randyjawa 

Hoping to spend more time riding my Legnano Gran Premio, I decided to do some upgrades, swapping the Stronglight cottered crank for a 49d. Since doing so, my chain is too loose...


When cutting chain, the chain is threaded through the derailleurs, set to big ring and big cog, then I cut the chain as short as possible. This has always worked well, however...

The Gran Sport on the bike does not take up enough chain slack. The derailleur is rated for 14-26 teeth and I am with-in that range. So, any special tips I should be aware of to get the chain to remain properly tensioned?

jj1091

No fixes that I know of. I had a Gran Sport Rd with 26t on a Raleigh, and it wasn't able to handle the range of gearing well. The lack of a tension spring on the main pivot just doesn't take up all the slack when in the small cog, and when I shortened the chain enough to remove the drooping it wouldn't go into the big cog. Beautiful derailleur, just a poor design. I ended up just going with the shorter chain and leaving it in the small chainring and riding it as a 5-speed.

Under load, the slack gets removed, but when it sits, there's quite a droop.

parken

Gran Sport rd was designed for half-step not for cross-over gearing (max 3 to 5 T difference on the front chain rings).

Road Fan

Randy,

My new 1968 Falcon (first road bike!) had a Gran Sport. The bike as-delivered had a half-step and the freewheel was something like a 14-24, but I don't recall exactly. It shifted well, but not as well as the Simplex installations on my buddy's UO-8. It was much better than the Huret Allvits, at least the ones in my neighborhood. My bike did not show any chain droop. I don't think chain droop is normal. It is the natural result of not having enough capacity to wrap the chain.

You could be overgeared in the front and going beyond the chain-wrap capability of the derailleur. I know the markings on the back of the parallellogram say "DA 14 A 26 DENTI," meaning it can handle a minimum 14 tooth rear sprocket, accommodate a maximum 26 tooth rear sprocket, and it simply gives no spec on chain wrap! The cage rotation is mechanically limited to 180 degrees and the jockey and idler wheels are about as close as they can safety be located. Before the Record was brought out, the Gran Sport was the racing derailleur, so it could have been intended only for the very narrow ranges of the day. I also have a pre-Nuovo Record, and its cage is able to rotate nearly 360 degrees. So if your freewheel is within the range, check the total chain wrap of your "new" 49d setup. Are the chainrings on your new installation the same as for your old one?

The lower pivot also might not be turning all the way through its range. I still have my old one, I upgraded to a Nuovo Record before the bike was swiped. Its pivot still turns through its full range, but not smoothly - it has never been overhauled.

So:

• You could have congealed grease inside the pivot
• The pivot could have been overhauled and the spring preloads not set correctly.
• There could be a mechanical issue restricting rotation, other than congealed grease.

Road Fan

Based on what you said, I suspect yours had (has?) the lower pivot spring preload incorrectly set, or at least needs overhauling (out with the old grease and in with the new). I had one on a new bike of the day and it rotated perfectly well - just was designed with a limited range.

Campagnolo did not do upper pivot springing in those days.

Hudson308 

I believe here's your answer, Randy.
The bikes I own with the GS as original equipment have a small spread at one end or the other, or both.

John E

My lowly 1962 Corsa had Huret derailleurs, but Bianchi gave it the same default gearing as on the Gran Sport equipped Specialissimas of the day: 52-47/13-26, which was about as far as one could push a Gran Sport. Capo used 52-48/14-22 on their narrow-geared models and 52-46/14-26 on their wide-geared, again with an 18-tooth wrap. Back then some of us resorted to running our chains one link too short and promising never to cross-chain large-large.

For what it's worth, I am setting up the Sieger with 49-45/14-26, and I am going to see if I can push it to 14-28, realizing I am going to have to get the chain length and rear wheel fore-aft position just right to make the latter work.

Kabuki12

I have a later version G.S. on my Raleigh Competition GS (1977) no problems with chain tension or slack. I think my largest cog on the freewheel is 24, maybe 26, up front standard 52/42 chain rings. Joe

USAZorro

You could experiment by pulling the wheel a bit further back in the dropout. Could answer the question of whether or not there's insufficient tension.

tiger1964 

I think I asked this before in another topic, but would a Record (unicorn?) or NR (less unicorn?) cage fit, and would it help due to offset between pivot point and pulley axis?

Hudson308 

I'm pretty sure the NR or Nuovo GS cages won't fit the first gen GS. I'm basing that on the fact that the repop Campy Rally-style cages currently being sold for the NR and Nuovo GS specifically exclude the first-gen GS in their application notes.

noobinsf 

Hmm... The guidance I've seen in my short time with this hobby is to run the chain around the big/big without threading through the rear derailleur.

Here is from the Park Tool site (emphasis mine), with link following:
https://www.parktool.com/blog/repair...-length-sizing

Maybe it's that simple? Maybe it just needs to be a bit shorter?

EDIT: Though now that I think about it, I am having a hard time envisioning how you manage the cage spring tension while you are sizing, so maybe your original post meant just the front derailleur?

