Head Scratcher
 

Got a odd one.


running 105 group set with a 34t rear cassette. Upgraded at a shop to that large cassette and a long arm rear derailure. Before this I was having some gremlins with this bike. Well it just will not for some reason stay "tuned" Had it to two separate shops both did tune ups, one replaced the cables but still I seem to get no more then 200-300 miles before I get some serious shifting and bind issues.

A little more data, bike is stored indoors, upright. Recently I discovered the rear derailleur hanger cracked. New hanger, another tune up and back is the bind and metal shavings sprinkled on the rear mech. This is now the second time for the shavings.

Is it possible the bike has an issue? Its a carbon bike, possible deformation in manufacturing?


Any ideas are appreciated.

Speeds?
New Longer Chain? what chain?
New cable... cable stretched?
What is the binding?

Was the new hanger checked for alignment? They, or the frame, are not always straight from the factory, and certainly should be checked after cracking a hanger.
Under-bar-tape cable routing? Housing not fully-bottomed in shifter socket? Do you shift under power?

Where are the metal shavings comiing from?
Look closely and you should be able too see.
Chain rub or cassette rubbing on the frame.
Find where they are coming from and likely solve your problem.
How did the hangerr break?

Two different shop mechanics have tried and failed to fix your bike so I'd suspect it's something out of the ordinary. Try this:

Check all of your cable housing ends. What you are looking for is one or two tiny wires sticking out of the ferrel. If you see that, it means that the cable housing wasn't cut straight across so it is gradually shortening itself. When that happens, the indexing drifts off. After you retune it it works fine for a period of time but drifts off again and has to be retuned. Replacing the shift cable won't fix this because the problem is in the cable housing.

Thanks all for the quick replies.

Speeds... Its now an 11-32 x2

Looking for the metal its accumulating on the back of the derailleur, and right at the bottom of the seat stay.

Double checked seems the cassette and chain are not touching the frame at all.

When the shop went up from the OEM 11-28 to the 32 they also put on a new chain, it was checked again recently and is not worn.

The binding is hard to explain. It sorta feels like the brake is dragging, Ive checked that many times and the brakes are not the culprit. But at times when pedaling hard something will pop in the drive line and and binding is gone.

I am going to have to get back and check the housing ends.

Check pedals and bb with the chain off.
Front and rear wheel bearings
Have a good close look at the chain as it passes thru th derailleur front and rear. Look for a bad link and where it was joined split link or pin.
Failing that it could be a knee or hip on the way out

That would be pretty darn bad! Luckily the binding does not occur on my spare bike!

Is the chain routed properly through the derailleur? Often times there is a tab between the jockey wheels. The chain may be on the wrong side of the tab.

If the hanger is cracked, I'd check that.

Also what is the capacity of your system? (front ring-front ring)+(big cog-small cog)=x
For example (50-34)+(32-11)=37 tooth capacity.
(50-34)=16, (32-11)=21 (16)+(21)=37
If your derailleur doesn't have 37 capacity in this example you are setting yourself up for problems.
Big/big puts too much pressure on derailleur springs and hanger. Or, conversly if adjusted so not to self-destruct in big/big, then small/small wouldn't take up slack.

Shimano is known for being conservative in their ratings, but it's probably not a good idea to disregard them completly.

How's the b-screw adjustment? Metal shavings from driving derailleur cage into side of gear, maybe?

Good news.

Thanks everybody for the input.

I followed some of the pointers and narrowed it down to actually being a rear hub issue.

After finding more metal around the base of the cassette I ran back to the bike shop. They pulled the rear wheel and found the cassette was climbing onto the splines on the free hub.
further into the investigation we found that the conversion cap had a groove cut into it, and after that the bearing housing on the hub was bad and allowed the whole hub to flex under load.

Most likely what caused the derailleur hanger to crack and was giving me some brake rub under load.

So a rebuild is in order for the rear hub, new cassette, and one last tune up and I hope the last gremlin is gone from this bike.

Huh?

[MENTION=461092]PoorBob[/MENTION]. This sounds familiar.

I had shifting issues I just could not figure out until I finally pulled apart the freewheel and found a bad hub bearing.

Its a good feeling to finally get a diagnosis and be on the way to repair. I'm glad you are getting it sorted out. :thumb:


-Tim-

It is also nice to find there is an actual issue and its not between the ears.

Pics always help.