How much tension should my bicycle chain have?

Question

Mine has A LOT of play. I can take it underneath with my finger, and move it up about 3-4 inches. More if I pull hard. Is that normal?

Answer 1

I agree with all the earlier advice except the way to measure chain length for dérailleurs.  You should check the [rotational] tension of the dérailleur cage with the chain running over both the front and rear smallest sprockets - if the chain is doubled back on itself on the cage that it touches itself you either have too long a chain or the dérailleur arm is too short for the width or range of your gearing setup.

Before making adjustments also run the chain over both the front and rear largest sprockets - then the cage should be angled forward so that the chain is hardly 'bent' as it goes through the cage, but , again, not so the chain touches itself.  If not - you need to either take out links and/or change the length of the dérailleur arm.

This is all quite complicated and needs some eye and experience - if in doubt get hold of an experienced biker or visit a decent repair shop -money well spent.

Finally - after all the above has been checked ONLY THEN tighten or slacken the rotational tension of the dérailleur cage.

Answer 2

Nope, it's a little bit loose. you may have to change the tension spring of your rear derailleur. Some brands have extra holes for the spring tension adjustment, similar to the holes in your brake springs. If none, then you'll have to change the spring.

Answer 3

If your bike had a derailler that would be normal. But if it is a single speed no derailler type bike, then that is loose. Tighten your chain so it has about 1 inch of play up and down. Make it real tight if your gonna do tricks, so your pedals don't move freely.

Answer 4

As others have noted, this may be normal on a derailleur'ed bike.  For a single speed, this is definitely dangerout to be riding.  One thing to note though, is that the gear combination for your bike is important when trying to gauge proper chain length.  You must place both the front and back derailleurs to the biggest cogs.

Sheldon Brown says:

"The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that they could be connected (outer link meets inner link), then make the chain one complete link (one inch) longer than that. In almost all cases, this will give the optimum length."

Single speeds should be hella taut.  If you wiggle the crank back and forth while the bike is stationary, there should be no change in the tension of the chain.  Ideally, there should be no movement of the crank without movement of the bike.