Hi,

So looking at this: https://cgi.ebay.co.uk/Forged-SINGLES...88a735778#shId if you use it in the unsprung pushing up position, why won't it work for fixed gear?

Thanks

Daven

Because you just install it on a splined freewheel hub as if it were a normal casette cluster of gears.. but with spacers in place of the gears you would have.

Because if you backpedal you will rip it off. That thing is for single speeds, and works quite well for them since they have freewheels.

I meant the tensioner

Yes, but why? If it is fixed in place, and you just slow using the pedals you aren't backpedalling just resisting forward motion. If you pedal backwards then isn't that the same as a just backpedlling on a freewheel?

I'm not convinced of this, you can back pedal a ss too.

Am I crazy? It looks like it would be fine in this position:

Because the the spring in the tensioner is firm enough to hold tension on the lower part of the chain when there isn't much pressure on it. While pedaling forward the top of the chain is under pressure but the bottom part of the chain is not. The first time you stop pedaling or apply back pressure this will reverse though and you'll have a moment of play where the pedals stop but the wheel keeps moving with it takes out the slack and then it will jerk to a stop. Best case scenario it will be a very jerky ride. Worst case, the jerking could rip the tensioner off, snap the chain, unthread the cog from the hub, or a whole host of other undesirable things.

Bottom line: It won't work well if it works at all.

It'll still be a jerky ride as every time you apply back pressure there will be a small lag time while the slack comes out of the lower part of the chain.

they said you can run it witout a spring, this is why I thought it could possibly work.

Why do people always want to put chain tensioners on fixed gears?

why do people cut the springs on their Hondas to lower them?

decided to read the thread after posting

People with frames that have vertical or really short horizontal/semi-horizontal dropouts.

How about the third chainring as a chain tensioner...on a FG.

Seems like it could handle the tension.

Exactly, I understand the problem if it is sprung, but if it is in a fixed position and unsprung then surely the difference in top and bottom tension won't matter?

+1

When you back pedal a FG bike, the bottom half of the chain becomes super tense and will bend that arm or at least turn it and relieve the tension that it's designed to keep.

This. Think about it: when you pedal forward (apply pressure), the top line of chain goes perfectly straight and is tensioned quite a bit but the bottom line can be slack. When you pedal backward, the top line of chain goes slack, and the bottom line gets tensioned. The chain tensioner would have to be very strong to resist the chain wanting to go perfectly straight on the bottom. This is why Sheldon says that even chain tensioners for downhill MTBs aren't strong enough for fixed gear use.

Funny that they put it on a bike horizontal drop-outs to demonstrate it.

I've always thought that this would be the smartest way to run a tensioner on a FG

can you explain what you mean?

someone should just get one of them and try it so there wont be any more debate on this topic

I seen it done on SS especially ones with Vert drop outs essentially you put a ring/cog between the chain to provide tension....it works though it looks funky

Commonly known as a ghost ring.
These will work as the ring "floats" so that chain slack is taken up on the non-driving side.

Just wait till it falls out. Used to use them on tallbikes, they never really worked properly. Wouldn't trust my life to an old ghetto-rigged chainring these days. Address the issue at hand, don't try to put band-aids on it. Get a half-link/eno/find magic ratio.