Wednesday, September 7, 2011

Assembling A Nuovo Gran Sport Rear Derailleur

This may seem to be a strange thing for my blog, but I have recently sold a Nuovo Gran Sport rear derailleur to a fellow in France. To save postage I have removed the cages so it would lay flat in a padded envelope. This blog is for the buyer to re-assemble the rear derailleur.

Scroll to the end to see a video of re-assembling this derailleur.

When you unpack the derailleur it will be in two parts; the body and cages.

In order to re-assemble the derailleur you will need a small flat head screw driver and a 15mm or small adjustable wrench. The first thing you will need to do is remove the slotted pin on the side of the lower spring housing cover as shown below.

Now turn the body over and you will see the nut for a presta stem screwed onto a threaded stud. This nut is not part of the derailleur, it is just being used to keep it together.

The threaded stud is the lower part of the lower pivot bolt that passes through the lower spring housing. Take a look below at how it goes together at the top, so if you push it out, you can push it back in again. There is a slot on the side of the housing. First see the tip of the lower spring resting at the base of the slot. The top of the spring it bent at a 90 deg angle and held in place by a black bushing that has a vertical lip that fits into the slot. Make sure if you push out the pivot bolt and bushing you re-install it with the lip in the slot, or the bushing will not seat properly.

Below is the bottom of the spring housing with the presta nut removed (don't do this yet, it is just instructional). You will notice I am pinching the bottom of the housing and the top of the pivot bolt together, this is the best way to remove the presta nut. You will also notice there are two holes in the bottom of the housing; the bottom of the lower pivot spring extends out one of these holes and I marked the one I usually use.

Now take a look at the cages above. You will see that the cage has a circular raised area on one side with a threaded hole and 4 smaller holes around the threaded hole ; one of the holes is marked with white.

The way this derailleur goes together is the part of the spring that extends out of the spring housing cover, also goes into the marked hole of the cages. Then the two are held together by the pivot bolt screwed into the center threaded hole. When you are ready to assemble the two parts have the 15mm or adjustable wrench handy.

Now remove the presta nut by pinching the housing cover and the top of the pivot bolt together as below while unscrewing the presta nut. Once this has been done pick up the cages and insert the extended portion of the spring into the marked hole in the cages, laying the cages flat against the end of the housing cover while keeping pressure on the top of the pivot bolt and the back of the cages.

Once your holding it together, slide a wrench over the top of the pivot bolt, center the threaded stud over the threaded hole in the cages try and screw the bolt into the threaded hole of the cage. If for some reason, the pivot bolt gets pushed out or the housing pops off, don't fret, there is a learning curve to this. Just push the pivot bolt back in, re-position the housing cover and try again.

Once the pivot bolt's threads get started, screw the bolt in until it stops and give it enough torque that it shouldn't come apart. Now that the derailleur is together, turn the cage counter clockwise about 90 deg and make sure it is not binding. If you put it together properly, the hole for the stop pin should be facing in the direction of the lower pulley (see upper photo). If there is no binding and the stop hole is in the right place, hold the body stationary and turn the cage 180 deg counter clockwise, until the stop pin hole is on the right side of the body.

Once the cage has been rotated 180 deg and the stop pin hole is on the right side, screw in the pin.

Once the pin has been installed, your done!

I also made a short video showing the derailleur being re-assembled.


  1. This was really helpful. Tried doing it on my NR with the pin in because I couldn't get it out at first and thought it wouldn't make that much difference. Got the pin out and easy as pie (after watching your video).

    Thank you!

  2. Nice step by step. Do you have any tips on reassembling the return spring and retaining bolt?

  3. As I said there is a learning curve, what you really need is three hands. Once you have the spring and housing together, you need to squeeze the housing so the bottom of the bolt pivot bolt extends out the hole. Once this is done you need to match up the tab from the spring and the hole on the fence boss. Then you have to place the fence over the housing and the transfer the pressure you had on the bottom of the housing to the back of the fence. The key is to try and continue to squeeze the two together so you can feel the bolt end when it is in place, then with your fingers still squeezing the top of the bolt and the back of the fence, take your open end wrench and screw in the bolt while you maintain the pressure that is holding the two parts together. It will probably take a couple of tries before you you get everything lined up and screw the bolt in, but once you do it will be easy the next time.