Hi,

It's time to change the timing chain on our tandem.

I've changed many "normal" bike chains, but I just wanted to be sure that my thought of just using two one-speed chains for a timing chain makes sense.

Thanks!

Mark

Before we switched to a belt, we used the same type that we used for the drive chain. That way one repair kit covers everything.

But the concept that one splices together two normal chains is valid?

More or less, as I recall, pre-belt, we used about 1.5 chains spliced together for the timing chain

That’s what we have done. If I recall, we used 6-speed chain, but maybe single speed would last longer? We have had no issues.

124 Spider,

I would not use a single speed chain. Under load your boom tube will bow (slightly). Now your timing chain has to flex as it is engaging the rings. Multi-speed chains are made to run like this, single speed are not. There have been reports of single speed chains coming off the timing rings because of this bow/flex of the boom tube that puts the timing rings out of alignment.

Tailwinds,
Charlie
S&S Santana Beyond

When we used a chain, I went to an 8-speed chain because it was cheaper (at the time) than the 9-speed the bike came with. I carried an 8-sp & 9-sp quick link then.

Same here, I matched the drive chain so I only had to worry about 1 size quick link for repair, the cost was not much of a factor to me compared to the hassle of dealing with 2 different chain sizes.

Yes, that's what you have to do. IIRC, takes about 1-1/2 chains. Save the other half.

I've been buying chain by the foot for our recumbent tandem - the timing chain and the main chain are both long.
https://t-cycle.com/collections/chain-in-bulk

Is this caution recommended for all tandem frames? I could see it for a round boom or a square one, but mine (Meridian) is oval, twice as wide as it is tall.

Yes. The tests were done before carbon fiber bikes, but all tubes flexed. Oval flexed the least, thus most tandem builders went to oval boom tubes. Also why Santana developed the "Z" coupler (initially for their boom tube), thus getting away from 2 round boom tubes (with small round S&S couplers) on their travel bikes. I would assume carbon fiber flexes too, but I do not know for sure as I only play as an engineer.

Mark Johnson, of Precision Tandems, once posted pictures to prove it. In the pictures his timing chain was taunt while they were coasting, and a had a belly on the bottom run as they were peddling.

Tailwinds,
Charlie
2016 S&S Santana Beyond (with an oval coupled boom tube)

Road Fan,

For pictures, go to www.precisiontandems.com scroll down the left side of the home page and click on "Tech Tips" then "Timing Chain Adjustment." Halfway down the page you will see the different pictures, peddling vs. coasting.

Tailwinds,
Charlie