[Closed] SS variable chain tension

Or the BB is bent, or the freehub doesn't run straight... Try to not worry about it unless it's really really bad!

tricky - on most cransets you can adjust the chainring position so that any slight ovalness is taken account of and the tension is even.

Clearly an Uno isn't going to allow that.

might be worth getting some callipers and measuring the ring to centre distance in various places plus the same with the cog?

not sure what you could adjust to compensate if it is out though.

The BB is a lovely crank brothers ti (with 5 year warranty). Ruddy thing has always creaked.

I'm using a normal freehub with those velospacers

Frame is a voodoo D-jab so uses sliding dropouts

Pretty much all SS setups have this to some extent. You can do all sorts of 'loosen bolts/hit with a rubber hammer' type thing to it but I never bother - just tension in the tightest spot.

what clubber said really, I guess - as long as it's not so slack at the 'slack point' that the chain can come off you'll be ok.

this isnt possible with the uno clubber

Cheers ppl.

Was just worried something was pretty wrong with the setup. How much tension should i have?

firestarter - Member
this isnt possible with the uno clubber

Well if you will use a silly SS-specific chainset that doesn't allow for one of the few adjustments a SS could use then I have no sympathy 😉

How much tension should i have?

Just enough to prevent the chain dropping off 🙂

About 1/2" total movement in the middle of the chain run while in the tighest spot is a decent target. It'll work much looser than that usually if your chainline is good.

I tend to go with a bit of slack at tightest point and as long as the freehub doesn't bind and start turning the wheel when you turn the cranks backwards as a start point.

I've just returned a superstar components sprocket which wasn't central on the freewheel (ie. the hole wasn't centred on the sprocket). Causing a similar problem and throwing the chain all the time.

It's not likely the Uno is oval IME, but nothing is perfect.

It is possible you have a slightly bent BB spindle though. Crank Bros products are prettier than they perform.

Axle not being square in sliding drop-outs might also contribute...

Most likely your chainring is eccentric on your cranks,
Sheldon Brown has a good method for balancing it out:

1. Position wheel and cranks so chain is at its most taut.
2. Loosen chainring bolts slightly.
3. Hit chain with a hammer, so it'll go slack.
4. Spin cranks round and repeatedly hit the chain unitl its the same slack/tautness all the way round.
5. Tighten chainring bolts, tighten chain.

Job done.

I did exaclty the same thing on my D-Jab last night

ir-bandito - the uno is a combined spider and chainring - there's nothing that can be loosened.

Actually I had this with a Middleburn spider on XTR cranks. Thought it was the BB axle but a new BB proved no better.

Good job its British Engineering eh?

*googles middleburn uno*
*recommends other posters do likewise*

so i guess that only leaves the BB or rear wheel, something isnt straight. How tight is tight? are you just being over picky?

ah. that's a bit of a sh!tter then.
I guess the next possibilty is the cog is eccentric on the hub. and I've not got a clue waht you can do about that.

Probably being picky. I moved the dropouts further in because it was crazy tight.

There's no chance of the chain falling off

I'm just a bit of a perfectionist. I'll get the expert tollah to look at it when i see him next

Strange one this. My fixed road bike set up has a tight spot. Don't like it but it's not a major issue.

My UNO/Royce bb/Surly MTB set up is amazingly free. No tight spots and minmal friction. Engineering loveliness.

I would suspect the parts in this order:

Chainring (you're stuffed!)
Sprocket (try another?)
BB axle
Rear freehub
Cranks (you're stuffed!)

Keep us posted!

Thouht it was just chain slack, as the bottam of the chain is under less pressure than the top!!

Then again I dont have the problem using WI freewheels just the cog spacer kits.

If you don't sort it you could use old style CX chain guides either side of the sprocket. I find when mine gets loose and drops off it stays on the freewheel ok until the chain is right off. Its bouncing of the chain wheel. Chain gides do stop this to a great extent.

Mmmmm... nice suggestion Matt! I'm hoping I can sort my chain dropping by replacing the SRAM chain, but a couple of guides wouldn't hurt and would look cool as well 8)

13thfloormonk - Member
...I'm hoping I can sort my chain dropping by replacing the SRAM chain

You're not using a derailleur chain by any chance? Their strong selling point is that they are designed to drop off sprockets easily (rely on the derailleurs to keep them in place).

Nah, a 1/8th PC1. Still dubious as to whats causing it, if a KMC 1/8th chain doesn't sort it I'll go KMC 3/32

I had many issues with a 1/8th set up, including the chain jumping off under load.

Since swapped to a [b]SRAM[/b] 3/32 chain, UNO, Surly and it's [i]flawless.[/i]

Hmm... sorry for the resurrection, just been out today with my new 1/8th KMC chain, and it was perfect. Actually slackened off a bit over the ride, maybe just bedding in or maybe not as stretchproof as they claim, but either way, it didn't drop once, and the SRAM PC-1 would have been off countless times the way I was riding today.

Obviously not conclusive in light of 69er's ^ post, but I'll be sticking to KMC from now on!