Choosing a derailleur hanger...
 

I've got an old bike without a RD that I'm putting a new RD on (clearly :)).

With no built-in hanger, where to start to find the right one?

Thanks.

Start by posting a picture of the rear drop out. This would help.

Without knowing what frame you are working on, it sounds like you need a claw to go into the dropout. They look like this: Various Manufacturers Rear Derailleur Adaptor Claw - Harris Cyclery bicycle shop - West Newton, Massachusetts

Once you have a claw, you can put just about any rear derailleur on that you like.

+1, you probably just need a generic claw.

The bike is a '82 Schwinn World Sport, one of the Giants.

So it's the frame that defines the choice, not frame + RD?

I look at this page, and it makes me think there's more to it...

All Wheels Manufacturing Replacement Derailleur Hangers

Those arent for your bike.

Those are for modern bikes with replaceable hangers. You just need a claw. RD doesn't matter unless it's something really odd. Frame doesn't even matter. If it has horizontal stamped dropouts, you need the basic claw.

The 1984 World Sport came with Suntour AR components and the RD had the old Suntour 4532 claw

http://velobase.com/CompImages/RDera...913B68E78.jpeg

I believe this web page is done by a forum member:

Derailleur Hangers Demystified - Red Clover Components

Very good, thanks everybody!

Buy this. It will work.

http://ecx.images-amazon.com/images/...EL._SY450_.jpg

Most derailleurs these days expect the same type of mount. Old Huret derailleurs are an exception.

Those are for frames with break-away hangers, usually on aluminum dropouts that aren't amenable to bending back into alignment after they've been damaged. They're considered a sacrificial part to prevent damage to the dropout itself, which would be much more problematic to replace.

Lots I didn't know, thanks everybody.

Did you find anything? I don't know of any bike shops on that side of town, the closest one I've gone to is probably all the way out on National & Lincoln (I told you I never go to that side of town anymore). I guess there's like more 'mom & pop' bike shops on the East Side. They'd probably just give you one, especially if you buy some other stuff.

Seriously, a lot of those old Suntour derailleurs will just come with the hanger on them.

Likely both the SunTour 4532 and SunRace hangers will work.

Having said that, from my own tinkering, the con and at same time pro of these non integral hanger claws is that by swapping one type for another you can adjust how large a big cog on cluster your derailleur will handle (besides adjusting B screw) and also change clearance against chain stay cross member when removing rear wheel. The Suntour I believe can be found in a longer length allowing a bigger cog but is angled forward compared to the straight SunRace which allows more wheel removal clearance. My own experience:

https://www.flickr.com/photos/767624...7634687109062/

A bike tinkerer not a bike mechanic,
Doug

I sure did, thank you.

I went to Vulture Space and did in fact grab an old SunTour Honor with the 4532 hanger attached. I'll break it down at home.