Fixie sprocket / single speed freewheel

[Boly]

I plan to add a single speed freewheel to the flip flop hub of my fixie just in case I need it.
I presently run on 18 tooth sprocket and have no option but to add an 18 tooth freewheel because I have little horizontal clearance to vary the tension on my chain via the drop out length.
I am trying to ensure that the circumference of both the sprocket and the freewheel is identical. I was recently told that it wasn't ? I fail to understand how 18x32 teeth can be spread across circumferences of different sizes and allow both of them to engage with a 3/32 chain.
I hope these ramblings make sense? My fixie sprocket is 18 tooth and 77mm across between the peaks of the teeth.

 

[Boly]

I plan to add a single speed freewheel to the flip flop hub of my fixie just in case I need it.
I presently run on 18 tooth sprocket and have no option but to add an 18 tooth freewheel because I have little horizontal clearance to vary the tension on my chain via the drop out length.
I am trying to ensure that the circumference of both the sprocket and the freewheel is identical. I was recently told that it wasn't ? I fail to understand how 18x32 teeth can be spread across circumferences of different sizes and allow both of them to engage with a 3/32 chain.
I hope these ramblings make sense? My fixie sprocket is 18 tooth and 77mm across between the peaks of the teeth.

Sorry, thank you!
Bob

 

[Ajax Bay]

I was recently told that it wasn't?

Do you value the credibility of that person; and why? Half inch pitch chains are, er, 12.7mm. 18 of those defines the mid-tooth height circumference of an 18t sprocket. End of.

 

[rogerzilla]

The chainline probably won't be the same - maybe that's what they meant. Get the fixed side right and let the freewheel side look after itself.

 

[sleuthey]

I fail to understand how 18x32 teeth can be spread across circumferences of different sizes

On this occasion failing is the correct thing to do.