikes, Shimano, Bosch and Mahle powered, various versions but all well maintained and working perfectly. There is of course negligible measured drag on all of them, but it‘s just that, the extra effort involved in pedalling them motor off is a result of weight, big tyres, long travel suspension etc and mainly the fact that you’ve effectively just lost the ‘phantom tandem’ cyclist that was assisting you up until you turned your motor off or your battery went flat.
What’s hard to understand? Seriously, get your own motor checked or switched out if it’s as bad as you describe.
if you want to feel what the motor resistance would feel like IF there was NOT a clutch mechanism isolating the cranks from the motor internals during normal pedalling , then just wheel your bike backwards along the ground (with the chain installed), this will rotate the chain backwards, and the chain ring backwards, and because the clutch only acts in one direction it will also rotate all the motor internals and you will feel resistance and hear the motor internal gearing whirring.
Just to back up Steve (and most others) , As everyone else has said, most modern motors used on emtbs have negligable resistance when pedalling with the motor off/no battery, what you are feeling when you pedal without assist is just how it feels to pedal a heavy full sus bike with softish tyres, plus a psychological effect of losing up to 600w of assistance.
Just to back up Steve (and most others) , As everyone else has said, most modern motors used on emtbs have negligable resistance when pedalling with the motor off/no battery, what you are feeling when you pedal without assist is just how it feels to pedal a heavy full sus bike with softish tyres, plus a psychological effect of losing up to 600w of assistance.
This is not an accurate statement, he was probably laughing at you
. The one way clutch does indeed exist and is the cause of the ep rattle that some people complain about. Just for fun I rode my N8e with an ep801 six miles yesterday with the assistance turned off again. Up hills are definitely more of a workout with a 160mm 56lbs Enduro bike, but I was able to average 10 miles an hour.
- Thread starter
- #51
I asked the question of ChatGPT,
Question: I ride an electric mountain bike (24kg) that has a Shimano EP8 motor. When the battery runs flat, I have to pedal the bike with the motor off. What is the drag imposed by the motor?
This is what I got:........
The Shimano EP8 motor is one of the better systems in terms of low-drag performance when the motor is off or the battery is flat. Shimano specifically addressed this in the EP8 (DU-EP800) redesign compared to the older E8000.
This improvement was achieved by:
Lab tests and experienced rider reviews suggest:
In terms of quantifiable drag:
The Shimano EP8 motor does not significantly hinder pedalling when the battery is flat. The main effort comes from your bike’s total mass and rolling resistance, not from internal motor drag. That said, it’s still a slog uphill—so carrying a spare battery or planning range carefully is wise on long rides.
Would you like range extension tips for EP8 bikes or advice on low-drag tyres?
Question: I ride an electric mountain bike (24kg) that has a Shimano EP8 motor. When the battery runs flat, I have to pedal the bike with the motor off. What is the drag imposed by the motor?
This is what I got:........
Pedalling Drag from the Shimano EP8 Motor
The Shimano EP8 motor is one of the better systems in terms of low-drag performance when the motor is off or the battery is flat. Shimano specifically addressed this in the EP8 (DU-EP800) redesign compared to the older E8000.
Shimano’s Claim:
This improvement was achieved by:
- Using a new gearbox design inside the motor.
- Minimizing internal clutch and gear resistance.
- Including decoupling mechanisms that reduce mechanical resistance when the motor isn’t assisting.
Independent Testing Results (Typical Findings)
Lab tests and experienced rider reviews suggest:
- Pedal drag through the motor (with no assist) is minimal but not zero.
- The resistance is comparable to riding with a low-friction internal gear hub.
- You may feel a light resistance during higher torque efforts (e.g. climbing), but it's not like dragging a dead motor or seized hub.
- Most of the perceived effort when the battery is flat is actually due to:
- The weight (as you noted)
- Tyre rolling resistance
- Geometry and gearing being optimized for assisted pedalling, not unpowered riding
In terms of quantifiable drag:
- Reviewers like E-Mountainbike Magazine estimate the additional drag imposed by the EP8 motor alone is equivalent to a resistance of about 5–10 watts at typical cadence and power—negligible compared to rider effort.
