[Closed] Single speed problem, Help needed.

looks like you've got a lot of chain, it would give a better wrap around the rear cog to shorten the chain and get a tensioner to push up. it'll make it more secure and less likely to go for a wander under pressure

Can't really see the chainline well from the photos. Couple of other suggestions though?

Can you get any more links out of the chain?

Can you try a different tensioner with a stronger spring?

What gearing are you running? If it is 32:14 for example, you would be better with 34:15 instead, which would give a similar gearing, but more chain wraparound.

yeah I know the chain line isn't too visible, I'll try get a better chain line picture tomorrow.
I cant take any more links out of the chain because if I take 1 link out(well 2, but you know what I mean I hope) then its too short to be even run without a tensioner.

The tensioners an old derailleur which I have modified and the spring is really quite tight.

Im running 32:16

You haven't got much wrap there, and the tension set up is worsening it by pushing the chain away from the cog. I think it's as simple as that.

Shorten the chain and fit a half-link (or link and a half) and fit a tensioner that pushes up for more chain wrap.

32:16 should be okay for chainwrap, but you could try 32:17. If you can't get a full link out, you could try a half link.

So basically its because there isn't enough chain wrap?
For what reason would it jump to one side but not the other though?

Hard to say why it went to one side, it's only done that once though right?
The converted mech if that's what it is might have been the cause.
Also is the cog a singlespeed specific one, the piccy is small but the teeth look very pointed...that might be my eyes though.
Going back to my first point though, tension up is way better. I have ridden a few conversions with some very 'careless' chainlines with no issues at all.

I doubt its the chain wrap thats a problem, is the chain the same age as the sprockets?

Its a single speed specific cog, a superstar one.
And ah right I see, I did modify the derailleur so it pushed up but I couldnt shorten the chain enough for it to actually tension the chain. So looks like I'll need a [url= http://superstar.tibolts.co.uk/product_info.php?cPath=58&products_id=269 ]one of these [/url] and [url= http://www.winstanleysbmx.com/product/22601/Gusset_Slink_HalfLink_Chain_Links ]this[/url]

[i]mollyiom[/i] Thinking about it, pretty much. Chains done about 50 miles, the cogs done under 100.

I'd say it's about wrap around.

I'd just use an old rear mech (complete).

Plenty chain wrap there. My money is on the tensioner flexing when you're putting lots of power into it. I'd try one of the gusset type fixed tensioners instead.

R.lepecha
My first inbred one of the year 2000 models had horizontal drop outs, it didn't take much movement of the wheel or stretching of the chain to get it jumping off.

right so fixed tensioner needed.

My money is on the tensioner flexing when you're putting lots of power into it. I'd try one of the gusset type fixed tensioners instead.

Utter guff.

Why on earth would a tensioner fixed to the frame flex? All is does is try to keep the chain in tension.

I'm really actually confused why I cant manage to get a link out of the chain because it looks like there's loads of it :S
Maybe there isn't loads of it, it a trick of the mind?

The tension is only in the top of the chain. The bottom is just feeding onto the sprocket. Banging around on a srung tensioner may accentuate the problem but yours is a [b]chainwrap issue[/b]. Your set up does look cack, it would probably be cured by a Gusset style fixed tensioner and a proper length chain.

The skinny sprocket probably isn't helping. Ideally you want nothing to move. I'd recommend 3/32 chain, 3/32 Surly sprockets. 1/8th is overkill and does have its own issues.

1/8 rules IME, as long as your tensioner can cope.

The skinny sprocket probably isn't helping. Ideally you want nothing to move. I'd recommend 3/32 chain, 3/32 Surly sprockets. 1/8th is overkill and does have its own issues.

I can see it's a 3/32 chain, but beware overly skinny sprockets, I've had probs in the past with a thin trials one.

Also had trouble with a large s/s 29er set up, I thought initially as a result of a big bendy steel frame. Was running 1/8 Middleburn Uno & Surly set up and when going full beans it would (sometmes) jump.

This twisted my melon for a while as I could see reason for the problems, but on the advice of Singlespeedstu I changed to a 3/32 Uno ring, Sram chain and Surly 3/32 = no problems at all. Bizarre but true.

And that ^^^^^ was with slidey dropouts, no tensioner.

I had a similar problem and I found out it was a chain wrap issue.

I tried to use a up rather than down tension as that gives you more chain wrap. Was ok but the besto solution was a half link to get a shorter chain. If you can remove a whole link, try that, if not try a half link.

Looking at the rear pic, I'd say you probably have to move the cog out 1 spacer.

Your front ring is probably about 48mm from centre depending on your BB and crank (check this). This means that your rear cog should be around 17 or 18mm from the dropout (and check this). To me it looks more, but I may be wrong.

Your front ring is probably about 48mm from centre depending on your BB and crank (check this). This means that your rear cog should be around 17 or 18mm from the dropout (and check this). To me it looks more, but I may be wrong.

yes its 48mm on the front, I did all that working out when I bought that crank because it was one of the only ones that runs on a 113mm Octalink BB, so it wants to be 17 or 18mm from the drop out?

Going on the http://www.sheldonbrown.com/chainline.html
article, it should be 19.5mm from the drop out I think. Rear chain line minus front chain line gives me 19.5mm.

Sorry, that's right. Small hours brain fade 🙂

Anyhow, what I was saying was to measure it to check, and as you have done so, that's not the problem.

Looks like you better change to pushing up and shorten the chain - just a bit more of a PITA when you drop the wheel.

BTW what sort of chain is it? Maybe a single speed specific chain would help (less lateral movement), eg BMX 1/8 or 3/32 depending on your cogs.

Buy a gusset chain tensioner, they are dirt cheap and will solve all your problems even if your chain line is slightly out. I ran one for a while before buying SS specific frames and it was a breeze to use. I simply can't see a bodged rear mech doing the job properly, unless anyone has can tell me otherwise?

Cheers,

Chain line matters little for 3/32 chains.

Rear mechs work very well as tensioners. I used a long cage and ran the chain under the lower cog only (inner cage removed).

[img] [/img]
[img] [/img]
[img] [/img]

I moved the cog over a spacer to centre the chainline a bit more.
You all seem sure on the not enough wrap problem but
[img] [/img]
[img] [/img]

They are run with about the same amount of chain wrap by people on here, with probably no issues?

I went out to test the new chainline, made it worce IMHO. So I've ordered a half link, and I'm going to get a fixed chain tensioner. Job sorted.

Oi, that's my Kona Lava Dome you've pictured there! 😉

I can say that chain-wrap was never a problem for me. A 1/2-link would probably have been better, but it was never an issue for me. I needed a sprung tensioner as the fixed one I tried didn't have quite enough adjustment fo take up the slack.

I haven't read the thread too carefully, but in the first set of pics it looks like the tensioner might not be exactly aligned with the cog. That could cause it to skip under power, but I never had it so badly that it dropped the chain.

EDIT: just thought I'd add that it was a Surly cog and chainring with a SRAM 8spd chain. It never slipped unless the chainline was off.

Are the Gusset Bachelor tensioners OK to push up?