Front or Rear Motor Preferences?

[alpharalpha]

I see a lot on the front and some on the rear, do rear ones present significant obstacles as I have a front one but am thinking of going with a rear but since my current e-bike is alluminum (steel front fork) I'd be looking at getting a steel bike which adds another bike to my stable.

 

[Sunder]

Obstacles? Yes
Significant? No.

It makes it more difficult to change inner-tubes, but I have to change one less than once a year. A friend was doing one every couple of weeks, the route he was taking.

Balance might also be another thing. I found with both the battery and the motor in the rear wheel, too much weight was at the rear, but I got used to it after a couple of rides.

 

[Chalo]

In the grossest sort of generalization, I'd say that front hub motors make tidier and more elegant conversions in the 750W and lower power range, and that the more power you add above that value, the more important it is to have the motor in the rear.

With a front motor, you get to keep a more functional bicycle drivetrain and a much stronger conventional rear wheel. The weight distribution is better and you have two wheels that can be driven simultaneously.

Remember that front forks are generally robust enough that you can grab a bunch of front brake and do a nose wheelie without hurting them. A modestly powered hub motor isn't in the same class of structural forces.

 

[alpharalpha]

Yes weight distribution is a pro for the front hub I think. As far as flats I use slime, I know it gets a bad rap but after riding home and finding over 40 goat head thorns in my tires I was sold. Tuffy liners eventually wear into the inner tube so no good. I use Marathon Plus on my e-bike, don't know if it's overkill as I've got Panaracer Pasela Tourguard "Kevlar" on my road bike, though I just did a little lookup on them and the right away on bike forums someone asking about them got answered "I think they are great. I've got over 2500 miles on mine without a flat." so maybe they're not the best comparison.
Now, I thought these hub motor kits had pretty beefy double walled rims, not so? And I didn't think about the use of both tires, guess I just assumed I could pedal with rear hub, as I often do--enjoyable to be casually pedaling along under power doing over 20 mph
I saw a rear hallomotor kit on that auction site, USA seller for $160 36v 500w, hard to imagine it's any good, are those any good? (though you guys are making some good points for low powered front hub, you can see my concern, a front failure has a high risk of fatality if you're riding on the shoulder of a road and get dumped in front of a car. And are the front torque arms that I have that go in the fender holes better or worse than the c clamp ones?

 

[dogman dan]

In general, front hub is only for bikes that cannot have a rear hub for some reason. Mostly this reason is things like the only brakes are a coaster brake, belt drives, shaft drives, internal gear rear hubs, and trikes that can only use a front hub. But in some cases, weight distribution is also a valid reason. If you are going to carry a 40 pound lead battery in back, you may want to move the hub weight up front. This arrangement was pretty standard when lead was the typical battery.

But now, with a 1000 watt hour lithium battery only weighing 16 pounds or so, The only reason you'd carry the motor up front would be if you plan to overload the back with cargo. Enough to wreck a weaker motor wheel. This cargo could of course be your own body.

But for most people, under 250 pounds body weight, the modern lithium battery can be carried on a rear rack, with a rear motor, and not affect handling aversely enough to care about when street riding.

For dirt trail riding, a rear hub is nearly mandatory, and then you attack the problem of moving the battery forward if it weighs more than 10 pounds.

So in short, it depends. Depends on the bike, depends on the rider, depends on the ride, depends on the weight of the battery involved,,,, and on and on.

But one thing for sure, Nothing super wrong with front drive, a simple coaster brake beach cruiser with a front hub can be a marvelous ride! You might seriously consider buying a cruiser for your next bike, and change your current bike to the rear hub. But after 10,000 commuter miles with front hub, I don't miss it any. I'm slightly more confident with any riding on dirt or gravel with the rear hubs on my street bikes, and don't wear out the motor wheel tire abnormally fast anymore. I could have had less tire wear, but I usually just gave full throttle and would spin the tire for a foot or so every start.

As for your torque arms, yes it's important shit. But your current ride is fine, your TA install is perfect. You can stop fetting about that.

 

[Chalo]

I use Marathon Plus on my e-bike, don't know if it's overkill as I've got Panaracer Pasela Tourguard "Kevlar" on my road bike,
[...]
Now, I thought these hub motor kits had pretty beefy double walled rims, not so?

Marathon Plus is one of the most heavily armored tires available. Pasela TG is very lightly protected, just one step better than an unprotected tire.

It isn't the rims that make hub motor wheels weak (though the rims are usually very cheap and crappy). It's poor lateral bracing angle, poor spoke insertion angle to the rim, and (paradoxically) too-thick spokes that make them weak and unreliable.

 

[dogman dan]

FWIW, I've had very little trouble with the too thick spokes wheels, provided the spokes were decent ones to start with. But those shit spokes on the cheap kits, or cheap bike wheels, one batch lasts forever, another batch has wheels exploding on the first pothole. It seems totally random.

But to be fair, I pay attention to my wheels a bit more than most I think, keeping any that loosen snug. Best way to have a wheel break spokes, keep trying to straighten it by overtightening the spokes. Once a rim is really bent, it's done. Best way to bend a rim, ride with loose spokes.

