Rear Wheel Drag

[Rjbur]

I’m a neophyte to ebikes so this is probably a simple question....

Took one of my new RadWagons out for a quick test drive around the parking lot at work and noted that each time I stopped peddling and coasted it felt like the rear wheel was slowing down the bike. Almost like regen braking was engaged but I did not see any numbers on display.

Do these motors just naturally put resistance like this or should they free spin like a regular bike?

This is my first ebike so I don’t know what to expect.

Thanks

 

[harryS]

The Radwagon is a direct drive so a coasting wheel has to turn the motor past its magnets. And since it is a fairly strong motor, it has strong magnets. Your get no moving parts and higher reliability, but higher drag is the tradeoff.

Geared hubmotors have a clutch that allows the wheel to turn more freely when coasting. There is some slight drag that you can feel if you spin the wheel by hand, but it doesn't impede riding.

Don't have a direct drive motor, but have read that if you crack a little throttle when you want to coast your bike while riding, it puts enough
electricity thru the winding to let the motor turn more freely.

 

[Rjbur]

Thanks!!! I was hoping it was something along those lines. Slowly learning about how these work...

 

[MadManMark]

HarryS answer was great, but an alternative to cracking the throttle you can just slowly continue pedaling while otherwise "coasting." That would arguably be a bit safer (you could hit a bump or slip or whatever and unintentionally rev the throttle)

 

[AHicks]

I've never noticed that much drag on my City. Are your tires inflated properly? Is it possible you have a brake dragging?

 

[mrgold35]

I have a Radrover geared rear hub and the wife has a Radcity step-thru. It takes very little effort or I usually have to pump the brakes to maintain a constant speed down hills on the rover. My wife has to be constantly pedaling to maintain the same speed or she will slow down too much with regen braking. We really didn't notice the differences between the two ebikes until we rode side-by-side.

Saw this Youtube video and the owner said the regen might be deactivated in PAS 0. I haven't tested this out to see if this works everytime once you select PAS 0 at anytime or other conditions must be met before regen is deactivated? Might be worth a try on longer hills if speed is more important than battery/brake life.

 

[AHicks]

When speaking direct drive, the regen does not come on when you stop pedaling. The ONLY time the regen is activated is when you are using the brakes. Some say theirs came on when exceeding the bike's 20mph (or whatever) speed limit, but I never verified that personally. Mine didn't for sure.

 

[eguy]

I get motor resistance when I go around 26+mph that feels like the regen kicking in but the display shows 0 watts. Not sure what it is but it's definitely mechanical braking from the controller or something otherwise the bike would continue accelerating. It's pretty annoying, honestly but is what it is.

 

[Rjbur]

I believe "harryS" has the right idea... Since it is a Direct Drive, I believe I am feeling the natural resistance of the motor. As I stated, I do not "hear" my breaks rubbing and the feeling I am getting is that of what I would think happens with Regen Braking, but since I do NOT have the brake lever pulled, its simply the motors magnets as "harryS" stated.

I sent the exact same question to Rad Support and received the following answer:

"Thanks for reaching out! Welcome to the world of eBikes, we are happy to have you on board! When your top speed is reached, the drag you are referring to is related to the magnetic resistance within the direct drive motor. This is a normal function for this type of motor. It's the controllers (controller is the bikes computer system) way of regulating voltage. When your speed increases, an output voltage is generated, if your speed were to just keep increasing, then the output voltage would also keep increasing and would then potentially damage electrical components. So the drag ensures that this does not happen.

I hope this answers your question, let me know if you have others or if you need anything else!"

He talks about top speed being reached... I believe the effect is the same as coasting at lower speeds... You reach top speed and the controller cuts the batter power to the motor and thus we feel the resistance of the motor kick in the same as when I coast at low speeds. The rest of his answer makes no sense about regulating voltage since I doubt regen braking at 20 to 25 mph would generate any significant voltage to damage anything. I do wonder about his speed increase statement and generating more voltage? Unless regen is engaged are we not simply consuming power and doing nothing when coasting??

So in summary, I believe "harryS" has the answer above in post #2,

The Radwagon is a direct drive so a coasting wheel has to turn the motor past its magnets. And since it is a fairly strong motor, it has strong magnets. Your get no moving parts and higher reliability, but higher drag is the tradeoff.

 

[MadManMark]

Yes, harryS has a good explanation, but the video mrgold posted makes a valuable point to know: if you switch to PAS zero, apparently the direct drive could be *completely* disengaged, and perhaps you can coast like a regular bike.

The next time I have non-slippery conditions that I feel comfortable in going that fast, I mean to give it a try. The's a hill on my commute that I could usually hit maybe 30mph going down on my old standard bike, just coasting, and I miss that feeling of speed/efficiency ...

 

[Rjbur]

Yes, harryS has a good explanation, but the video mrgold posted makes a valuable point to know: if you switch to PAS zero, apparently the direct drive is *completely* disengaged, and you can coast like a regular bike.

The next time I have non-slippery conditions that I feel comfortable in going that fast, I mean to give it a try. The's a hill on my commute that I could usually hit maybe 30mph going down on my old standard bike, just coasting, and I miss that feeling of speed/efficiency ...

