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  1. #1
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    Front wheel or rear wheel kit?

    Hi All,

    I'm new to e-bikes and am looking at the kit options right now and am wondering if there are any big considerations between front and back wheel kits, and if I can install any of them with my basic mechanical skills (I'm no expert). My main question is how much mechanical/electrical skill do I need to go the conversion kit route. I'm not sure if I'd need to take this stuff to a bike shop for help or if most people can figure them out on their own.

    Any comments on how these options that I've found would be good for my situation would help a lot:

    A "quick-install" version I found: http://cleanrepublic.com/hill_topper...rsion_kit.html

    A "beefier" version I've been considering: http://www.werelectrified.com/ProductDetails.asp?ProductCode=BD36+Kit

    Thanks for any advice!
    Last edited by NewbE-biker; 11-06-09 at 11:14 PM.

  2. #2
    Senior Member nwmtnbkr's Avatar
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    I'm repeating my comments from an earlier thread you started, but if you have an aluminum fork, do not use a hub motor on the front, unless you replace the fork. The drop outs on aluminum forks are cast and subject to failure without warning due to the toque of the hub motor (torque arms aren't really the answer with aluminum).

    Clearly, such a failure could cause serious injury. There's a strong debate about the safety of hub motors in the bike forums on Endless Sphere. One of the members there has a link in his signature with a photo that's absolutely painful to look at--a photographer snapped a photo just as a rider's front drop outs failed and he was pitched face first into the front tire, which was no longer attached to the bike. You see his nose being pushed in by the tire.

  3. #3
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    The front kits are easier to install, but require torque arms and steal forks. Rear kits are safer overall and more stable as they put weight in the correct location for a bike. The more power or regen braking you use the better is the rear wheel kits.
    I have gone with the rear wheel route.

  4. #4
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    You should use torque arms for rear too.

  5. #5
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    nwmtnbkr, did that failure in your photo, happen while a torque arm was being used?

    How many such front-wheel-dropout failures have happened with torque arm(s) in use? And how many with no torque arms?
    '72 Schwinn Sports Tourer, original except for seat and 116psi tires
    48V 1000W black unbanded rear hubmotor kit from YXM Corp, 48V 20Ah LiFePO4 batt
    '79 Schwinn Twinn Sport 10sp tandem, 47#, now 14-speed with 12/34, aero wheels
    '07 Trek 7700 hybrid, 27sp, 20" frame, Conti UltraSport 700Cx28 116# tires, sweet
    '04 Trek 7500 hybrid, 17.5" frame, soon to be 48V 1000W rear-hubmotor electric bike

  6. #6
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    Hi All, wow fast replies, very helpful, thank you. Nwmtnbkr, that's an impressive picture. I certainly get the point, and I have read about the torque arms.

    I guess that brings up another question: Those two kits I was looking at looked like they had different size motors. The motor in your picture looks really big compared to the total wheel area. If I use a 'smaller' motor like in the http://cleanrepublic.com/hill_topper...rsion_kit.html link will it put less force on the forks than if I use a bigger motor? Thanks again!
    \
    PS I do have an old Giant Sedona with a steel fork if that does make a difference.
    Last edited by NewbE-biker; 11-06-09 at 11:16 PM.

  7. #7
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    I would opt for a rear wheel kit every time. Simple reason is that there are no bikes with forks that are rated to handle that kind of abuse. It doesnt matter if its 250w-1000w. The stress put on the forks and headset is far to great. Possibility of failure is very high even on crome stuffs... Speaking from experience here. I had a costumer who insisted I install a front wheel 48v/500w kit on her 4 year old(never ridden) GT MTB. She rode the bike for about 210 miles just on the street. Then she rode it for about another 75 or so on a mix of street and light gravel trails(open land). The bike was perfect. No signs of stress or wear. I replaced the neck assembly 1 time at about 230 miles for her mostly because she left it out on the rain and washed the grease out accelerating wear. Long and behold one day I get a call from her husband. He told me she was on the way to the local deli and the frame gave out on the lower tube at the neck. The weld let go. She was going about 17 mph downhill. She broke her rist, lost most of the skin on her jaw(front and center), chipped 2 teeth and shattered her right hand along with an asorted mix of bumps and bruises.

    Rear kits ftw! Install a torq arm and your set! Its the strongest part of the frame and the safest. Just wach out for aluminium frames and swingarms. Even the top end stuff doesnt like to be bent for lont periods of time. Taking or expanding a total of 1/2 an inch on most aluminium bikes is about all you should hope for. Any more and longevity decreases. Especialy with a 1000w kit on a mtb that hits the trail.

  8. #8
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    This always seems to be a hot debate. People are very passionate on both sides - some prefer fronts - some prefer rears. Here are some of the main points to consider:

    --------------------------

    FRONT HUB MOTOR:

    + Easier to install
    + Equalizes weight of bike (if batteries are on the rear)
    + Handling is preferable to some riders

    - Not as 'stealthy"
    - Forks can fail (with steel forks and a torque arm, it's much less likely)

    REAR HUB MOTOR:

    + Less noticable (hidden behind freewheel and/or disc brake)
    + More torque due to additional weight in rear
    + If dropouts fail, less likely to cause injury

    - Harder to install. Have to worry about gearing and derailer.
    - May not accomodate 7-speed freewheel (common on most bikes)
    - Bike may become 'tail-heavy' and harder to handle (if batteries in rear)

    --------------------------

    These seem to be the major points. I'm sure others can add to this list...

