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Chainstretch(15 posts)

ChainstretchChrisK
Dec 9, 2002 5:32 AM
I have very recently converted a caad4 frame to fixed gear.
With the limitations of the vertical dropouts I have had to use a 38/14 but I now have a very tight chain. It is rideable but very tight. My question is, how long does a chain take to stretch, even the small amount required in my case. I have never really noticed chainstretch when riding a geared bike as it doesn't make much difference. I don't want to change the chainring and sprocket only for the chain to stretch and then get too loose. My own fault for trying to use a vertical dropout frame I suppose!
re: ChainstretchDave Hickey
Dec 9, 2002 7:07 AM
The chain is not supposed to stretch. Over on the single speed site of MBR, they talk about 1/2 length chain links. I've never tried it but it might give you the correct tension. Another option would be to install a 13T rear. That will give you an additional 1/8". As a last resort, you might be able to file down the front of the dropouts but I don't recommend it. It might make them too weak.
I worry more about chain sway ...Humma Hah
Dec 9, 2002 9:08 AM
... Chain stretch IS important on a gearie, because it wears the corncob. If you let the chain stretch badly, when you put a new one on, it will probably skip on the worn cogs.

On a singlespeed, I usually replace a chain long before the stretch gets noticable, because I don't like the chain to flex much side to side. When a chain gets wiggly, it's more likely to hop a cog and come off.
Cannondale?LC
Dec 9, 2002 10:03 AM
I got an old CAAD2 frame laying around that I would like to try as a SS but with the vertical dropouts I figured it was hopeless. What size frame are using and what gear combos did you try before ending up with 38/14?

BTW chains don't really stretch, but rather wear at the bushings and elongate. I have never seen any measureable difference before about 700 miles, but if the chain is really tight it might wear faster.
Cannondale?ChrisK
Dec 9, 2002 10:25 AM
As long as you know, or can measure the chainstay length very accurately you can use the following site to give you the range of gear ratios that will ensure the chain is tight enough;
http://www.peak.org/~fixin/
Unfortunately I went very slightly under rather than slightly over so the answer for me is to probably buy another ring and sprocket
Cannondale?granola82
Dec 12, 2002 7:44 AM
I converted my old Caad2 over to single speed for commuting/bad weather and I haven't had a problem with it yet. I'm running a 42/12 on a size 54 frame and I managed to get the chain tension just right by taking out a few links...the key is to get the chain straight.
I got a lot of help/advice from the harris cyclery page...lots of good articles and helpful stuff.
42x12?LC
Dec 12, 2002 10:41 AM
I am not strong enough to push that gear on anything but a flat road :( What did you figure for the chainstay length and what would be the next increment? I got 39, 40, 42, and 50T chainrings along with just about every size cog.
re: Chainstretchfixedgearhead
Dec 9, 2002 11:26 AM
The other issue of a to tight chain is excessive bearing wear. You will wear out the cogs and chainwheel also. All my bikes have some slack in the chain and have never had either problem. I do know of a guy who wore out his bottom bracket because he thought that he should have the chain tight so that it didn't jump off. It really has to be loose to jump off. Probably more than 3/4 inch at the middle of the chain span. Loosen that chain up and save all the other components.

fixedgearhead
perhaps a chain tensionerTig
Dec 9, 2002 1:10 PM
If I had the same problem, I'd just add a few links of chain and bolt a chain tensioner to the unused rear derailleur bracket. Problem fixed! (no pun intended) The Surly Singleator looks like a good one, but I haven't heard any good or bad opinions yet.
this Soulcraft one looks even betterTig
Dec 9, 2002 1:19 PM
From ExcelSports.com:
This tensioner is different than others on the market mainly because it locks the tension in. Rather than rely on a spring to give chain tension, which can allow your chain to bounce around, The Convert solves the problem of chain drop. When you need to take your wheel out, depress the Lock Lever and The Convert becomes free-floating. Soulcraft uses a Roller rather than a pulley wheel because it cradles the chain for quieter movement. Easy to use, simple and better yet, it actually works right.

perhaps a chain tensionerfixedgearhead
Dec 9, 2002 1:24 PM
Never, never, never use a chain tensioner on fixed gear. It will wrap the chain when you backpedal and kill you. Single speed is ok but never fixed. See Sheldon Browns info on this.

fixedgearhead
What about the different method of the Soulcraft model? -nmTig
Dec 9, 2002 2:22 PM
What about the different method of the Soulcraft model? -nmeddie m
Dec 9, 2002 3:39 PM
The Soulcraft chain tensioner will not work with a fixed gear any better than any other tensioner. One thing you could try is the Fix Me Up hub with an eccentric axle that allows a few millimeters of adjustment even with vertical dropouts, but it might be cheaper to find an old steel frame.
What about the different method of the Soulcraft model? -nmfixedgearhead
Dec 9, 2002 3:44 PM
I know that the soulcraft supposedly locks the tensioner in place but the forces at play during backpedaling are so great that I fear that they would overpower the set screw or whatever locks it in place and you would get the dreaded chainwrap which would lock up your rear wheel faster than you could say 911. On a single speed no problem. Not on a fixed. Attempt it at your own risk.

fixedgearhead
Consensus of opinionChrisK
Dec 10, 2002 3:45 AM
I get the feeling that people don't see chainstretch as a potential problem. The easiest and neatest way around this is to purchase a new ring/sprocket combination that will allow for a slightly looser chain. My chainstay length is 15.9 and the combination I was using was for 15.885 which mattered more than I though, but i can use a combination that will give 15.91 which in theory means it should be correct.
Thanks for the replies