Bicycle Mechanics - Chain/Cassette Rub

I put a new cassette on my bike about 3 weeks ago. I went from 12-25 to 12-23. Everything was fine until last Saturday, when I went for a 53 mile ride on a hilly course. I rode a the flats prior to Saturday ride and had no problems with the chain/cassette rub.

I noticed that when I'm in my middle front (tripple) and big rear (23) the chain rubs against the cassette. How did I noticed? I makes a very loud rubbing in sound, unlike the chain rubing againt he derailleur. This would happen when I'm mashing up a hill in this gear.

However, I went out for a ride Tuesday and noticed that the chain now rubs on the 21 and 23 cog in normal a normal ride. Was wondering if I need to look at to remedy this. I don't want want to ride my bike until I fix this, 'cuz it sounds pretty bad.

Your description is not clear. Where does the chain rub?

IOW, when you are on the 23, the chain is supposed to sit on the teeth of the 23. Do you mean it's sitting half way between the 21 and 23? If so, then two possibilities:

- All gearing selections are noiseless except that one, in which case it is the Low limit screw that needs to be adjusted.

- All gearing selections are noisy. Check your derailleur by standing behind your bike. You will probably notice that the derailleur isn't in line with the cogs. Then you need to adjust the indexing.

Check http://sheldonbrown.com/derailer-adjustment.html


BTW, one of the likely reasons for your problem is that the wheel might not have been inserted in exactly the same position than previously.

Regards,

It's really weird. It was just the cog 23 that was making the sound. But now it's cog 21 and 23, so it's not the low limit. The sound is more prevalent on the 23. And because it's not making the sound on other gears, it's not cable indexing. I'm stumped!

Was I supposed to make any adjustments to the chain length, derailleur, etc. when I installed the new cassette?

If your other cassette was badly worn, your chain is undoubtably worn too. It might just be that the chain isn't seating right between the teeth of the cassette. Did you replace the chain too?

No, didn't replace the chain. The cassette and chain are fairly new. They have about 500 miles on them. The only thing I did was put on a new cassette.

Can the chain be too long, going from 12-25 to 12-23. If so, can this be what's making the sound. I might have to resort to taking it to the LBS to have them look at it. I would like to solve it you guidance from the forum, so I can learn by trial-and-error, but not at the risk of damaging components.

Are you certain it is not just the front der needing to be trimmed? It seems almost impossible for the chain to be rubbing on the cassette. You mentioned mashing uphill. Is the rubbing constant or rhythmic, like only when you are pushing down on the right side? There is enough flex in the chainring and frame to cause a rubbing noise on the right side when really mashing. As Michel mentioned it could be pulley noise from the guide pulley being slightly out of alignment with the cog. Put hte bike on the workstand and see if the guide pulley is directly in line with the cog. There isn't enough difference between a 25 and a 23 to need chain length adjustment. You mention that you only have 500 miles on the chain and old cassette. Is the bike that new? You may just have a little slack in the cable. It just sounds like you need to tweak the low limit or adjust the cable tension. You are cross chaining just a teeny bit, but it shouldn't be enough to make a lot of noise.

It might be interesting to pop the original cassette back on just to see if the problem stops.
This would eliminate chasing a ghost.

I'm thinking it could be a coincidence, and the real problem could be something other than the cassette, as Rainman and others suggested.

Many bike mechanics recommend using a new chain with a new cogset. It's worth a try, particularly if your chain has elongated significantly.

Thanks for the feedback, guys. I will go through the check of adjustments. If that doesn't work, I'll put the old cassette back on to see if there's any difference.

I still think it could be the rear derailleur. Put the bike in a work stand or just hang it from the ceiling. I use a piece of rope tied to the garage door track with a loop on the end slipped over the seat. While turning the crank in the offending gears carefully (watch your fingers) push the derailleur in towards the wheel or pull it out towards you just a little. When you find which way stops the noise adjust the cable accordingly. Pushing it = tighten the cable a bit. If it gets quiet when your pulling it loosen the cable just a bit. Then you have to shift through all of the gears and make sure that they are all quiet. Just play with it for a few minutes. I've fixed many noisey gears by playing with the derailleur adjustment. I did have one munged Ultegra derailluer that looked fine but was bent or worn out and had to be replaced to get a quiet drive train. You might want to disconnect the cable from the derailluer and while holding the loose end of the cable run the shifter through all of its positions and see if the cable is sticking. Good Luck.

Thanks NIBYAK, I will give this a try too.

Sorry it took a while to update you guys on this, I've been out of town on business.

Anyway, played with my bike last weekend. I made adjustments to ders and cables, but still getting the rubbing/grinding sound. I changed the cassette back to the original and had the same result.

To make the long story short, it turned out that I needed to lube everything. Now my drivetrain is running great, now noise at all. Thanks for everybody's help.