  9. #9
    Senior Member nwmtnbkr's Avatar
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    Quote Originally Posted by Little-Acorn View Post
    nwmtnbkr, did that failure in your photo, happen while a torque arm was being used?

    How many such front-wheel-dropout failures have happened with torque arm(s) in use? And how many with no torque arms?

    Little-Acorn,

    The photo that I've linked is actually one of a personal bike of an e-bike builder who knew the risks of putting a hub motor on an aluminum fork, but did it anyway. I believe he used torque arms. Fortunately, when his drop outs failed, he wasn't in heavy traffic. He had some minor injuries from being thrown, but fortunately, nothing serious. He posted the photo and described how foolish and dangerous it was to put a hub motor on an aluminum fork in his blog as a means of warning others.

  10. #10
    Senior Member nwmtnbkr's Avatar
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    NewbE-biker,

    If you want to go with a front wheel hub since you have a steel fork, use torque arms. Torque arms are essential. The raging debate at Endless Sphere is whether any hub motor is safe due to the long-term affects of torque. I did not use a hub motor. I've got the Currie conversion kit which has a chain-drive motor mounted on the rear wheel. I now live in the northern US Rockies and need a lot of torque for the areas I ride. If I lived in a relatively flat area, I might have considered a rear hub, but to get good torque with a hub motor, you need to go with a large motor and they're fairly expensive. My Currie kit has great torque and is one of the most affordable kits on the market ($299 with 1 SLA battery pack). It doesn't go fast, about 17 MPH (with knobby tires--road tires might add about 2 MPH), but I don't want speed I want power assist on the hills here.

    Here's a photo of my bike with the kit installed. You can see the motor on the rear wheel, below my panniers.


  11. #11
    xtrajack xtrajack's Avatar
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    I went with a front hub. I was thinking that in the snow I would have 2 wheel drive, which for some reason I think might be a good idea.
    As an aside, it generally is not a good idea to poke holes in your battery. That is the voice of experience.

  12. #12
    Senior Member nwmtnbkr's Avatar
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    xtrajack,

    Will this be your first winter with the hub motor? What winter tires do you use? I've made my own studded tires for this winter. I'm hoping we have a milder winter this year.

  13. #13
    eBiker alfonsopilato's Avatar
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    xtra, let me know how that 2-wheel drive thing works out for ya in the winter if you decide to go with the front hub

    for me, if there is snow/ice on the road, i ain't risking it and yep i have studded tires. i work in the city and slippery pete could be a badly injured one (and no my name is not Pete, not that there is anything wrong with that name )

    rain and streetcar tracks are enough of a hazard for a bike. (don't get me started on that topic... )
    Last edited by alfonsopilato; 11-09-09 at 06:08 PM.

  14. #14
    eBiker alfonsopilato's Avatar
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    nwmtnbkr, very nice bike.. VERY nice

  15. #15
    xtrajack xtrajack's Avatar
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    Nwmtnbkr, This will be my first winter with the front hub motor. (If I get my battery back before winter is over) I roll with Nokian Mount and Ground 160's, 26x1.90 tires in the winter.
    I will keep you folks posted as to how the 2 wheel drive thing works out.

  16. #16
    Senior Member nwmtnbkr's Avatar
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    xtrajack,

    Do you have a LIFEPO4 battery that you had to send back to China for warranty work? International shipping can certainly take a while. Long tail bikes are supposed to handle very well in snow, at least according to owners who post in the utility bike forum. You should do well. Hopefully, you get your battery back soon.

  17. #17
    xtrajack xtrajack's Avatar
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    Nwmtnbkr,

    Yes I do have a LIFEPO4 battery, I didn't have to send it to China. I sent it back to the retailer I got it from in North Carolina. I think that they will have to send it to China to get it fixed. They have had it since mid September.
    It isn't a warranty issue, some Yo-Yo poked a couple of holes in one of the cells, accidentally. Guilty as charged. I expect that it will probably cost me about 100-150 dollars to get it back.
    As far as how the Xtracycle handles the snow and ice, I didn't have any issues last winter. Last winter, was the first winter since '84 that I rode all winter. I was a lot better equipped last winter than I was in '84.
    I am looking forward to seeing how the 2 wheel drive concept works out.
    Blessings

  18. #18
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    Hi all, Ok, so i'm still comparing these kits and it looks like that first 'quick install' one I was looking at has a "lithium polymer" version: http://www.cleanrepublic.com/hill_to...rsion_kit.html

    I'm now leaning towards a front-wheel kit for the reasons Ecowheelz noted above, and having 'easy' and 'lithium' is sounding like a good combo.

