rear motor feeling, dis/advantanges

[martinko]

I have a front motor (not goldenmotor) and I am not too happy with it simply because I am used to ride with a lightweight front wheel.

Can somebody with a rear wheel motor confirm that the "feeling" of a rear motor is more like that with a motorless bike? Are there other things to consider with a rear motor? Advantages/Disadvantages?

Cheers,
Martin

[norkmeister]

I have never ridden a front motor, but I have just got my bike up and running with a rear motor.  My thoughts for the advantages of a rear motor were:

1: You never see a front-wheel drive motor bike
2: If you put the power down at the wrong time while cornering on an iffy surface the front wheel will just drop out from under you.  A rear wheel will simply skid out.
3: The weight distribution on the rear would be better since most of the weight would be back there

The main disadvantage I have felt at the moment is that my bike is a hard tail MTB.  With the weight of the rear hub and my battery mounted on a rear luggage carrier there is a lot of extra weight in the rear triangle which it wasn't designed to carry.  I am thinking of trying to make some sort of mount which will sling the batter under the cross bar to move that weight forward. 

When you go over a reasonable bump you REALLY feel it.

Cheers,
Jeremy.

[martinko]

I have never ridden a front motor, but I have just got my bike up and running with a rear motor.  My thoughts for the advantages of a rear motor were:

1: You never see a front-wheel drive motor bike
2: If you put the power down at the wrong time while cornering on an iffy surface the front wheel will just drop out from under you.  A rear wheel will simply skid out.
3: The weight distribution on the rear would be better since most of the weight would be back there
...

thanks for sharing your thoughts on this.

This brings me closer to the conclusion, that a front-wheel-motor is kind of a misconcept, except for some very special use-cases maybe. Interesting to see that over 90% of the offered conversion kits are restricted to front-wheel this time...

Cheers,
Martin.

[OneEye]

There are some difficulties in rear motor applications, which is perhaps why manufacturers have generally leaned towards the front-motor:

1.  Cost: the additional freewheel and gearing adds to the manufacturing cost and thus the retail price
2.  Too many parameters: Do you make a rear wheel hub with 3 sprockets, 5, 7?  What sizes?
3.  Width:  The wide motor and a large gear cassette may be too much for the rear dropouts (although fitting in the front dropouts is sometimes a problem also)
4.  Centering:  With the shorter spoke lengths due to the motor casing, dishing the wheel to center is not always possible
5.  Ease of installation/removal:  It takes quite a bit more knowledge of bike maintenance to install a rear wheel kit than a front wheel kit, especially if the number of sprockets on the rear wheel does not match the original number and spacing on the bike.
6.  Weight distribution:  Some riders will prefer a more even weight distribution across the bike, rather than having the motor, batteries and the bulk of the rider weight on the rear wheel.

I'm not suggesting your preference for a rear wheel kit is 'wrong', I'm just putting up the alternative perspective.

[norkmeister]

I did have the problem you mention with the dishing.  My rear wheel is not centred, but tracks straight and they were able to adjust the brakes to work.

I have seen a fair few people with rear drop out problems on this forum.  Most complaining about a 160 mm drop out. My supplier specifically orders them from golden with a 135 mm drop out and from my inspection of the wheel it could be even less since there is still a fair sized spacer on the non sprocket side.

Another problem is the rear derailleur.  My rear cassette was 9 gears, the new one is 5, the bike shop was unsure if they could get the derailleur working correctly and no one makes a 5 gear derailleur anymore.  In the end they were able to get it working.  There is one gear up top at the back that requires to clicks to get to and 2 to get back down, but with the motor on you will rarely go into that territory.  Yesterday I only changed my gears once on the way to work in a 16 km trip.

What I have found I need now is a bigger front gear.  I am topping out at around 46 kph on the flat due to the cadence required to go much faster without sprinting.

[martinko]

...
I'm not suggesting your preference for a rear wheel kit is 'wrong', I'm just putting up the alternative perspective.

thanks, I love controversial discussion :-)

After having read (and I simply couldn't stop for hours) about "torque arms" (why didn't my vendor tell me about that?), my preference for rear motors has gone up to incredible heights.

Putting a 5kg+ monster with a torque power like a horse on an innocent front fork, that has normally nothing to do than some careful breaking (not to hard, to avoid "saltos"), seems crazy to me now.

