Interesting that that mid level Roubaix is using the BSA Threaded BB ,
Perhaps that way Specialized does not have to pay royalties to whoever has the BB30 Patent .
On that model of Roubaix they are using Praxis Works Cranks, so perhaps better pricing on the BB and Crankset as an OEM setup. Also Praxis Works is located only about 50 miles away from Specialized so they are going with a Local Company, ( Think Globally, Buy Locally ).
In regards to Chain Line when using an adapter that fits into a BB 30 Frame Shell , that will allow you to use a threaded BB, The Chain Line should be roughly the same. When you look at a BB30 crankset, and a Shimano Hollowtec II Crankset,
one difference is that the Shimano has a longer spindle , even though they both fit into a 68mm wide shell. The Shimano has the spindle go further into the Crank where the Chainrings are, there is space in there to fit the chainrings around the outside of the outer bearings.
Also on the note of Adapters BB30-BSA Threaded, Mechanics that I have asked have said that the only one that works even halfway decently is the Praxis Works one. the others will rotate in the BB Shell, they have to be press fit into the shell and they do not grab onto / bite into the shell so they wind up rotating a little .
So We ( all who have BB30 or other pressfit Bearing Shells on our Road Bikes / and a few MTB's , would have to go through the following costs to get your Friction Drive to work/fit.
Praxis Works BB30-BSA Adapt $ 89 plus Tax, ( Edit : $ 75 plus tax and shipping , and some antisize so a little over $ 100 )
then
A Shimano Hollowtec II or simular Crankset plus Tax - $ 85 - $ 200 +
so
nearly $ 200-$ 300 to get it to work.
At those prices , I will have to wait until you develop a way to mount the Friction Drive on BB30 Bikes.
I do have a Full Suspension Frame I have not yet built up that has the BSA Threaded BB, but how would the Friction Drive follow the Wheel/Tire while it is doing its job ? Moving at an arc of up and forward .
I would be interested if that can be accomplished , and it would go up very steep % of Grades for long distance climbs. like up the Mountain in Bright , VC.
the F.S frame I have is a single pivot design.
Kepler said:
As much as i would like to make the drive fit the BB's you have listed, the drive at this stage is designed for screw in bearing holders as fitted to English BB68 bottom brackets. There are conversion kits available to convert BB30 / BB 86 / BB92 / Pressfit to screw in cups however I am not sure what they do to the chainline.
Interestingly, the big manufacturer's are going back to screw in bearing cups on their medium range road bikes. check out the latest range of Specialized bikes.
https://www.specialized.com/au/en-au/115487 this bike has screw in bearing cups. You are Looking at my next friction drive project.
This means my current test bike with my latest drive is going up for sale at a bargain price