    Also, like extrajack's story, for me I think U.S. support would really be a big difference from sending stuff all the way back to China if there was some maintenance issue. Thinking thinking...

  19. #19
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    Newb, I'd think twice about getting a lithium-polymer (LiPo) battery. They are powerful and fairly lightweight, slightly more so than an equivalent Lithium-Iron-Phosphate (LiFePO4) battery. But if abused, Lithium-polymer batteries can turn nasty in a hurry, which LiFePO4's won't. LiPo's have been known to leak dangerous chemicals, and even catch fire and explode if overcharged, overheated, etc. LiFePO4's generally don't, even if abused.

    People tell me that, as long as you use them properly, and charge them with a charger specially designed for LiPos that is very careful about their charge state, Lithium-Polymer batteries won't give you these problems. But I personally prefer "idiot-proof" more than I prefer "elegant". "Idiot-proof" is well suited to my temperment and intellectual capacity.

    How do you know that your e-bike won't get knocked over some day, and whack the battery pack on the edge of a concrete curb? If it had a LiPo battery on the rear rack, I'd want to be a long way away when that happened. But if I were on the e-bike when it happened, and had my legs tangled up in the bike and chain while the LiPo was spouting flames just behind my derriere where I couldn't see it......

    If I were you, I'd ask that vendor if he has any LiFePO4 batteries.

    I also like the larger motors, that that vendor seems to deride. I have built two e-bikes so far, one front drive and one rear, both with 48V 1000W hubmotors and 48V 20Ah LiFePO4 batteries. Both have top speeds of 30mph. I'm not sure where that vendor gets the idea that a 1000W motor can push you at 50mph - I'd like to know which 1000W motor can do that! Even so, I'd be very leery of going 50mph on a bicycle frame that wasn't designed for such speeds. 30mph seems comfortable to me, though the wind gets cold in the winter, even in San Diego! (Yes, I know what cold is, I've lived many years in Minnesota, Summit County Colorado, and Thule Greenland). Biggest problem here is eyes watering and blurring my vision.

    Of course, as he says, a bigger motor will use up your battery faster. At the 20+ speeds these motors are capable of (and the 250W motor isn't), they certainly use more current. But what if you deliberately limit your aggressiveness on the throttle, to speeds of 15-18mph? If these were smaller and larger gasoline engines, then the larger one would use more gas at 18mph than the smaller one did. But they are electrics, and I believe things are quite different. Jury is still out here. But it's nice to have a little extra oomph available when you come to that steep hill after a long, tiring day.

    Many common e-bike batteries, both SLA and LiFePO4, have pretty low max-discharge rates. And a small battery pack of this kind, just cannot produce the amps needed when you push a larger motor up a hill. Lithium-Polymer batteries DO have higher discharge rates, and can produce the amps needed, though as I mentioned this will run them down more quickly, obviously.

    But there are some newer LiFePO4 cells that DO have high discharge rates. The manufacturer Headway produces some of them (so do several others), and other high-discharge LiFePO4 cells are available from the website www.HobbyCity.com - click on "Batteries/chargers", and then on "LiFePO4". Batteries made from these cells, can feed a larger motor just fine. Bad news is, (1) They are all in China, and (2) you have to build your own battery from the cells they send you. If you wanted a bolt-on "easy, 5-minute" conversion, these ain't it.

    Sounds to me like your vendor "Clean Republic" has some advantages - mostly a quick and easy installation. But their use of lithium-polymer batteries worries me greatly. And as I said, I personally prefer the larger motors, even if I seldom use their full capability.

    The last time I ordered a hubmotor kit, it was from YescomUSA.com in southern California, about 100 miles from where I live (San Diego). It was delivered two days later, and went on without a hitch. I had to remove the right handgrip and shifter to put the throttle controller on (I prefer thumb throttles over twist-grip throttles), and put the grip and shifter back on afterward, which added about 10 minutes to the installation time.

    I'm using a large (48V, 20Ah) LiFePO4 battery from Vpower.hk in Hong Kong, which usually goes on the back rack. Takes time to get it, obviously, and I don't see any way around that. You might contact www.evcomponents.com in Seattle, WA and/or www.SDElectricBikes.com in San Diego, and ask if they have any read-made LiFePO4 batteries in the size you want.

    I get the impression that this industry just hasn't reached the "easy do-it-yourself" stage yet, though that may change in the next few years as e-bikes become more popular.

    BTW, for an e-bike of the performance level you're looking at, you can buy a complete e-bike at Wal-mart, who has the EZip and I-Zip lines, fairly inexpensively.
    '72 Schwinn Sports Tourer, original except for seat and 116psi tires
    48V 1000W black unbanded rear hubmotor kit from YXM Corp, 48V 20Ah LiFePO4 batt
    '79 Schwinn Twinn Sport 10sp tandem, 47#, now 14-speed with 12/34, aero wheels
    '07 Trek 7700 hybrid, 27sp, 20" frame, Conti UltraSport 700Cx28 116# tires, sweet
    '04 Trek 7500 hybrid, 17.5" frame, soon to be 48V 1000W rear-hubmotor electric bike

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