Hey, forgive me if this has been covered before.

I just finished my road conversion and am using a Durable ace cog, Sugino ring, old school Ultegra (tricolor) crank, kmc 8 speed chain, and formula sealed bearing hubs.

My chain line is dead straight, and everything is new. My ring is fairly out of round (or drilled out of round is more likely), and my chain tension varies between 1/2 an inch of movement in the tight spot and an inch or so at its slackest. I've tried my ring on every one of the 5 positions on the crank and I've also tried rotating my crank on the spindle to find a better spot. Sheldon's method won't touch it.

While riding the bike is mostly silent. With the exception of chain noise. If I put pressure on the pedals, there it's about as loud as a chain going around derailleur pulleys, maybe a bit louder even. From what I can tell, it seems to be more the cog that the sound is coming from, and if I don't put pressure on the pedals it's silent.

I've read a lot of people saying that new components just need to 'wear together' a bit for a few rides. But I'm wondering if it's the tension variation in my chain that is causing it, and it won't go away.

Thoughts?

Thanks.

If the sound is constant, it's unlikely to be from an out of round chainring. Can you try a different cog? Clean chain/fresh lube? If it comes and goes in synch with your pedalling, it may be the chainring.

It is in sync. Every down stroke of the right crank which would be the slack portion of chain.

The chain is new with factory lube.

Ride your bike.

No bueno. Replace it with a single speed specific 1/8 inch chain.

Still too tight.

Which chainring in particular? Might be worth stepping up to a better SS/track specific chainring. While I have been able to work around off-center rings like yours before, it's just so much nicer when the ring is round and straight and you can just slap everything together and it runs smoothly.

This is the ring:

Sugino Standard Chainring > Components > Drivetrain > Chainrings | Jenson USA

I chose that because a lot of SS specific rings are fatter and stick out from the mounting arms of the crank. I figured this being marketed as SS/or 8 speed, it'd be thinner and fit the crank better. It does.

Is the cog a 3/32 inch cog?

Gotcha. I've used those on several derailleur bikes with good results. Note that they are marketed as being good for "single-ring use", i.e. 1xX drivetrains, and the 130 BCD version flat-out says "(not intended for singlespeed use)". I think that's an admission that since these are cheap chainrings meant for derailleur bikes, they might not necessarily be round enough for picky fixed-gear riders.

But like [MENTION=164476]Scrodzilla[/MENTION] says, just ride your bike for now. My fixed-gear is a conversion built up from old road components, too, and sometimes I notice drivetrain noise and sometimes I don't. If you haven't already, you might see if oiling your chain (and then wiping it down thoroughly afterward) quiets it down.

That's crazy, I've never seen that disclaimer before. I actually got mine through QBP (I work with a company who has an account) and they are listed as singlespeed rings specifically. That's nuts.


Lubing a chain is easy, and I'll try that. But I think I might just pick up another ring and see what that does.


Squid, the cog is a 3/32.

Thanks guys.

I do my best to completely ignore chain noise except re: lubrication or mismatches between chain wear and cog wear. (I rotate cogs between several bikes.) I have found in general that chains like Izumi run noisy as do UAI cogs. I think that is because there is less rounding of plates and teeth. But I also feel this is probably a hair more secure re: throwing chains sop I am happy to live with the noise. (And I always find if I ride harder, the noise tunes out.)

Ben

That's interesting. I can see why people might assume a chainring with no ramps or pings or specially-carved teeth might be SS-specific, but with the ones we've linked to, Sugino is trying to support riders with vintage (pre-1990 or so) bikes. Which I applaud.

Agreed. It looks just like the Shimano rings I took off of the crank I'm using (which is what I was going for ironically).

The slack chain could be swaying sideways as a result of slight frame rock or flex so the chain is running not quite true into the cog or chainring, hence making noise that it doesn't when the chain has less slack. You say your chain slack is between 1/2" and 1" If I were you, I'd pull the wheel back to get less than 1/4" at the tightest. As long as the chain never goes tight, you are OK there.

If my guess is right, your chain is doing its best to derail.

I only run 1/8" everything as close track quality and spec as I can afford both for the wear properties and to minimize the chance of throwing the chain. (I do on-the-road wheel flips and cog changes sometimes many times a ride, often when I am not at my shop mechanic's best, often riding down big downhill immediately after.)

