I have had two back surgeries and have permanent nerve damage in my legs (always numb and weakness). If I am riding a bike with gears, I prefer road bike gearing and geometry but I can only go on short rides on them. If I set them up with higher stem and cross-top type levers or MTB riser style bars I can ride farther. It's not the road shock, it's the seating angle. I just don't enjoy riding the comfort type bikes. I don't know why, I just don't. My current bike is a stock 1987 Trek 330. I will be soon "upgrading" the stem and/or bars to get a better riding position so I can ride longer. I figured I would rather go on shorter rides on a bike I enjoy riding opposed to longer rides on a bike I don't like. Many people would disagree with my opinion but that's why cycling is great .