Fixed Gear Chainline

Raam

Does anybody here know much about getting the chainline to run straight?
I had my bike in for service and it got a new chain. Now the bike sounds like a diesel engine when I put down any power, if I ease off, there is no sound. The shop checked my bearings (fine) and put a different chain on (sounds dissappeared briefly). They say there is no more they can do. It's wrecking my buzz. I dunno how the bike sounded completely new as it was 6 months old when I bought it, but I do know that it was not making this sound when I got it. I've lubed it, but it makes no difference. Any ideas?

Itsfixed

What make/model of bike is it?

I've had chainline issues before, which took some head scratching to sort out, but once you know what to do, its easy to resolve.

I'm assuming your frame has a 120mm OLN, as most track/fixie specific bikes do.

If you look at the chainline from the rear of the bike and its out, then you might need to consider a longer or shorter length bottom bracket.

I have a fixie with an unusual 135mm OLN, so I needed the longest BB I could get my hands on, which was a 118mm, (they're usually 108 or 110) and, in addition, put the chainring on the outer ring. (its a double ring crankset, rather than a single one)

I also have a frame with a 120mm OLN, and I put another old double crankset with the shortest BB I could get, a 108, but still had to put the ring on the inner mount in order to get the chainline straight, if that makes sense.

However, I'm assuming that you have a single chainring crankset, so a longer or shorter BB is the way to do it.

niceonetom

Raam wrote: »

It's wrecking my buzz.

jayz dats shockin dat is.

have you changed anything other than the chain? bb, cranks hub?

if all that's been changed is the chain i struggle to see how the chainline could be effected. are you sure you're not running the chain too tight? noises that only appear under load ad then disappear when you ease off makes me think of that... a new chain running tight on a worn cog/ring could be noisey?

failing that, i've had success with minor chainline issues by moving the chainring to the other side of the spider (moving it about 3mm one way or the other), bit of a bodge but it can save messing with BBs.

Raam

Itsfixed wrote: »

What make/model of bike is it?

Genesis Flyer

Itsfixed wrote: »

I'm assuming your frame has a 120mm OLN, as most track/fixie specific bikes do.

Itsfixed wrote: »

However, I'm assuming that you have a single chainring crankset, so a longer or shorter BB is the way to do it.

Yes, single chainring. I was hoping I could do something with the plane of the wheel, i.e. shift it left/right a bit.

niceonetom

Raam wrote: »

120 spacing it is.

Chips Lovell

Sure the chainring isn't touching the chainstay? I've had that happen to me.

Raam

Chainline has always been slightly off, but the buzz-wrecking sound has only manifest now.

niceonetom wrote: »

have you changed anything other than the chain? bb, cranks hub?

BB was "checked" in the service. What "checked" means is beyond me. I told 'em that I heard a clicking out of it, but that sound is no more.

niceonetom wrote: »

are you sure you're not running the chain too tight?

I've tried different chain tensions, but no joy. I can experiment more.

niceonetom wrote: »

noises that only appear under load ad then disappear when you ease off makes me think of that... a new chain running tight on a worn cog/ring could be noisey?

The worn cog had crossed my mind, but I'm not sure I'd know one if I saw one.

niceonetom wrote: »

failing that, i've had success with minor chainline issues by moving the chainring to the other side of the spider (moving it about 3mm one way or the other), bit of a bodge but it can save messing with BBs.

Oh er

PeadarofAodh

Raam wrote: »

Oh er

That about sums up my thoughts too!

fish-head

The bike is too new for it to be a worn cog. Maybe you just need to tighten the crank onto the BB a little more, seeing as the shop probably took it off to 'check' the BB.

Raam

fish-head wrote: »

The bike is too new for it to be a worn cog. Maybe you just need to tighten the crank onto the BB a little more, seeing as the shop probably took it off to 'check' the BB.

Thanks, I should point out that it is about 18 months old now.

stuf

have you put a 1/8" chain on a 3/32" back and front? 1/8" chain should be ok if either the chainring or cog is 3/32" but if both are then you'd probably get a good bit of rattle.

fish-head

Raam wrote: »

Thanks, I should point out that it is about 18 months old now.

I'd say it's got a fair bit of life left in it yet! Have a look though, I'm sure you'll be able to tell.

Raam

stuf wrote: »

have you put a 1/8" chain on a 3/32" back and front? 1/8" chain should be ok if either the chainring or cog is 3/32" but if both are then you'd probably get a good bit of rattle.

Dunno about actual chain sizes, but originally it had a "big" chain, and was replaced with same. Then it was changed to a "regular" chain. So, regardless of chain, I get the same noise

Raam

I've flipped the wheel to freewheel mode, so I'll see how that goes tomorrow.
The chainring isn't touching the chain stays.
The cogs don't look worn to me.
Haven't done anything with the BB yet.

