I’m new on eBikesForum. I few months ago I started thinking about converting one of my old road bikes (rim brakes) to an eBike for my son to use in bike lanes and on paved bike trails. I researched DIY eBikes and concluded I needed a mid-drive with torque sensing that was programable. Advice from Douglas Howerth at Velocite Velo led me to select a ToSeven DM02.
While I was researching eBike kits and negotiating with Douglas an aluminum MTB with disc brakes – a 2014 Mongoose Stat - popped up on Craigslist with a price way lower than the value of my road bike so I bought it.
Once I received the DM02 I could not slide it through the Mongoose bottom bracket even though the treads were BSA. I searched for this problem on the Internet and on eBikesForum and didn’t get any hits.
The minor diameter spec for BSA threads is 1.335 / 1.323 so the ID of a BB tube in a welded frame before the threads are cut needs to be no larger than 1.335 but can be smaller. The OD of the ToSeven (and, I assume, other mid drives) is 1.315 so there should be 0.020 to 0.008 clearance, BUT if the tube initially has a smaller ID or if it is distorted by welding there may be no clearance which was the case with my Mongoose.
Reamers of the correct size are $200 so instead I bought a 1” diameter grinding wheel at Home Depot and using my electric drill removed high spots in the center of the BB until the ToSeven slid through easily. It took about 1 hour.
I’m hoping that in the future others may stumble on my post and realize they are not alone. It will also be nice if replies include other brands and / or other frame types that may not initially have enough BB clearance for a mid-drive kit.
While I was researching eBike kits and negotiating with Douglas an aluminum MTB with disc brakes – a 2014 Mongoose Stat - popped up on Craigslist with a price way lower than the value of my road bike so I bought it.
Once I received the DM02 I could not slide it through the Mongoose bottom bracket even though the treads were BSA. I searched for this problem on the Internet and on eBikesForum and didn’t get any hits.
The minor diameter spec for BSA threads is 1.335 / 1.323 so the ID of a BB tube in a welded frame before the threads are cut needs to be no larger than 1.335 but can be smaller. The OD of the ToSeven (and, I assume, other mid drives) is 1.315 so there should be 0.020 to 0.008 clearance, BUT if the tube initially has a smaller ID or if it is distorted by welding there may be no clearance which was the case with my Mongoose.
Reamers of the correct size are $200 so instead I bought a 1” diameter grinding wheel at Home Depot and using my electric drill removed high spots in the center of the BB until the ToSeven slid through easily. It took about 1 hour.
I’m hoping that in the future others may stumble on my post and realize they are not alone. It will also be nice if replies include other brands and / or other frame types that may not initially have enough BB clearance for a mid-drive kit.
