Rear derailleur hanger bolt hole... too big

[Jawon]

I'm working on a mid-80's Trek 620 touring bike. It's got a Suntour rear derailer that I want to replace with a newer Campy, but the bolt hole is too big. Is there an easy way to make this work? Thx!

 

[axsepul]

Which hole? The one on the frame or the one on the deraillure

 

[Jawon]

The hole on the frame is too big for the bolt on the derailer

 

[axsepul]

Its hard without pictures but you can do three things.

1. Weld a nut in the hole of the frame that takes the size of the bolt on the deralleur

2. Remove the bolt on the derailleur and drill a hole so it will take the bolt that goes with the frame

3. Don't do anything and keep the original derailleur

 

[Wolf]

All the direct mount rear mechs I have seen over the past 30yrs- including suntour- have used M10 thread, usually 1mm pitch, although I believe campy have used M10 x 26tpi which is close enough to fit a standard M10 thread over such a short length as the width of the hanger.

Is the hole in the dropout threaded or plain, if plain then did the suntour mech you have come with a tophat nut which fits in the dropout from the rear? This is a simple way round the problem anyway, I have used M10 axel nuts and turned them to form tophat nuts to use in frames with damaged mech hanger threads.

 

[Jawon]

3. Don't do anything and keep the original derailleur

That option is looking better and better :x

All the direct mount rear mechs I have seen over the past 30yrs- including suntour- have used M10 thread

Ah, thank you for the education. Nice to know this is a standard. Upon further inspection, it's my bonehead mistake... the thread on my derailer bolt was actually broken off and at a quick glance the remaining nub looked too small for the hanger hole. So now my problem is sourcing some Campy spare parts! Argh.

Is the hole in the dropout threaded or plain, if plain then did the suntour mech you have come with a tophat nut which fits in the dropout from the rear? This is a simple way round the problem anyway, I have used M10 axel nuts and turned them to form tophat nuts to use in frames with damaged mech hanger threads.

Neat trick, will keep that in mind.