8 Speed chainring on a 9 Speed drivechain?
I've done some searches and couldn't come up with an answer. I have an old 8 speed Dura Ace crankset lying around (I don't know, but it looks like the old Uniglide design, all the teeth are the same height), that has practically 0 miles on it. I want to replace my 9 speed Ultegra 42 teeth chainring that's bent beyond repair, with the 42 teeth Dura Ace chainring. Will this work? I know I'll probably lose some shifting smoothness of Superglide, but if it will work reasonably well, I want to use this perfectly good chainring. Will doing this accelerate chain/drivechain wear?
me have long head tube
Chainring will give you no problems with a 9-speed chain. Main thing is that you make sure you have a 9-speed chain if you're using 9-speec cassette. But the chainrings are barely wider, if any; main diff is that "9-speed" cranks space the chainrings slightly closer together, but the difference is minimal and in practice there is very little chance of your getting a narrower chain stuck between the two chainrings. Just go with it, and call us if you have any problems.
Alternately, that era of DA cranks were beautiful, beautiful things. You could use the whole thing on your bike, or sell it on eBay, and just get a new 39t small ring for your Ultegra - may as well have a wider gear range unless you ride on nothing-but-flats anyway.
Taking "s" outta "Fast"
According to shimano your drivetrain will burst into flames.
I did it back in the day when 9sp first came out and had no problems. Like you said, maybe a little slower shifting, but that's more due to the tooth profile.