csteelhead1988
1 µW
- Joined
- Apr 15, 2022
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Has anyone converted a 2012 giant defy composite 2 to an e bike? I would like to do a mid drive system and am not sure where to start? Any help would be greatly appreciated!
HELP! 2012 giant defy composite 2 conversion?
- Thread starter csteelhead1988
- Start date
This one?
https://99spokes.com/bikes/giant/2012/defy-composite-2
![5af6d[1].jpeg](https://endless-sphere.com/sphere/data/attachments/179/179354-ed94f71c9c5f5f4286abf9d7e669a1cf.jpg "5af6d[1].jpeg")
https://99spokes.com/bikes/giant/2012/defy-composite-2
Chalo
100 TW
Right off the bat, I'd suggest a road bike like that, with short reach brakes that allow a maximum 25mm to 28mm tire, isn't really suitable for e-bike speeds and conditions. Do you really want to spend all your time on the bike scanning for imperfections in the surface that could end your ride?
I also note that a drop bar bike offers no place to put a throttle. If you're using PAS only, that's not an impediment, but I wouldn't want to go without a throttle as an override.
Mid drives exert their reaction torque by rotating backwards opposite the rotation of the cranks. If that's a plastic frame as it appears to be, you will need to protect the underside of the down tube from damage in case the mid drive unit loosens and smacks into it. A strip of metal mounted under there with double stick tape should be enough protection.
Lightest.bike's mid drive would be a good pick for a sporting road bike like that, but it is looking more like vaporware every day. And it won't be cheap if it finally appears.
Bafang M510 looks like another appropriate choice that might be available sooner and in greater quantity. Or not-- time will tell.
If you already own that bike, and you like it, then don't screw it up by converting it to an e-bike. A better donor for an e-bike conversion would be a steel bike with straight round frame tubes, rack bosses, generous tire clearance, and flat or riser bars. Surly Bridge Club and Fairdale Weekender are currently available examples, but the '80s, '90s and '00s gave us many to choose from.
I also note that a drop bar bike offers no place to put a throttle. If you're using PAS only, that's not an impediment, but I wouldn't want to go without a throttle as an override.
Mid drives exert their reaction torque by rotating backwards opposite the rotation of the cranks. If that's a plastic frame as it appears to be, you will need to protect the underside of the down tube from damage in case the mid drive unit loosens and smacks into it. A strip of metal mounted under there with double stick tape should be enough protection.
Lightest.bike's mid drive would be a good pick for a sporting road bike like that, but it is looking more like vaporware every day. And it won't be cheap if it finally appears.
Bafang M510 looks like another appropriate choice that might be available sooner and in greater quantity. Or not-- time will tell.
If you already own that bike, and you like it, then don't screw it up by converting it to an e-bike. A better donor for an e-bike conversion would be a steel bike with straight round frame tubes, rack bosses, generous tire clearance, and flat or riser bars. Surly Bridge Club and Fairdale Weekender are currently available examples, but the '80s, '90s and '00s gave us many to choose from.
larsb
1 MW
Agree, the small tires are always an issue as well as the incredibly tight tire clearance around most road bike forks and rear triangle. If you’re willing to spend a few $ on upgrading with new fork, brakes and tires and maybe even using wider front tire than rear then sure - why not?
Chalo has a good point that composite frames are not the best for conversions and not what i would choose, they are sensitive to point stress (..any mount you need to have for battery and motor..)
Also riding geometry on this type of road bike will be focused on a tucked aero position and needs legs pumping to counteract some of the weight of your upper body if you’re using the bike seriously. I tried a conversion like this and didn’t really like it. I think more upright riding bikes are an advantage for electric conversions in the long run.
Chalo has a good point that composite frames are not the best for conversions and not what i would choose, they are sensitive to point stress (..any mount you need to have for battery and motor..)
Also riding geometry on this type of road bike will be focused on a tucked aero position and needs legs pumping to counteract some of the weight of your upper body if you’re using the bike seriously. I tried a conversion like this and didn’t really like it. I think more upright riding bikes are an advantage for electric conversions in the long run.
larsb
1 MW
Edit: i just saw that this frame has a press-fit bottom bracket. I think that’s a showstopper as the bottom bracket is often one of the mounting points for many mid drives and that won’t work on a press-fit.
Chalo
100 TW
larsb said:
That's not a deal breaker, but it does mean that sleeves will be necessary to locate the mid drive unit on the BB shell. Luna Cycle offers some such adapters for American shells and other more recent BB styles.
https://lunacycle.com/pf-41-adapter-for-pressfit-bottom-brackets/
It's really just the fragility of a bike like this that should disqualify it for e-bike conversion. The technical challenges can be overcome.
SlowCo
1 MW
On a race bike like that a Kepler friction drive would be ideal:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269&start=75
https://endless-sphere.com/forums/viewtopic.php?f=6&t=74269&start=75
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