You cannot coast as a regular bike... The Radwagon has a "Direct Drive" motor and thus it will always have some amount of resistance in free coasting mode. Yes it will have more resistance when you activate the regen braking and that is what he says in the video where he states he definitely "feels" the regen braking. He is also going down a steep hill and thus may not "feel" the natural constant resistance of the motor.

I was on "flat ground" going slow and stop pedaling to coast, I feel the motor slowing down the bike. It does not, even in PAS 0, free coast with no motor resistance. I'm sure if I was going down a hill and my 200+ pounds and the weight of the bike and gravity assistance engaged ;-) the motors resistance and slow down would be hard to notice. In the video he was coasting over 20+ mph so it would be hard for him to feel any resistance from the motor.

On flat ground, go maybe 5-10 mph and then free coast and eventually you will feel the bike slowing faster that it should or would if it was free wheel spinning like a non-ebike. As harryS put it, a down side to direct drive motors....

 

[JRA]

I use Statorade in my DD hubs to help keep heat down and as effective as it has proven for that I also feel that it reduces the tension between the magnets and the stator while not under power. To the point where both hubs show little to no drag at all and can be pedaled normally although the overall weight is a factor when hills or headwinds are encountered but still able to be overcome.

https://www.ebikes.ca/product-info/statorade.html

 

[Rjbur]

I use Statorade in my DD hubs to help keep heat down and as effective as it has proven for that I also feel that it reduces the tension between the magnets and the stator while not under power. To the point where both hubs show little to no drag at all and can be pedaled normally although the overall weight is a factor when hills or headwinds are encountered but still able to be overcome.

https://www.ebikes.ca/product-info/statorade.html

That sounds interesting / exciting!

Guess I'll have to wait for my "Limited 1-Year Warranty" before trying this or I'm sure they would consider this a warranty voiding factor since you have to pull the motor cover off and your injecting a substance into the motor.

 

[JRA]

That sounds interesting / exciting!

Guess I'll have to wait for my "Limited 1-Year Warranty" before trying this or I'm sure they would consider this a warranty voiding factor since you have to pull the motor cover off and your injecting a substance into the motor.

Actually the best way to insert it is to remove one of the brake rotor bolts and drill into it with a bit that won't effect the threads and insert the Statorade via the syringe it comes in. If you are careful about removing the metal shards as you go you shouldn't get any in the motor itself. Replace the rotor bolt and off you go. You may need to use more in the future so just mark the bolt with the hole for future use.

 

[AHicks]

You cannot coast as a regular bike... The Radwagon has a "Direct Drive" motor and thus it will always have some amount of resistance in free coasting mode. Yes it will have more resistance when you activate the regen braking and that is what he says in the video where he states he definitely "feels" the regen braking. He is also going down a steep hill and thus may not "feel" the natural constant resistance of the motor.

I was on "flat ground" going slow and stop pedaling to coast, I feel the motor slowing down the bike. It does not, even in PAS 0, free coast with no motor resistance. I'm sure if I was going down a hill and my 200+ pounds and the weight of the bike and gravity assistance engaged ;-) the motors resistance and slow down would be hard to notice. In the video he was coasting over 20+ mph so it would be hard for him to feel any resistance from the motor.

On flat ground, go maybe 5-10 mph and then free coast and eventually you will feel the bike slowing faster that it should or would if it was free wheel spinning like a non-ebike. As harryS put it, a down side to direct drive motors....

I believe "harryS" has the right idea... Since it is a Direct Drive, I believe I am feeling the natural resistance of the motor. As I stated, I do not "hear" my breaks rubbing and the feeling I am getting is that of what I would think happens with Regen Braking, but since I do NOT have the brake lever pulled, its simply the motors magnets as "harryS" stated.

I sent the exact same question to Rad Support and received the following answer:

"Thanks for reaching out! Welcome to the world of eBikes, we are happy to have you on board! When your top speed is reached, the drag you are referring to is related to the magnetic resistance within the direct drive motor. This is a normal function for this type of motor. It's the controllers (controller is the bikes computer system) way of regulating voltage. When your speed increases, an output voltage is generated, if your speed were to just keep increasing, then the output voltage would also keep increasing and would then potentially damage electrical components. So the drag ensures that this does not happen.

I hope this answers your question, let me know if you have others or if you need anything else!"

He talks about top speed being reached... I believe the effect is the same as coasting at lower speeds... You reach top speed and the controller cuts the batter power to the motor and thus we feel the resistance of the motor kick in the same as when I coast at low speeds. The rest of his answer makes no sense about regulating voltage since I doubt regen braking at 20 to 25 mph would generate any significant voltage to damage anything. I do wonder about his speed increase statement and generating more voltage? Unless regen is engaged are we not simply consuming power and doing nothing when coasting??

So in summary, I believe "harryS" has the answer above in post #2,

You need to look further into regen and how it works. It has nothing to do with the resistance you might feel when coasting at a low speed. Nothing.

Regarding what's going on with that resistance in PAS 0, turn your bike over and give the rear wheel a spin. Notice how it doesn't spin near as long as a conventional bike wheel might? THAT'S due to the magnetic resistance, and it will do that even with the power turned OFF.

