How tight should the chain be?
 

I recently completed the conversion of a mountain bike to single speed, using a Surly Fixxer, a freewheel, and a Salsa chainring on a road crank.

I was dismayed to find that with the gear I was using, the chain, while not ridiculously loose, was a bit sloppy, but with two links removed from the chain, it barely fits in the dropout.

Now, you can't really see the chain sagging, but you can flop it up and down with your finger and it feels loose. I have ridden it, though, and it doesn't who any signs of slippage.

I am considering putting a halflink in it.

What do you guys think?

well, to adjust the chain tension properly (without a chain tensioning device such as a surly singulator) you need track ends or horizontal dropouts, not vertical dropouts, which i assume is what your mountain bike has. the chain needs to have just enough slack that its not binding or tight, but not enough slack that it can derail itself. depending on the current tension of the chain a halflink could do the trick.

I run mine just tight enough to not fall off, but then you have to put up with the "nice bike, cap'n slackchain" comments.

No, it doesn't have track dropouts, but it does have horizontal dropouts. They're not long enough, it seems.

Actually, my chain is probably about like that, and so far no problems. Very quiet.

then i would suggest the half link solution. you don't want to run the chain too tight and screw up you bb or hub bearings.

I don't quite understand michaelwlf3's post.

Does he have too long a chain or too short a chain?

For myself, I buy a KMC 610 chain and it comes out of the box way too long.

I put all the parts in place, including the chain and a mid-size sprocket (in my case, 17t), and make note of where I have to break the chain in order to make it a little too long.

I break the chain at a length, where, when I put it on with the master link, I will have some slack.

So, I put on the chain with the master link and look at it and think about it for a full minute.

At that point, I seriously consider whether I can break the chain again and have enough chain to use my sprocket of choice, with the axle halfway between its full travel, aft and forward, in the horizontal dropouts.

If I have any doubts, I don't break it again.

With the chain on the bike, I pull the wheel and axle back until I have no visible slack.

No visible slack.

I tentatively tighten everything down and then I place the pedals in all the clock positions and check the chain for tension throughout the full rotation of the crank.

I look for a half inch up and down (total) without any effort (two fingers mildly pinching the chain and wiggling it).

I spin the crank and feel for a totally liquid movement.

If it doesn't feel totally liquid, and if the wheel and crank won't spin forever without any input from me, I loosen it a hair and try again.

I use a cheap Sugino/SR chainring from Harris Cyclery and I use only EAI cogs because I find them both consistently round.

I have also centered my chainring using the Sheldon Brown method.

In the end, I have a silent chain with no visible slack and no resistance to spinning.

It helps to use chaintugs.

I use two MKS chaintugs and I get silent, liquid movement with no slack.

The no-slack part give me a greater sense of control, especially at very slow speeds.

Your chain should be this tight:

http://www.sosenka.cz/m13.jpg

m.

I'd think that was way too slack for street riding, especially brakeless...

no way, you can ride with even a little more slack than that if you want. if you find the crank position where the chain is the tightest, and set the chain tenion to where its not binding the chain will naturally have more slack in the rest of the crank rotation.

Usually the given rule is a 1/2" of slack.

Dude your bike should be that tight. Not a carbon fetishist but mmmm....

Travsi wrote:

"...you can ride with even a little more slack than that if you want."

Why would a person want any slack, let alone "a little more"?

Some people say chains don't stretch, but, in my limited experience they do stretch when new and then they stabilize.

So, when I put on a new chain, after the first thirty miles or so it gets a little slack in it and I can feel it in in my pedals as delay.
I mean, I can really feel it and I don't like it.
It makes the bike feel vague and sloppy.
So, after 30 miles I tighten it up and it stays that way for a long time.

As I wrote earlier I have centered my chainring and use EAI cogs, and I presently don't have much variance in chain tension during crank rotation.
I have recently ordered a Shimano Biopace chainring from Harris Cyclery and I expect to have some chain tension issues with that chainring; perhaps more than I will tolerate.
Still, I like to experiment.

I set my chain tension so that I can push it about 3/8" of an inch one way or the other. No annoying slack feeling, no undue stress on bearings from too much tension.

As for setting tension without track ends or horizontal dropouts, there's also the Eno Eccentric hub, which is super high quality and a very elegant solution IMO.

If you're not going to use the eccentric hub with vertical drops, then you need this:

http://www.peak.org/~fixin/personal/fmu/php/fixmeup.php

It can't account for chain stretch, but it will get you very close.

i like to set my chain so it doesn't feel wobbly when trackstanding. that is, there's not that half second after your bike stops and before your pedals do.

That reminds me, is the chain usually the main cause of noise or is it the chain line? I've personally never had a problem with noisey chains but have passed people that sound like they're running a freewheel its so loud.

ken cox-
"Why would a person want any slack, let alone "a little more"?"

you should try riding with a bit of slack, the chains runs smoother. thats why you see alot of track bikes (in the velodrome) with quite a bit of slack.

...someone back me up on the slack issue!

Travsi wrote:

"...thats why you see alot of track bikes (in the velodrome) with quite a bit of slack."

I wonder if the serious track racers don't see slack as a way of avoiding even the slightest mechanical drag.

When I adjust my chain I can make it so tight it creates noticeable rotational drag.
As I loosen it, at a certain point I experience a sudden and significant reduction in drag.
At that point, the chain has no visible slack and no delay in forwards/backwards impetus.
If I loosen the chain further I detect no increase in smoothness nor quietness; if further loosening the chain further reduces mechanical drag it does so in such a tiny amount I can't detect it.
I test the chain on the work stand by spinning the rear wheel up to full speed with the pedals and then letting the whole system coast down to a stop.
If I've got it right it spins silently and coasts forever.
Presently, my chain has no visible slack and no noise; it coasts forever; and, it gives me instantaneous braking and feedback.

I ride fixed for the control and precision and not for the speed.
I like the "steamroller" sensation and I lose that with a slack chain.
Perhaps if I raced at a velodrome I would put some slack in my chain.

hmm, how do you know w/out dsetroying them?

ken cox-
"I wonder if the serious track racers don't see slack as a way of avoiding even the slightest mechanical drag."

i'm not sure, but that seems like a plauseable reason...

i also use the same approximate process as you (ken), but i usually spend less time and would rather have more slack so i'm sure there is no binding. and i know what you're talking about when refered to the endless "coasting" of the drivetrain. a problem i have though, is the slight un-roundness of the chainring/cog that gives more slack in some areas of the rotation. i guess i could try sheldon's chain bolt loosening/chain-taping thing...


******bagonwhlz-
"hmm, how do you know w/out dsetroying them?"

if the chain is tight, real tight, it applies uneven and possibly destructive stress to the hub and bb bearings. you can usually hear and feel a clicking-type noise when the chain is too tight.

with a slightly oblong chainring, where the chain goes from slack to tight, which is preferable - to er on the side of slack or tight? my chain likes to go from either zero slack to 1/2" slack or with the slighest adjustment of the tensioners from 1/4" slack to what feels like almost a full inch. with zero slack i get a little noise, but am i risking throwing the chain with almost an inch of slack? if that photo is any indication i would say i'm safe, i guess.

HMMM, just noticed as I was flip flopping my wheels for the 10th time this weekend that my rear hub bearings don't feel real smooth at all. but my chain has been loose enough to push on the pedals a split second before the bike responds. I got the wheel 3 weeeks ago, maybe less. No way I could need to service the hub that soon is there? maybe I should make a separate post.

Thank you! A picture is worth a thousand words!

It's actually slightly tighter, I think, but not much tighter.

My dropouts aren't long enough to adjust to the gear selection I am using.