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Time/mileage between changing chain

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Time/mileage between changing chain

Old 05-27-19, 05:53 AM
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SpinnerPC
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Time/mileage between changing chain

Hi guys,
New to tandem world. We bought ourselves a 9-sp full Ultegra 2003 Cannondale tandem looking like new for less than us$750 (shoes, rack, panniers included). Yep I think it's a steal. We've put about 2000km since and the left (coupling ?) chain is quite slack now.
1) What tool is required to adjust the front bottom braket ?
2) How long/far do you go between changing chain ? I am a powerful rider (PAM over 375W) and I go almost 4 to 5000 km for my chain on my road bike. (cleaned and lubricated regularly)
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Old 05-27-19, 06:57 AM
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As for when to replace the chain, the answer is before it wears out. Invest a few dollars in a chain wear measurement tool and check it (and all your chains).

Adjusting the eccentric is a matter of the specific design. Most have 4 (2 each side) locking set screws. Losen all 4 and use a pin spanner to rotate the eccentric to tighten the chain. I prefer to use a bottom bracket wrench to turn the eccentric but it only fits on 2 of my bikes.
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Old 05-27-19, 09:38 AM
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Hey SpinnerPC, nice pickup and a good deal. As advised get yourself a Chain Checker for about $6, or so. With so much chain on that tandem, you'll be using it a lot.

You'll also want to check the timing chain rings to make sure they are not overly worn. They should look more like a 'U' than a 'wave' or an asymmetrical saw-tooth. A little bit of asymmetry is to be expected on well used chain rings, as you might expect on a used bike. But at some point they'll be too far gone. Look at pictures on-line to get some sense of when.

Sheldon Brown suggests some method of exchanging front and back timing chain rings to extend their life, but I was never clear on exactly what he described.

If the chain is still within spec (using the chain checker) you can adjust the eccentric to take up the slack. As mentioned, there are several different ways eccentrics are secured in the front bottom bracket.

On my Cannondale, the eccentric is two pieces. A small wedge is pulled into the main part of the bottom bracket with (I think) a long 4mm bolt. If that's the style your Cannondale has, here is the method I use:

Crank comes off. Unscrew that bolt. Go to the hardware store and get another one about 12mm longer. Screw this longer bolt almost all the way into the wedge from the same side it came out. Have the head of the bolt just clear of the eccentric, sticking out about 1/8" or so. Tap the head gently with a hammer until the wedge is knocked loose.

Then, using a pin spanner, you should be able to rotate the eccentric until all the slack disappears. It doesn't take much rotation. And don't be afraid to make the chain kind of snug, not guitar string tight, but a bit tighter than you might think.

Also pay attention to chain ring alignment. In my Cannondale the eccentric can be moved left or right a little to make sure the chain runs straight off one chain ring onto the next one.

Take out the longer bolt and put the original one back in and tighten it all up. You should be good to go.

If that eccentric hasn't been serviced in a while and is difficult to move, it would be a good idea to take it out and grease the whole thing up and grease the interior of the bottom bracket too.
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Old 05-27-19, 12:31 PM
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You may find the timing chain on your tandem will last through a couple of drive chain replacements. At least thatís been the case over the last 29 years for us. Itís likely a result of the timing chain not having to endure the wear and tear of front/rear shifting and not running with some lateral flex as caused by most gear combinations in the drive chain.
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Old 05-27-19, 04:42 PM
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Our experience with chains was ~9-11k miles for timing and ~2k miles for drive chains. Drive chains lasted at
most half what a singleton drive chain lasts. Consider changing your shifter cables more often as well.
We broke several, of course only on century rides. You can extend the life span of the timing chain rings
by swapping the front one to the back and vice versa. Turns out the chain rubs on the opposite sides of the
chainwheel teeth in front and back so you can get 2-4k extra miles out of a timing CW set that way. In
my experience timing CWs last 10-15k miles, but they are cheap. Make sure to have the appropriate quick
links spares in your saddle bags for either chain. Also check to make sure you can easily rotate the front
BB eccentric. First time we tried on ours broke one allen and bent two others before it came loose.

It should be noted that this was a lesser problem with the second eccentric adjustment and subsequent
adjusts over the years were straight forward. I made sure to lube up the device and the allen set screws
after each adjust after the first snafu. Mine (Comotion) did not require crank or chain removal.

Finally there is no reason to use the same timing chains as drive chains. 5-8 spd chains work fine in timing duty.
Just make sure the quik links are available for the chain you use, as timing chains are ~25% longer than
drive chains.

