bax76

Hi,
I have strange issue, on my new old bike.
Everything shift perfect, except one thing, from rear smallest cog, to the next one, it shift very poor.

I play with B screw, on rear derailleur, no change.

Derailleur is perfectly under cog, but no shifting.

Try with three different chains.

When chain come to rump, it shortly jump, an restore back to smallest cog.

Only thing I can notice, is that smallest cog do not have Campagnolo written on surface (maybe Miche).
Smallest cog has 13 teeth, next one 14th.

No trace of any physical damage of system.

Any idea, how to proceed ?

P!N20

So just to clarify, when you’re in the 13 and you try to shift to the 14, it just returns to the 13?

I’m assuming you’re in the big ring when this happens?

What shifters are you using?

bax76

Yes, I am using big ring, but its the same on middle ring in front.
13 to 14 won't go. Everything else shift in a blink of an eye.

Even if I over shift a little bit, it's struggling.

I have some Campy 3x8 brifters.

Meybe that Campy/ Miche, I suspect its a Miche the smallest one, is out of synchro.
So its not little bad, its unusable. Only way is to go two cogs up, and than go back one step.

I have also visually inspected spacing, between cogs, that's all looks fine.

P!N20

OK. So can you keep adding tension to the cable so high gear is on the second to smallest cog? If so, at that point you could just back off the tension a bit so you know the cable is at maximum tension for that gear position - if that makes sense.

What derailleur are you using? I assume it’s made for 8 speed.

I’ll have to compare my Campy and Miche cassettes to see if there’s any difference.

Are your cables in good condition? Nothing worse than trying to adjust gears then you find a frayed cable.

P!N20

So comparing my Campy and Miche cassettes, the small Campy cog doesn’t have ‘Campagnolo’ on it, but it does have the little circle on it which aligns with its friends.

The Miche small cog measures approx 1mm narrower than the Campy equivalent - I’m struggling to work out if that would make much difference.

bax76

Thx for Your efforts
I have a lot of hands on experience, on older bikes.
To me, all mechanics looks perfect, rear derailleur looks appropriate and original for that bike, along with rest of stuff.
Bike looks like a new one.
I think its Mirage.


descargar imagenes con link de instagram

nlerner

Have you checked the alignment of the RD hanger? I have found that by eye they might look straight but it only takes a degree or two off to affect index shifting.

bax76

Is Cog narrower or spacer between smallest cog and next one?
If it is a spacer, maybe I can use some small additional washer between last two cogs?

smd4

It might be better to ask this over at the "Bicycle Mechanics" sub-forum.

jrg1244

I had a similar issue with my 11 speed Campy Potenza. Smallest cog (11) to next one up shift was flaky at best, rest of the cogs shifted fine. In my case, it ended up being a missing ferrule in the downtube cable stop. The end of the housing was blowing out just enough to effect the shift at lower cable tensions. I clipped the housing clean, added a ferrule and slam bang - shifting was perfect. Just an idea that hopefully helps you.

bax76

Thx, I'll check that too, I will try to measure distance between cogs, maybe the smallest is from 9speed set, there must be some reason....

If I add additional washer between last two cogs, than attacking angle of chain will be better, toward the ramp.

motochick 

Every shifting issue I've had that couldn't easily be corrected by small adjustments has been a bent derailleur hanger. Every bike I have ever bought has had a bent hanger to some degree. My new method when getting a new bike is to strip it down, align the frame, dropouts and forks, then the hanger, then build. No more shifting issues. Of course it helps that I have all of the tools to do this....

bamboobike4

Synchro or Ergo?

bax76

Bike is around 98, I am not sure if that helps with answer?

AndyK 

If you can put it on a stand, and shift from 13-14, you can probably see if there is a bent hangar or other alignment issues. I have Campy 8-speed and it's the most precise rifle-bolt like shifting out there!

bax76

From what I see on stand, alignment is good.
But I remember that when I hang a derailleur on hanger, there was a slight play in screw, the one that tie derailleur with hanger . Nothing unusual, but it can be a reason maybe.

AndyK 

You may need a new hanger if the threads are stripped. The derailleur shouldn't move around left to right when mounted. That may cause erratic shifting.

bax76

Threads are ok, but during turning around screw, body of derailleur is slightly moving, like that screw is slightly bent....

I felt that lot of times, but never had any shifting issues with other derailleurs.

AndyK 

I guess if the derailleur is somehow bent, so the screw moves it around (I can't see that short fat screw bending) as you turn it?

bax76

Here is reason. You can see that the ramp on smallest cog is out of sync to other cogs, Meaning, there is no bent tooth to accept chain, from ramp,
There is one teeth misalignment.

Check these dots on cogs on top of screen., Dots mark ramps...

P!N20

Yeah right, I can’t even think how they would be misaligned; usually the splines dictate which way the cogs go on. Maybe it’s from another era or it has been modified.

P!N20

OK I just thought of something.

The smallest cog on a Campy cassette should have the spacer incorporated - is yours like that? Campy did do a 14T and 16T small cog, but the 12T and 13T are much more common.

Notice there isn't a separate spacer between the smallest and second cog: https://www.disraeligears.co.uk/site...e_page_75.html

Your big cog is a 28T, which Campy didn't do, so it suggests someone's been mucking around with the cog order.

If there's play in your RD, that's probably not helping either. I had a old Shimano 600 RD that wouldn't play nice until I discovered it was moving around the place.

bax76

Here I draw some line, and what is issue.
I have measured distance between cogs, and noticed that there is smaller distance between two smallest.

I hoped that that was an issue, create custom spacer, but again the same.

Then I realized that these cogs are not possible to mix, because of misalignment.

So the smallest one has offset of half tooth, and that is problem.....

P!N20

Yeah, what's got me is how it has come to be misaligned. The next cog is a 15T right? Campy splines (of that era) only allow you to put cogs on in one orientation - unless the cog has been modified.

Still interested if there's a separate spacer in between the 14 and 15 or it's part of the 14.

(You can get 1mm spacers, if you need to go down that route: https://www.ebay.com/itm/284428988389)

bax76

Smallest cog has 14 teeth, next one 15th.

​​​​​​There is no spacer between then. Integrated Spacer is part of cog 14, like in your picture.

Cogs have not been modified. Biggest one is also without Campagnolo stamp.
​​​​I suppose misalignment is caused by mixing brands of cogs, or maybe smallest one is from 9 speed set?


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