Measuring chain tension for singlespeed, how?

Apologies for bimbo question but am unsure of how taught the chain needs to be. I came across mention of being able to lift up chain half an inch at the mid-way point, is this correct?

I do use a chain tensioner but feel chain may have become a little slack due to muddy trails. Obviously don’t want to over-tighten either.

As always, thank you. 🙂

what you said is fine, if the chainline is good you can get away with a slacker chain as well – it won;t derail as easily.

~10mm/half inch is probably about right, as long as there’s some movement so it’s not under tension and not so slack that it falls off or rattles it’ll be fine.

Thanks for replies. 8)

Also worth checking it with the crank in a few different positions: mine has definite ‘tighter’ spot (ie where the chainring is a tiny bit further forward relative to the rest of the time) so I get my chain tight-ish in the tight patch so it’s not too waggy in the ‘slack’ patch. (my crank is an xt so I am assuming it is the cruddy old no-name chainring at fault)…

does this mean you’re out and about riding again? 😀

I always thought the half inch of slack related to motorbikes where the chain tension will vary as the suspension moves. With bicycles I’ve always set the tension as tight as it will go with the pedals still able to turn freely. Bike frames are relatively flexible things and if you look at the lower chain run when you’re really leaning on the pedals you’ll see it sag quite noticably.

julian – thanks for that, will check.

hey phil – how are you? I’m pootling but had an off last week in a slippery gully, landed on my bad side with the haematoma! More bruises to add to the collection. 😳

Still waiting on date for op though and trying to WTFU. 😉

i’m good, hungry… but good.

bruises are good, they encourage blood flow to the area….*

*i am not a doctor

I do it by feel but the inch thing would be about right – this is with horizontal track ends. On my mtb I use a tensioner and a halflink* chain and I normally make sure it is 1 or 2 links longer than the minimum to give me some room to repair in case it snaps (which it did last week!)

*initially had chainwrap issues, standard chain didn’t work and I’ve never tried again so I always buy halflinks now to save faff.

Are you using a Singlespeed specific chain? If you are you can get away with more slack as they don’t want to derail, I run mine with a little bit of visible sag in the chain when looking at the top of the chainring to sprocket and its fine, I’d say 3/4 inch

I have a Deore chainring on my Soloist, but find that if I have much more than 10mm, I get the chain rolling off the chainrings. Maybe I should invest a SS-specific chainring…

Wee update – have been twiddling and reckon all’s OK. 8)

However, chain is single speed specific (Sram PC1) but doesn’t appear to have a power link. Am confused as to what needs to be done if chain breaks, not that it has so far.

Also, how often does an ss chain need replacing?

Thanks. 🙂

half inch deflection at the slackest point – chainrings are not round or perfectly centred, so this can take up the slack.

Replacement is when the chain checker says >75%. Not that often to be honest.

Hmmm i have a SRAM singlespeed chain (not sure of specific model) but it came with a powerlink so unless they do a range of singlespeed chains (mine was a cheapy) then i’d imagine a link will work.

From memory the SS Powerlinks are different to the 8/9/10 spd ones and just look like a standard link. Both the pins are attached to one of the side plates and the link is opened by flexing the 2 pins together. You can tell which one it is as the pins don’t have dimples in. I’ve only ever been able to get them apart with those Park Tools Powerlink plier things though.

I hope that makes some sense!

c-g,

The PC1 chain uses a 2 Piece Snap-Lock instead of the symmetrical quicklinks on 7-10 speed chains.
You would need to source a spare for trailside repair as well as a couple of spare links.

If your drive train has a 3/32″ sprocket and 7/8/9/10 speed chainring (basically not 1/8″), then I would buy one of these KMC Rustbuster chains for £6 which come with a 2 or 3 piece link but can use regular 8-speed quicklinks:

http://www.chainreactioncycles.com/Models.aspx?ModelID=25653

PaulD

Thanks again for useful info. 🙂

Chain came off yesterday, it had been hitting the chainstay and looked a little too slack. Increased tension but doesn’t appear to have made any difference, barely able to increase any more.

Might need to investigate whether chain has stretched but think as a first step I will remove chain tensioner, give it a clean and try again.

Maybe put a half link in there to regain some tension?

Do you happen to have a loose chainring bolt?

Chainring bolt? Good call, will have a look at that.

Do singlespeed-specific chains stretch?

it had been hitting the chainstay and looked a little too slack

If it was hitting the chainstay, I should say so!

DrP

I speak from recent experience. My chain was falling off my singlespeed, repeatedly. Faffed around for ages before I noticed that my chainring bolt was loose.

And by loose, I mean about half a mile down the trail, lost forever.

All chains will stretch a bit, but given that a singlespeed chain is probably a lot burlier than a flexy geared-bike chain, I doubt it’d stretch enough to matter. I’ve certainly never noticed it happening much with the SRAM shopper-bike chains I tend to use.

The chain does not stretch, it just wears away.
That is the link pins (rivets) wear by abrasion.
All cycle chains use a hardened chrome steel rivet that will rust.
You have approx 100 of these, so if each wears 2/1000 inch that equals an extra 0.2″ chainlength, or nearly half a ‘link’.

It is recommended to change the chain before 1% extension, which is only 0.5″ on the whole length, or just 5/1000″ wear in each link.

Wear is faster on a derailleur geared bike because of the lateral bending that constantly moves grit through the link.

This is why a wax lube is the best, it keeps the muck out and is flexible.

So for the best life on a SS, I recommend the KMC Z610RB Rustbuster Singlespeed in 3/32″ width at £6 delivered from CRC.

Go on, spoil yourself.

PaulD

PaulD – Member
…for the best life on a SS, I recommend the KMC Z610RB Rustbuster Singlespeed in 3/32″ width at £6 delivered from CRC.

+1

I’ve broken SRAM chains in the past. Haven’t used them since but I haven’t heard they have improved.

That much slack points to something wrong. Loose chainring maybe, but more likely the wheel has moved in the dropout.

What sort of chain adjustment do you have?

Could also be the chainline is not spot on. What rear wheel have you got and how have you space the sprocket?

Do singlespeed-specific chains stretch?

PC1’s do. Well, not technically as above, but they effectively elongate due to increased slack as all chains do over time. PC1’s seem particularly prone in my experience, particularly when new/newish. Over time they seem to settle down into a slightly worn state and don’t get worse as quickly! weird, but it’s happened with several PC1’s with me.

pc1s aren’t as good as they used to be imo. seem to have a lot more play now & need to be tighter to stay put.

kmc are best ime.

http://www.charliethebikemonger.com/kmc-z610-hx-chain-332-41-p.asp

😀

Just back from the workshop aka kitchen. 🙂 It looked as though the slider had slightly dislodged itself. So I’ve removed the wheel, given everything a good clean and put it back together. Chain tension is now as it should be and I’m happy. 8)

Using a Surly Tugg Nut by the way.

Thank you again for suggestions. 🙂