Summary: EP8 Motor Drag
| Factor | Contribution to Resistance | Notes |
|---|---|---|
| Motor drag (internal) | ~5–10 watts (low) | Improved over E8000 |
| Extra weight | Significant (10–12 kg) | Always present |
| Tyres | High resistance | Wider, softer MTB tyres |
| Gearing | Less efficient when unpowered | Optimised for torque, not cadence |
| Frame geometry | Minor impact | Slacker angles slow on flats |
Verdict
The Shimano EP8 motor does not significantly hinder pedalling when the battery is flat. The main effort comes from your bike’s total mass and rolling resistance, not from internal motor drag. That said, it’s still a slog uphill—so carrying a spare battery or planning range carefully is wise on long rides.
Would you like range extension tips for EP8 bikes or advice on low-drag tyres?
It’s kinda what we’ve all been saying Steve?!I asked the question of ChatGPT,
Question: I ride an electric mountain bike (24kg) that has a Shimano EP8 motor. When the battery runs flat, I have to pedal the bike with the motor off. What is the drag imposed by the motor?
This is what I got:........
The Shimano EP8 motor is one of the better systems in terms of low-drag performance when the motor is off or the battery is flat. Shimano specifically addressed this in the EP8 (DU-EP800) redesign compared to the older E8000.
This improvement was achieved by:
- Using a new gearbox design inside the motor.
- Minimizing internal clutch and gear resistance.
- Including decoupling mechanisms that reduce mechanical resistance when the motor isn’t assisting.
Lab tests and experienced rider reviews suggest:
- Pedal drag through the motor (with no assist) is minimal but not zero.
- The resistance is comparable to riding with a low-friction internal gear hub.
- You may feel a light resistance during higher torque efforts (e.g. climbing), but it's not like dragging a dead motor or seized hub.
- Most of the perceived effort when the battery is flat is actually due to:
- The weight (as you noted)
- Tyre rolling resistance
- Geometry and gearing being optimized for assisted pedalling, not unpowered riding
In terms of quantifiable drag:
- Reviewers like E-Mountainbike Magazine estimate the additional drag imposed by the EP8 motor alone is equivalent to a resistance of about 5–10 watts at typical cadence and power—negligible compared to rider effort.
Factor Contribution to Resistance Notes Motor drag (internal) ~5–10 watts (low) Improved over E8000 Extra weight Significant (10–12 kg) Always present Tyres High resistance Wider, softer MTB tyres Gearing Less efficient when unpowered Optimised for torque, not cadence Frame geometry Minor impact Slacker angles slow on flats
The Shimano EP8 motor does not significantly hinder pedalling when the battery is flat. The main effort comes from your bike’s total mass and rolling resistance, not from internal motor drag. That said, it’s still a slog uphill—so carrying a spare battery or planning range carefully is wise on long rides.
Would you like range extension tips for EP8 bikes or advice on low-drag tyres?
And AI just polishes it and feeds it back to us.
“Give us your watch and I’ll tell you the time… “
- Thread starter
- #55
I was trying for an unbiassed opinion that was definitely not mine or ours. I realise that it probably won't (not can't) make stuff up, it has to have sources from somewhere. It quoted its sources: Shimano and E-Mountain Bike magazine and other "Independent Testing Results". It did not detail what they were, but from experience, it would if asked.
My pedals still spin freely when not encumbered by the chain.
TheKaiser
Active member
The clutch that causes the rattle operates such that it engages when the cranks turn forward or chainring rotates backwards, no? In other words, it disengages when you backpedal, and engages when pedaling normally. The rattle occurs because when coasting on a descent you are in a sort of "no mans land" where you are neither keeping the clutch consistently engaged with forward pedaling, nor keeping it consistently disengaged with backpedaling. That causes the chain growth/flailing to rapidly and repeatedly yank the chainring counterclockwise, engaging the clutch repeatedly as if you were ratcheting your pedals forward in rough terrain.This is not an accurate statement, he was probably laughing at you
I ask because, in your description, you seem to be implying that the clutch would be disengaged when pedaling with the motor power off, preventing excess drag from the motor. There may be a separate clutch that does that, but from my understanding of the rattle problem, a "motor off drag reducing clutch" would operate in the opposite direction to the rattle-causing clutch. Or am I missing something here?
I believe the motor spinning engages the clutch, it definitely doesn't sound like I'm spinning the motor when I'm riding with the assist turned off. Have you ever spun an electric motor through a planetary gear set? It's as loud as when it's running. Riding my ep801 without assistance is silent.
Our non-Smart Bosch CX Gen4 motors without assistance are also completely silent.
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