Regen is an internal function that basically turns the motor into a generator that's trying to put a bunch of power into the battery all at once. There is so much drag created in this process at higher speeds it can be used as a (very sophisticated) brake that works very much like an engine brake in a car or truck that's going down a big hill. Used improperly it CAN get to the point where stuff starts getting hot.... hot enough where people paying warranty costs start worrying about it.

That regen/brake is turned on only with switches in your brake handles, and may POSSIBLY be energized automatically when the controller's speed limit has been reached, though assuming all systems are like that would be a mistake (automatic engagement when speed limit is reached). -Al

 

[Rjbur]

I guess I’m not making myself clear...

You need to look further into regen and how it works. It has nothing to do with the resistance you might feel when coasting at a low speed. Nothing.

I agree... I stated that since I did NOT have the break lever pulled it was simply the resistance of the motors magnets due to the direct drive nature of the motor as harryS stated.

Regarding what's going on with that resistance in PAS 0, turn your bike over and give the rear wheel a spin. Notice how it doesn't spin near as long as a conventional bike wheel might? THAT'S due to the magnetic resistance, and it will do that even with the power turned OFF.

That’s exactly what I am trying to say... I have had it upside down and I have spun the tire... its that same resistance I’m feeling while coasting that is slowing me down...

Regen is an internal function that basically turns the motor into a generator that's trying to put a bunch of power into the battery all at once. There is so much drag created in this process at higher speeds it can be used as a (very sophisticated) brake that works very much like an engine brake in a car or truck that's going down a big hill. Used improperly it CAN get to the point where stuff starts getting hot.... hot enough where people paying warranty costs start worrying about it.

That regen/brake is turned on only with switches in your brake handles, and may POSSIBLY be energized automatically when the controller's speed limit has been reached, though assuming all systems are like that would be a mistake (automatic engagement when speed limit is reached). -Al

Agree again and understood...

My simple question was why I was feeling resistance when coasting. The simple answer was that it’s a direct drive motor and that’s what’s causing the resistance and not regen braking as I’m coasting at low speeds 5-10 mph.

I have a friend with 3000+ miles on his Radwagon. Before anyone says anything, yes many people have much much more. Anyway, he noted that when he reached the 20 mph limit the sudden cutoff of the motor was noticeable. I need to ask him if he noted a change (lower) in the amount of resistance when he coasted and let the speed fall below 20 mph... If so, then possibly regen braking was engaged and then disengaged by the controller. Here’s hoping not!

I am still waiting for Santa to put the bikes under the tree. I have only taken one very short test drive thus far. In that video where he was going downhill I don’t think he experienced any auto regen happening. It seem to only happen when he pulled the breaks.

 

[AHicks]

Most of us can't feel that drag at low speeds. The bikes coast fairly well. I think you'll agree after riding it for a bit.

If this is an older Rad your friend owns, it could very well be set up differently than the newer stuff. They're making improvements to the programming they use all the time.

 

[Rjbur]

Most of us can't feel that drag at low speeds. The bikes coast fairly well. I think you'll agree after riding it for a bit.

If this is an older Rad your friend owns, it could very well be set up differently than the newer stuff. They're making improvements to the programming they use all the time.

He has a 2018....

I’m betting he feels it because he’s going “up” a slight grade/hill when it happens. I’m sure we would all feel it if we were pedaling and actually assisting the motor and suddenly our best friend (the motor) stops helping us.

I’ll have to spend more time with him talking about his experiences. I’m sure with time I’ll learn to ignore the slowdown and just keep pedaling.

Today’s mission.... bring the 2 RadWagons home when my wife is not around and find a place to hide them till Santa can delivery them. ???

 

[AHicks]

For sure there is no doubt when that motor drops out at whatever speed you have it set at, even when going down a hill. It's not applying any type of braking force on that event though. It's just not applying the boost it was just previous to that moment. No big deal. On some hills, you'll continue accelerating even after the motor stops providing boost! We winter in a coastal area, with a lot of rolling hills. They're the reason we went electric to start with. Too old to go far after climbing just a few of them. Some of them get pretty tall, and long. We can see 26-27mph, maybe more on occasion - even though the motor kicked out at 20 something. Wife get's nervous at those speeds, and I watch where I'm going and what's going on around me pretty closely. Both of us use our regen frequently! The drag of the regen can frequently supply enough drag to hold your speed in check, so you don't end up at 30+ while you start considering how to get stopped for that stop sign at the base of the hill. -Al

 

[Dirkdaddy]

Interesting discussion, new to ebikes have a Wing Freedom and on last ride there were some reasonable downhills over 25mph and I could definitely feel the drag from the motor when I stopped turning the cranks to turn on the assist motor. It was annoying coming from a conventional bike that would have coasted much better. I did check brakes and other things but its the rear hub motor. From what people are saying its endemic to the design and have to live with it. The Wing comes with a fairly basic controller but it does have a lot of settings however Wing doesn't want people messing with it as they have a warranty so I am not sure what all the settings are. Do all mostly have a regen braking setting? That would be nice but I don't think its turned on.