# 1/8" vs. 3/32" - How do I know?



## Nickel II (Jul 18, 2003)

I want to buy a new freewheel and have no idea if I am supposed to be getting a 3/32" or 1/8"?

The bike is an IRO Mark V. I emailed them this morning but haven't heard back yet.

I checked their website and it doesn't mention the size of the chains, chain rings or freewheels. It does say the cogs are 3/32", but I just want a different size freewheel for now.

One would think a 1/8" is a bit more durable so I'd prefer to get that, but I don't want to get it and find the chain and chain ring are 3/32".

If I measure these myself, how do I measure them? Those are pretty precise measurements to use a ruler and eyeball it.


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## Dave Hickey (Jan 27, 2002)

If your chain is 3/32", you need a 3/32" freewheel....If your chain is 1/8" you can use either 3/32 or 1/8' freewheel


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## Nickel II (Jul 18, 2003)

Dave Hickey said:


> If your chain is 3/32", you need a 3/32" freewheel....If your chain is 1/8" you can use either 3/32 or 1/8' freewheel


Is it going to say somewhere on the chain what size it is? If I measure it myself, what am I measuring? The gap of the area that the teeth would fit into (the inside part of the chain)? Or the entire width of the chain - including the metal?

I do have calipers I can use to measure.

Sorry, I learn something new about bikes everytime I have to replace a part.


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## Fixed (May 12, 2005)

*what do you have?*

Do you have any chains or cogs that you know the size of? You could compare.

If you have a 1/8" cog or chainring, a 3/32" chain will not wrap around it, but will sit up on the teeth. 

Sometimes a chainring will have the size stamped on the back somewhere. Same for cogs.

You could measure your existing cog/freewheel, the width of the teeth. 

Some websites incorrectly identify this spec as "pitch." This is not pitch. Almost everything is 1/2" pitch, the distance between adjacent teeth or links of a chain.


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## Nickel II (Jul 18, 2003)

Errrr. No response from IRO yet. Is it stupid to worry about this? Sounds like a 3/32" will work all around so there is no risk in getting that size.

I tried measuring last night, no luck. I can't tell. I have some links from my old geared bike that is likely 3/32" and it appears to be the same size as the chain on the IRO, but the difference is so small I really can't tell.

If the rest of my components are 1/8", is there any advantage to sticking with that? Or should I just get 3/32" and not worry about everything being 1/8" or 3/32"..


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## Dave Hickey (Jan 27, 2002)

Nickel II said:


> Errrr. No response from IRO yet. Is it stupid to worry about this? Sounds like a 3/32" will work all around so there is no risk in getting that size.
> 
> I tried measuring last night, no luck. I can't tell. I have some links from my old geared bike that is likely 3/32" and it appears to be the same size as the chain on the IRO, but the difference is so small I really can't tell.
> 
> If the rest of my components are 1/8", is there any advantage to sticking with that? Or should I just get 3/32" and not worry about everything being 1/8" or 3/32"..


If you compared a geared chain to the chain on your IRO and they look the same, it's 3/32.

The difference between a 1/8" and 3/32" is obvious when compared side by side


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## Nickel II (Jul 18, 2003)

Gotcha - Thanks Dave.


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