Singlespeed & Fixed Gear - How crucial is a chain tensioner?

I have recently picked up a Giant Tran Send with an Alfine internal gear (I know it’s not single speed, so I’m kind of cheating here). The bike came with a tensioner because the frame has a vertical dropout. I managed to change the gear ratio so the chain length is exact, if not near, so a tensioner won’t be needed… there is a little bit of slack but not enough to worry at this point…. BUT… as the bike is still very new (only about 200km) and the chain is probably not fully worn-in yet, I’m expecting the chain to build up even more slack. So…

How much slack is acceptable?

Do I need a tensioner to take up the slack as it build-up before a new chain is needed?

The photo shows how it looks like without the tensioner.

looks fine.

The max range of chain slack will see you dropping it on bumps. It'll have to be pretty loose for this to happen.

Since it's in a trainer, I can't tell if it has a rear QR or not. If it does, I would use a Chain Tensioner in this instance as QR will slip if you really crank down hard. That's likely why it came with one.

I personally hate chain tensioners. I think I'd be fine with that setup short term, but I wouldn't like it in the long run. Not saying there's a logical well-thought out reason for me not to like it in the long run... just my personal perference. Eventually, I'd try to weld on horizontal dropouts or put an eccentric rear hub on it... or swap out the frame completely.

Since it's in a trainer, I can't tell if it has a rear QR or not. If it does, I would use a Chain Tensioner in this instance as QR will slip if you really crank down hard. That's likely why it came with one.

Every single word in this reply tells us you didn't read a single word of the OP's post, nor looked at his picture.

I happen to like using tensioners. They make it easier to adjust chain tension for me. That being said you can easily make your chain tension too tight with tensioners.

The nice thing about having it near perfect is that if/when you do need a tensioner, you will be able to use it in push-up mode, which is way better and looks better too.

Thanks for all the replies!


Since it's in a trainer, I can't tell if it has a rear QR or not. If it does, I would use a Chain Tensioner in this instance as QR will slip if you really crank down hard. That's likely why it came with one.

The rear hub is not QR, the Alfine gear hub requires the rear axel to lock in place.


I personally hate chain tensioners. I think I'd be fine with that setup short term, but I wouldn't like it in the long run. Not saying there's a logical well-thought out reason for me not to like it in the long run... just my personal perference. Eventually, I'd try to weld on horizontal dropouts or put an eccentric rear hub on it... or swap out the frame completely.

I'm with you about having a tensioner, that's why I took it off the first place. I did plan to swap out the frame in the future, but all the frames I'm looking at has vertical dropout too.


The nice thing about having it near perfect is that if/when you do need a tensioner, you will be able to use it in push-up mode, which is way better and looks better too.

What you mean by "push-up mode'?

Every single word in this reply tells us you didn't read a single word of the OP's post, nor looked at his picture.

Failure was your only option. How would I have even said that it's in a trainer if I didn't look at the picture? And I did read the post, which said that the tensioner is not on there now. You can run tensioners with QR skewers, I'm not saying it's smart, or appropriate, but it can be done. In fact, the tuggnut comes with a 6mm adapter for this. You can put a bike with a bolt-on hub or QR hub in a trainer, the bolt-on will not function properly, but that's not the area of clarity here, it's what is actually happening in the picture. Now, I will grant that I was not aware that the Alfine locked in place, but I stand by my comment, and still stand by it. I apologize for offering any advice, as your contribution in this thread has clearly been nothing short of godlike.

Failure was your only option. How would I have even said that it's in a trainer if I didn't look at the picture? And I did read the post, which said that the tensioner is not on there now. You can run tensioners with QR skewers, I'm not saying it's smart, or appropriate, but it can be done. In fact, the tuggnut comes with a 6mm adapter for this. You can put a bike with a bolt-on hub or QR hub in a trainer, the bolt-on will not function properly, but that's not the area of clarity here, it's what is actually happening in the picture. Now, I will grant that I was not aware that the Alfine locked in place, but I stand by my comment, and still stand by it. I apologize for offering any advice, as your contribution in this thread has clearly been nothing short of godlike.
Chill pill. A tuggnut or other "chain-tug" style tensioner is not what this thread is about. The picture shows a bike with vertical dropouts, so a chain tug isn't necessary and won't do anything. This thread is about a singleator style tensioner used for single-speeds with vertical dropouts (as shown).

OP: "push up" mode is when the jockey-wheel of the tensioner is underneath the chain, pushing the chain up. It provides more chain-wrap around the rear cog and looks better.

Push up (a zip-tie helps):
http://www.singlespeed.net/articles/tension/singulator.jpg

Push down:
http://www.singlespeed.net/articles/tension/SS_2.jpg

I apologize for my very reactionary comment. I know that the tuggnut would not be applicable in this instance, but did want to cite tensioners that can be used with QR levers, which was again, only mentioned in a reactionary sense and is indeed not what this thread was about.

Chill pill. A tuggnut or other "chain-tug" style tensioner is not what this thread is about. The picture shows a bike with vertical dropouts, so a chain tug isn't necessary and won't do anything. This thread is about a singleator style tensioner used for single-speeds with vertical dropouts (as shown).

OP: "push up" mode is when the jockey-wheel of the tensioner is underneath the chain, pushing the chain up. It provides more chain-wrap around the rear cog and looks better.

Thanks! I think eventually I'll look into adding a smaller tensioner like the Sette Tensioner (http://www.setteusa.com/images/main/chain_tension.png). Anyone with has experience with Sette product?

I also read about using a zip-tie to secure the tensioner. Is that really needed?

Adding a zip-tie to that chain tensioner (that pushes the chain up) is helpful because with all of the force on the chain it constantly wants to force the tensioner down - by adding the zip tie you pull the tensioner up preventing it from slipping down over rides.

Just came back from a 50km ride through all different kind of surface imaginable (street, bike path, forest/dry mud, thin rock/sand, and even some old 17th century rock paved road). Chain didn’t come off, which is good… but I did notice the chain making more noise when going through rougher terrain. The chain bounces around more without the tensioner. I guess this is a tradeoff of having no tensioner.