Fixed gear chain tension

[TwoWheelsDC]

Droopy is too loose, but there should be about a half-inch or so of play if you grab chain at the top and move it up and down. Also, too loose is probably better than too tight, since a tight chain will damage your rear hub and cause extra resistance in the drivetrain. If you hold up the rear wheel and spin the pedals, they should spin freely and fairly quietly. Too tight and you’ll notice how quickly the pedals stop and the extra noise.

[OneEighth]

But you want to check the play a multiple spots until you find the tight spot on the chain where there is less play and make sure that it does not bind at that spot. Just like a motorcycle.

[Harry Meatmotor]

@OneEighth 99605 wrote:

But you want to check the play a multiple spots until you find the tight spot on the chain where there is less play and make sure that it does not bind at that spot. Just like a motorcycle.

Chain rings (when mounted on a the crank) are usually slightly eccentric. One way of fixing this goes like this:

1) set the chain tension to be no tighter than to allow 0.5″ to 0.75″ of vertical play in the chain, measured halfway down the chainstay
2) loosen all the chainring bolts, but not loose enough that the chainring becomes loose – about 1/2 to a single turn on each bolt
3) using the handle of a hammer, and while turning the cranks, tap the chain mid-chainstay
4) you’ll see where the eccentricity of the chainring/crank is because the chain play will decrease as you spin the cranks – tap the chain when it tightens to pull the chainring closer to the rear hub
5) once you’ve centered the chainring on the crank (i.e. chain play is constant through an entire pedal stroke) retighten the chainring bolts and double check the chain tension by moving the hub in the dropouts

One other trick is to walk the hub backward in the dropouts by only pulling the wheel towards the driveside/nondriveside at a time. for example, loosen the driveside hub nut and grab the rim near the chainstay, pulling it towards the chainstay. then tighten the driveside hub nut. then loosen the nondriveside hub nut and grab the rim near the nondriveside chainstay and pull it back to center between the chainstays. do this several times until there’s proper chain tension and the the rim is centered between both the chainstays and seatstays.

[jrenaut]

Man, I thought fixed gear was supposed to be simple.

The one side at a time thing sounds doable, though. Thanks, all, for the help.

[Harry Meatmotor]

@jrenaut 99634 wrote:

Man, I thought fixed gear was supposed to be simple.

The one side at a time thing sounds doable, though. Thanks, all, for the help.

honestly, the only time i ever really worry about chainring eccentricity is on actual track bikes (that are actually going to be raced on a track), and it’s more for smooth pedal feel through the pedals than anything else. wonky chainrings are noticeable at high power/high cadence. on anything else fixed-gear, leaving the chain on the looser side if things will tolerate any chainring eccentricity and is a lot less hassle.

[Bruno Moore]

The “one side at a time” trick is the one I use. One thing I’ve found when checking fixie chain tension is that listening to the chain can be more helpful than looking at it—there’s a certain sound that overtightened chains make that’s pretty easy to hear, but hard to see while it’s moving. Maybe it’s just me, but visual cues always seem debatable and never quite clear, while getting the bike to “sound right” is much less ambiguous.

[jabberwocky]

I never worried about slight chainring eccentricity on my fixies. Just check the tension at 90 degree rotations and make sure it isn’t too tight and you should be good. The chain doesn’t need to be super precisely tight. You want a small bit of play (it shouldn’t be under tension on the stand). Just make sure it isn’t loose enough to come off. Fixies throwing a chain is sort of unfun.

[jrenaut]

I noticed that mine was loose when I was slowing without the brake – there was a funny “hop” in the pedal when I was getting slack in the chain rather than slowing the bike. I’m on the cargo bike with the kids today, but hope to maybe sneak out somewhere on the fixie this weekend…

[vvill]

I go by the 0.5 to 0.75 inch loose rule although I’m not super strict on policing my bike set up regarding chainline, tension, etc (I have a dixed cog after all). I usually only look to adjust stuff if it feels/sounds off.

Chain stretch means you’ll have to pull the wheel back a bit every now and then. I do the one side at a time thing too. Both my FG + SS have fairly new chains right now so they sound pretty quiet but I did have to re-tension the FG’s chain a few weeks ago.

[TwoWheelsDC]

@jrenaut 99648 wrote:

I noticed that mine was loose when I was slowing without the brake – there was a funny “hop” in the pedal when I was getting slack in the chain rather than slowing the bike. I’m on the cargo bike with the kids today, but hope to maybe sneak out somewhere on the fixie this weekend…

Sounds maybe borderline too loose…but really, short of the chain popping off (too loose) or binding your drivetrain (too tight), it’s mostly personal preference. I prefer to stay on the tighter side, but my rear cog isn’t perfectly round (pretty sure it’s the cog and not my Omnium ring) so there is a slight bit of tension variance throughout the rotation…so I just set the tension based on the tightest section and I’m good to go.

[Steve O]

I’m thinking mine might be a bit on the loose side. I was coming down the hill after crossing the Roosevelt Bridge into VA and using backpressure to slow. My chain popped right off. At first I thought I had broken it, except I think that’s almost impossible.

It looks pretty good, though.

[ATTACH=CONFIG]20339[/ATTACH][ATTACH=CONFIG]20340[/ATTACH]

[huskerdont]

@Steve O 192779 wrote:

I’m thinking mine might be a bit on the loose side. I was coming down the hill after crossing the Roosevelt Bridge into VA and using backpressure to slow. My chain popped right off. At first I thought I had broken it, except I think that’s almost impossible.

It looks pretty good, though.

[ATTACH=CONFIG]20339[/ATTACH][ATTACH=CONFIG]20340[/ATTACH]

Interesting, I had mentioned on your strava ride that it might be loose, but it doesn’t really look it. I suppose it could be from a worn chain or ring, or maybe a bit of debris getting between the chain and ring.

I put a Surley Tugnut on my old fixie that pretty much stopped the loosening from happening. Unfortunately, my State has the same setup as yours, and I’ve bent the little understrength screws they’ve put in the frame to keep it from happening to the point that when I need to fix a flat, it has become difficult to unscrew. (Really need to replace those stupid screws before I forget.)

[OneEighth]

+1 for Surly tugnuts

[drevil]

@OneEighth 192783 wrote:

+1 for Surly tugnuts

Surly Tugnuts are nice, but expensive ($30). If you don’t need a bottle opener, consider simpler ones that work just as well, like the Redline ones which are ~1/4 the price ($15/pair) and come in different colors:
[ATTACH=CONFIG]20341[/ATTACH]

Whatever you get, avoid the ones that have 2 smaller bolts like the Spot Rocket Tensioner. They’re a PITA.

[josh]

@Steve O 192779 wrote:

I’m thinking mine might be a bit on the loose side. I was coming down the hill after crossing the Roosevelt Bridge into VA and using backpressure to slow. My chain popped right off. At first I thought I had broken it, except I think that’s almost impossible.

It looks pretty good, though.

[ATTACH=CONFIG]20339[/ATTACH][ATTACH=CONFIG]20340[/ATTACH]

You gotta have the track slack! But yeah I’ve crashed going over a bump and my chain popped off when I had a little too much slack.

[Author]

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