Dropping chain with Carbon-Ti N/W 30T chainring

Discuss light weight issues concerning mountain bikes & parts.

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CGT
Posts: 342
Joined: Fri Jan 05, 2007 5:33 pm
Location: Stockholm, Sweden

by CGT

Getter wrote:The CL in the 11T looks more extreme in the 36T. Its usually the other way around.

Here is my setup. Mine looks to have less of a bend in the chain in the 11T than yours, but more than yours in the 42T.

My CL is 47.7mm.


Thanks for your reply and the pics, Getter. I sent the pics of my chainlines to Carbon-Ti, and they replied that it looks perfect, so that should not be the cause of my problems. Besides, any changes to the chainline would mean adding more BB spacers to the driveside, where I'm already running 2x2,5 mm spacers. This doesn't seem like the right way to go.

@TheRookie: I had no idea of this N-N-N-W-construction when I bought it. There are built-in spacers to distance the chainring from the crank arm, here you can see how it looks: http://www.carbon-ti.com/products/chain ... 04-special

I believe this is necessary on a 30T ring in order for the chain to clear the chainring tabs on the crank arm.

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Getter
Posts: 848
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Location: So Cal

by Getter

If you've ruled out everything else...maybe try a new chain? You never know...it's always the small quirks that can mess you up.

I just noticed the gaps in the NW pattern... :noidea:

I've used XX1, Race Face, Ridea, Wolf Tooth...and I've never dropped a chain.

Exar
Posts: 352
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by Exar

Have you tried a different chainring? Maybe just borrow one, install it, and you'd know within 5 minutes if your problems are still there.
Chains to the right!

CGT
Posts: 342
Joined: Fri Jan 05, 2007 5:33 pm
Location: Stockholm, Sweden

by CGT

I think I will do that. Unfortunately, it will be difficult to borrow a 30T N/W, but I'll give it a try. Otherwise I have a regular 32T chainring (non-N/W) that I can try with, but that's a completely different component as far as I'm concerned.


DanW
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Location: Here, there and everywhere

by DanW

Few things....

A 30T chainring will always compromise your chainline a little due to the required offset. Just stick to a 32T. Working marginally harder on the climbs is preferable to chain drops. Extralite make a 30T with the least offset IIRC if you really do insist on sticking with it and chainline is your only issue.

The clutch definitely does often need to be adjusted from new. I make it as tight as possible before it interferes with shifting and there are guides out there like http://www.pinkbike.com/news/Tech-Tuesday-Inside-Shimanos-Shadow-Plus-Mech-and-How-To-Adjust-.html

Chain length is also crucial

The chainring design should be last on the list of problems (if we ignore the offset required for the 30T for a second). The clutch mech does the majority of the work keeping the chain on. You should be able to get away fairly well with the right clutch tension, chainline and chain length only.

Marin
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Location: Vienna Austria

by Marin

Disagree on the chainline (further left/inside is preferable) and the clutch - you can run without clutch just fine, but with a regular chainring the chain will drop even without riding over bumps, just from shifting in the rear - even with clutch.

I tried both options on several bikes (MTB, folding, commuter, CX).

bikemaniack
Posts: 331
Joined: Thu Jul 16, 2009 9:33 pm

by bikemaniack

What I saw,is that the Ti chainring is much different than for example sram chainrings. You have here one tooth wide,than 3 or 4 are narrow,maybe this is the reason.

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LeDuke
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Location: Front Range, CO

by LeDuke

Get a proper chainring. I'm not sure if Carbon-Ti were just trying to save machining time or what, but that makes no sense. Sounds like a really poorly designed and executed product.

bikemaniack
Posts: 331
Joined: Thu Jul 16, 2009 9:33 pm

by bikemaniack

Maybe the reason,why the chains drops is,that this chainring compared to sram chainring have less wide tooths.In sram NW chainring we have one narrow,than one wide chainring,here we have one wide aand 3 narrow tooths.

CGT
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Joined: Fri Jan 05, 2007 5:33 pm
Location: Stockholm, Sweden

by CGT

Again, thanks for all the input everyone, I really appreciate it.

