tubesocksFred

Hi,

I was going to get a low end bike for someone, which has a Shimano Tourney A070 rear derailleur. I noticed it has an extra stamped link that looks like a b-link, which is used to extend the derailleur back. On searches of that derailleur, it is frequently sold with the end as a claw hanger instead of the usual mount screw, so I assume the derailleur is designed for bikes with no dropouts.

Now on the bike I saw, it already has a RD dropout, so adding this hanger on top of the dropout would just lengthen everything and change the geometry. The setup would look like this fellow member's:




I also found a website's picture that shows claw hangers should not be mounted on a dropout



Are the bike mfg installing these RD wrong? If when I do get the bike, should I be removing that link and mounting the RD directly to the bike's dropout? This would at the minimum increase rigidity of the RD, and maybe have the chain wrap around the freewheel more.

Iride01 

If the bike was manufactured with it, then it probably needs it if still original cassette size. They are just another version of the things people buy for their bikes to lower the DR when they go to a larger cassette than was spec'd for their DR. Or sometimes it's needed for other considerations.

If you remove it, you need to ensure that your DR pully wheels won't get sucked up into the cassette and spokes.

If you are installing a new DR, then you have to figure that out for the specific situation you have. Some bikes don't have the same dropout configuration as others with respect to DR mounting.

dsaul

I don't know what the website was trying to demonstrate with those pictures, but both of those derailleurs are properly installed. Perhaps they were trying to demonstrate that the claw hanger derailleur on the right can not be installed on a bike that has a derailleur hanger like the one on the left?

You also appear to be using the wrong terminology, as dropouts are the slot that the wheel axle is inserted into. The thing that the derailleur is attached to is a derailleur hanger, which can be claw type, removable or integrated(a non-removable part of the dropout).

tubesocksFred

Yeah, the pix on the left says "NO", which is don't mount a claw hanger DR on a built in hanger. But that is what the mfg installed derailleur did on the top picture, albeit the derailleur has a bolt on end instead of a claw hanger. one.

I realized i used the wrong terminology. I never had to deal with hangers until I came upon these type of bikes. rear drops always had hangers

dsaul

What you are seeing in the top picture is not a claw hanger. It is just a stamped steel part of the derailleur that is meant to emulate a direct mount derailleur. That derailleur is meant to be attached to a hanger exactly as it is pictured.

tubesocksFred

The Tourney derailleur comes in with either a claw hanger or standard mount:

Claw hanger:



Standard mount:


If I can just use the standard mount over the dropout, then I can bypass the extra length and flexibility of the bike's built in hanger.

dsaul

You can't remove those mounts from the derailleur. The derailleur was designed to work with the mounts in place, removing it will put the pivot in the wrong location

tubesocksFred

But if I went out and bought the claw hanger version, and mount it on the dropout, then the pivot bolt would line right around where the rear hanger would be. So if I mount the standard mount like the claw hanger version (in the dropout), then it achieves the same thing.

Maybe Shimano was just going cheap, kill two birds with one design. Usable for bikes in big box store and bike shop.

dsaul

Its a $14 derailleur, buy two so you can have a working one after you destroy the first one.

tubesocksFred

I want it to be destroyed, so I can upgrade to a real one, but then the whole interoperability of components between different grouppos requires alot more looking into.

Ironfish653

7-speed? Pretty much any 7-9 speed Shimano RD will work. You don’t need to try to mod a Tourney; get an Altus, or Alivio, or heck, even an Exage 400 from 1993 would work.