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Another "chain pop" thread... but it's a new chain and cog!

2K views 13 replies 8 participants last post by  max-a-mill 
#1 ·
I just swapped to a 17t cog on my bike and now I get the dreaded "chain pop" but not under heavy load. It only happens when I start to pedal (light pressure) after coasting. I've yet to drop the chain and it only happens a few times a ride, but it's driving me nuts.

The chain is a relatively new SRAM PC850 (I think). It was a basic 8-speed chain that I picked up late at REI since they were the only place open when I bought the bike and converted it from the tall street gearing. I did 2 rides on it with the old 18t cog. Not a single pop. I regeared to 17t and started getting the pop. The old 18t cog is an Absolute Black and the new one is a Box Components chromoly.

Chainline is dead nuts on, best as I can tell. I did notice some waviness in the chain when looking at it from the rear. It sorta swerves left and right. My chain is not tight but not too loose. It has the standard 1/2in vertical slack. There are no noticeable tight spots in the drivetrain.

My theory is that the chain pop is the chain trying to ride up the cog then popping back into place. Could it be the little beveled edge in the side plates of the 8-speed chain that's designed to assist in shifting on geared bikes? Or maybe my chainline is still off? Or maybe that $10 SRAM chain is just a POS?

I'm tempted to just order a KMC Z610HX chain and see if that fixes it. I really want it to just be caused by a shitty chain.
 
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#2 ·
Sram 8 speed chain is not the issue, sorry. It's been a go-to chain for many SSers for years. I'm not familiar with the Box cog, is it 1/8, 3/8?

You said "chainline is dead nuts on", then asked if the "waviness" is an issue. have you measured it? What makes you think it's strait?

Often, this can be a problem resulting from frame flex (or some kind of axle/bearing flex), but if you weren't having problems before, it's a component or setup issue. Something changed.
 
#5 ·
Just a thought here; I run an AbsoluteBlack oval ring on my single speed and at one point started swapping some parts around between my bikes. I decided to move the that ring from my SS to the full suspension bike (wanted a larger ring for the SS) after about 30 miles and the 11spd chain wouldn't mesh with with the ring. I thought I was going crazy, so I started emailing back and forth with AbsoluteBlack. They confirmed that they use a very soft metal on their rings, and he was certain that even after only 30 miles the 3/32" chain I had been running wore the ring in enough that it wasn't going to mesh with an 11spd.

If you let your last chain stretch a whole lot, your ring may be worn in and not meshing all that great with the new chain. You may need to give it a little bit and let the chain stretch out a bit.
 
#6 ·
Pics of your setup would be helpful. Just to get an idea what your drivetrain looks like, and where the possible problem spots could be.

I'd doubt it's the chain but it's tough to say with this stuff. If you're using a tensioner, that can play a role. Pawls in the freehub could be slipping in the drive ring (bad news). Chain ring might be what's skipping.

One thing I've had success with is planting the front wheel against something solid (like a wall) and finding something to support myself. Put weight on the pedals, torquing the drive train in various spots to see if you can replicate the noise. This should allow you to get some serious effort into the pedals and see if there are any obvious problem spots (like flexing).
 
#7 ·
I’ve been building and riding singlespeeds for over tens years, so you’d think long enough to experience some of these chain/sprocket issues, that plenty of others seem to and yet I never have.
To date, I’ve only ever used Middleburn and HBC chainrings and Chris King stainless and Surly sprockets, always with KMC Z610-HX chain.
I set my chainline first by eye and then check by measuring from the c/l of the chainring to c/l of the seat tube and from c/l sprocket to inside of dropout. However, it’s just a roller chain running over a couple of sprockets and a millimetre or two either way isn’t going to make much difference.
Same for tension - I usually have about 10mm of deflection possible in the middle of the run but occasionally it’s been more/less and it’s worked fine. In ten years I’ve only once lost a chain and that was when a bunch of heather fed itself in between the chain and sprocket.

Drivetrain noises are most likely to be as a result of worn chain/new sprockets or vice versa. However, in my experience, either chain or sprocket has to be pretty bad for this to occur. Whether I’ll experience any of this with my switch to oval chainrings (which, unfortunately all seem to be N/W these days) remains to be seen.
 
