Tech question?

i have a big ass chain, dedicated s/s rear ring, and a solid steel front ring. i also have a spring loaded tensioner. thechain is about three quarters of a link to long. half links stretch out and mutate too quickly, not an option.
i’ll try 34x19.
i have two other single speeds, which run 32x16, one has a eccentric bottom bracket, the other has sliding dropouts with chain tugs. but this bike is long travel and heavier hence the 32x18. much funner ride.
thanx for the help in making a decision.

i jerry rigged a s\s, and i figured out a good gear for the bike. anyways, it has a 32x18 set up and i’m having chain slack issues. in theory if i ran a 34x20, to take up the slack, would it be close to the same ratio as the 32x18? i want to be sure before i spend money on new rings…

I’m assuming this is on a vertical drop out bike. If so, get a chain tensioner. It looks like a deraillure without the fancy bits. They have em at Sportwheels.

calculating gear inches for each, the 34x20 would be slightly easier 34x19 or 36x20 are both a tiny bit harder but are closer to your original 32x18 gearing.

a great resource for this is here:

could try putting a half link in you chain too, it might work.

copied from MTBR =

What is the “4-tooth rule”?
The “4-tooth rule” states that by adding or subtracting 4 total teeth to a single speed’s gearing, the overall chain length should remain unaffected (NOTE: See clarification/restrictions below).

Why does this matter? It usually boils down to that quest to find the perfect gearing without the use of a chain tensioner on frames with vertical dropouts. There are a couple of tools mentioned in the “Are there tools that can help me decide what gear ratio to use?” section that will help to determine if this is possible on your bicycle frame. If you find that a particular gear combination will work without needing a tensioner, the 4-tooth rule implies that you should be able to add or subtract 4 teeth without affecting the chain length. However, variations in manufacturer measurements & tolerances may affect the actual compatibility & fit.

Another useful application of the 4-tooth rule is a 2-speed bicycle (blasphemy, of course) equipped with both road & mountain gearing. For example, the use of two front chainrings and two cogs could provide 34:14 and 32:16 gearing that can be manually changed without affecting your overall chain length. This can be particularly helpful for “on-the-fly” gear changes without (or with limited) use of tools.

there was a calculator i had book marked once… but it has been removed… but this gives the formula… mine has a 32-18 with no tensioner, not the best for everything but perfect for leisure rides!

a half link will take the math out… but it will never get quite tight enough … and chances are you will be using old mtb cassettes and chain rings, the half link will eat those for lunch in no time.

here is another great link… lots o information here … owto.shtml