Do I need this bolt?
 

Quick question. I recently got a derailleur that did not come with a hanger nut (the nut between the derailleur bolt and the hanger). Can I just screw it into the hanger or is this part critical?

Pictures please. I've never heard of a "hanger nut" and I think I know what you are referring to as a "derailler bolt" but I'd like to be certain before giving any advice.

Look more carefully.

My bet is there is a snap ring that holds the bolt in place. Don't pull that snap ring out because there's a spring in there and it's a lot easier to take the snap ring out than it is to put it back.

It looks like this and threads into the derailleur bolt:

That looks like a chainring nut to me. I've never seen anything that looks like that on a derailleur.

Well, the derailleur hanger bolt threads into this nut to allow it rotate within the hanger. I'm just concerned whether or not it'll fall out without it.

Can you take a picture of the derailler and your frame where the derailler attaches. I'm still not clear as to where the problem is.

I can say one thing though. There is rarely, if ever, redundant hardware on anything, especially a bike.

I'm having trouble imagining where this bolt/nut goes...
need pics of the derailer and derailer hanger.

If that nut sits in the hanger and the RD bolts to it, then heck yes it will fall out without it. There will be nothing to bolt the RD to.

But I suspect there's something more to your question. Are you talking about mounting a different RD on the hanger? If so, then the nut may well be redundant. The thing may be a reducer for that specific bolt pictured, which looks to me like a non-standard size.

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If you had model numbers for the components in question, the answers could be much more than guesses.
:lol:

Originally Posted by Retro Grouch http://www.bikeforums.net/images/buttons/viewpost.gifThat looks like a chainring nut to me. I've never seen anything that looks like that on a derailleur.



If a nut like that is in the derailleur hanger, could it be a helicoil or something similar? Some type of thread saver.

That bolt is necessary for the replaceable rear derailleur hanger to attach to the frame. IT must be installed or the hanger will fall off.

It's not a helicoil, it's a stock part. There are replacable derailleur hanger designs that are fastened to the frame with a chainring nut/bolt combination. My son-in-laws Bianchi's derailleur hanger is held on that way.

To the OP, yes you need both the bolt and the nut.

So the nut and bolt in question are used to attach a replacable hanger to the frame then, right? And not the derailleur to the hanger. Would have been nice to have that info/pictures from the OP.

That's my take since I know for certain there are replacable hangers fastened with a chainring nut and bolt set and I've never seen a derailleur that required a nut to fasten it to its hanger.

But, yes, confirming pictures would be very useful.

exactly what kind of derailluer are we discussing? that looks like it mught be a bolt assembly to attach something like an old Hurrett or simplex derailluer to its hanger not to attach it to the frame. using this derailluer without the spefic hanger may cause problems.

Here's an example (note: this is not the actual derailleur):
http://i383.photobucket.com/albums/o...Picture043.jpg
http://i383.photobucket.com/albums/o...Picture044.jpg

One of my derailleurs lack the nut. The derailleur screws in just fine into the hanger without it and seems to stay put. That's why I'm wondering if that piece is critical.

what kind of derailluer is it? is this a nonindexing derailluer? there is no spring under the 'nut'? without knowing a bit more about the derailluer I am going to say tou need it. that nut screws on to the pivot (mounting) bolt and some sets or stops in a certain spot. then when you attach the derailluer to a hanger it acts as the stop to allow the derailluer to pivot fore and aft when changing gears. the derailluer may mount on the frame without it but it may not pivot and if it does it may come loose.

You answered my question. The nut does allow the derailleur to pivot. Without it, it did not move (but still shifted fine). I went to my LBS and picked up a spare. Thanks for the help everyone!

your welcome. goodluck with your mystery component.