The design with some of the "wide" teeth not being truly wide I don't understand either. The weight saved by this must be 1-2 grams maximum. I did not realize this when I bought it, and most of their product pictures does not show this "feature". On the 30T ring, 15 of the teeth are supposed to be wide, but 5 of these are only wide on the outside and narrow on the inside, leaving only 10 truly wide teeth.

DanW wrote:Few things....

A 30T chainring will always compromise your chainline a little due to the required offset. Just stick to a 32T. Working marginally harder on the climbs is preferable to chain drops. Extralite make a 30T with the least offset IIRC if you really do insist on sticking with it and chainline is your only issue.


Thanks for your input, Dan. However, I think the chainline is pretty good actually. In theory, you would like the chainring slightly offset inwards to the bigger cassette cogs (as opposed to have it dead center on the cassette), as the larger diameter of the bigger cogs result in a larger angle for the chain. For example, a 42t cog has a 4,2 times larger diameter than a 10t, so the distance from where the chain leaves the chainring and engages the cassette is shorter. Or imagine running 100t cassette cog, you would need to offset the chainring inward to compensate for the larger diameter.

So I don't think the chainline is the problem here, and they could have constructed less built-in offset if they had wanted to. Besides, I have this chain drop issue not only on the 11t cog, but also on the 13.

DanW wrote:The clutch definitely does often need to be adjusted from new. I make it as tight as possible before it interferes with shifting and there are guides out there like http://www.pinkbike.com/news/Tech-Tuesday-Inside-Shimanos-Shadow-Plus-Mech-and-How-To-Adjust-.html

Chain length is also crucial


I will give the clutch a proper look, but I don't expect it to solve my problems. But it's worth a try. Chain length should not be an issue, the chain is far from slack on the 11t cassette cog. I'm only running a 11-36 cassette, and if I would have run an extender (say 40t or 42t even), the chain would have had to be longer. So my current length should not be causing these problems in my opinion.

DanW wrote:The chainring design should be last on the list of problems (if we ignore the offset required for the 30T for a second). The clutch mech does the majority of the work keeping the chain on. You should be able to get away fairly well with the right clutch tension, chainline and chain length only.


That would be my hope too, but as far as I'm concerned, the chainline and length are correct (chainline also confirmed by Carbon-Ti), so that leaves the clutch, the chain and the chainring design.

To be continued...

TheRookie
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by TheRookie

CGT wrote:. However, I think the chainline is pretty good actually. In theory, you would like the chainring slightly offset inwards to the bigger cassette cogs (as opposed to have it dead center on the cassette), as the larger diameter of the bigger cogs result in a larger angle for the chain. For example, a 42t cog has a 4,2 times larger diameter than a 10t, so the distance from where the chain leaves the chainring and engages the cassette is shorter. Or imagine running 100t cassette cog, you would need to offset the chainring inward to compensate for the larger diameter.

You think? the differences are tiny (like less than 0.5mm), plus once the sprocket is larger than the chainring its engaging later on the chainring reversing the effect, yet that is spaced in a lot more, and .....its spaced in and falling off the outside - says it all.
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DanW
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by DanW

Chain length should not be an issue, the chain is far from slack on the 11t cassette cog. I'm only running a 11-36 cassette, and if I would have run an extender (say 40t or 42t even), the chain would have had to be longer.


It's all about getting the length right for the current cassette and chainring- if you don't then the mech doesn't have the right tension to function as intended and it is much more subtle than a normal mech. I think Shimano say big-big plus two full links as one would normally do but I may be mistaken on this

TheRookie
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by TheRookie

Correct, big-big (missing the rear mech) and an overlap of at least a pair of links.
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CGT
Posts: 342
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Location: Stockholm, Sweden

by CGT

TheRookie wrote:Correct, big-big (missing the rear mech) and an overlap of at least a pair of links.


Yeah, well this formula is not bullet proof as you have to account for chain growth on a full suspension frame. But as previously stated, chain length is not the issue here.

by Weenie


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