I had 9 bikes and when I started adding heavy mountain bikes and e-bikes I needed to add more space as hanging them off a hook or wheeling them up and down stairs was not an attractive option. I put together a 8x10 foot shed where it is easy to store 5 of the heavier bikes and wheel them from the shed to the SUV for transport. I sold an old Dave Scott Criterium bike and gave away a custom road bike with full Campy Record components to get down to the 2 CF road bikes, 2 CF road e-bikes, one FS bike and two hardtail bikes.