Ben

A certain amount of chain noise is normal, especially under load. If you've ever head a car engine with timing chains, or a chain driven machine you'll be familiar with the classic whirr of chains. Bikes are no different, except for size and speed.

The sound is inherent in the nature chain drive (see chordal action to understand) and unavoidable, though it can vary chain to chain within a range.

The reason you hear chain noise in SS bikes is that they're silent otherwise. Consider the source here, but chain lube can make a big difference, so you may want to experiment with that.

One last note. Your chain is too slack. Pull the wheel back with the chain in the tightest position and take out most of that 1/2" of sag leaving only a vestigial bit, so the chain is never under tension.

I'm really surprised to read this. OP says that when rotating the cranks without load, the chain is silent. But when he mashes the sound appears. That is the exact symptom I have experienced from a too tight chain.

1/4" seems mighty snug to me. That's like up 3mm and down 3mm.

Carry on.

Chains have only two conditions; taut and slack. Any tension is improper, and any slack is OK. More or less slack won't affect chain noise, which is generated in the tensioned driving loop.

However the OP reported variance from half an inch to an inch of vertical play. The half inch would be OK, but an inch may be enough to allow the chain to come off, which is why I suggested reining it in.

Note, that I saidon't to bring the slack as close to zero as possible without getting there at the tightest place. So if he follows my advice, he'll end up with the slack varying from near zero to a bit over half an inch.

See, that's what I find interesting. Interesting because I'm not an engineer and don't understand the technical side, but I've experienced the opposite. More than once.

I rode a friends single speed bike and if I just rotated the cranks lightly (kinda floating to match the current speed) things felt and sounded OK. But once I started getting on it, it felt tight/rough and sounded nasty. I checked the chain and it was not worn and was well lubed. Tight vs loose spots were there but insignificant. Rifle sighting indicated a satisfactory chain line. I checked for slack. I could move the chain up (from center) about a quarter inch and down a quarter as well. So technically, 1/2" of slack existed. But it felt tight, not free to move up and down. I adjusted it to my usual amount of SLOP (impossible to derail, but very slack) and I couldn't reproduce the noise or the rough feeling.

Another friend later complained about a noisy drive train after installing a new chain. The above story played out again identically.

Dunno. Shrug. Chalk it up to SS phenomenon I guess?

You're confirming what I said earlier. Chain noise comes from the driving loop's tension and will be proportional to the load (tension).

As long as the lower loop is slack, it doesn't contribute, nor does the upper loop when there's no load, since proportional to zero is zero.

Chain noise has two main sources. The first is the unavoidable effect of chordal action, which creates fluctuating load in the system because of the momentum of both the wheel and crank. The chain is pulled tighter then slackened a hair with every tooth passing 12 o'clock.

The second source relates to the chain's effective pitch and the shapes of the teeth. I'll use an analogy to explain how. Imagine playing basket ball. You throw a perfect "nothing but net" shot which sails through the hoop silently. As long as the ball never touches the rim all your shots will be silent. But nobody is that good and most shots that go through aren't perfectly centered and so bump the rim as they pass, making a noise.

Now consider the chain and the sprocket as they mesh. In theory the chain is held by the teeth at 12 o'clock and the next tooth swings cleanly into the gap between the rollers as it rotates up to 12 o'clock. Or if you prefer, the roller swings down into the trough between the next teeth as it winds onto the sprocket. (both are true, it's a question of outlook).

A chain operates very close to that theory, and if the chain's pitch and the cuts of the sprocket's teeth were perfectly matched, it's "nothing but net". But things aren't perfect, and the chain's effective pitch will be a bit long due to wear, and roller play which allows it to settle to a smaller diameter on the sprocket. Since the pitch is now greater than the sprockets, the next roller is out of position and bumps the teeth as it meshes, making the same (though much smaller) sound as your less than perfect basketball shot ---- "tick".

So you're riding along, pedaling a 48t chainring at a 90rpm cadence --- tick,tick, tick......... 432 ticks per minute, which is what you hear as a grinding or sawing sound. The greater the pitch error, and the higher the tension the harder those little bumps are and the louder the ticks. The faster you pedal, then higher the pitch. Note that the same thing is happening at the lower loop, but with no load the ticks are quieter and you don't notice them.

Thanks. I had to look that up. Very interesting, and makes a good argument for bigger sprockets.