Commuting - Chain Stretch Help...
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09-05-06, 07:53 AM
So I've read here time and again that fixed gears are the lowest maintenance of all of the bikes out there. Nothing to adjust, just a little oil on the chain...etc... Well, that leads to my question. My fixie has needed to be adjusted several times for a loose chain, I even dropped the chain yesterday which scared the beejesus out of me. How often should one make this adjustment? Is my chain cheap or is this normal on a fixie? Any advice is appreciated.
Chains don't actually "stretch" per se...the teeth on your chainrings wear, as does the metal on the chain. How old is everything, and is the chain the appropriate size for whatever chainring/cog you're using? A converted bike may have 9 speed chainrings, but perhaps a purchased chain intended for fixed gear use, or vice-versa.
I'm going to assume, for starters, that you have a bike with horizontal dropouts and that the chain has been "pulled" correctly by setting the rear wheel at the appropriate point in said dropouts. (Not trying to talk to you like you don't know anything Dave...I know you've been a regular on this board...just trying to cover everything.)
Is your front chainring ramped? If this fixie was converted, a ramped chainring could be part of your problem.
Chain drop is almost invariably due to a bad chainline, and if that is paired with a ramped chainring...yikes! That's a recipe for drop right there.
An option to look into, though probably not ideal for you, is a tensioner along the lines of a Surly Singulator, or you could even set a derailleur back there with the limit screws locked in place to tension the chain for you.
09-05-06, 08:26 AM
do you mean the surly tuggnut? no spring-loaded chain tensioner like the singleator or derailleur will help with chain drop on a fixed-gear bike and if you rely on them for chain tension you will probably hurt yourself. Single-speed, yes, fixed gear, no.
chain drop could also be due to your axle creeping forward. make sure you use good locknuts and tighten them down well.
if you have track ends, you can use the tuggnut to pull your axle back and thus your chain taut. You may be also able to use it on horizontal dropouts (front-facing), but I'd check with the folks down in FG/SS.
I had a lot of skipping problems when I was running a shimano biopace ring. Now that I switched to a non-ramped round ring, and new locknuts, no problems.
09-05-06, 08:37 AM
If you're having consistent chain tension problems, then you need to attack the base-most questions first:
1) Do you have (near) horizontal dropouts?
** If not, then you need to look at either a chain-tensioner or an ENO Eccentric hub.
2) Is your chainline straight?
** Dropping a chain is a rare thing on a straight chainline. Check those measurements!
3) Worn chainring/cog teeth?
** Manky lookin' teeth will cause skippage, which can lead to a drop.
4) Tight axle nuts?
** I'm assuming you're running a track-nut rear axle, and not an FG conversion on a QR axle.
5) Proper chain size?
** You can run a 1/8" chain on 3/32" gear, but not vice-versa.
6) Chain "stretch."
** Put a ruler with the first mark on the center of a pin. The 12" mark should be on a pin center as well. More than 1/16" off that center mark, and it's time for a new chain. (I go with 1/8" on a geared bike, because of derailleur compensation for some extra 'stretch.' Fixies are less forgiving in that manner.)
09-05-06, 09:25 AM
i don't care what you want to call it, but all new chains "stretch" a little while breaking in.
once your chain breaks in it should be good to go and you shouldn't have to make anymore adjustments till you have to replace that thing.
unless you got one of the other problems mentioned above anyway...
on my fixie i typically just check the chain tension to make sure things haven't gotten slack for some reason everytime i go ride. all you have to do is wiggle the chain around and look for more play than you usually have.
especially riding fixed i recommend you check your chain often for strectch! with one of these...
i have had a chain completely wear out on me in 3 months before! skidding and general fixedgear trickery is hard on chains.
09-05-06, 10:07 AM
I'll look closer at these different options when I get home tonight. I have horizontal drops. The chain line is straight as the shop told me a month or so ago that it wasn't and put in a shorter bottom bracket to compensate. So the chainline was done by the shop. What I notice is that it will be good and tight for awhile but eventually when I apply reverse pressure on the pedals it feels as if I am catching a little bit of slack before the pressure starts to work. So I take off the bolts, pull the tire back further, make sure it is straight, and retighten bolts Sheldon Brown style. It is a fixed gear conversion with nuts but what is the difference between that and a track nut? Maybe it is slippage. Thanks for all the responses, you are helping to narrow the problem down here...keep it coming. Thanks, Dave
09-05-06, 02:03 PM
if there's a gap between forward pedalling and backpedalling, then you can probably tighten your chain and nuts a bit more.
The way you describe the nut tightening (haha) doesn't sound quite right. Here's what I learned from SS/FG forum: pull wheel back by the non-drive side until it is reasonably tensioned, tighten non-drive side nut (your wheel should angle a bit towards the non-drive side at this point). center wheel (i.e.: push towards drive side), tighten drive side nut, and if all's kosher, retighten both sides. With trial and error, you'll find out how much deflection to the non-drive side you'll need to achieve good tension. My basic rule of thumb is to give the wheel a little push--it should keep going at least one or two revolutions. If it stops faster than that, the chain's probably too tight.
With my old wheel, a cheap suzue jr build, I had problems with the nut slipping forward on tightening, so you might want to check that and maybe invest in some new axle nuts.
Sounds like slippage to me, whatever the cause, anyways.
09-06-06, 05:08 AM
If you are running cheapo $6-$10 chains they will "stretch" rather fast. I was adjusting my chain tension on a weekly basis before I finally decided to splurge on a good chain. Now I adjust only rarely. You may just have a cheapo chain.
09-06-06, 06:00 AM
Sounds like slippage to me.
maybe but then your wheel would be off center again cause only your driveside is gonna slip.
if the chain is loosening and the wheel is staying centered in the drops chain "stretch" is really all it could be right?
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