I'm a 5'8"/80kg rhino on wheels. I feel you on your own bod-spec. If you want to get fitter on a bike you'll have to work that money maker rather than ride a couch up and down the trail. A superbike could act as a crutch that prevents your progress in this arena. Upsell yourself to get...
This is my conundrum. My she rides a midweight and is concerned that she's holding me back. If I get too much motor, I stand to cause her no end of grief. That would be a win-lose for me. I can't afford another loss! The doghouse gets cold in the winter.