Last edited by sch; 05-29-19 at 02:30 PM.
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Old 05-28-19, 06:28 AM
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Originally Posted by sch View Post
You can extend the life span of the timing chain rings
by swapping the front one to the back and vice versa. Turns out the chain rubs on the opposite sides of the
chainwheel teeth in front and back so you can get 2-4k extra miles out of a timing CW set that way.
This is great to know! Perhaps this is common knowledge to many, but in all of the years I've been tandeming, I've never heard of this before. Thanks for the tip!
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Old 05-28-19, 10:45 AM
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Originally Posted by Alcanbrad View Post
As for when to replace the chain, the answer is before it wears out. Invest a few dollars in a chain wear measurement tool and check it (and all your chains).

Adjusting the eccentric is a matter of the specific design. Most have 4 (2 each side) locking set screws. Losen all 4 and use a pin spanner to rotate the eccentric to tighten the chain. I prefer to use a bottom bracket wrench to turn the eccentric but it only fits on 2 of my bikes.
Thanks. I already have a chain tool. It indicates .75. As I can get close to 5000km on my road bikes (with proper cleaning and lubrication) I am surprised with the wear of this chain on the non-drive side.
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Old 05-28-19, 10:56 AM
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Thank you all.
Something's strange. The drive side shows 0.5 on the Park chain wear tool. According to previous posts, it should be more; unless the preious owner did change it.
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Old 05-28-19, 10:58 AM
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Originally Posted by joeruge View Post
....

Crank comes off ...
No way to do it without removing the crank?
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Old 05-28-19, 02:51 PM
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Hey Spinner, I stand corrected - if you have the same arrangement as I have, you should not have to remove the crank. The the wedge-bolt is accessible from the non-drive side of the front crank without taking off the crank-arm. However, if the eccentric is at all recalcitrant, (which it could be with sweat and Gatorade running down into for who knows how many years) it would be a good idea to remove it and apply grease or anti-seize to the whole assembly. In that case, you will have to remove at least one side of the crank.

Your first job is to get that wedge loose! Once again, remove the bolt that's into the wedge, and get a longer one that uses all the threads of the wedge and leave about 1/8" sticking out of the eccentric. You can probably get away with the using existing bolt but the reason to get a longer bolt is to make sure you have maximum thread engagement in the wedge. You don't want to back out that existing screw and then bugger up the fewer threads you are screwed into.

Get something like a nail-set whose point can fit into the hex socket of the longer bolt. The nail-set will give you a little more room to swing your hammer, make it less likely that you will strike the crank arm. The pointy end will help it stay in place until the deed is done.

If the eccentric is stuck in there, don't go hammering on the bottom bracket spindle - you could ding the bearings or races of the BB. Spray some penetrating fluid in and around the eccentric/BB shell and let it work for a while. Use your pin-spanner back and forth until it moves.. If you must use a little 'gentle persuasion' get a piece of pipe thats big enough to go over the spindle and still bear on the face of the eccentric. This likely will not work if you have external bearings. An external bottom bracket tool will actually give you a lot more turning torque than a pin spanner. Good luck!
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Old 05-28-19, 08:57 PM
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As I understand it, Sheldon Brownís point (referenced earlier) was that the captainís timing ring only wears on the front of the teeth, whereas the stokerís ring wears on the back. So in theory, one can swap the rings fore/aft when they begin to show wear.
Iím not sure I have the intuition on this one, as it looks to me like both synch rings are pushing the chain forward with the front of the teeth. But Sheldon generally has it right, so I will defer.
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Old 05-28-19, 09:36 PM
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On the eccentric bottom bracket, I feel thi need to add my $.02

There is several styles of bottom bracket. I have a Bushnell on my Rolhoff. It's fantastic. Allen wrench & spanner is all that is needed. Or, alternativly, 2 allen wrenches. 1 in a spanner hole, the other in an adjacent spanner hole rotated against the first.

On my tandem, I had the "other" style that had a cylinder and a wedge that locked in, in a similar manner to that of a quill stem. DO NOT try & free the wedge by threading in a bolt & banging it out with a hammer like you would for a quill. If it is truly stuck or you encounter difficulties it is easy to blow the aluminum threads clean out. The thing will be ruined...and still stuck.

The proper method for freeing that style of eccentric is to pound out the eccentric body away from the wedge.