I appreciate all the replies you guys have given

fish-head

Have you considered the Giant Bowery?

Raam

fish-head wrote: »

Have you considered the Giant Bowery?

I've considered nicking the wheel from the gf's one

Raam

Well, what do you know. I flipped the wheel to free-wheel mode and there is barely a whisper out of her.

stuf

Raam wrote: »

Well, what do you know. I flipped the wheel to free-wheel mode and there is barely a whisper out of her.

booo! fixed wheel good - free wheel bad

Raam

stuf wrote: »

booo! fixed wheel good - free wheel bad

Yeah, I'd rather it was fixed too. I'll have to have a stab at getting the chainline to run straight.

stuf

The wheel should be symmetrical so it's surprising that the chainline would be out only on the fixed side and work perfectly on the free.

Probably been asked before but are you sure the cog/lockring haven't loosened at all? Anything got stuck between the cog and hub to push it out slightly?

By eye, does the chain look out of line on the fixed side and straight on the free side? If so, is it the cog or the chainring which is further from centre? I would imagine the cog if the free side works fine.

The last thing I can think of which seems a bit silly to me is that the cog could have an asymmetric cross section which would allow small line adjustments to be made by flipping it.

thesunwashot

How off is the chainline? Is there a pic (apologies if there is one - my work silently block flickr images and such like).

Did parts get changed when it was serviced? Was it only the chain? If so cog wear does seem to be a likely cause.

If you have the old chain you could measure the wear:

http://www.sheldonbrown.com/chains.html

If the chain has stretched more than 1/8" over 12 links that is considered enough to damage the cog.

You will find that chains of fixies will stretch more because they deal with braking force as well as the standard forward drive.

Raam

Thanks for the replies guys.

How off is the chainline? Is there a pic (apologies if there is one - my work silently block flickr images and such like).

I'll get pictures later this evening (none yet).

Did parts get changed when it was serviced? Was it only the chain? If so cog wear does seem to be a likely cause.

Just the chain was changed at the service. The freewheel side hasn't been used since you changed it over way back

Probably been asked before but are you sure the cog/lockring haven't loosened at all? Anything got stuck between the cog and hub to push it out slightly?

It's possible that the cog is loose, I haven't checked yet

By eye, does the chain look out of line on the fixed side and straight on the free side? If so, is it the cog or the chainring which is further from centre? I would imagine the cog if the free side works fine.

By eye, the fixed side is clearly off, the free-wheel side looks straight.
I'll verify the orientation of the fixed side.

blorg

My own cog and lockring are loose at the moment and it's making a bit of a noise as a result.

thesunwashot

pedaling forward should tighten the cog so unless there is a problem with crossed threads it seems strange.

blorg

In my own case, pedalling forward does indeed keep it tight but pedalling backwards loosens it again, the lockring is a couple of mm out from the cog. Need to tighten it when I get my hands on a tool again.

thesunwashot

Probably a good plan to get that sorted in case the lock ring works its way loose and you get yourself a suicide hub.

I can give you a lend of a lockring spanner if you need it

fish-head

blorg wrote: »

In my own case, pedalling forward does indeed keep it tight but pedalling backwards loosens it again, the lockring is a couple of mm out from the cog. Need to tighten it when I get my hands on a tool again.

Pop round if you wanna borrow mine again, buddy.

blorg

Thanks guys- might well take you up on that Fish-head! I have one on order.

Currently it is going fine, looked up that term suicide hub and it is not as bad as it sounds, I am just using the brakes :eek: and taking it easy with the skid stops. It does stay tight unless I try one of them.

There is no major risk here, on a bike with brakes, right? Thinking of taking it out tomorrow for a longish spin up the mountains.

thesunwashot

no you're fine if you are using brakes. plus the lockring is still there even though it is not done up properly.

jollylee

Its obvious that if the bike is noisey while on a cog thats been used for a while and fine on a cog that hasn't got much use then the fixed (used) cog must be worn slightly and isn't matching the new chain. Have you tried a new fixed cog?

That'd be my first thing to try before attacking the BB.

Raam

jollylee wrote: »

Its obvious that if the bike is noisey while on a cog thats been used for a while and fine on a cog that hasn't got much use then the fixed (used) cog must be worn slightly and isn't matching the new chain. Have you tried a new fixed cog?

That'd be my first thing to try before attacking the BB.

Thanks Jollylee, I haven't tried a new one yet. As it happens, I was considering getting a smaller "fixed cog" so I can get a higher gear. Maybe now is a good time to do it

Is something like this suitable?
http://www.chainreactioncycles.com/Models.aspx?ModelID=12164