[Xanti Andia]

I have a question as a follow-up to the previous timing chain thread:

http://www.bikeforums.net/showthread.php?t=410451

Do most people change of the timing chain when worn beyond 1/16" per foot tolerance, or can you just keep wearing out the timing chain and chainrings together?

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[TandemGeek]

I tend to replace the chain once it starts to fall between 1/16" and 1/8" of wear, or a little past 75% on my Park CC-2 Chain Checker (http://www.parktool.com/products/detail.asp?cat=5&item=CC-2). Our timing rings cost about $85 per set and because the rings use only 34t, if they get overly worn it becomes problematic to install a new chain. You can rotate them four times to extend their life 4x if they wear a bit too much; however, I'd prefer to not replace them at all vs. replacing a $30 sync chain about once every 5,000 miles. I also tend to dump my drive chain a bit early to help preserve my cassettes and chain rings.

Bottom Line: Chains are consumables, just like tires. When they reach a certain point they've simply got to go.

[Xanti Andia]

I Our timing rings cost about $85 per set and because the rings use only 34t, if they get overly worn it becomes problematic to install a new chain. You can rotate them four times to extend their life 4x if they wear a bit too much; however, I'd prefer to not replace them at all vs. replacing a $30 sync chain about once every 5,000 miles. I also tend to dump my drive chain a bit early to help preserve my cassettes and chain rings.


I do the same, though I have not gotten as much as 5,000 miles on the timing chain, I got half of that last time. Maybe a lesser chain, probably not as careful chain maintenace.

Argument could be made that if you keep the same chain three times longer, $ 90 of chain is more than $85 of chain rings. On the drive chain you will start seeing performance problems with the chain worn beyond 1/8" so the economics are different. In any case I know we are not riding tandems for economics.

[TandemGeek]

Argument could be made that if you keep the same chain three times longer, $ 90 of chain is more than $85 of chain rings.

Absolutely true. Running the chain & rings until they're both shot is the most cost effective approach, and can be made more so by using the more inexpensive chains and steel rings.

A sync chain and rings are about as low-tech and low-demand as any chain drive you'll find on a bicycle in that they only handle the captain's power (+ any drag from a stoker who's not as efficient as they could be) using a 1:1 ratio. In this respect, they'll outlast a fixed gear bike chain by at least an order of magnitude and even the most poorly maintained chains don't significantly impact performance so long as they don't become loose enough to derail.

Anyway, I think it's fairly obvious that I'm a bit particular about maintaining my equipment and I've just never been able to bring myself to knowingly use a chain that has worn to the point where it begins to accelerate wear on a chain ring or cassette cog. The other little nuance with sync chain wear for me is that I'm overly sensitive to riding position changes. As that chain wears the eccentric begins to clock around, raising and moving the front bottom bracket. Dumping the chain at a normal wear interval curtails fit issues for me as well.

So, my personal solution isn't necessarily what I'd put into a tandem maintenance manual for general consumption.

[swc7916]

A bunch of questions:

Do you find that timing chains last longer than drive chains? Does it make sense to rotate the timing rings each time you replace the chain in order to spead the wear?

With regards to the Park CC-2 Chain Checker: It seems that all recommendations for chain replacement use 1/16" elongation per foot of chain as the criteria, yet the CC-2 tool measures stretch as a percentage of chain length; Why is that? I just got one and measured both of my tandem chains at .5% wear with about 550 miles on them. This seems a bit excessive, but do chains have an initial stretch or "break-in" and then stretch slowly after that? (The new chain on my single is so tight that the chain checker wouldn't fit even at the 0% setting.)

[TandemGeek]

Do you find that timing chains last longer than drive chains? Yes, by quite a bit. Again, all the sync chain does is transmit the front rider's power to the rear crank axle at a 1:1 ratio. The drive chain must handle the combined load of both riders and must deal with the added wear and tear that comes from the very small cogs as well as the higher torque of the 'granny' gears if a team rides in places where the alpine/granny/small chain ring actually gets used.

Does it make sense to rotate the timing rings each time you replace the chain in order to spead the wear? You can and it does work; however, it can become more trouble than it's worth relative to keep track of how long a given chain's been in use. I gave up on this practice a while back for both the sync and drive chains and use my limited attention span to check wear a bit more frequently.

CC-2 tool measures stretch as a percentage of chain length; Why is that? It probably seemed more intuitive to use a percentage for consumers vs. 1/32", 1/16", 1/8".

do chains have an initial stretch or "break-in" and then stretch slowly after that? That's been my experience with both motorcycle and bicycle chains. There are a lot of variables here, right down to the different brands of chains, the types of lubricants that they are shipped with and how temperature might affect their viscosity, not to mention how someone might prep their chains for use. Smart folks who pile on the miles seem to slap on a chain with the factory lubes and slather on additional lubes only if the chain begins to squeak before it's time to chuck it. Me, I strip off the factory lubes and do my own thing once the chain is clean.

[Niobium Rocket]

Are there timing chain specific chains?
I ask this in light that the drive chain on my Santana is for a 10-gear cluster...therefore, fairly narrow.
Wouldn't a wider, beefer chain make sense for the timing chain. Slight increase in weight and big
increase in longevity?

What does everyone think?

David

[TandemGeek]

Are there timing chain specific chains? I believe Wipperman may have marketed a tandem sync chain, but there was nothing special about it other than the length. Larger-volume shops will tend to buy chain on a spool and just cut both drive and timing chains to length and you can often times buy chain by the foot from them for less than the cost of buying two standard length chains to splice into a timing chain.

Wouldn't a wider, beefer chain make sense for the timing chain. Again, sync chains are low-tech and aren't subjected to significant loads except on multi-seat tandems like triplets, quads and quints where the rear-most chains carry exponentially higher loads with each additional rider. However, once again, it's the drive chain that takes the real abuse, so any chain will work. That said, if someone didn't mind the added weight and slight up-tick in drag they could most certainly use a pair of 1/8" track rings with a 1/8" track chain, which would be bomb-proof and fairly long-lasting. Going the other way, a gentleman in Florida has been experimenting with a kevlar reinforced belt-drive system that is nearly maintenance-free, incredibly long-lasting, lighter, and nearly as efficient as chain drive.

[swc7916]

a gentleman in Florida has been experimenting with a kevlar reinforced belt-drive system that is nearly maintenance-free, incredibly long-lasting, lighter, and nearly as efficient as chain drive.

That's really interesting - A belt on the drive side would require a different type of gearing mechanism because it has no side-to-side flexibility and can't derail, but since the timing side is a fixed gear ratio it should work great.