Originally Posted by
grymg
Alum. will be lighter, but it varies. There are steel frames that weigh lighter than aluminum frames. It can also depend on the quality of the aluminum.
Aluminum is weaker than steel obviously. So therefore the tubes are larger in cross section to make up for this. However this adds weight. So it is lighter, but not as much lighter as you might think.
There's truth in what you say, but not enough to make it exactly right.
You don't ride on aluminum or on steel. You ride on a bike frame that's made with steel or aluminum tubeing. There are many factors that will affect it's weight and ride qualities. Picking out only one or two of those qualities and saying "that's why" doesn't cut it.