Noisy chainwheel after reversing rear sprocket. 40 x 16 system. Help!

[gearoidmuar]

I've just done my second oil-change at 6100 m and put on a new chain (old one, the second since new stretched 1/16). I've maintained the rear sprocket in phase with the chainwheel as Sheldon Brown recommends. The chain is now making a helluva racket. Sheldon advises reversing the chainwheel at this stage, but will this work, and if it does, should I keep the chainwheel in phase (use the narrow links on the worn teeth) or otherwise?

Anybody know? Otherwise I'm going to have a lot of noise for quite a while. The drivetrain had been totally silent, apart from when I changed the first chain, when it was noisy for 2 or three weeks, but not like this.

[Beave]

I would think that if you are reversing the sprocket and chainring, that you could start a brand new phase relationship using either set of links, since you are basically starting with a fresh gear set. My understanding is the chain rollers only contact one side of the tooth, and flipping your rings around will make the chain contact the unworn surfaces. I'd guess that you are hearing a chain that was worn a bit too long, and now it is aggressively trying to dig a comfortable pattern out of your rings to match the brand new chain pitch.

Is your bike equipped with sliding dropouts or an eccentric? Mine has a chain tensioner, so I have to follow the basic rules that apply to deraileurs when it comes to chain wear and replacement. But if I had a sliding drop or EBB, I would just wear the chain and sprockets out together in a phase relationship. Seems like alot of folks are getting 10K+ miles when doing it this way. Assuming you have the adjustment range to keep the chain tensioned.

Now for my question: For those with a bike equipped with sliding drops or an EBB: Say you run a chain, sprocket and chainring together in a phase relationship until it is worn so much that you can't compensate for the chain growth and it is now time to change the chain. Can you fit a new chain, then change the phase relationship by one tooth instead of flipping the chainwheel and sprocket?

[gearoidmuar]

I tried it with the original phase and then the new phase on the chainwheel. Same noise. I'll try reversing the chainwheel and report on it. The chain wasn't excessively worn. Just stretched 1/16 inch in one foot. I've actually measure it with a ruler, but check my chain with a Rohloff gauge quite regularly.

[peddles]

"Now for my question: For those with a bike equipped with sliding drops or an EBB: Say you run a chain, sprocket and chainring together in a phase relationship until it is worn so much that you can't compensate for the chain growth and it is now time to change the chain. Can you fit a new chain, then change the phase relationship by one tooth instead of flipping the chainwheel and sprocket?"

No, I think not.  The phase relationship is maintained to accommodate the fact that the chain wear is seen in alternate links and the chainring and sprocket (where the number of teeth is even) wear alternate teeth to accommodate this. So with a new chain and old sprocket/chainring there is no phase relationship between chain and teeth and would result in similar noises as previously existed. When the chainring/sprocket are reversed they present unworn faces to the chain and a new relationship begins.

[Andre Jute]

The phase relationship is maintained to accommodate the fact that the chain wear is seen in alternate links and the chainring and sprocket (where the number of teeth is even) wear alternate teeth to accommodate this. ... When the chainring/sprocket are reversed they present unworn faces to the chain and a new relationship begins.

That raises the question whether there is any advantage to retaining the directional phase of the chain. And, by extension, of reversing the chain when chainring and sprocket are reversed.

Hobbes

[gearoidmuar]

Well, I reversed the chainwheel and it's as noisy as hell. AND I changed the phase on the chainwheel and it's just as noisy. Reversing chainwheel made NO difference.
I've two choices. Wait for it to wear in (I'll give it 200 miles) or change the sprocket and the chainwheel. I do have spares.
My spares include a 15 and 42. Will go for them.

[geocycle]

I replaced my sprocket after 10k miles.  I was going to just turn it but it looked pretty worn with the teeth reaching sharp points.  Also some folk have reported that seals could be damaged by rough edges.

The new chain was very noisy on the chainwheel just as you described.  I turned it cf Sheldon to no great effect so in the end I just put a new chain wheel on and silence was immediately restored. I'm sure it would have meshed in eventually but ...

Curiously I've had to replace the chain a couple of times and neither gave me a noise problem like that after changing the sprocket.  I put it down to less wear at earlier stages although I am not really sure.

[gearoidmuar]

What's odd about this is that this does not happen with derailleur systems. I presume that this is due to the even even tooth distribution. In future I'm going for 15 x 42 or even 44.

[gearoidmuar]

A couple of very noisy spins later I gave in.
I changed chainwheel for a 42 and sprocket for a 15, tightenend all the chainwheelnuts with a new tool for same and now have a stealth Rohloff and a bigger top gear.
I like 42 x 15. I certainly did not use the no1. in 40 x 16 more than a half a dozen times, and only because I had it.

[travellingman]

I really don't want to sound contentious here but this whole thing about running chains 'in phase' is total garbage. The concept of reversing sprockets/chainrings maybe has some merit and if you have no other option I guess it's acceptable. However, choosing to run a new chain with an old sprocket/chainring combination or vice versa is plainly a false economy. It goes against all sound engineering practice.

To prove my point two people on this thread have proven to themselves that despite their misguided efforts the only way they've got a new chain running correctly is by replacing the sprocket and chainring at the same time.

There are far more relevant variables to ensuring the long life of a chain, sprocket and chainring combination. Those being protection from contaminants (i.e. a chaincase), lubrication, adjustment and accurate chainline.

[gearoidmuar]

I really don't want to sound contentious here but this whole thing about running chains 'in phase' is total garbage. The concept of reversing sprockets/chainrings maybe has some merit and if you have no other option I guess it's acceptable. However, choosing to run a new chain with an old sprocket/chainring combination or vice versa is plainly a false economy. It goes against all sound engineering practice.

To prove my point two people on this thread have proven to themselves that despite their misguided efforts the only way they've got a new chain running correctly is by replacing the sprocket and chainring at the same time.

There are far more relevant variables to ensuring the long life of a chain, sprocket and chainring combination. Those being protection from contaminants (i.e. a chaincase), lubrication, adjustment and accurate chainline.

I think you're right about the phase thing. I replaced chainwheel and put a new sprocket in as I was at it and I've silence.

But there's more than that. I've never noticed a noisy chainwheel on a derailleur system when the chainwheel was a bit worn (i.e. there was no phase element). Chainsuck might rear its ugly head, however.
From now on, I'm riding 42x15. 40x16 was a bit low for me. I almost never used no. 1 gear, even in hilly touring and could've got by without it.