Traction problem with Big Bear

Marwood Hill

Esteemed Pedelecer
Mar 28, 2016
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Big Bear LS has got touring type handlebars as standard. I've fitted similar to mine as i like upright seating position.


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trex

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May 15, 2011
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swept back handlebars give you more upright sitting position and reduce weight on the front wheel. That won't matter after you change to rear wheel drive.
 
D

Deleted member 4366

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Take all that junk off your rear rack and put it on the front one, or get a triangle bag and stick it in there.

Next, shorten the two tie-bars at the front of the battery, so you can get the battery as far forward as possible without interfering with the seat spring mechanism.

Finally, lean forward when you go up-hill.

Even when the wheel spins, it's no problem. The bike will remain completely stable, so it's nothing to worry about.

I've ridden the bike, and I didn't experience any wheel-spin. I've ridden along-side Russ (forum Admin) when he was riding one, and his wheel wasn't spinning either. It therefore seems a logical conclusion that your wheelspin is something to do with that junk on the back of your bike or the way you sit on it.
 

Marwood Hill

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Mar 28, 2016
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I'm climbing a 33% gradient. Weight well forward. Nothing heavy on rear rack. Nothing on front rack because it doesn't help. If this hill was damp, i would have to walk up.

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trex

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Nealh

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If your bike came with 1.95 fitted then you should be able to fit at least up to 2.35" tyres, 2.1 or 2.25 are fairly standard sizing.
 
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Marwood Hill

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Mar 28, 2016
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One other thought. Could the gears be removed from the rear wheel and put into the front wheel. Then the front wheel put into the rear? There seems to be enough distance between the dropouts?


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trex

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the rear motor has thread to install your freewheel, the front motor doesn't.
 
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Fordulike

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Feb 26, 2010
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One other thought. Could the gears be removed from the rear wheel and put into the front wheel. Then the front wheel put into the rear? There seems to be enough distance between the dropouts?


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No, that wouldn't be a viable option. Best bet is try to deal with traction issues on your current set-up, which I think can be minimized by fitting more suitable tyres.
 
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trex

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just a thought for climbing steep hills with your Big Bear.
The throttle overrides the asist and lets you control the bike more accurately. How about stop pedalling and climb more or less entirely on throttle?
 

Marwood Hill

Esteemed Pedelecer
Mar 28, 2016
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The problem with these electric motors is you just can't get the wheel to turn slow enough. The minimum throttle speed just makes the wheel judder. Turn throttle a tiny bit more and wheel turns too fast and spins.


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chris_n

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Apr 29, 2016
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On gradients like that you need rear wheel drive, if it was a car you could reverse up! Even with rear wheel drive you will have to keep your weight on the front to keep the wheel on the ground. You can play with tyre width and compound all you want you will only improve the situation by a couple of percentage points.
 
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D

Deleted member 4366

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The reason the tyre spins is that there isn't enough weight on it. It's nothing to do with tyres, throttles or anything else. To solve it, you have to bring some weight forward. When you're climbing a steep hill, the battery and all that junk on the rack will be behind the rear axle, which is very bad for this problem. You don't seem to be grasping that simple point. Move the battery forward and get rid of everything else on the rack.

My riding mate has the 500w version of your motor on a bike with pulled back handlebars. It runs at about 28amps, so makes a lot more torque than yours. He has a 8kg battery on his rack, but it's tucked right up against his seat-post. He has no problem with traction. We ride up hills as steep as 30%, which is about as steep as hills go. Your battery is about a foot further back, which is not a good position for a heavy battery.

Before the bars were changed. Also, note that it has heavier forks, which helps a lot.

 
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Marwood Hill

Esteemed Pedelecer
Mar 28, 2016
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Before seeing your post d8veh i have this morning been moving the battery forward. The battery is right forward now, up to the seatpost and at an angle so all the weight is in front of the rear axle. Loooks a bit strange but if it works! Trials this afternoon.


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Marwood Hill

Esteemed Pedelecer
Mar 28, 2016
345
155
North Devon
The battery could be moved even further forward by cutting the rack about a bit and bolting it to the crossbar. Flat and vertical. What do you think?


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