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Technical Q and A with Lennard Zinn: A question of chain length

  • By Lennard Zinn
  • Published Jun. 1, 2010
  • Updated Feb. 8, 2011 at 8:25 AM EDT

Dear Lennard,
You made a goof in your recent column regarding the woman with a SRAM XX 11-36 cassette and rear derailleur, and a Red compact crank. The XX rear derailleur is capable of taking up the slack between the 34-11 and 50-36 ratios. The user most likely doesn’t have enough links in her chain!

We set up bikes with 11-36 rear ends and 50-34 fronts all-day everyday at my shop here in Sonoma County. We’ve got lots of hills and lots of dentists who refuse to admit they need a triple!
-Jerry Likes Bikes

Dear Jerry,
You’re absolutely right. Sometimes I answer these questions too late at night with a deadline looming. Fortunately, there is something we can all learn from here about chain lengths from different manufacturers.

I got in touch with the reader who sent the question. As you said, she needed a longer chain. She wrote:

Thank you for writing again. Before I even got your first answer, my husband bought a new SRAM chain and put the set-up together with the entire chain, I am thinking it was 114-116 links, did not count them. Anyway, it now works PERFECT with the 50/34 crankset and 11/36 cassette, very crisp shifting. So … I will just keep the old chain for when I use the 28 cassette and use this new chain for when we go to the mountains. Sorry we didn’t count the links, but the receipt says it was a SRAM PC1031 10-speed chain.

I forgot to say, before buying the new chain, we looked up how to size a chain on the Park Tools website–very useful information. On the original set-up 11-28, hubbie used a fancy KMC chain, which was 112 links.

Thanks again. Maybe you have helped someone else also who is looking at this.
-Maxine

This example does illustrate the fact that not all chains come with the same number of links. Shimano chains come with 116 links, SRAM chains come with 114 links, and it doesn’t say on the KMC Web site, but at least in Maxine’s experience, those come with 112 links.

When we set up our huge full suspension 29ers, we often use a SRAM chain at full length and take a couple of links out of a Shimano chain. That’s with the 18-inch (457mm) chainstay length shown in the drawing and with a maximum cross gear of 44 X 34 teeth. But if we were to increase the big chainring size or largest cog size, we would start running into problems with SRAM chains.

Chainstays on tandems generally run longer than on a single, and the large chainring and largest cog both tend to be bigger than on a single. That’s because you can go so much faster on the flats and straight downhills with two people powering the bicycle and the wind resistance not a lot more than a single rider. Yet you go so slow uphill, due to two people loading it down and not able to efficiently coordinate riding, especially out of the saddle. So the likelihood of coming up short on the chain is high, as Maxime found out.

If your chain straight out of the box is too short for your bike, it’s not a good idea with a 10-speed chain to add a link or two more with a chain tool, due to the likelihood of breakage of the narrow chain. Instead, I would use two master links to hold in the extra links.
-Lennard

Dear Lennard,
How does one measure wear on cassettes and chain rings? It’s easy to do for a chain but what about the components of the drive train?
-Lorne

Dear Lorne,
Rohloff makes a simple “HG-IG-Check” tool that checks for cog wear. The tool only works on cogs smaller than 21 teeth.

On the chainring, inspect it visually for wear. It’s soft aluminum, and it’s petty obvious when it’s been damaged by an elongated chain.
-Lennard
Readers can send brief technical questions directly to Zinn.

Got some mountain bike tech questions? Check out Lennard’s FAQ on Singletrack.com


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Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Zinn’s column appears here each Tuesday.

FILED UNDER: Bikes and Tech / Technical FAQ TAGS: / /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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