63rickert

Rode this morning with 14-26 rear and 48-38 front on the Bates with late 50s Gran Sport. No problem. The derailleur has just been a joy since I got it, have had no need to get into the guts. The Carré has 15-24 rear and 38-50 front with early 60s Gran Sport. Again, it just works. I've had the 14-26 wheel on the Carré, there was still no problem and I did not even bother with chain length beyond confirming big-big would not cause immediate problems. Wide range front rings would have been rare in the era these changers were made but there were tourists who saw the potential and reliability of Gran Sport. The available clearance on a Gran Sport front is something of a clue to what Campy was thinking.

speedevil 

I think the park tool site recommendations are more applicable with modern derailleurs (slant parallelogram design) than the older Gran Sport/Nuovo Record/Record derailleurs with the straight cage. I've always sized the chain by going through the RD while on big-big and made it just long enough that way.

I use a double-ended clip made from coat hanger wire to hold the chain under tension from the RD while pressing out the pin to install the master link. In fact I keep the clip in my tool bag while riding, along with a pair of nitrile gloves in case I have to work on a chain on the side of the road. But that's me.

randyjawa 

Firstly, though Park Tool is a respected entity, in my mind, I will always go big to big through the derailleurs. That ensures that I will not chain load the rear derailleur if I accidentally try riding big on big. That said...

I had the system working on my Legnano with the Stronglight cottered crank which sports a 50 - 45 tooth count. My 49d sports 52 - 42. The freewheel is the same so the problem must lay in the tooth count difference between big and small rings.

And there-in lies the problem. I was hoping for a 52 - 42 ring set, pulling a five speed 14 - 26 cog set. Nope, and even without everyone's advice (which i do appreciate), the rear derailleur design did seem inadequate for the drive specs. Sadly, this might mean saying good bye to the Gran Sport stuff, in favor of Nouvo Record. I do have the shifters, front derailleur and even a period correct PATENT only NR rear chain hopper (but will probably go with my 72 rear d.

No real biggie. I will just install the cottered set, once again, and be happy with that. Now, what to do with that dang 49d?-(

The Golden Boy 

Slightspeed

I'm running a 6 speed 28t on my '64 Legnano Roma with the original Gran Sport derailleur. To get chain clearance between big gear and jockey wheel, I just unscrewed the drop out screws and ran the wheel back till it cleared the chain from the jockey. I'm running a 52/42 crank and it takes me everywhere but the Eroica hills. I have a spare Suntour VGT Luxe that I am running with a 34t Megarange on my Super Course. I may try it in the Legnano one day, but the 28t is useful for 90% of my rides. The 54 year old Gran Sport has no problem taking up slack on this set up, even allowing big big on occasion. Sorry for the dirty picture.

63rickert

Double checked my two Gran Sport setups. The 50-38 with 15-24 rear has no chain slack at all in little-little. The 48-38 with 14-26 has very slight slack in little-little. I can't do what Slightspeed has done because it's a gear claw. In 1950 those Campy dropouts weren't around yet. I've also run with a 13 tooth small sprocket, the derailleur does not complain.

iab

It has been quite some time since I took one apart, but iirc, the spring on the bottom pivot has a couple of load positions. Make sure you have at "11".

Road Fan

Yes, Dave, they do!

Bad Lag

Man up!

Put the original crank back on and shut up. This here is C&V and we don't like whiners.

merziac

I have been having similar issues on my Paramount and while my experience is limited with these I understand the limits which I am pushing without a doubt. It was surprisingly capable for the most part. The RD is one with the barrel adjuster that actually gets in the way sometimes. I put Magistroni 46x49 rings on the Campy Sport crank with 14x26, thought it was 28, and rode it for a week without any damage however finicky it was. Now changed to Simplex 48x52 up front. Chain was droopy in smaller gears while too tight for big, big so it was sketchy and resulted in very limited range between being to loose and too tight. Do these springs tend to break from age or tension if you increase the preload?

Please ignore the cable loop, nothing final yet.

merziac

Also hoped the 52 would stop the skipping in high gear, no such luck. The GS seems overwhelmed and at its limits. Maybe its just weak and/or old like me.

randyjawa 

Some really good ideas in this thread and I will take the GS apart for a look and see. I do intend to figure this out and, to those who have been successful, you are all inspiration to get-er-done.

Some pretty decent old bike, too. My favorite.

Road Fan

I have to say I have no idea of the durability or failure modes to be expected. My inclination (only if I really needed to do this!) would be to disassemble the mech or at least the lower pivot and small wheels, clean, inspect and assess. I think the only way to say anything is on a case=by-case basis, since these parts may date back to 1951. At one point Ebay prices for them were quite high, so at that point I decided not to do anything with mine that might compromise it.

Please share your research! I would imagine close optical inspection of a cleaned spring would tell you a lot. I would not be surprised if there are no flaws or signs of wear or fatigue.