Hey guys,

Ok, I just got a new single speed, photo to follow...

however, it seems the bike seems to have a low frequency "rumble" whilst pedaling. I'm just wondering what would cause this? There is no rubbing anywhere, and the brakes are nicely aligned now. Could it be to do with the tension in the chain? Or is it a hub related issue?

Thanks in advance,
Daz.

Its Alllllllllllllllllllivvvvvvvve!

Is your wheel on straight? It only Happens when you pedal? Is it just a sound, or is it a severe vibration? More info!!!

sounds like a chainline problem to me.

Overtensioned chain. Move your wheel forward a tiny bit.

If you live in NV, maybe you felt an earthquake.

Ditto what Blickblocks said, it sounds like a tight spot on the chain.

If your chain is ok check your bearings.

Check them for what? You've figured out a simple way of objectively quantifying the wear on bearings?

They probably mean check if your cones are overtightened.

You can either hold the axle and spin the wheel up and feel through your fingers for any rumbling or tight spots trying to turn the axle in your fingers, or take the chain off and tighten the wheel back in the frame and spin the wheel up and feel or listen on the chain stay with a screwdriver [stethoscope stylee] for the same
As Blickblocks said the cones may be too tight if the lock nut comes loose they can cause the inner cone to tighten up on the axle bearings and cause seizure.

If you want to do it properly strip the axle out and clean off the grease and look for any pitted marks in the case hardenened surface of the bearings surfaces.

If they are sealed bearings well just change them, they are usually cheap enough, replacements for Goldtechs are £12 a pair

Failing all that if you're still not sure take it to your local bike shop

Faster just to take 5s, loosen off both axel nuts and test for tightness. It'll be immediately obvious anyways. Assuming it's a loose ball track rear hub. (Don't think they're many of those around).

Here are a couple of pics that might help a pitted bearing surface where the case hardened surface has started to break up.


and a typical axle/cone layout.

Let's not get ahead of ourselves here, the OP Hasn't even gotten back to us on the simplest of determinations yet (chain or hubs?)

sorry I thought you wanted a brief on bearing checking

It does sound like a tight chain though, or it is an Izumi chain, I use them and they do run noisier than other chains but they are bulletproof and outlast others, a small price to pay

Hey guys,

Ok, firstly, thanks for all the helpful suggestions. I loosened the chain and that seems to have gotten rid of the horrible rumble, it still rumbles, but just not as much. The bike had a tensioner on one side, so you could effectively change the alignment of the wheel. But by being on one side, changing the tension of the chain like that messed with the alignment of the wheel, and hence the brakes.

Anyway, I took the wheel off and re-seated it a few times and it seems better. How loose should the chain be though? Now if I pedal (with my hand - bike upside down), their is quite a bit of movement.

Thanks again,
Daz.

I always pull the chain taught then spin the wheel slowly checking for tight spots and if there is any binding slacken it off slightly until it spins freely.
If the chainwheel and sprocket are not too worn that should do it, if they are worn then check at the slackest spot hopefully you won't be able to move the chain more than 3/4 of an inch.
check the fixie FAQs here;
FixieFAQs

It depends how fast your cadence gets aswell, if you potter around slowly you can get away with a slack chain, around here there are some rolling and steep hills and descending at high rpm means I prefer to keep my chain tight as possible to avoid it geting thrown off.
Most of all mind your fingers always check from the outside of the chain don't get your fingers cut off by the sprocket

wtf? WHat were you thinking when you typed this?

You're joking right? I quoted the post right in my reply.

Still don't get it.

I'm still not clear on one thing: the OP said he just got a new singlespeed. Freewheel or fixed?

When checking your bearings, you'd be looking to see how dirty the grease is and if there are metal shavings in it. You would also be checking for pitting in the races and cones. Easy enough?

Regarding the original question, My money's on the chain making noise due to either alignment or tension which ever likely stemming from a cheap deformed chainring.