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  1. #1
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    Bionx broken axle - 2nd time - and warranty question

    I managed to break the axle on the Bionx on my Trek. That's twice in 3 years. I don't jump curbs and I try to avoid rough road surfaces but I am commuting in NYC and put around 3000 miles a year on the bike. Breaking an axle means that the wheel is useless even though the motor is fine because replacing the axle is a huge job, or so Bicycle Habitat says. They had a spare wheel lying around and I got it for $400. Not too bad since mostly they're around $800. This is the G1 version. Apparently the Bionx system uses a threaded freewheel instead of a cassette, and hardly anyone uses that anymore because part of the axle is unsupported and is prone to break. That' s just where this one sheared off.

    Is breaking an axle that common on Bionx wheels? I haven't read much about that but I'm a pretty easy rider on it, rarely going above assist level 2, and I weigh around 190. It seems to me that breaking an axle should not happen.

    The first wheel was replaced by Trek under warranty. I am absolutely unable to find out what the warranty is on my new wheel. It should be two years but all I can find on paper is the Bionx warranty covering systems, not replacement parts. I emailed Bionx last week and have heard nothing. I'll check with Bicycle Habitat when I bring the bike in to replace the freewheel in a few days - they didn't have one in stock so it just came in.

    I did speak to a nice guy at NYCEWheels and he thought that breaking an axle might not be covered since the warranty is only for manufacturing defects, but I'd argue long and hard over that. A $400 or $800 dollar wheel should not break under normal usage.

    Anyone know about this stuff?

  2. #2
    Senior Member chas58's Avatar
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    That is weird. I would not expect an axel to ever break. I have never heard of that on normal bikes, and I am surprised you are having that problem. Most e-motors have a bigger axel than a normal bike to lock the motor in position (so it doesn’t spin).

    It should be really easy to replace an axel. Maybe there is a part that is hard to find? Last time I looked my motor used sealed bearings. If you can replace the bearings, replacing the axel should be easy – assuming you have the part you need. Maybe ask in the mechanics forum?

  3. #3
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    Quote Originally Posted by dgk02 View Post
    I managed to break the axle on the Bionx on my Trek. That's twice in 3 years. I don't jump curbs and I try to avoid rough road surfaces but I am commuting in NYC and put around 3000 miles a year on the bike. Breaking an axle means that the wheel is useless even though the motor is fine because replacing the axle is a huge job, or so Bicycle Habitat says. They had a spare wheel lying around and I got it for $400. Not too bad since mostly they're around $800. This is the G1 version. Apparently the Bionx system uses a threaded freewheel instead of a cassette, and hardly anyone uses that anymore because part of the axle is unsupported and is prone to break. That' s just where this one sheared off.

    Is breaking an axle that common on Bionx wheels? I haven't read much about that but I'm a pretty easy rider on it, rarely going above assist level 2, and I weigh around 190. It seems to me that breaking an axle should not happen.

    The first wheel was replaced by Trek under warranty. I am absolutely unable to find out what the warranty is on my new wheel. It should be two years but all I can find on paper is the Bionx warranty covering systems, not replacement parts. I emailed Bionx last week and have heard nothing. I'll check with Bicycle Habitat when I bring the bike in to replace the freewheel in a few days - they didn't have one in stock so it just came in.

    I did speak to a nice guy at NYCEWheels and he thought that breaking an axle might not be covered since the warranty is only for manufacturing defects, but I'd argue long and hard over that. A $400 or $800 dollar wheel should not break under normal usage.

    Anyone know about this stuff?
    Bionix motors have to be split to replace the axle. This means dismantling the wheel. Also, they use a hollow (all the way through) axle. As for using a screw on freewheel, I think all hub motors do.

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    Quote Originally Posted by rotiferuk View Post
    Bionix motors have to be split to replace the axle. This means dismantling the wheel. Also, they use a hollow (all the way through) axle. As for using a screw on freewheel, I think all hub motors do.
    I have a tread in the mechanics forum and that is proving helpful. I think the main problem is that Bionx uses the bend of the axle to determine how much assist to apply, so fixing a broken axle is akin to buying a new wheel. I suspect that even if an axle breaks on another type of hub motor, then replacing the axle would be a lot easier. I like the way the Bionx works but not if it means that I need to spend $800 every other year or so to keep it going.

  5. #5
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    Quote Originally Posted by dgk02 View Post
    I have a tread in the mechanics forum and that is proving helpful. I think the main problem is that Bionx uses the bend of the axle to determine how much assist to apply, so fixing a broken axle is akin to buying a new wheel.

    Indeed.

    'A torque sensor on the rear axle detects the most minute pressure applied by your feet and instantly the
    BionX kit springs to life.'

    http://www.nycewheels.com/bionx-kit-discovery.html

    Quote Originally Posted by dgk02 View Post
    I suspect that even if an axle breaks on another type of hub motor, then replacing the axle would be a lot easier.
    Yes, I think the majority of hub motors can be disassembled by removing a motor side cover. Also, I believe it is possible to
    press a new axle into place - with the right equipment. Otherwise it would be necessary to purchase a replacement stator unit.

    Quote Originally Posted by dgk02 View Post
    I like the way the Bionx works but not if it means that I need to spend $800 every other year or so to keep it going.
    Have you considered a crank drive system? These take advantage of your gears. This system is made in the USA.

    http://www.ecospeed.com/electrify-your-ride/commuter/
    Last edited by rotiferuk; 04-21-13 at 02:39 AM. Reason: fix quotes

  6. #6
    Bicycle Repair Man !!! Sixty Fiver's Avatar
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    My friend has had the same issues with his Bionx and has replaced the axles himself... the 9 speed freewheel used on the Bionx is a wek link as it creates a condition where far too much axle is unsupported and this causes axle failures.

    When we build custom freewheel hubs and a wider range freewheel is required we build in an additional cartridge bearing that lives at the outside of the freewheel body and provides considerably better support. Our hubs are already optimized for freewheels and as such, axle breakage is not an issue and believe this could be applied to Bionx equipped bicycles.

  7. #7
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    Quote Originally Posted by Sixty Fiver View Post
    My friend has had the same issues with his Bionx and has replaced the axles himself... the 9 speed freewheel used on the Bionx is a wek link as it creates a condition where far too much axle is unsupported and this causes axle failures.

    When we build custom freewheel hubs and a wider range freewheel is required we build in an additional cartridge bearing that lives at the outside of the freewheel body and provides considerably better support. Our hubs are already optimized for freewheels and as such, axle breakage is not an issue and believe this could be applied to Bionx equipped bicycles.
    How difficult is it to replace the axle? The shop was not enthusiastic about trying it and they know a lot more about it than I do. I would think that they would have some experience doing it if the problem is common.

  8. #8
    Senior Member chas58's Avatar
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    Quote Originally Posted by rotiferuk View Post
    ... As for using a screw on freewheel, I think all hub motors do.
    Except for the new(ish) Bafang CST, which uses the same spline used on normal mountain bike hubs.

    http://www.greenbikekit.com/index.ph...dc-motor.html#

    bafang-cst-bldc-motor-for-mountain-bikes.jpg

  9. #9
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    Quote Originally Posted by chas58 View Post
    Except for the new(ish) Bafang CST, which uses the same spline used on normal mountain bike hubs.

    http://www.greenbikekit.com/index.ph...dc-motor.html#

    bafang-cst-bldc-motor-for-mountain-bikes.jpg
    That seems awfully cheap. And a 700C wheel for a mountain bike? This kit with LiOn battery is under $300 (front wheel but still?). What's the deal with this place?

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