Spellscape

Hi all
Should I shorten chain? On smallest chainring and 3-4th cog on back it skips under load, on big chainring this is not an issue.

Velo Mule

This problem can occur when the cogs on the freewheel are worn. This tends to happen when you get a new chain and it doesn't mesh right with the worn cogs on the freewheel. Is that a new chain? Did the problem occur after you put the new chain on?

If the freewheel cogs are worn, the best bet is to simply replace the freewheel with a new one. SunRace freewheels are relatively inexpensive and good. There is a technique to file the teeth on the cogs so that they engage on the chain better, but it is not a technique that I know about.

Let us know what you find.

Spellscape

It's possible. I will change them both. But is chain looks too long anyway?

shoota 

You have the gear combos backwards in your photos for showing chain wrap. Show one pic of big chainring + big cog, and another pic with small chainring + small cog.

SurferRosa

But who rides in those?

shoota 

Half of my friends. *eyeroll*
But am I wrong? Those combos will show us how the whole system is working, and if the chain length is good.

randyjawa 

My thoughts, exactly, until I realized that some uninformed people do.

SurferRosa

That's not how I do it, but everybody has their way, I guess. I don't really care what the length is in small/small nor big/big.

Spellscape

Photos not for riding but for showing chain size and
​​​ tension

krakhaus 

Looks fine to me. Your Derailleur still has a good amount of recoil on the small cog. It's probably a worn freewheel.
Edit: your photos are backwards. You need to have the chain on the small ring / small cog to tell for sure.

79pmooney

There is one simple reason for ensuring that big-big always works. This is especially true if 1) you ride hills and 2) if you like to ride hard up hills. Because if you do 2), you arrive at the top in reduced mental status and that first shift isn't always well thought out. If you have too short a chain, hauling that left lever back first can be very expensive. It is possible to kill the rear derailleur, dump the chain into the gap between biggest cog and spokes, damage, even break spokes, even damage or break the hub flange, scrape the chainstay with the chain, bend or break the dropout, bend the chain beyond use and probably a few more things. I've done my best to keep my research to a minimum but I've done most of these.

Too long a chain can get you in trouble but that is not common. More likely, you will hear the chain rubbing on itself or the derailleur cage and sag onto the chainstay when you ease up. I've often set up triples to too long a chain in the small-small and use it without second thought on the level stretches of long climbs rather than do two double shifts.

SurferRosa

Biggest issue with my bikes -- and they all have some form of Campy short cage derailleur on them -- is the jockey wheel spacing to the big cog. I just have to make sure that the chain is short enough that the upper rd wheel doesn't interfere with the big cog ... when on the small ring, of course.

BFisher

I assume you are running 28 tooth lows? I've never tried to go that low with my vintage Campy setups, but understand it can take a bit of finesse to get it going.

SurferRosa

Sorry, should have clarified that. Yes, that's right. Only one is 13-25t, the rest are 14-28t. I seldom ever use the 28t. But, when I have to, they all work reasonably well. If I ever have a problem going that low, it's with the NR ones, not the Victory or SR.

Spellscape

Here is more photos

SurferRosa

^ Rear derailleur cage looks a little wack in that top photo of post 15. Is that the cage limit where it's hitting the stop pin/grub screw? In other words, why isn't it keeping better tension on the chain? Using a finger, can you push the idler pulley up from that position?

Spellscape

cage is fine but point where it's mounted to hanger slow to return

pastorbobnlnh 

Chain is at least a link or two--- too long. See how it droops in the small sprocket/small chainring combination? Remove a link and try again in that combination and the large sprocket/large chainring combination.

While we are not supposed to ride in those combinations, it is helpful to make these mechanically safe when we accidently shift there when not paying close attention, i.e. when we're exhausted from a long ride, etc..

For instance, my '71 Paramount set up for long steep climbs needed to handle a 38/50 and a 16/31, "just in case" I accidently shifted to either of those positions.

dddd

On the OP's Huret derailer (just like on old Suntour derailers), the cage pivot is concentric with the top guide pulley. So shortening the chain has no effect on the position of the top pulley relative to the cogs.
And the mounting pivot is fixed so no movement there while riding.

Your Campy derailers of course have plenty of offset between the cage pivot and the top pulley so respond well to shortening the chain to clear bigger cogs.

Spellscape

Now I'm officially lost - photos with my bike on MBK catalogue - they clearly have much shorter chain

SurferRosa

^ Just because they're marketing folks, doesn't mean they know everything about the product they're selling. Bike setup in vintage catalogs is often kludged.

HTupolev

And quite a lot of informed people, either to avoid a big double-shift, or because they're 3/4ths of the way up a climb in 95-degree heat and pushing 180bpm and find themselves in need of another gear and just don't think the shift over very carefully. The latter happens sometimes even to people with too-short chains who, were you to ask them in other circumstances, are completely aware that the attempted shift would make their drivetrain explode.