Converting 9 speed Trek 1500 Triple to Double

Now I've done quite a few searches for converting triples to doubles on the forum, but none seem to answer a few specific questions that I have.

I know that the 105 triple front derailler will work with a double crank if I set the limits correctly. And I know i will need a new bottom bracket for the double crank. However, the questions I have a more related to the rear derailleur and the fact that the bike is a 9 speed.

Do I need a different type of crank for a nine-speed?

Will the current ultegra triple rear derailleur work with a double in the front?

Since it's a new crank, and i have already put almost 2.5 thousand miles on my bike, and the cassette, crank and chain have all worn together. Should I replace the chain and rear cassette as well, to prevent the crank from wearing prematurely fast?

Much easier to make the triple to double switch than vice versa.

No need for a new crank. You can remove the inner chainring and use a double BB. If you already have a double crankset, then OK, but no need for new derailleurs-the long cage RD will work perfectly fine with a double just as it works when you are in the large or middle chainring of the triple. You are correct that the FD will work fine. Generally 8, 9, or 10s cranksets will work fine in the 9s drivetrain, although front shifting is a bit sluggish with 8s chainrings. No need for a new chain or cassette unless either is worn and otherwise in need of replacement anyway. Good luck.

You haven't specified why you want a double - presumably your largest ring isn't big enough? If so, you could simply change the big ring to 53T, remove the granny chainring, lock out the granny position with the lower limit screw and put a few extra links in your chain (unless you NEVER accidentally ride in the big/big combination). You would only swap your BB to a shorter spindle if you were being bothered by excessive q-factor.

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