In Regards to heavy ISIS Bottom Bracket, ( and heavy old school Square taper BB's also )
I have been wondering when we consumers can finally be rid of that old and heavy system of bearings for our cranks on bicycles.
A few years ago I got a Road/Gravel Frame that has a BB30 Shell , I did not like the Idea at first, but once I bought the Bearings and Crankset, and felt how very light weight they are and felt the improvement on how smooth they spin , I was very happy, not wanting to ever go back to having to use a Square Taper/ISIS , BB.
Now because of the fact that a Frame Maker has to make that frame with very precise tolerances , we are seeing more bikes going back to the Threaded BSA standard , or , still having a press fit BB, but one that can make up for the not so precise made BB Shell.
The newest form of Crankset for MTB's as you probably know is the Direct Mount Crankset System.
Now that I have a couple of used ones that I have taken apart, I see the advantages, and for E-Bike ( Mid-Drive ) DIY systems, I now think it is the way to go.
The BB for Direct Mount can be either press fit, But also good for us a thread in / outboard bearing can be used, that takes off allot of weight from the old Square Taper and Cartridge BB's'
By using the easily removeable cranksrms from the spindle, just a custom made for E-Bikes Spindle can be made,
Spindle that is a couple of mm's longer that can accommodate both a freewheel , and two chainrings,
It can be made to allow the use of washers/spacers that can be put on either side of the chainrings and / or freewheel
so as to give us a better and custom chainline.
I greatly prefer the motor chain to use the inner chain position. It's visually cleaner, I can put a tiny 24t sprocket on the inside position which fits all frames, less lateral force. Downside is the derailleur chainring is about 1/4" farther outboard but straight chain is still in the middle of the cassette. The ISIS BB is needlessly heavy; a custom crankset might save a pound of weight. Four of the ACS freewheels on the motor have broken (one poor guy broke two in a row with less than 50 miles). No issues with the crankset freewheel.
Suggestions and criticism welcome. Updates of design and testing to follow.