1/8 Chain - Stretch or What?

[токамак]

So I've been riding with this SRAM PC1 chain since January - 1190 miles so far, and I've broken it (intentionally with quick-link and then chain-tool) to fit a couple of different sprocket sizes. I have my chain fairly taut - YACF regulation non-slack, but not overly-taut either, except that in the last month where I've used these different sized sprockets the wheel position has ended up right at the front of my forward facing drop-outs - so I've pulled the wheel back extra hard to make sure I get a good purchase on the drop-outs with the track nuts.
Last week I decide to go back to the original sprocket I had started out with, but now I can't adjust the chain to make it a good fit - either chain way too slack and no more room in drop-out, or wheel not fitting into drop-out enough to be safe - the minimum 2 links making the difference.
I can only assume that my chain has stretched, but I am surprised by the amount and in just over 6 months. Has anyone else experienced this?

[Ian H]

You've got short, Campag-style drop-outs that only have 25mm or so of adjustment. You need a half-link.

[токамак]

They're actually Gipiemme drop-outs - and certainly shorter than some Campag ones I've seen. I might try these half links you mention. I was surprised though because not long ago I could get the wheel in a good position with this given sprocket and chain.

[bobb]

You've got short, Campag-style drop-outs that only have 25mm or so of adjustment. You need a half-link.

<pedant>He has medium 30mm Gipiemme dropouts </pedant>

Edit: Not quick enough!

[Greenbank]

<pendant>

Irony (or not).

[bobb]

Whatever.

[токамак]

Greenbank, I know you're an experienced Audaxer and fixed wheel rider - got any useful observations you could add to this thread?

[MSeries]

Fit a new chain and you'll be back to where you started,no ?

[токамак]

Yeah - I've got a spare (new) chain and I'll be putting it on for the Dun Run in a couple of weeks - for now I've just stuck with a smaller sprocket and shorter chain.

[Greenbank]

Greenbank, I know you're an experienced Audaxer and fixed wheel rider - got any useful observations you could add to this thread?

Haven't ever had a problem. I use SRAM PC1N chains and only have 25mm or so of dropout to play with (zoom in on this pic: http://www.greenbank.org/bikes/tempo/tempo6.jpg ) but that's more than enough.

Previous PC1-N did about 5000km before it became too stretched and I replaced it. Current one has 2692km on it and no hint of stretch.

Taking one complete link out will shorten the chain by 25.4mm but it'll only move the wheel back/forwards 12.7mm.

I wouldn't think a half link is necessary, and half-links are more prone to stretch anyway.

If I did need to use my bail-out 18T sprocket (67" gear instead of the usual 71") then I may have to remove a link from the chain, but that's why I carry a chain-tool (and some spare links should I screw it up) with me at all times, and the extra faff stops me using the bail-out gear.

[Ian H]

I've run fixed bikes with short, long and track drop-outs. You're definitely restricted with the short ones. If you have just the right size ring and sprocket you'll get adjustment from new at the front of the drop-out to worn at the back. It might only be a matter of one tooth — a half-link is the equivalent.

[bobb]

Going back to the OP - the chain sat nicely mid-dropout in a combination of X x Y. A couple of links were added to accommodate a larger sprocket.

Once larger sprocket was no longer needed, the exact same links were taken out. Wheel didn't fit in the same place.

The OP wasn't about half links or drop out length, more to do with WTF? Do fixed use chains really stretch that much in a short period of time?

*Not trying to hijack* 

[Ian H]

Going back to the OP - the chain sat nicely mid-dropout in a combination of X x Y. A couple of links were added to accommodate a larger sprocket.

Once larger sprocket was no longer needed, the exact same links were taken out. Wheel didn't fit in the same place.

The OP wasn't about half links or drop out length, more to do with WTF? Do fixed use chains really stretch that much in a short period of time?

*Not trying to hijack* 

I think he did mention over-tightening at one point.

[токамак]

Hmmm, wondering if I've stretched the chain from running it very tight just recently? I certainly haven't put the miles into it that Greenbank quoted for his setup. In this picture you see my original setup (January) - wheel fairly far back in the drop-out, chain nice and taut:


Now though using the same chain and sprocket the wheel is either right at the back of the drop-out, and the chain too slack, or, I remove two links and then the wheel is too far forward to be stable.

Do fixed use chains really stretch that much in a short period of time?

This is what I wanted to enquire about - in Greenbanks experience they do not. Perhaps I have over-tightened when I should have used a half link...?

[Ian H]

Judging from the photo you've got very little adjustment left. Try it: it takes very little forward adjustment to produce a very baggy chain.

[Greenbank]

1/16" wear on 12 links (which most people use as a sign for replacement) would be about 1/4" total stretch on a 48 link chain (I counted the links in the photo of mine).

A 6.35mm elongation would mean the wheel would move 3.18mm back.

[rogerzilla]

My KMC/Wipperman Anti-rust chain hasn't stretched at all, despite being run through a very wet winter with minimal maintenance.  It only cost about six quid too.

[Deano]

I've got vertical dropouts on my fixie (slightly filed back to allow some adjustment).  A chain lasts about 1500 miles at the most, and that is at the risk of a disturbingly slack chain.

I've used a Wippermann anti-rust star chain and cheap Sachs PC-48 chains.  It didn't make any difference.

[Fixedwheelnut]

 I have lifted my report on Izumi chain I'll repost it in accessory section.


 Izumi V Supertough 1/8th chain clicky linky here

I have used these chains on most of my fixies and have been very impressed with them, and after approx 10,000 miles on my Ron Cooper I have just had to change one for the first time.

 The drive chain has got through three chainrings and three sprockets, poss four as I have changed the wheel round a few times, and one chain

 Across the twelve links I had 3/16th" wear, over the full 100 link length of the chain I had approx an extra link in stretch/wear

 The screw and nut connection works well and also means it can be removed easily for thorough cleaning as and when required. I must admit I was a bit dubious of this at first and constantly checked it to make sure it was tight but it has  been fine 

[cometworm]

I'm going to resurrect this thread as I've got a similar problem. I bought a bike in May which I have been running as a singlespeed since then, not doing a huge amount of miles - less than 1000 miles in total. When I came to fit the fixed sprocket today the chain doesn't really fit properly.

Have I accidentally bought a 3/32 sprocket, and am thus being a complete div, or is it possible that I've worn out the chain by running it too tight? The weird clunking sounds I assumed to be caused by a slack chain could have been from an overly tight chain? The situation certainly resembles the "old chain on new sprocket" picture on Sheldon Brown's page.

[rogerzilla]

A 1/8" chain goes onto a 3/32" sprocket, no problem.  I suspect your chain is stretched.  To measure it, it should be clean (otherwise the gunk fills the gaps round the pins that are actually causing the apparent stretch) and hanging freely.

[cometworm]

Thanks, that's the conclusion I'm coming too as well - there will be a trip to the bikeshop to clean/service/shop...