# Bicycle Mechanics - How many more chain links do I need? 16T to 20T freewheel

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lolitsJeff
09-24-10, 09:36 AM
I bought a 20T freewheel to replace my current 16T on my single speed and I need to lengthen my chain to free up some clearance. How many more chain links am I going to need, 2-3?

I figure if there are 4 more per full circle and the chain is in contact with half the circle at a time, that means at least 2. I'll ask the guy at my LBS but I'm curious if anyone knows off the top of their head.

ultraman6970
09-24-10, 09:42 AM
Figure it out, it is not rocket science besides nobody knows what bike u have and stuff, the only person who can know those things it is you, take the chain out and add some links thats all, obviously if you are still short add another pair. Not rocket science.

lolitsJeff
09-24-10, 09:44 AM
I'm preettyyy sure it's rocket science:rolleyes:

fietsbob
09-24-10, 10:04 AM
1 inner link with 2 rollers, and 1 outer link to attach to the next inner link is essentially 3, a bike chain is standard at 1/2" pitch ..

Look over the shoulder of the smart kid in class to get the answer and copy it. :bang: :lol:

DMF
09-24-10, 10:57 AM
In theory each tooth uses 1/2" of chain. Calculate the required extra length and post your answer here.

In practice, though, there's a good chance you don't need any. To be sure, go through one of the chain fitting procedures when you put the new freewheel on.

DaveSSS
09-25-10, 07:53 AM
The answer is 1 inch of chain, the minimum increment that the chain length can be increased.

Although each tooth is 1/2 inch of pitch, the chain only wraps half around the cog, so a 4T increase needs another inch of chain.

fietsbob
09-25-10, 12:45 PM
Half links are made in 3/32 + 1/8" width if you still need another 1/2 inch..

If you buy one of the trick single speed chains they use all half links,
the side plate has a Z bend
to be an inner on one end and an outer on the other..

tj90
09-25-10, 07:08 PM
20 teeth - 16 teeth is 4. 4 teeth (3 spaces) is 1.5 links. Assuming the wheel is the middle of the dropout, add 1 link. The wheel will be slightly closer to the crank, I think....

DaveSSS
09-26-10, 02:24 PM
A 4t increase is not 1.5 links, it's two links or 1 inch.