 

[mvadventure]

Having had both, a front wheel Crystalyte 48 volt 1000 watt motor with batteries over the rear wheel on a Boss brand cruiser and now a Pedego Interceptor with a 500 watt motor on the rear wheel with the lithium batteries behind the seat I appreciate the differences in ride and handling. I find very little difference in handling or ride comfort but have noticed tire wear on the front motor was noticeably more prevalent than with it on the rear. That could be because the Crystalyte motor is heavier then the Pedego motor or simply because of wheel slippage. What I didn't find riding on sandy paths was excessive tire slippage from the front motor setup. On the Crystalyte setup the front wheel was better for me as when, initially, I had SLA batteries over the rear wheel and later LIpo4 batteries in the same location, reasonable balance was achieved. With the lighter motor and battery setup on the Pedego weight distribution doesn't seem to be an issue.
The only difference I've noticed in changing a tire over either configuration is realigning the disc brakes on the Pedego which can be time consuming but is significantly easier on the front wheel without the motor.
Even though it's not part of the thread, the Crystalyte setup, while efficient, was a conversion rather then a factory installation. As a result it was not water proof or even rain resistant. Riding in the rain stood a good chance of shorting either the motor or controller and keeping wires waterproof is a bigger challenge then simply wrapping them in electrical tape. But....mine was a first generation I put together more then 12-14 years ago and improvements in controller and motor water resistance may have been made. My existing 48 volt 15 AH lithium battery is substantially lighter then either the SLA's or the LiPo 48 volt 20 AH and that's got to make a difference too.
For what it's worth I had well over 6K miles on the Crystalyte and it was running strong when I sold it.

 

[Drunkskunk]

Stick it in the front. Stick it in the rear. Stick it in both. It really doesn't matter as long as you enjoy the ride, right?

Oh, we're talking about bicycles. My mistake.


It's really a matter of personal preference. At reasonable power levels and riding conditions on a conventional bike, the performance is about the same. There are a lot more caveats with a front motor, though. Not good on slippery terrain, not good on rear loaded cargo bikes, not suitable for high power, not for use with carbon, aluminum, or exotic forks, not for internal use, do not induce vomiting, see your doctor if the itching persists.

The real advantage of putting it n the rear comes when you decide to venture outside of what is considered normal. All those freaky things you've seen other people do, or read about online, you can get away with when your ride can take it in the rear. Sure, it's a little harder to put it in, but ultimately you can be much rougher with it that way, and push your ride way past what you thought were the limits. You can pump much more juice into it, and it will take it, and beg for more.

Wait, Bicycles. Ah heck, same answer.

 

[dogman dan]

FWIW, after 10,000 miles of commuting with front hub, racing at 50 mph with front hub, riding front hub in dirt, I now have not one bike in my stable with front hub motor. I loved the front hub, but came eventually to much prefer it in the rear.

But if I had a nice Copenhagen style bike with IGH and belt drive, I'd slap a front hub on it and go another 10,000 miles with no hesitations at all.

As for carrying the weight better, I'm in love with my bob trailer now. Now I don't need to put the motor in front, so I can overload a rear rack.

 

[alpharalpha]

Not feeling as uncomfortable with front wheel set up now but for future setup I'd go with a rear hub, and put my prismatic cells in the back of the burley trailer so I can use my full 36v of cells.
Is a kit like this any good?
http://www.ebay.com/itm/36V800W-26-...091844?hash=item56831fe084:g:7hYAAOSwwpdW2Q8z

 

[OptimusPrime]

(paradoxically) too-thick spokes that make them weak and unreliable.

Could you expand on this?

 

[AF7JA]

But if I had a nice Copenhagen style bike with IGH and belt drive, I'd slap a front hub on it and go another 10,000 miles with no hesitations at all.

This is why I went with a front motor (350W geared). on my commuter, I have a NuVinci N360 on the rear, further, it is driven by a gates belt drive and an eccentric bottom bracket, this ruled out a mid drive. It seems to work well.

One thing I really like is that the front motor and the N360 are very similar in size and appearance. This gives the bike a very balanced look.

 

[alpharalpha]

Do you have a pic of your bike, tried to find it on your posts to no avail, but maybe I missed it.

 

[Chalo]

(paradoxically) too-thick spokes that make them weak and unreliable.

Could you expand on this?

Rims flex when loads are applied. Spokes can only pull; their job is to support the rim. Most of the forces applied to a wheel cause the spokes to get temporarily looser, not tighter. Spokes are more elastic the thinner they are, which gives two benefits:

First, they stay snug when the rim flexes inward towards them. That allows them to stay tight, rather than repeatedly going slack and tight over and over which tends to make thick spokes unscrew.

Second, thin spokes are like very short travel suspension for your rims and hubs when dealing with shock loads. Their elasticity limits peak forces and helps prevent cracking at the spoke holes.

So when you use spokes that are too thick for the rims they're laced to, they chronically become loose and have to be trued up frequently or else have the nipples glued in place (which makes servicing a nuisance). And they crack the other components, especially the rims.

People use too-thick spokes as protection against spoke breakages, when the real remedy for that is high quality spokes, correct tension, and stress relieving the wheel at the time it's built.

 

[dogman dan]

Exactly right.

Yet when the wrong spoke was chosen anyway, it still helps if the spoke itself is made from good steel. So one wheel may last a week, the other 10,000 plus miles, both using the wrong, too thick spoke. Crap spokes just break constantly, no matter what you do.

What will really screw you, is trying to tighten those too thick spokes tighter to fix it. That will just break whichever is weakest, the rim or the spoke.

Same thing with running too loose, too loose doesn't support the rim and puts strain on other spokes in the wheel.

 

[alpharalpha]

Hey Dogman, when you had your Aetoma motor did you find the spokes adequate? This kid at a bike shop thought they were too small but after reading Chalo's post I think they are the right size (though trueing them myself they are all ended up pretty tight.)

 

[dogman dan]

I never broke spokes on those old aotemas. But mine did have the thick 12g spokes. Those were front motors, so generally see less shock. And I was running them on shock forks, so they got some chance to not stress the spokes quite as much on the bigger bumps.

The cheap ass rim was a problem on those motors, I did bend them fairly easy.

But again, those cheaper motors came with the cheapest possible spokes. One week, they are ok, another, total shit. so it's pretty much random which you get. You'll know in a week or two if you got the shit.