Bicycle Mechanics - Picking the right front derailleur

Right now I'm switching my make-shift double setup into a real double, and I want to be sure I'm getting the right front derailleur.

The bike is a 2004 Trek 1500 with a Tiagra triple front derailleur (top swing, bottom pull.)

I'm assuming this would work?
http://www.pricepoint.com/detail/11292-105_SHIUD3-3-Parts-57-Derailleurs/Shimano-Ultegra-Double-Front-Derailleur-6500.htm

It looks right, but the only measurement is the 1 1/8" clamp-on size. I'm assuming that is right, too, since my seat tube looks pretty normal.

Just found this one, looks like the same specs:
http://www.nashbar.com/profile.cfm?category=83&subcategory=1037&brand=&sku=2971&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Front%20Derailleur

Thanks in advance :)

You most likely have a 31.8 seat tube - so it should work.

31.8 millimeter = 1.251 968 504 inch

The 6500 is a 9-speed double derailleur designed to run with 53/39 chainrings but is tolerant to wide variations.

Al

Right now I'm switching my make-shift double setup into a real double, and I want to be sure I'm getting the right front derailleur.

The bike is a 2004 Trek 1500 with a Tiagra triple front derailleur
What do you expect to accomplish by swapping out the front derailer?

The derailer you have now should work as well as anything.

Sheldon "Save Your Money" Brown

What do you expect to accomplish by swapping out the front derailer?

The derailer you have now should work as well as anything.

Sheldon "Save Your Money" Brown

Actually this derailleur sucked even when I had the stock triple on there (ie when it was new!) I could adjust it properly but that adjustment lasted maybe 3 days, so I'm happy to buy a new one :)

Wouldn't a double front derailleur work better for a double crankset?

But my main concern was getting the right size for my seat tube...

My post is a 27.2 but my seattube gets a tad bigger as it goes towards the BB, so I'm not sure whether it would be 28.6 or 31.8.

Anyone know for sure, or know which bikes generally have which size seat tube?

Luckily I just checked inside my front derailleur clamp - it's a freakin 34.9!

This will be a fun replacement to find...

Actually this derailleur sucked even when I had the stock triple on there (ie when it was new!) I could adjust it properly but that adjustment lasted maybe 3 days, so I'm happy to buy a new one :)[quote]
The Tiagra derailer is just as good quality as the Ultegra, except for being a wee bit heavier because some of the Ultegra's parts are aluminum, instead of steel.

If it doesn't stay in adjustment, that's 'cause something is too loose, has NOTHING to do with the quality of the derailer. If you had mentioned in what way it went out of adjustment, I might be able to guess what is loose.

See: http://sheldonbrown.com/derailer-adjustment

[QUOTE=BloomBikeShop]Wouldn't a double front derailleur work better for a double crankset?I don't see any reason to think so.


But my main concern was getting the right size for my seat tube...

My post is a 27.2 but my seattube gets a tad bigger as it goes towards the BB, so I'm not sure whether it would be 28.6 or 31.8.

Anyone know for sure, or know which bikes generally have which size seat tube?
Steel frames are generally 26.8. Aluminum frames commonly have fatter tubes.

If you remove your present front derailer, and look inside of the clamp part that holds it onto the seat tube, you will see the size stamped into the metal.

I still think you're wasting your money to replace this.

Sheldon "If It Ain't Broke..." Brown