Rubber/rawhyde mallets are not your friend. Shock force from a real metal hammer is what does the freeing action.
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Old 05-29-19, 09:34 AM
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Originally Posted by base2 View Post
On the eccentric bottom bracket, I feel thi need to add my $.02

There is several styles of bottom bracket. I have a Bushnell on my Rolhoff. It's fantastic. Allen wrench & spanner is all that is needed. Or, alternativly, 2 allen wrenches. 1 in a spanner hole, the other in an adjacent spanner hole rotated against the first.

On my tandem, I had the "other" style that had a cylinder and a wedge that locked in, in a similar manner to that of a quill stem. DO NOT try & free the wedge by threading in a bolt & banging it out with a hammer like you would for a quill. If it is truly stuck or you encounter difficulties it is easy to blow the aluminum threads clean out. The thing will be ruined...and still stuck.

The proper method for freeing that style of eccentric is to pound out the eccentric body away from the wedge.

Rubber/rawhyde mallets are not your friend. Shock force from a real metal hammer is what does the freeing action.
We have a Bushnell on our tandem, and it's easy to adjust. We bought the tandem used, and I ended up having to replace the wedges inside the bottom bracket, but it was an easy job, and we haven't had a problem with it. Our old tandem had the wedge-type eccentric like your Cannondale, and I found it much more difficult to work with.
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Old 05-29-19, 01:37 PM
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I have to agree with base2. You definitely do not want to be 'banging' on that wedge bolt. A gentle tap is all that I've ever had to give it (after making sure I had maximum thread engagement with a longer bolt!) to release the wedge. Anything more than that, attacking if from the other side makes a lot of sense. I have not had to use this method myself, so I have nothing to add to base2's very thorough description of how to do it.
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Old 05-31-19, 01:20 PM
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Chain wear: You don't need a special chain wear indicator to determine chain wear. Just a ruler does the trick. Measure a 12" length of chain while under rear derailleur or timing tension pin center (or edge) to pin center (or edge - just the same one!) and see how much elongation has occurred. Anything over 1/16" over a 12" span requires replacement. Anything over 1/4" may necessitate cassette replacement.

And some of you may notice you experience FASTER timing chain wear compared to your main drive chain. How can that be? Contradictory, right? Since the main chain has both riders' power going through it, you'd think main chains would wear twice as fast. Well, the opposite can be true. I experienced this and thought I was hallucinating. Luckily I happened to be attending Interbike in a few weeks, so I made note to bring it up with DuMonde Tech. They confirmed my experience and said they too had seen the same in their testing. The rep I spoke with had a theory: since a timing chain is going through only two positions during it's life - straight and at the same arc angle on the single timing chainring - it wears faster. As opposed to a drive chain that sees all sorts of arc angle permutations through myriad chainring/cog combinations, that the chain pins & rollers wear longer. Not sure if it's true, but it could be the reason, or one of them.

Timing chainring swapping - just reverse the two while maintaining their orientation. That way a chainring in the front that was formerly "pulling" and wearing on the front edge of the teeth, becomes a chainring being pulled on from the backside of the teeth. Also, you can reduce chain tension variations by loosening the chainring bolts just enough to get the rings to "break loose" and self-center. You rotate your timing chain to the tight spot and tap it with something. Doing this repeatedly while adjusting chainring bolt tightness will allow you to reduce the low tension spots in your timing chain through its rotation. Just be sure to torque down those bolts at the end!!!

And no hammers on eccentric wedges (if it can be avoided)!!!

Don't take a hammer to the bolt to un-wedge it. Your EBB will probably have an access hole on the opposite side which will allow you to thread another bolt in from the other side. The best way to do this is loosen the bolt in the EBB, then introduce the second bolt on the other side before removing the original EBB bolt. Run the new bolt through a washer (or one or two stacked cone wrenches - the holes are perfect) and into the EBB. The idea is to catch the threads with the new bolt as the original bolt unscrews. I recommend this so that the barrel nut inside the EBB doesn't shift, preventing the new bolt from engaging the hole and threads. Once the new bolt has engaged the threads, you may remove the original bolt. Then tighten down the new bolt you installed (with grease on head and threads) to dislodge the wedge. This works great for wedges that have been in a long time and/or without adequate or disappeared grease. Do not use anti-seize on threads or bolt heads - you NEED lubrication here! If you're really concerned about corrosion, then mix some anti-seize into your grease for this application.

Also, the crank arms do not need to be removed to perform the above. Just need to rotate cranks occasionally to make yourself room while working.

I just had to mention this because I've seen enough recommendations over the years to "hit it really hard with a hammer," which I consider bad advice and a great way to bend the wedge bolt and do all sorts of damage to the EBB and BB shell and environs.

My $0.02
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