SS Chain tension.

andyrr

This might be something that is common but more noticable with a SS setup than gears :
when I check the chain tension on my Trek SS, to allow a reasonable allow of slack at the tightest, measuring at mid-point, the slackest point of the revolution is then quite a bit more. Haven't measured it but if, say, I adjussted it to have the slackest to be about right then at it's tightest the chain is almost complketely tight. Something in the transmisison is therefore not running 100% true - I'm guessing it is the BB/crank, it's running the originals here (12 months regular-use in) so replacement might be on the cards but I just think it's a bit crappy that I can't have a nice consistent chain tension.

Monty Dog

Probably the chainring is not true and may be compounded by the crank / mounting bolts. Try slackening off the chainring bolts a touch and turn the cranks to see if it evens-out and then re-tighten? Try remounting the chainring at a few positions too? Quality machined chainrings are way more accurate that pressed ones. I aim for a bout 1cm of vertical 'play' in the chain at the mid point - any tighter and it tends to be noisier / less smooth.

andyrr

Cheers, good suggestions there.
Prior to this biek I'd never ruin SS so chain tension wasn't an issue really.
Not all that long after I started using it the chain actually came off when riding and the end result was it jumped into the hub-side and chewed a couple of spokes. That would be with insufficient tension. I'm wondering if I sometimes run a little too much as tension as I'm now on my 3rd freewheel (all Shimano ones) as the bearings go rough as hell after a time and too tight a chain would excerbate this. More even tension would give the drivetrain an easier time of it.

Monty Dog

Bar- tight = buggered chain & knackered hubs IME. Slacken it off a touch. Unless you are running top-end NJS chainset, hubs and chain there needs to be a bit of 'backlash' in the drivetrain.

mz__jo

It's not impossible that the problem might be caused by uneven chain wear (a tight spot). Chains for ss don't need to cost a fortune, try sticking a cheapy on and see if it has any effect on your problem. If it's that don't waste your time trying to play with rings (although a tight spot on the chain can be the cause of subsequent uneven ring wear). If the line is right it should be possible to have a useable transmission even with a bit of uneven wear.

andyrr

Fitted new chain (gold KMC 3/32) and there was still noticable tight/slack discrepancy which I didn't seem to see much improvement from by loosening the chainring bolts. I think I need to slacken it off a little as I tend to run it very slightly too tight as opposed to too loose as I'm a bit paranoid about the chain jumping off the sprocket after having that happen a couple of times. I know, having run motorbikes for years, that too tight is bad as is too loose and getting a happy medium takes a biut of fiddling.

andyrr

Still messing around with this :
Chain is the newish KMC gold 1/8"
I'd swapped to an older freehweel as the existing one was goosed but after about 4 days of being left in the garage unused I wheeled the bike out on Monday night awaiting use on Tuesday and - lordy, rough as a badger's, backpedaling felt dreadful, - really rough and stiff so, at 11:30pm I swapped to another, newly purchased, Shimano freewheel. Runs smooth and chain tension as per normal ie ok,ok, ok, tight, ok, loose but no more dramatic than normal.
Riding to work I had repeated 'cracking' noises from the transmission - not 100% sure if it is the crank area (BB/chainring bolts) or rear (freewheel). Varied between almost once per rev to nothing for miles. On the way home I hardly felt any of these at all : it's like when the stress on the transmission is hard and constant (it's more uphill heading home) the issue isn't present. I was getting this about a year or so ago, Halfords nearest to my work (I know, I know ... but I'd bust a chain and some spokes on the way to work that day and the guys there were good enough to drop other jobs and sort me out) had reckoned it was a knackered headset noise being transmitted to other parts of the bike - sorry but it was not that, once I'd had new rear dropouts supplied by the dealer and chain tension a bit better the noise had gone. Or it had until now !

Last night at home I got all 5 chainring bolts undone.
Left these loose and twirled the pedals.
Tightened them up having greased the bolts.
Got the chain tension to a happy medium.
Ride to work - crack, crack - aargh driving me mad !
BB has no detectable play. Chain runs pretty smooth.
Chainring (original on the Bontrager crankset) is showing signs of wear on the teeth so I might try to find an alternative - not sure the BCD - std track ?
Whilst that awaits I might try rotating the chainring position to see if the chain tension can be evened-out.

andyrr

This a worthwhile purchase ?
http://www.wiggle.co.uk/token-tk140-track-chainrings/
Token TK140 Track Chainring ? Seems quite cheap and Token a decent enough make ?
I see a Wiggle review for it indicating the same issue as I currently have - getting good chain tension all round.

John.T

Intermittent cracking noises often caused by water in the hub bearings. You should be able to run a SS drive train almost to destruction without any trouble. And you will almost never get even tension.

Monty Dog

How is the chainline? The cracking could be the chain sideplates catching on the edge of the chainring / sprocket

andyrr

Well, I think the cracking noise may well have been the hub bearings - I greased the hub really well last night (obviously cheap hubs front and rear as there is a tiny window of smoothness where otherwise they turned roughly/had play but this AM's commute was ok.I had done this a few hunderd miles previously but it needed done again - will try to make it a monthly job from now on.
I couldn't be bothered tbh to also spend time rotating the chainring to see if I can make an improvement to the consistency of the tension all the way round - that's next and also I think a new ring to be ordered soon since the existing one's teeth is getting worn and hopefully an improved quality one will be rounder.
That Token one was the a 4-bolt : I need 5 : 130BCD I guess (will measure to be sure) ? Cheapest I found was a Brev one for £17.99o at Evans.