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I noticed on the largest sprocket of my SRAM Red cassette, after every 8th tooth, the tooth is missing. I looked at one on line and noticed the same thing. What is the purpose of not including these three teeth on the sprocket?

Picture from ebay

  • Can you add a photo -- either of your actual sprocket or a stock photo from SRAM's site? – RoboKaren Feb 5 '17 at 18:39
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    I can't find a SRAM Red 1098 cassette on google, but things like this are normally there to improve shifting. – Batman Feb 5 '17 at 18:54
  • RoboKaren....I added a picture. I hope it got uploaded correctly. There is also a pic of one at ebay.com/itm/Sram-Red-Og1090-11-26-10-Speed-Cassette-4333-21-/… – Paul K Feb 5 '17 at 19:03
  • Batman - that makes sense, especially when going to a larger sprocket. It does not look too common, however. – Paul K Feb 5 '17 at 19:04
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    I edited the picture from ebay in, @PaulK. Feel free to revert or to use a different photo if you want. – RoboKaren Feb 5 '17 at 23:47
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In general, when you see oddly shaped teeth or variations on a cassette/chainring, its there to facilitate shifting (such as Shimano Hyperglide, and ramps/pins you see on chainrings/cassettes; see this link for some examples).

In this case, SRAM calls it their "Open Glide" technology. To quote them: "OpenGlide tooth ramping allows for faster chain transition between cog postions. We employ OG on the radical OG1090 cassette for sure and higher shift speeds."

And here is a figure SRAM provides:

enter image description here

The marketing blurb from Art's Cyclery says: "SRAM's open glide technology refers to the shift gates created by removing teeth at key spots on the cogs to facilitate fast, effortless shifting going up or down or under power."

Whether it actually shifts better or not is a matter of debate, but a quick search says that generally not. I'd guess SRAM also found that to be the case, because they don't do this on cassettes in their current product line.

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    I have this "feature" on a SRAM force cassette as well. Never found it to work better/worse. I wonder if there are any chain wear effects? – Rider_X Feb 5 '17 at 21:34
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    I'd guess that it might wear a bit less, but not enough to be significant in any way -- it would depend on the period of the links being caught on a tooth, and that would also depend on the GCD of your chainring size and teeth on the cogs. – Batman Feb 5 '17 at 22:01

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