I inherited my brothers racing bike when he upgraded; it is an aluminum framed Olmo "equipe" of uncertain age, though I'm guessing not more than 5-10 years. I got it 1 year ago in very nice cosmetic shape with new wheels (aksium) and components (105), and haven't ridden it all that much.

Recently on I ride I noticed that when I was climbing the rear wheel rubbed against the right chain stay. The paint was rubbed off down to the metal at this point, so it makes me wonder if it has been doing this for longer and I didn't notice. It only does it when I'm pushing hard with my right foot. The wheel is true and seems dished properly and is also firmly in the dropouts. I observed that if I stand up on the pedals with the brakes on and push hard, the frame flexes a lot down by the BB, and I can actually make it flex to the point that the stay touches the wheel.

Do Al frames wear out? I don't see any visible cracks... Or is this a normal amount of flex and I just need to run skinnier tires on this frame (I've got 700x23 on now)? It doesn't seem to have much clearance down there to begin with.