I have just finished my first fixie conversion and have a question or two on chain noise.
I am running a 3/32 drive train with a 1/8 (temporary) chain. The chain line is within a millimeter or so of being straight. I have tightened the chain so that the cranks spin without catching but there is minimal droop in the chain between cassette and sprockets.
While riding there is a little bit of general noise in the drivetrain which I expected with the different size chain.
The problem I noticed is when going downhill at very high crank rpms (150 ish). Everything is fine untill I hit the point where my legs are just keeping up with the cranks and the chain is essentially slack. When I hit a bump like this, I suddenly get a rather large grinding noise from the drivetrain. This scared the crap out of me the first time, as I though I had thrown the chain and was about to get personal with the pavement. When I stopped and checked the bike the chain tension all looked fine and there seems like there is nowhere near enough slack to throw it off.
My questions basically are: Is this sort of thing normal and anything to worry about? Is +/- 1mm an accurate enough chainline to prevent throwing the chain? Should the chain be as tight as physically possible before it interferes with the chainring turning or just tight enough so the chain cannot come off?
I have really enjoyed the first few rides on the fixie and will join one of the brisbane rides soon.
how tight your chain is depends on how round your ring is.
On my 1st conversion, the chainring I was using was not perfectly round so I had to have extra slack on the chain to compensate for the “tight” spot.
You’re basically right, the chain should be as tight as possible without interfering with the spinning of the cranks. Good way to check is to pick the bike off the ground and spin the cranks. Let go of the cranks and watch them spin. They should spin freely for a reasonable amount of time.
Using mis-matched drive parts and an off chainline will result in some noise. But I’m not familiar with the grinding noise you describe when riding fast. Have you checked the teeth in your chainring? Maybe it’s as simple as a small stone flew into your drive briefly? That has happened to me before and caused some temporary grinding.
I don’t think it is road junk, like a rock, as it has happend a couple of times now and it is always when the chain is untensioned and I hit a bump.
I will try and tighten the chain up as much as possible (without jamming) before I commute home today and see if it makes any difference, though it does seem fairly tight already.
Inane…turn up on Friday night, and we will gladly sort out the issue. I usually find that if I hear an awful noise coming from my bike, a few clicks on my i-pod and they go away…for a while.
I must of stuffed up with some part of my build as my chainline was actually 3mm or so out. I am sure I checked it when I finally finished my conversion but it was definately out when I checked again.
I have used an old chainring as a temporary spacer and though it looks very odd it has fixed the chainline and removed most of the noise. I will have to find a better solution when I have some time.
I will be away on friday Rhino or I would turn up and show off my bike, even with its double front chainring
I wouldn’t worry about throwing the chain. If you can’t push it off the ring with your fingers whilst the wheel is spinning (SLOWLY!), then it’s going to take a lot to derail it.
My chainline’s off by 1-2mm, and I’ve never had an issue.
Sweet, where do I get a hook up for the 'roids then?
Even if the chain does come off occaisonaly it’s not to bad, usually locks up the back wheel first, hell I was flying down Brunwsick st one night, chain skipped and skidded for about 15m and I shit you not, the smell of burning rubber filled the air. Passer bys were a bit confused. Anyway, I have been running a 16t cog and unbeknownst to me I am missing four teeth and it still works fine. Talk about a townie…
Should I refer to you as a pedantic fixie rider? Is there such thing as a pedantic fixie rider?
I’m just a little confused; in early post you mentioned your chain line was out by 1mm. OOOOHHHHH my GOD, quick we need a senior mechanic STAT.
Dude apart from the fact the measuring your chain line to the mm is rather, (no offence to anyone) but rather camp. I’ve seen chain lines so far out i wonder how the wheel even turns. Somehow these fixies never miss a beat.
Chain tension as indicated by ‘whatthekoon’ is usually perfect doing the whole crank spinning thing.
Too much on a chain that is not compatible will mean loads of noise and excessive wear. (crank the lube)
In closing if ya chain looks pretty by line of sight, then leave the bugger alone. The beauty of trackies is that once ya chain tension is set, dude the rest is history.
I seem to have alot of chain noise at the moment, it could be that I haven’t lubed my chain for a long time and dont have a straight-chainline…but I doubt it. Any other ideas on what I can blame?
