I've got an XTC carbon that I'm currently running ss. I can't use an EBB with my current crankset, so I'm using a Soulcraft Convert tensioner. It works great, But I'd like to run without it if possible.

I don't want to drop the money on an eccentric ENO hub'd wheel just yet, so my only other option is trying to get a halflink to work with my current gearing (32x20). I know chainstay length will determine whether or not I can make this work, but is there a formula I can use that will tell me first whether or not this is possible? I have no idea what the magic gearing is for this bike. I know Adam Craig ran a 34x18 with a half link on his XTC, but I'm not Adam Craig, so that gearing is out.

Thanks

2. Use the 4 teeth rule.
Adding 4 teeth in all will create the need for a whole link of chain. (inner half + outer half)
Adding (or subtracting) 2 teeth total will create the need for a half link to be installed.

If he can run 34x18 with a new chain, you can run 32x18 with a new chain + a half link.
or

And so on.
Hope that helps!

P.S. I have never gotten a magic gear calc online to work for me.

Or a magic gear for that matter

3. Good clarification. I'm currently running 34x18 on my EMD. I'm not sure I will be able to turn this gear in the hills so I've thought of sticking a 20t out back. Adding a half link will get it done.

Thanks.

How hard would a 36x16 be to turn?

4. This helps a lot actually. If I can run 32x20 with no half link I'm golden. I'll give it a shot this weekend.

Thanks!

Originally Posted by Sheepo5669
Use the 4 teeth rule.
Adding 4 teeth in all will create the need for a whole link of chain. (inner half + outer half)
Adding (or subtracting) 2 teeth total will create the need for a half link to be installed.

If he can run 34x18 with a new chain, you can run 32x18 with a new chain + a half link.
or

And so on.
Hope that helps!

P.S. I have never gotten a magic gear calc online to work for me.

Or a magic gear for that matter

5. Thanks, Jim, for the info on the 4-tooth rule. I didn't know that one! I, too, have not had lots of luck with the online calculator.

My Slingshot had a magic gear at 38x16. I wanted to get closer to 2:1 ratio, so I moved to 38x20. Alas, it was not magic, and I had to add a tensioner.

So, I guess you can call the 4-tooth rule a rule of thumb.

6. This might help with figuring out chainstay length vs. gearing:

http://eehouse.org/fixin/fixmeup.php

7. Did you get a new chain when you added those 4 teeth? I was pretty sure that is exact.

I have used it in the past with a filed axle(for adj) and it has always worked. But the filed axle could take up a few mms of change

8. Hi Jim -

No, it was an old chain. That could account for the difference.

Filed Axle?!? What is this insanity!??

I've never heard of that trick. I assume you can file a bit of your axle and not loose strength? I suppose you could file a bit of your dropout as well...

Yeah, perttime, that's the online calculator that I've seen before. But, as a noob, I can't say I've really put it to the test, either.

Interesting conversation. Thanks for sharing the knowledge!

9. If the chain is too tight by 1-2mm, you can file a flat spot on the axle and it will gain you a hair more space. Bonus with a filed axle is that, after ykour chain stretches a bit, you can then rotate it to the rounded spot and take up the slack.

10. Originally Posted by Sheepo5669
Use the 4 teeth rule.
Adding 4 teeth in all will create the need for a whole link of chain. (inner half + outer half)
Adding (or subtracting) 2 teeth total will create the need for a half link to be installed.

If he can run 34x18 with a new chain, you can run 32x18 with a new chain + a half link.
or

And so on.
Hope that helps!

P.S. I have never gotten a magic gear calc online to work for me.

Or a magic gear for that matter
This is most but not the whole story. When you move to a taller (harder) gear ratio, keeping with this "4-tooth rule," the angle between the two lengths of chain increases, necessitating a shorter chainstay. This is why, when you get your dingle dialed in on the 31/19 combo, your chain is too tight when you try to move it to the 34/16 combo.

11. Oh, that makes sense, Zaskar! With the 38T front, I do have a larger diameter ratio between the front and back, mixing it up a bit.

I made the hills tonight with my 38x20. So, I'm interested in a 38x19 2:1 ratio now. Between half-links and flat-spots, I hope I can make the magic!

I hope I've not usurped I.A.N.'s original post! Still, good conversation!

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