Road Bike, Cycling Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
660 Posts
Discussion Starter · #1 ·
I can't seem to figure out why after turning the "H" screw counterlcockwise like the Campy documentation says the cage doesn't want to let out any slack and clear the 26th tooth cog on my cassette. Does anyone know how this adjustment screw ca become damaged or broken? Mt derailleur seems to be in excellent shape. The top pulley is running into the second from largest cog in the back.

Thanks for the help!


Niko
 

·
Banned
Joined
·
2,767 Posts
Check to see if you have too much tension on the appropriate cable. Or go to the Park Tool website and go through the RD installation procedure to be sure everything was done correctly.
 

·
Registered
Joined
·
10,160 Posts
highly unlikely...

A RD should not require a specific "chain tension" to function properly in either of the largest two cogs.

There is only one correct chain length that will insure proper operation. That's the LONGEST length that keep the chain from rubbing on the upper pulley chain guide in the little ring and smallest cog. A shorter chain is not a solution. The full story:

Two simple tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination; remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on itself or the chain guide tab as it passes under the upper derailleur pulley. If you want to see how much lower pulley movement will occur, without removing the extra inch of chain, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity.

Second, the chain must be long enough to avoid over-extending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated wrap capacity. If you deliberately exceed the derailleur's capacity and the derailleur is over-extended in the big ring/largest cog combo, then you must either avoid that combo or add another inch and avoid using the little chainring and the smallest 3 or 4 cogs (since the chain will hang loose).
 

·
Registered
Joined
·
10,160 Posts
new setup???

There is always the possibility of a non compatible hanger, but it's not likely. Campy gives dimensions for the hanger somewhere in their instructions.

If the screw's function is in doubt, take the RD off and clean it thoroughly in mineral spirits, then relube, or just give it a heavy shot of WD-40. Tun the screw through it's entire range to be sure it's working.

I'd check the chain length, per the instructions I provided in my other post and see if that fixes the problem. Failing to clear a 23T would be extremely unusual. The only difference between your RD and a medium or long cage is the cage. Any of them should clear a 29T cog.
 

·
Kant phuckin sphell
Joined
·
650 Posts
You sure?

C-40 said:
A RD should not require a specific "chain tension" to function properly in either of the largest two cogs.
Just for kicks I went out in the garage and put a loose chain on a bike with the same set up as OP. It rubs if there is not enough chain tension the pulleys will rub the larger sprockets. They would have to be really slack.

Checking chain tension is the first thing I do on any bike with a shifting problem.
It is easy and only takes a couple of seconds.

It is also important to know if this problem just started to happen, or if a new part was recently installed.
 

·
Registered
Joined
·
10,160 Posts
very sure....

the bull said:
Just for kicks I went out in the garage and put a loose chain on a bike with the same set up as OP. It rubs if there is not enough chain tension the pulleys will rub the larger sprockets. They would have to be really slack.

Checking chain tension is the first thing I do on any bike with a shifting problem.
It is easy and only takes a couple of seconds.

It is also important to know if this problem just started to happen, or if a new part was recently installed.
How do you check chain tension? Are you confusing length with tension? A chain would never lack "tension" in any cog except the smallest ones and then only if the chain was too long, or the spring in the derailleur that applies tension is worn out.

The procedure that I described insures proper chain length. When you have a setup that's at the maximum wrap capacity of the RD (like the poster), you can't remove 1 inch of chain without over-extending the RD in the big ring and largest cog, unless the chain is too long in the first place. That's what the little ring/smallest cog test does; it insures the chain is not too long.

I have two bikes setup with a 38T wrap (53/39/28 and 12-25 casssette) that exceeds the 36T capacity of a campy medium cage RD by two teeth. The chain will hang loose in the 28/13 or 28/12 (which no one would ever use). I have no problem with the upper derailleur pulley clearing the 23 or 25T. I did compare the clearance with more chain "tension" in the 39/25 cog to the clearance in the 28/25 and there is more clearance. I have the screw loosened up about as far as it will go, but it does clear in the 28/25.
 

