# Tandem Timing Chain Adjustment



## Znugg (Feb 16, 2008)

Hello everybody,

I did a search and did not find any information on this.

Do you have any suggestions on adjusting the timing chain?
How much tension?
What size chain rings?
What kind of chain rings?
What kind of chain to use for it?

I am currently using two Middleburn Hardcoat 30T and SRAM 951 chain.

Question: Is this normal? When I adjust the timing chain, certain point of rotation on the crank causes the timing chain to be tighter than other. 
Example (under min. load by using my hand to rotate the crank on the bench):
If I rotates the captain or stoker crank with my hand on the bench, at some point on the timing chain it is tighter than other point. The other point of the rotation has chain slack. So basically the timing chain tension is not even all the way through the rotation of the crank.

Any suggestions will be helpful. 

Thanks.


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## Znugg (Feb 16, 2008)

Hello everybody,

I did a search and did not find any information on this.

Do you have any suggestions on adjusting the timing chain?
How much tension?
What size chain rings?
What kind of chain rings?
What kind of chain to use for it?

I am currently using two Middleburn Hardcoat 30T and SRAM 951 chain.

Question: Is this normal? When I adjust the timing chain, certain point of rotation on the crank causes the timing chain to be tighter than other. 
Example (under min. load by using my hand to rotate the crank on the bench):
If I rotates the captain or stoker crank with my hand on the bench, at some point on the timing chain it is tighter than other point. The other point of the rotation has chain slack. So basically the timing chain tension is not even all the way through the rotation of the crank.

Any suggestions will be helpful. 

Thanks.


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## Trails4Two (May 12, 2008)

*tension*

The exact amount of timing chain tension seems to be a matter of team preference: some want a very tight chain to make sure it doesn't fall off - some want a slightly looser chain so if it does get forced off, it could be rotated back on. My feeling is that it should be tight but not so tight that it has resistance in rotating. I'll try to measure the amount of distance I can move our chain when I get home.

How uneven is your tension? It really shouldn't be very much different at all. Check the chainrings to make sure they are centered on the cranks. If it's not that, I'm not sure what's next: bent bottom bracket? Misaligned or poorly faced bottom bracket shell?

Good luck!


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## TandemNut (Mar 12, 2004)

On average, we look for 1/2" to 3/4" of deflection with moderate pressure on the middle of the chain. 
The rings can be slightly off-center sometimes. There's a link somewhere on DF for a way to mitigate that, involves loosening the chainring bolts somewhat and turning the cranks.
Most tandems have a tight spot and loose spot on the cranks at some point. If the timing rings are centered on the spider, you can try rotating one of the rings 90 degrees.
If it doesn't come out in the rings, then Chris is right; it's a bb or shell or crank arm issue.


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## Trails4Two (May 12, 2008)

I measured the deflection on our timing chainand, guess what? It was 5/8" just like BugNut said! You might think he built it or something like that.


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## Gevorg (Dec 7, 2004)

Here is the good link for adjusting the timing chain tension.
http://www.parktool.com/repair/readhowto.asp?id=23
12 mm or 1/2" is about right, tightness at one spot of the rotation is ok, as long as chain does not bind according to park tools link, if chain binds at tight spot you need to add more deflection or try to recenter your timing chainring so the center of the chainring coincides with center of the rotation of the cranks.
Here is the link on how to recenter the timing chainrings and some different strategy on how tight chain should be
http://www.precisiontandems.com/tiptimingchain.htm


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## reamer41 (Mar 26, 2007)

Znugg said:



> Hello everybody,
> 
> I am currently using two Middleburn Hardcoat 30T and SRAM 951 chain.
> 
> ...


In my little world, the tight spot issue is 'normal.' I've had all of 2 tandems, and on each this occured, with a total of 4 crank sets. I am also using middleburn rings and cranks -- the spiderless setup for the timing chains so the adjustment on the spider technique won't fly. I've had a small assortment of bottom bracket on this bike, so I suspect it's in the manufacturing tolerances of the cranks and/or rings.

I just don't worry about it! I adjust the timing chain so it's just tight at the tight spot, but not tight enough so it vibrates if you pluck it or strike it along the tight spot. So just barely not tight at the tight spot. Like has been said above -- will not cause binding or resistance set up this way.

--Charlie


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