At 51 I just returned to road biking after an extended absense. I picked up a used Gios steel frame Compact Pro from a LBS in Germany that was my size. Since this is a standard racing road bike frame I had the handlebars raised about 2 inches with some spacers, as I thought it would be more comfortable since I am now older and less flexible.
However, I am finding that after about an hour of riding my lower back start to ache with a vengence, and I'm not sure why - the LBS owner is at a loss.... The conventional wisdom seems to be that when a bike is properly fit, it can be ridden for hours without fatigue. Not so here....
I checked the overall fit using some of the basic fit calculators you can find on-line, and eveything seems to be within range for my body dimensions (i.e frame size, top tube, set height, etc).
The advice seems to run from experimenting with the small changes to the current set up (i.e. try a shorter stem/higher handlebars, move the seat forward), to the more radical of scrap the standard race frame and go to a "relaxed"/senior friendly frame like a TREK Pilot.
Any suggestions on what to try? Is is usual that getting a proper fit takes some tinkering?