Quick FIXIE fix until I can get one together permanently

[Polar Bear]

Some of you keen types will have noticed that I have two threads running re: fixi'ng.   Well, impatient as us cyclists I can be, I got to pondering the possibility of using my audax bike with a fixed rear wheel.

It currently runs a mongrel transmission of a Shimano triple chaiset with 26 / 38 / 48 rings and a 9-speed Campagnolo 12-26 rear end.

I got to wondering if I could use it for fix'ing whilst I acquire a permanent FIX so-to-speak

Obviously I'd need a different rear wheel, and a pre-shortened chain to swap but could I still use the chainset (middle ring only) and leave everything else in place?   I would feel inclined to screw down the mechs just in case I found myself 'shifting'.

What do you think guys?  Also, can you get sprockets for fixed compatible with 9-speed chains?

The wheel wouldn't go to waste because it would become part of Heinz when he gets built.   Oh, oln on the audax is 130.

[hubner]

I'm not sure, but aren't 9-speed chains too narrow for 3/32 fixed sprockets?

[Polar Bear]

I'm not sure, but aren't 9-speed chains too narrow for 3/32 fixed sprockets?

Well, the internal spacing is, I believe, the same as for eight and seven speed chains, just the outer dimensions smaller.

   

[bikenerd]

The chain will fit on the sprocket.  However, the side plates are too thin to be used on a fixed.  The extra torque generated when setting off from a stop tends to bend the side plates on a 9 speed chain and pop them off the rivet.
I tried a 9 speed chain on a single speed mountain bike and had to walk home when I'd run out of spare links to put in the chain!  

[Craig]

Just checking the obvious: does your audax bike have horizontal drop outs? Otherwise, you will have difficulty getting the chain tension right.
If you have vertical dropouts, you might be able to play around with different sprockets and chainrings until you get lucky with a 'magic gear'.

[Polar Bear]

Just checking the obvious: does your audax bike have horizontal drop outs? Otherwise, you will have difficulty getting the chain tension right.
If you have vertical dropouts, you might be able to play around with different sprockets and chainrings until you get lucky with a 'magic gear'.

Ah, good point.  I'll wobble out to check ...

[Polar Bear]

    

Vertical I'm afraid.  That's that plan scuppered!

[hubner]

The chain will fit on the sprocket.  However, the side plates are too thin to be used on a fixed.  The extra torque generated when setting off from a stop tends to bend the side plates on a 9 speed chain and pop them off the rivet.
I tried a 9 speed chain on a single speed mountain bike and had to walk home when I'd run out of spare links to put in the chain! 

I'm not convinced by this, if merely setting off in a high gear will make a 9-speed chain, or any chain,  fall apart, then we should be seeing massive pile-ups in every pro race etc. I gather any chain will withstand twice the force any human can generate before breaking.

[bikenerd]

I'm not convinced by this, if merely setting off in a high gear will make a 9-speed chain, or any chain,  fall apart, then we should be seeing massive pile-ups in every pro race etc. I gather any chain will withstand twice the force any human can generate before breaking.

A derailleur will allow enough play in the system to allow the torque to be applied gradually, I think. I haven't tried to formalise it, but myself and another person I know tried 9 speed chains on single speed mountain bikes and popped the plates off the rivets a lot.
I wouldn't recommend using anything more than an 8 speed chain on a fixed though.

[Polar Bear]

I've dug out an 8-speed chain as well so I should be OK then. 

[Biggsy]

   

Vertical I'm afraid.  That's that plan scuppered!

Not really.  There are solutions, including half-links and chain tensioners.  The fixie fans* should tell you more about these.

* I'm not one myself cos I like my gears too much!

[Chris N]

Half links aren't really a solution for vertical dropouts unless you're going for a magic gear anyway - they just give you a bit more scope with ring/sprocket sizes.

Tensioners are definitely not a solution - when you leg brake you'll back the tension off and the chain will slacken.  Again, it's all in the FixieFAQs.

[Biggsy]

Thanks for correcting me, Chris.

I must have been thinking of hub gears and single speed freewheels - where chain tension isn't quite so critical.

[hubner]

I'm not convinced by this, if merely setting off in a high gear will make a 9-speed chain, or any chain,  fall apart, then we should be seeing massive pile-ups in every pro race etc. I gather any chain will withstand twice the force any human can generate before breaking.

A derailleur will allow enough play in the system to allow the torque to be applied gradually, I think. I haven't tried to formalise it, but myself and another person I know tried 9 speed chains on single speed mountain bikes and popped the plates off the rivets a lot.
I wouldn't recommend using anything more than an 8 speed chain on a fixed though.

Since a derailleur (and chain tensioners on single speeds) only keeps the chain from the bottom of the chainring to the bottom of the sprocket tight, in normal pedalling without changing gear, it doesn't play any part in transmitting force, whether gradually or not. Only the top part of the chain transmits force, ie from the top of the chainring to the top of the sprocket.

[andrew_s]

   

Vertical I'm afraid.  That's that plan scuppered!

For vertical dropouts and a bike frame you don't want to spoil, the only real option is a White ENO eccentric hub - about £110 plus rim, spokes and wheelbuild, or £155 for a wheel.
The axle moves on a circular arc, so you've got to consider brake adjustment and mudguard clearance when tensioning the chain. Other than that, it works really well.

I suppose if you are feeling brave you could try a phantom sprocket / flying chainring.

[Polar Bear]

   

Vertical I'm afraid.  That's that plan scuppered!

For vertical dropouts and a bike frame you don't want to spoil, the only real option is a White ENO eccentric hub - about £110 plus rim, spokes and wheelbuild, or £155 for a wheel.
The axle moves on a circular arc, so you've got to consider brake adjustment and mudguard clearance when tensioning the chain. Other than that, it works really well.

I suppose if you are feeling brave you could try a phantom sprocket / flying chainring.

That lot looks fantastic but a bit over my current available budget.   

[bikenerd]

Since a derailleur (and chain tensioners on single speeds) only keeps the chain from the bottom of the chainring to the bottom of the sprocket tight, in normal pedalling without changing gear, it doesn't play any part in transmitting force, whether gradually or not. Only the top part of the chain transmits force, ie from the top of the chainring to the top of the sprocket.

Okay, I can see that.  However, I don't believe that 9 speed chains are as strong as an 8 speed chain and, from experience, wouldn't use one unless I had to, i.e. on a 9 speed derailleur system.  There must be some physical reason why the 9 speed chain snapped all the time on my SS MTB, but the 8 speed chain didn't.  Is there a real physicist or mechanical engineer that knows the answer?
If 9 speed chains really were as strong as any other chain, wouldn't track riders use them rather than the 1/8" chains with really thick side plates  that they use?  I know there's a minimum weight for track bikes but decreasing any rotating mass would be an advantage.

[Polar Bear]

OK, I have hatched another quick fixie route plan.  My turbo bike has the requisite slopey horizontal dropouts, forward facing mind,.  It is a cheap steel mtb.

All I need for a quick fix is a 26 inch back wheel ...