Making an electric tandem

Nxkharra

Active Member
We have a tandem bike which I am planning to put a motor on.
Could you please share your experience.
How much would it cost?
What components need to be changed?
Who can do this?
 

SST

New Member
I posted a response on another thread earlier in the year: https://electricbikereview.com/forums/threads/e-mt1000-750w-mid-drive-project.611/page-2#post-184152 . I did a conversion on a 2005 Cannondale Tandem with a BBS02 mid-drive. You can see some of the comments and pictures from that thread.

Installation-wise, I chose to mount the mid-drive in the stoker position. It made more sense from a power / efficiency / drivetrain wear perspective. Not too much more work than for a regular mid-drive conversion if you're already familiar with that. I looked at my build notes and here are a few tips:
  1. Cannondale has a small stem (post) below the BB at the stoker position on the bottom of the frame. It stuck out about 1/4" and I use a dremel to cut that off. The standoff is used for mounting a screw to route the derailleur cable under the frame. It took about 5 mins and was the biggest hassle for the build. I had to cut it as it interfered with the mounting of the mid-drive motor.
  2. Use a gear sensor if you're going mid-drive - there's a lot more power going through the drive train on a tandem
  3. Cannondale used a Truvativ spline vs square crank BB. I had to find a left tandem crank with a square crank to match the timing side.
  4. The new tandem left crank needed a different chainring to match (the old one was 104BCD and the new one was 110)
  5. I needed an extension cable for the controller / brakes for the mid-drive
  6. Make sure you tune your braking power. You can get a lot of speed on the tandem and with all that weight, you want to make sure you can stop reliably. I chose this model as it had 200mm disc brakes.
So $$ beyond a single mid-drive conversion was <$100 for the extra parts. There weren't any issues finding them online. The conversion took longer because I also took the opportunity to make some unrelated updates to the tandem.

It would be a lot less expensive / simpler to add a rear hub motor to the tandem, but we wanted a mid-drive as we primarily used the PAS for climbing and the tandem ride experience is closer to what we expect (explained in the other thread).

My wife and I put on about 30 - 40 miles per week on the tandem since the conversion. Let me know if you need more detail. Hope this helps!
 

Nxkharra

Active Member
Wow. What a clean and nice job. Unfortunately we just sold our tandem last week. I had it posted since we could not ride it due to our age and strength.
since I did not hear anything in this post decided to take the offer.
we had a Cannondale 29er. Beautiful one. Perfect for this setup.
mph well.
I have my electric and if she decides to ride we will buy an electric tandem.
many idea who makes a good one.
Saw one of Petgo. OK I guess.
 

Thomas Jaszewski

Well-Known Member
Great recap. Sadly not many shops are up to speed and end users get buried in seemingly endless details and issues. We produced some custom parts for a short time but the market just wasn’t there.