Compact Crank Trouble

NikH said:

Hi All,

I just received a really nice B-day present from wife. A campy record 50/34 compact crank with a compact front derailleur and new chain.

My bike shop installed it and I have to say that it really has made a huge difference on the hills. I am running a 12-25 cogset. Unfortunately there is a problem.

Initially, it was considerably noisier than my old campy 53/39. Lots of chain noise and it seemed to be shifting in a very sloppy way; not with the smoothness that I have grown to expect. My dealer has adjusted it twice now without any improvement.

Today we went on a 60 mile 4,000 ft ride. During one of the ascents, I was in the 34 chainring and in the 19 cog. When I started bearing down, the chain kept slipping. This was quite frustrating. When I got home and put the bike on the stand, I noticed that the chain was rubbing on the 17 cog. I adjusted the rear derailleur but then the problem moved to the 12 and 13 cog positions. Adjusting it basically moved the problem to a new pair of cogs. I couldn't get it to shift any better.

I talked to my shop who said it was probably a worn cogset. It has approximately 3,000 miles on it but I am about as fanatical as anyone regarding keeping it clean and properly lubricated. So I decided to put this wheel back on my other bike with the 53/39 set up to see how it worked and it has no issues - smooth shifting and very quiet. I then put my other rear wheel with an esentially new 11-21 cogset on this bike and it was a nightmare.

Any thoughts? I am ready to take it back. Has anyone else experienced this problem. Should I look for a new mechanic?

3000 miles. Yes, it is worn out. That is why you get skip with a new chain. And the symptom of rubbing against an adjacent cog is because the the chain is sitting too low in the teeth due to the wear. Look carefully at the rollers of the chain. They should fit precisely in the cog shape, not have space on either side of the roller.

Insight Driver said:

3000 miles. Yes, it is worn out. That is why you get skip with a new chain. And the symptom of rubbing against an adjacent cog is because the the chain is sitting too low in the teeth due to the wear. Look carefully at the rollers of the chain. They should fit precisely in the cog shape, not have space on either side of the roller.

That's nonsense.Read his post again with the comprehension switch in the on position.

NikH said:

Hi All,

I just received a really nice B-day present from wife. A campy record 50/34 compact crank with a compact front derailleur and new chain.

My bike shop installed it and I have to say that it really has made a huge difference on the hills. I am running a 12-25 cogset. Unfortunately there is a problem.

Initially, it was considerably noisier than my old campy 53/39. Lots of chain noise and it seemed to be shifting in a very sloppy way; not with the smoothness that I have grown to expect. My dealer has adjusted it twice now without any improvement.

Today we went on a 60 mile 4,000 ft ride. During one of the ascents, I was in the 34 chainring and in the 19 cog. When I started bearing down, the chain kept slipping. This was quite frustrating. When I got home and put the bike on the stand, I noticed that the chain was rubbing on the 17 cog. I adjusted the rear derailleur but then the problem moved to the 12 and 13 cog positions. Adjusting it basically moved the problem to a new pair of cogs. I couldn't get it to shift any better.

I talked to my shop who said it was probably a worn cogset. It has approximately 3,000 miles on it but I am about as fanatical as anyone regarding keeping it clean and properly lubricated. So I decided to put this wheel back on my other bike with the 53/39 set up to see how it worked and it has no issues - smooth shifting and very quiet. I then put my other rear wheel with an esentially new 11-21 cogset on this bike and it was a nightmare.

Any thoughts? I am ready to take it back. Has anyone else experienced this problem. Should I look for a new mechanic?

I don't know what the crankset would have to do with the rear shifting,since you seem to have eliminated a worn cassette as a cause.

My guess would be that the new chain wasn't shortened enough for the compact crankset, so that you're not getting enough tension to keep the chain on the cogs. There are several checks to make for proper chain length...wonder if your LBS did them before pronouncing you need a new cassette.

Yes, I'd look for a shop with a real mechanic. None of this is rocket science.

Thanks for all the responses...

The chain length idea is one I thought about. I was there when they put the chain on and it seemed that the length was more by eye than through any measurement or process. The reason I thought it was incorrect length is that the chain almost seems to sag relative to the chain set up on my other bike with the 53/39.

The wear concept is also possible but seems to be low probability because it works fine on my other bike. If it were worn cogs, it would behave poorly on my other bike too.

The club that I ride with swears by this mechanic at another LBS. I feel bad about thinking of taking it there since the shop that I purchase everything from has been really good to me. However, I guess there is nothing wrong with buying stuff at one place and servicing at a second place. I am assuming that this mechanic will have a different prognosis than the shop I usually go to.

NikH said:

Thanks for all the responses...

The chain length idea is one I thought about. I was there when they put the chain on and it seemed that the length was more by eye than through any measurement or process. The reason I thought it was incorrect length is that the chain almost seems to sag relative to the chain set up on my other bike with the 53/39.

The wear concept is also possible but seems to be low probability because it works fine on my other bike. If it were worn cogs, it would behave poorly on my other bike too.

The club that I ride with swears by this mechanic at another LBS. I feel bad about thinking of taking it there since the shop that I purchase everything from has been really good to me. However, I guess there is nothing wrong with buying stuff at one place and servicing at a second place. I am assuming that this mechanic will have a different prognosis than the shop I usually go to.

One more thing that seems weird. When I was going down a descent and pedaling in reverse, the chain binds. It doesn't fall of but if I try to force it; I bet it would. That is another reason that I was thinking that the chain is too long.

NikH said:

One more thing that seems weird. When I was going down a descent and pedaling in reverse, the chain binds. It doesn't fall of but if I try to force it; I bet it would. That is another reason that I was thinking that the chain is too long.

Sagging is never good. The Parktool site has a couple of simple checks for chain length.
www.parktool.com/repair_help/FAQchainlength.shtml

Haven't tried pedaling in reverse, but you should be able to spin the crank backwards without anything falling off. The binding could also indicate your RD isn't correctly adjusted, or the hanger or RD is bent out of alignment so that the pulley is not in same plane as the cog.

I'd say find another LBS. A good mechanic will most likely be able to spot your problem and fix it in a couple of minutes.

Thanks to all for the responses...Here is the happy ending. Took the bike to another LBS recommended by numerous people.

There were three problems.

1. The pin that links the Campagnolo chain together was put in from the wrong side. Good lesson about reading directions to my OLD LBS mechanic.

2. Improperly adjusted cable tension.

3. Another derailleur adjustment that I don't understand. It evidently adjusts chain tension. Mine was set for a 29 sproket.

When these were made...the bike works better than new. 😄

Thanks again for all of the suggestions

Nik H