Singlespeed & Fixed Gear - New SS cog on my JamieRoy - Knocking noise

I've been riding my 46x17 fixed gear on my JR for about two weeks (since I got it) and recently went in to the LBS to get a 18 gear SS cog installed so I can do uphills/downhills. The guy was sorta busy but got the chain tensioned right and whatnot after I tested the new gear three times with the same knocking noise. After the third try he told took the bike out himself and told me the gear/chain just needed to be broken in or the bike needed to adjust to the new gear after being ridden on a fixed gear for the entire length of it's life.

Anyhow, the knocking noise comes only at higher speeds/higher RPMs. Slow accelerations don't make any noises. And this all started happening only after the new gear was put on so it can't be an existing problem.

Was the LBS guy right? Do SS gears need to be broken in?

Was the LBS guy right? Do SS gears need to be broken in?Total BS. Just curious, which LBS told you this?

Chain tension may be too tight. Check to see if you don't have a tight spot on the crank rotation.
Also, just to be sure, check to see if you don't have a stiff link.

the bike needed to adjust to the new gear after being ridden on a fixed gear for the entire length of it's life.


lol
Find a different bike shop asap.

It's a shop in Pasadena. The guy who does work on my bike is actually pretty well known in my area.

We checked the chain tension three times, it was at first a bit short of tight, then we loosened it a tad and now it's a bit short of slack. And what do you mean by a right spot on the crank rotation? Stiff link?

If you didn't have a knock when riding on fixed, then you don't have a stiff link. A stiff link is caused when the pin is pushed back into the chain plates, compressing the whole assembly which causes a tight spot if not corrected.

If the chain is on the loose side (as you mentioned) and you don't have a stiff link, it is possible you have a bum freewheel. Never heard one clunk before ( I assume you got a Shimano or ACS) but I guess it could happen if it were short a bearing or two. If you got an White Industries ENO, I HIGHLY doubt it's the freewheel. Since it is new, see if they have another freewheel and see if it happens to that one as well.

A tight spot in the crank rotation would indicate too stiff chain tension. Shimano and ACS freewheels are nowhere close to round. Pair that with an imperfect c-ring and you can get bad tension.

the chainring might be slightly out of round, causing the chain to get a sudden burst of tension at a particular point in the rotation.

Most cheap freewheels are poorly machined. On my rig, I'll occasionally get some regular knocking sounds...but can usually remedy it if I backpedal a bit and situate the chain differently. Suspend the back of your bike, and spin the wheel like it would while coasting. Can you see the chain tightening and slackening? Try to watch for when it is the tightest, then stop the wheel. Adjust your chain tension (keeping your wheel in that position!) and see if the sound goes away.

Also check whether your wheel is aligned in the dropouts. Uneven chain line can bollocks up a cheap freewheel. If nothing else works, try taking the wheel off and slowly spinning the freewheel by hand...listening to the ratchets engage. You might be able to feel a rough spot. Hiroshima is right, though: Shimano and ACS freewheels are junk...I'm saving for an ENO, after ruining one Shimano, and buying another that was crap right out of the box.

The wheel's aligned and backpedaling gets rid of some of the knocking, it just dampens it. I'm probably going to take it back next sunday and try to get another cog.

The thing is...after riding my fixed gear for two weeks (my first two weeks ever riding a fixie), I can't stand riding long distances with the SS. The only reason I have left to go with a SS cog is for steep downhills. I should've gotten a fixed/fixed hub instead but it's too late for that. How much would it cost to get a formula fixed/fixed hub and have it re-laced?

Good luck getting another freewheel...they're considered to be 'disposable' by many people, so your LBS might balk at returning it. I'm surprised that you prefer fixed for long distances, I'm the other way round.

Formula hubs are $40+, and a wheel rebuild is about the same (though it probably changes from one shop to the next...and assuming they can reuse your old spokes, etc). It might be a good chance for you to learn wheelbuilding... For the cash, you might be able to find a complete wheel online...eBay maybe. Somebody correct me if I'm out of line on my prices.

Have you checked your freewheel? Can you hear it rubbing when you spin it by hand [taken off the bike]? You can lube them with some light viscosity oil. Be sure it's not chain lube or something else sticky, or the pawls can stick.

Ok I went back to the shop today (in 106 deg socal heat!). The guy told me he'd just order a new one with the correct chain width size. Can a wrong chain width size really make a knocking noise? I figured he'd just sold me a shoddy cog.

Okay I'm growing more and more tired of this noise. I'm to the point where I'm considering buying an ENO FW and while I'm at it I'll pick up a Sugino Crank and the most expensive BB I can get my hands on. I want my fixie silenced!!

Okay I'm growing more and more tired of this noise. I'm to the point where I'm considering buying an ENO FW and while I'm at it I'll pick up a Sugino Crank and the most expensive BB I can get my hands on. I want my fixie silenced!!

It isn't fixed if you run a freewheel-- fixed use thread-on cogs (not a ratcheting mechanism). The freewheel's probably junk. An ENO will be well-made, but they are loud because of the number of pawls/ratchets. Take the chain off your bike, take the wheel off...move all of the parts individually. Can you feel anything interrupting the turn of the cranks? Have you oiled the freewheel like I suggested? Unless you've got money to burn, be sure you've tried to fix everything.

I've only greased it up some more. As for oil, all I've got on hand right now is silicone oil. I was seriously considering dishing out some cash for an ENO to silence her once and for all. Are ACS freewheels any better?

Oh and when I said I wanted my fixie silenced, I meant the bike in general not the fixed gear. Sorry.

You realize ENO freewheels are LOUD......but in a nice, pleasant way. Maybe later I'll shoot a short vid clip of my freewheeling ENO cog so you'll get some idea what this thing sounds like.

Ohhhkay so I took the bike to my other LBS to get it checked out, seems they know a tad bit more about hubs and fixies. After a 5 minute inspection, he concluded that the hub needed to have it's bearings re-greased or something.

I did notice when I had the rear wheel off earlier that when I bounce it off the ground, the freewheel does make a bit of a rattling noise. Oh and there's no stiff links so can my 2nd LBS be right? If so, I'm taking it in to get it tuned and whatnot. Guy said he'd charge 15 bucks and it'd take a few hours.

that noise from the freewheel is because the outer part which is the cog itself doesn't fit on its bearings perfectly so it wobbles a bit, this is very common with ACS freewheels, doesn't hurt the bike, just makes noise and yes it is irritating

I quit using ACS freewheels because they are noisy as hell and devekop knocks... I have had much better luck with Shimano freewheels in both respects.

+1 on the chainring suggestion. Check yer alignment.

But if it's actually a freewheel you bought (too lazy to scroll up,) then I'm wouldn't be surprised if it is the culprit. Freewheels especially can have a little wiggle in their rotation, just like a chainring, but unfortunately it's not really fixable. I have an AC Racing freewheel on my commuter that causes such a problem. It's a good idea (lets you run a 15-tooth freewheel,) but a crappy product (they're out of business now,) threw off my chainline calculations because it rubbed up against my hub, and, more pertinently, has a bit of a wobble to it. If you turn the cranks on my bike, you can actually see the chain tighten completely then slacken. It gives it character.

So yeah check your freewheel and chainring.