·
Registered
Joined
·
660 Posts
Discussion Starter · #8 ·
Just got in will report back after installing chain...

that may have been the probem - Its just that i thought i remembered the der. moving when I adjusted "H" whether or not the chain was installed or not.
I'll report back asap...

thanks as always for the help...


Nik
 

·
Registered
Joined
·
660 Posts
Discussion Starter · #10 ·
i think its the "screw function" problem.

I have the chain on with moderate tension as in the steps c-40 (and Campy instructions suggest.)

Now with chain on small/small combo and no sag in the chain but modest tension I have the chain on 13 tooth (smallest cog) and 39 in front and the chain hits pulley and pully cage tab. Then while pedaling as I turn scew H in diagram above the cage doesn't seem to move either away or closer. I went to both ends of the scew limit to see if I could detect movement. The der, is not moving although when I turn screw H I do see a tiny ring with teeth rotate while I turn the screw but the derailler doesn't move.

On the plus side the tension on the chain did seem to allow me to get the chain onto the 26th tooth cog without hitting the der. - but now I have the small cog issue.

I will try to spray lube into der as outlined by c-40.

Any other suggestion would be greatly appreciated.

Nik
 

·
Kant phuckin sphell
Joined
·
650 Posts
Try this....

Pinch the chain up top. See if increasing the tension helps move away the bottom pulley from the cassette.

Edit: I meant top pulley.

Seriously forget campy directions!
They say "10 - 15 mm Max" they dont even use the right symbols and they give you imaginary points of measurement. I have 20 - 30 mm on all bikes in my garage right now and they all shift beautiful. The one ones with short cages all have around 25mm.

The H adjustment screw should increase tension a fair amount but you might not see it move.
Good luck
 

·
Registered
Joined
·
10,160 Posts
chain's too long...

If the chain is hitting the upper pulley guide tab in the 39/13, then the chain is 1 inch too long.

It's tough to see the drailleur move as the screw is turned, but there are some small "teeth" on the derailleur, that you can see moving as the screw is turned. Worst case, you can remove the screw entirely, then you should have maximum clearance. If it clears then, reinstall the screw, just until you feel some resistance on it as it's turned.
 

·
Registered
Joined
·
660 Posts
Discussion Starter · #14 ·
Thanks all. It was chain tension.

I was hesitant to take off another inch but then when c-40 said 4 teeth = 1 inch of chain I realized having the chain the same as my other chorus equiped bike with a 12-25 freewheel would work with the 13 -26 . I was concerned the 26th wouldn't work if I took out more link. But it did. Not that it looked to good in the 53/26 but I don't plan on using that gear anyway.

But thanks again to all.


Nik
 

·
Kant phuckin sphell
Joined
·
650 Posts
Hmm....

C-40 said:
If the chain is hitting the upper pulley guide tab in the 39/13, then the chain is 1 inch too long.

It's tough to see the drailleur move as the screw is turned, but there are some small "teeth" on the derailleur, that you can see moving as the screw is turned. Worst case, you can remove the screw entirely, then you should have maximum clearance. If it clears then, reinstall the screw, just until you feel some resistance on it as it's turned.
So I would guess.......... that there is not enough chain tension.
"If the chain is too slack it can cause that problem." :0
Trust me If I even though I was wrong, with you, I would held my breath.
 

·
Registered
Joined
·
10,160 Posts
duh...

the bull said:
So I would guess.......... that there is not enough chain tension.
"If the chain is too slack it can cause that problem." :0
Trust me If I even though I was wrong, with you, I would held my breath.
Your problem is that you're not willing to admit that there is no method to MEASURE "chain tension". If you'd told the poster to shift into the little/little combo and look for a slack chain, you'd get partial credit for your answer. I'd award more points if you provided a small clue about how much chain to remove.
 
1 - 17 of 17 Posts
Top