2015 Dash rear wheel doesn't spin freely

Paul E.

Active Member
#1
First I thought it was the normal cogging of a gearless hub motor but it seems to have gotten worse and doesn't seem reasonable: the bike is really heavy to pedal unpowered and when the wheel is off the bike, you can hardly turn the axle by hand. There's no rattling or grinding that would indicate loose magnets, it's just tight and sticky. Surely this is not normal?

I happened to see a support doc that said too tight freehub nuts could cause that but when I checked them, they were totally loose.

Any insights anyone?
 

J.R.

Well-Known Member
#2
First I thought it was the normal cogging of a gearless hub motor but it seems to have gotten worse and doesn't seem reasonable: the bike is really heavy to pedal unpowered and when the wheel is off the bike, you can hardly turn the axle by hand. There's no rattling or grinding that would indicate loose magnets, it's just tight and sticky. Surely this is not normal?

I happened to see a support doc that said too tight freehub nuts could cause that but when I checked them, they were totally loose.

Any insights anyone?
Your first thought was likely right on the money Paul, normal cogging. You wouldn't be able to grab the axle with a couple of fingers and turn it, those magnets are really strong. If you take an open ended wrench, place it on the axle flats and turn it very slowly you can feel each magnet grab and let loose. The axle on a direct drive hub motor won't spin freely. If I spin my direct drive motor wheel with the bike off the ground the wheel will only spin a half dozen times +/-. In comparison the front wheel will spin for minutes. I don't think anything is wrong with your bike.

Good luck, good spring riding!
 

Paul E.

Active Member
#3
If I spin my direct drive motor wheel with the bike off the ground the wheel will only spin a half dozen times +/-.
See, that's what I imagined would be normal, but when I try to turn the axle not just with a couple of fingers but with the best grip I can, it takes effort, and with the bike off the ground it's impossible to spin the wheel more than a few rotations.
 
Last edited:

J.R.

Well-Known Member
#4
It should take a good push. Try to gently spin it with a wrench and see if everything feels alright. If you have any doubts you may want to take it to a shop. This is one of those things you need to see and feel, hard to diagnose online. Your "doesn't spin well" might be my "wow, spins great".
 
#6
Neodymium magnets are indeed strong but they are near copper windings.. ever pick up an old copper penny with a magnet? I don't think so. This is why I personally feel cogging effects are over-estimated by many users. Energise those coils and now forces come to life, electromagnet/permanent magnet. On my 2014 Dash the motor would actually rub internally when it was new (first 6 - 8 weeks). This occurred mostly at the end of a ride when the motor was warm, not hot. Fortunately the condition went away after a few months. BTW - it was not very audible, something I could feel and barely hear. Make that video! -S
 

J.R.

Well-Known Member
#7
Here's a dramatic view of cogging, no DC yet as there's no windings. Big power in these magnets for sure.


A DD ebike hub, this is what I've seen (and felt) with my wheel on a trueing stand.


I hope this helps.
 
#8
BTW - The top motor has permanent magnets on the rotor, 36 of them. The Crystalyte X5 motor is a beast, nothing like what the Dash has. Latter generations have seen 5 Kw pumped into them! -S
 

Paul E.

Active Member
#10
If you take an open ended wrench, place it on the axle flats and turn it very slowly you can feel each magnet grab and let loose.
When I do that, I feel mostly smooth and steady fairly heavy resistance (like an overtightened bearing) with only extremely faint actual cogging mixed in. That can't be right, right?
 

J.R.

Well-Known Member
#11
When I do that, I feel mostly smooth and steady fairly heavy resistance (like an overtightened bearing) with only extremely faint actual cogging mixed in. That can't be right, right?
Not sure, no way of knowing online. Take to a LBS if you have concerns. My wheel is exactly like this video.

 
#12
Would not be the first new bike to have tight cones, my 2014 Dash had a front wheel with crazy tight cones. I know you checked them out but maybe it warrants another look or J.R.'s suggestion of a trip to the shop if you don't have the thin wrenches and mechanical chops. I've also seen new wheels overpacked with grease. Good luck! -S
 

ebikemom

Administrator
Staff member
#13
This thread is interesting to me for understanding the difference between direct drive and geared hub motors (did I get that terminology right?)