Topeak 140 setup

Make a mark on your path / patio with the valve at the lowest point.

Roll the bike forward exactly one circumference so that the valve is back at the bottom. Mark the path.

Measure the distance between these points. That's your actual - not probable - circumference.

Rest of it? Follow the leaflet to the letter, esp the bit about lining up the magnet with the lines on the sensors.

Prob worth buying a new battery too. The one that's in won't last long. A new one will. 2½ years so far on mine after 8 months on the original. You'll lose all your settings & data when you change it so best to do it now.

It's good. Cadence, avg speed, avg cadence, max speed etc so all the stuff you need from a comp. Downsides if any are the long press needed to reset - button takes a lot of pressure and needs about 3 seconds but if you hold it down much longer it goes into another mode that I ought to read up on but never think to. The display isn't ever so visible in the dark, but I've never seen one that is. Might be my old failing eyesight though.

It's good. Set it up properly and it'll work well.