Long time rider, but new to SS - so bear with me. I'm riding an Inbred 29er, SS and my chain keeps coming off about every other ride. Here's my set-up: surly 22T cog, Salsa 32T SS ring on old-school Kooka cranks, and a 1/8" KMC Z chain. Decent chain tension and I believe my chain line is pretty good. But, when I'm really putting the power down on a techy climb, the chain sometimes comes off. What's the deal? Would a 3/32" chain solve my problems? FYI - my entire drive train is nearly new (no old parts with new parts going on here).

I've heard about old school cranks being flexy and contributing to chain drop - any input on that?

2. Where is the post on measuring out chain line - that worked well for me. Its not my idea but if you measure out the line you can know for certain.

Step one - measure the diameter of the tube that holds your seatpost

Step two - measure the from the outside of that post to the outside of your ring

Step three - divide the first measurement in half and subtract that number from the one you got in step two.

You now have your chain line up front and you need to check it in the rear.

Step four - figure out your hub size and divide it by 2.

Step five - measure from the flat on the chain stay to the rear cog

Step six - subtract the number from step five from step four and compare with the front.

Six easy steps and you know how far off it is. I was alot further off than I should have been and I got it down at ~1mm.

3. Originally Posted by pulsepro
Long time rider, but new to SS - so bear with me. I'm riding an Inbred 29er, SS and my chain keeps coming off about every other ride. Here's my set-up: surly 22T cog, Salsa 32T SS ring on old-school Kooka cranks, and a 1/8" KMC Z chain. Decent chain tension and I believe my chain line is pretty good. But, when I'm really putting the power down on a techy climb, the chain sometimes comes off. What's the deal? Would a 3/32" chain solve my problems? FYI - my entire drive train is nearly new (no old parts with new parts going on here).

I've heard about old school cranks being flexy and contributing to chain drop - any input on that?
I ride a 29er Inbred, too. No chain drop problems so I doubt it's frame flex. I run HSC 195mm cranks and they're so way overbuilt that I am positive that my cranks don't flex. That may be one difference between your setup and mine. Those Kooka cranks are pretty soft (I think they were mfg'd out of a relatively soft alloy plus I don't believe they were heat treated, which may be why so many of them failed back in the day).

Also check for bent teeth on your chainring and your cog. Just one tooth slightly out of plane can screw everything up quick.

I run 8-spd chains. Never a problem.

Good luck.

--Sparty

4. How do you tension your chain? If you aren't using a tug with a QR, I could see the rear wheel moving forward after a ride or two.

There is also a possibility that something is out of round. I have only dropped chain under two conditions- terrible chain tension and because my OG cog (I was experimenting, dammit) was ramped.

If the chain keeps coming off, you should sell the bike.

5. Yeah - how is your rear wheel secured in those slot dropouts on the Inbred? Perhaps it is sliding forward as umarth suggests, and thus creating too much slack in your chain.

If that's the case, send me a PM and I could let you try a surly tugnutt to see if that will help keep the rear wheel from "slipping."

Cheers,

Mark

6. Thanks for the helpful replies. I'm using a bolt-on DMR hub with a chain tug on the drive side. Rear wheel is not moving. I did however, calculate my chainline as suggested - it was off a solid margin. The chainline is dead-nuts now according to the math and my Park ruler. No trail time on the bike yet with the new chain line.

Regarding the Kooka cranks - I bought them new in 1997 with a genuine Canadian made Race Face taper lock BB and rode them exclusively for almost 8 years. The cranks still work fine and the BB is as smooth as day 1.

7. pulsepro: I had issues with a single speed chain getting thrown (sram) and switched to a 9speed LX chain, been tits for something like 8 good long rides so far. I think my chain issues were a bit finickier due to having a steel frame.

8. Originally Posted by phlite
pulsepro: I had issues with a single speed chain getting thrown (sram) and switched to a 9speed LX chain, been tits for something like 8 good long rides so far. I think my chain issues were a bit finickier due to having a steel frame.
Sram 8's for my steel frame. They have held up well even with 30:15, which according to some is unduly hard on all the parts due to less distribution of the stress. Actually the cog did finally throw a tooth on a hard climb... but the 8 chain that was on it survived (might say it won).

9. Originally Posted by struggleT
Sram 8's for my steel frame. They have held up well even with 30:15, which according to some is unduly hard on all the parts due to less distribution of the stress. Actually the cog did finally throw a tooth on a hard climb... but the 8 chain that was on it survived (might say it won).
I run Sram 8-spd chains as well, including (multiple) power links. Steeps & epics -- no problems in 10 years of singlespeeding.

--Sparty

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