Carbon frame hub motor fitting

Fortunateone

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Joined
Aug 2, 2022
Messages
3
Location
Portland, Oregon
I'm looking at outfitting my carbon framed road bike with a hub motor. But I'm not sure how it's going to fit without a dropout. Here is my bike https://www.specialized.com/us/en/sirrus-4-0/p/174696?color=279693-174696 if you look closely at the fork you can see that the dropout is closed. Are there any hub motors that would fit that? I realize this isn't the ideal bike to convert but I'd really like to make it work. Any guidance is much appreciated. Thanks!
 
Id go with a mid drive of somesort as far as im aware its impossible to fit it to the rear as like you say theres closed dropouts and little area to fit a torque arm to stop the motor spinning in the frame.
 
Ianhill said:
Id go with a mid drive of somesort as far as im aware its impossible to fit it to the rear as like you say theres closed dropouts and little area to fit a torque arm to stop the motor spinning in the frame.
That BB may be a bit too thick for a Bafang drive. One would need some good measurements. Something else might work. https://endless-sphere.com/forums/viewtopic.php?f=2&t=117026&p=1725210#p1725210
Sirrus 4.0 ND 01.png

The other option is:
The Grin All Axle Hub Motor https://ebikes.ca/product-info/grin-products/all-axle-hub-motor.html
 
Ianhill said:
Id go with a mid drive of somesort as far as im aware its impossible to fit it to the rear as like you say theres closed dropouts and little area to fit a torque arm to stop the motor spinning in the frame.
Thanks for the input! Looking into attempting to fit a mid drive motor. The BB is kind of bulbus though, definitely not a typical style I'm assuming for the internal cables.
 
LewTwo said:
Ianhill said:
Id go with a mid drive of somesort as far as im aware its impossible to fit it to the rear as like you say theres closed dropouts and little area to fit a torque arm to stop the motor spinning in the frame.
That BB may be a bit too thick for a Bafang drive. One would need some good measurements. Something else might work. https://endless-sphere.com/forums/viewtopic.php?f=2&t=117026&p=1725210#p1725210
Sirrus 4.0 ND 01.png

The other option is:
The Grin All Axle Hub Motor https://ebikes.ca/product-info/grin-products/all-axle-hub-motor.html
Interesting! I'll have to read up on that hub motor. Although I'd really prefer a geared hub because I plan on pedaling unassisted. Thanks for the reply and great info!

Edit: Also, based on your sweet diagram, it looks like the bafang mid drive may fit. Thanks for taking the time to put that together!
 
Fortunateone said:
Ianhill said:
Id go with a mid drive of somesort as far as im aware its impossible to fit it to the rear as like you say theres closed dropouts and little area to fit a torque arm to stop the motor spinning in the frame.
Thanks for the input! Looking into attempting to fit a mid drive motor. The BB is kind of bulbus though, definitely not a typical style I'm assuming for the internal cables.

I think its more for crank stresses, carbon weave has its strength in the direction of the pattern so multiple layers are used to get the required load strength needed in all directions, im not expert mind I've never had or worked on a carbon frame but id assume there is an insert that gets wrapped same as the headtube for the fork the bearings would sit in something other than carbon ?
 
Fortunateone said:
I'm looking at outfitting my carbon framed road bike with a hub motor. But I'm not sure how it's going to fit without a dropout. Here is my bike https://www.specialized.com/us/en/sirrus-4-0/p/174696?color=279693-174696 if you look closely at the fork you can see that the dropout is closed. Are there any hub motors that would fit that? I realize this isn't the ideal bike to convert but I'd really like to make it work. Any guidance is much appreciated. Thanks!

Your throughaxle is a 12x100mm through axle. The grin all axle motor will take care of your needs. It has a 12x100 mount. That's for the fork. Fork mounts are underrated for the wrong reasons. It improves weight distribution but it does slow steering down as you've got a larger mass on the front wheel.
 
FuzzyWuzzy said:
It improves weight distribution but it does slow steering down as you've got a larger mass on the front wheel.
Interesting. Do you steer by turning the handlebars or by leaning the whole bike?
 
99t4 said:
FuzzyWuzzy said:
It improves weight distribution but it does slow steering down as you've got a larger mass on the front wheel.
Interesting. Do you steer by turning the handlebars or by leaning the whole bike?

I say this unironically, but neither. We countersteer. I learned it from motorcycles but all humans do the same thing on any 2 wheel linead object.
 
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