Front der causing chain to drop off big ring, help please.
I've recently inherited a Cannondale XS800 with Shimano 105 STI shifters and Ultegra crank (double). Since the 105 shifters does not distinguish between double or triple, I can sometimes cause the front der to shift beyond the big ring causing the chain to drop off onto the crank.
My main problem is that the "high" adj screw has already bottomed out on the front der but it still doesn't keep the front der to move beyond the big ring. I have went to Parktool's website, followed Shimano's instructions, etc., all to no avail. Everything is lined up as instructed (as far as I can tell). Does anyone have any idea how to fix this? I can't find any way of moving the front der more inward (towards the frame) such that the high adj screw will do what it is suppose to do.
Any help or idea would be greatly appreciated! Thanks in advance.