#8 ·
agree with sinkers: make sure it's not your hub/freewheel. when the pawls on the freewheel don't engage well; it makes for terrible noises too.

or everyone else: maybe it's just the noises of everything bedding together; new chain on worn cog/ring noises. does it actually skip or just make noise? would some extra lube make it quieter?

also agree with onespeed, that chain is just fine; i have used many with no issue.

so many variables... i bet you just have to put some miles on it and everything quiets down; unless it's your freehub.
 
#9 ·
Thanks for all the suggestions everyone. I've been messing with the bike for the past few nights now and I think I've got it narrowed down to the freehub. I measured my chainline with my calipers and it's +/- 1mm, degreased then relubed the chain, and really cranked down on the cassette lockring. I noticed that the Box Components cog doesn't fit as snug on the freehub body as the Absolute Black did, so I was thinking that was the noise. It wasn't. The popping I'm feeling is also a skip now, and it feels like the freehub pawl isn't fulling locking in. My feet will lunge/spin forward a few degrees until the next pawl locks in.

The bike is a Salsa El Mariachi SS (I'll try and upload a pic in a bit) and I bought it used so miles is unknown. It seems in relatively good shape and it was setup for street riding when I got it so I don't think it was abused too badly.

The bike is also creaking now, coming from the rear hub. The axle spins pretty smooth so I don't think that's the culprit. With the wheel off and the cog removed, I can feel some play in the freehub to the hub. It makes some clickity clack noises as I manipulate it so I'm thinking that's the cause of the creaking.

I guess it's just time to convert to 27.5 with a new wheelset, unless it's real cheap and easy to rebuild the freehub on the Salsa hub.
 
#11 ·
So one thing that you could do (in theory) is pull that freehub off and look at the pawls and drive ring. The end cap on the axle may be threaded (will have flats on it) or just pop off. Get the end cap off and pull really hard on the free hub and it should pop out.

The reason I say (in theory) is because I've noticed quite often that freehub damage can be very subtle. It doesn't take much boogering for a pawl to start screwing up a drive ring or vice-versa. If it's skipping the way that it sounds like it is, I'd say it's likely toast regardless of what it looks like, but it may be worth it to see if there's anything obvious.

As far as fixing the freehub, I'd guess that the drive ring is probably toast in which case you're probably looking at a hub replacement (IME, that ring requires a special tool to replace and isn't worth the effort).

All of this is why I'm starting to lean towards ratchet type drive mechanisms vs. pawl type.

Good luck.
 
#12 ·
So one thing that you could do (in theory) is pull that freehub off and look at the pawls and drive ring. The end cap on the axle may be threaded (will have flats on it) or just pop off. Get the end cap off and pull really hard on the free hub and it should pop out.

The reason I say (in theory) is because I've noticed quite often that freehub damage can be very subtle. It doesn't take much boogering for a pawl to start screwing up a drive ring or vice-versa. If it's skipping the way that it sounds like it is, I'd say it's likely toast regardless of what it looks like, but it may be worth it to see if there's anything obvious.

As far as fixing the freehub, I'd guess that the drive ring is probably toast in which case you're probably looking at a hub replacement (IME, that ring requires a special tool to replace and isn't worth the effort).

All of this is why I'm starting to lean towards ratchet type drive mechanisms vs. pawl type.

Good luck.
I agree 100% with everything said. I have experienced the freehub popping before and it can be difficult to narrow down and sounds exactly like a chain popping over the ring or cog. I think you said it occurs after you freewheel and that is exactly how mine presented itself. Open you hub up and give it a look. Again like said above the damage can be very slight, so be particular.
 
#13 ·
Have your hub inspected at a LBS. They will have a better idea of what they are looking at and if you can get parts for it. I forget who makes Salsa hubs, but you may be able to just replace the damaged parts. Hubs require maintenance, and occasionally new parts, it's not necessarily a bad design. Granted it's not a high end hub.
 
#14 ·
it could just need a need a new freewheel. fix it immediately or it will get worse and worse until eventually you will be able to freewheel in both directions. probably at will the furthest point from your car/house... ;) this just happened to me for the second time on a stock low end trek wheel. luckily this time i felt it happening and knew what i was feeling so i was able to nurse it home before it completely exploded.
 
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