IOW, especially as I plan to convert bikes for other people too, I simply will not touch their front fork. It's not only the risk of the dropouts being ruined by a spinning axel, it's also the risk of simply breaking the whole fork by a combination of too heavy forces of all kinds, including simply too much weight.

And even the consequences of an accident caused by the front wheel are usually -very- different from that of a rear wheel.




 

[redrocket]

just a small note:
My first ebike conversion was a front wheel (bl-36). It lasted 2 days until the fork broke and I went over the bars.
The bike was a 20 year old street bike with a weak fork. I broke my radius bone.

While I still have the cast I am planning a real wheel conversion....

[ahend]

It lasted 2 days until the fork broke and I went over the bars. The bike was a 20 year old street bike with a weak fork. I broke my radius bone.

What a catastrophe, sorry to hear that. I suppose you could have come out far worse off, but a busted arm… ouch!

Can you tell us more about the failure? Did one fork arm snap, or collapse, or did a dropout disintegrate? Did you have a torque arm? What was the fork made from, mild steel, chrome moly?

Take care of that arm!

Andy

[OneEye]

PICTURES!!!

Preferably of the bike, but if you want to post pictures of your arm feel free. 

[Mel in HI]

I too would like to see pictures of how the fork broke.  More from a perspective of how I might examine/reinforce if necessary.

[Dave]

OneEye covered the biggest difficulties of a rear wheel kit pretty well (points 4 and 5 in his list), but the downsides of putting that much weight & torque on the front fork outweighs those difficulties pretty handily. If you've got either a decent bike shop close by or a decent grasp of bike mechanics, dealing with a rear wheel kit shouldn't be a problem.

I bought a rear wheel kit last fall, spent the winter tinkering with it (very sporadically), have had it on the road a fair bit this spring, and can confirm your impression that the feel is very close to that of a standard bike. There was a time when I did a little bike touring, where it was common for me to have 40-60lbs packed on a bike, and found there that the weight was easiest to deal with when it was on the rear wheel. Put too much weight in the front panniers and you have trouble keeping a line and keeping control in corners. I haven't ridden anything with a front hub motor, but my guess is it'd be much the same.

When people ask me what it's like riding my bike, the closest I can come to describing it is that it's like you're always riding downhill. The only time I can really tell I have an extra 30-35lbs on the back is when I hit a bump and when I'm trying to park it. Otherwise it just feels like my bike has always felt, and handles like it always has, at least when riding on the road; I don't plan on taking it offroad.

As for mounting difficulties with a rear wheel kit, the biggest problem I had was with fitting a standard width freewheel on it and dishing the wheel to center the rim in the frame. What I'm finding with some time on the road is that I don't use but two or three gears, so having a five speed cluster is totally unnecessary. I'm planning on putting a single speed freewheel on it, and using only the front chainrings to change gears. Eliminating the multi-speed sprocket should have the added benefit of also eliminating the centering issue.

[smarties]

The rear triangle doesn't support the hub's weight! It only drives it.
Since most of the rear racks mainly put the weight on the rear drop outs area,
once again, the rear triangle doesn't suffers a lot about the battery's addionnal
weight...

[dutchcyclingman]

a front wheel motor fits in every bicycle
if you have a hub gear  like a shimano 7 or 8 speed  there no place for a motor

i have a front wheel 750w and it feels oké
but you still feel the extra weigt when going from left to right at more than 30km/h
most of the time I go straigt
i have made a aluminium bar  on the inside of the front fork  in the top part  this helps
fork has no suspension an is made of renolds 531

but next wil be rear motor [for the forces]


this is a great idee for GM to make a motor with a 7 or 8 speed hubgear inside the motor 

[Leslie]

Often people who have rear wheels and battery packs on the rear rack suffer from poor weight distribution.

I use "suffer" from 27kgs of SLA lead on my bike and attepting to rack it on the rear made my bike feel awkward.

People who have fromt motors do not complain about having the packs on the rear rack.

I guess its down to the way you distribute the weight on your bike.

I put the lead packs right in the middle and slightly towards the front.

As long as you distribute the weight evenly upon both wheels, this includes rider weight as well, optimum traction can be seen to benifit steering and the general safety of the ebike.

It is better to have more weight in the back than the front as the front wheel will slide out into the gravel.

Keep it to a 1 rear to 1 front ratio and no more than 5 rear to 3 front ratio.  Never the other way.