Tandem Cycling - Advice on frame size - 26" tandem vs 700c/27" single road bikes

I'm on the verge of purchasing an older Burley tandem with 26" wheels. The frame is a 21"/18.5" (53.5cm/47cm) ctt, but I usually ride a 58cm road single frame and my girlfriend rides around 56cm.

I think the frame sizes would work for us if we go by mountain bike sizing. I haven't found much info on tandem sizing on 26" vs 700c frames, does it sound like this tandem size will work for us or is there something I'm overlooking?

I'm an analog kind of guy whose living in a digital world. Here's what I would do:

I'd take my road bike with me to look at the tandem. Set your road bike along side and see how the saddles and handlebars match up. Then make your decision based upon if the differences look like something you could live with or adjust away.

First importance is that captain can straddle bikel with legs far enough apart for pedals to move without causing injury. I suspect this is not a problem.

Check seat height adjustment - most likely not a problem.

If you are using drop bars on the tandem I would not use mountain bike sizing. Look at the captain's top tube length and see if you can get the captain's bars in the same position as your road bike (or a little closer/higher) by changing out the stem.

Ride it by yourself and see how it feels.

Good luck.

For most of us the first thing is (effective) top tube length. You can raise or lower the saddle a whole lot further than you can move the bars forward and back. You may need to buy a new stem to get the bars the right height and offset from the saddle.