Originally Posted by Road Fan

The most critical thing is saddle height. It's important for power production and knee health. The power thing is important even for us 50+ers, not because we race (yet some of us do) but because we need to make the most of the strength we have. We do increase our strength, but we start with less than do the 20-somethings. Easiest way to check it is to put on a pair of flat shoes, put the bike in a doorway, and get on. Make sure you can reach the door way sides to hold yourself up. Put your HEELs on the pedals and pedal backwards. When you leg is at maximum extension your knees should just lock straight with no rocking of your pelvis. If you pelvis rocks it's gonna hurt, and if your knees don't straighten you could end up putting excess stress on your knees - could lead to a knee injury. We don't have time to waste healing knees or undercarriage chafings, so this is important stuff.