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Using 11 speed cranks with 9 speed: spacers in the crank?

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Using 11 speed cranks with 9 speed: spacers in the crank?

Old 09-21-20, 03:35 PM
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adlai
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Using 11 speed cranks with 9 speed: spacers in the crank?

I just received an 11 speed crankset in the mail and I noticed that the space between chainrings is very narrow. It is noticably more narrow than an 8 speed crankset.

The chainrings themselves look fairly thick, about the same if not larger than the 8 speed chainring.

If I am using the crankset on a 9 speed system, does it then make sense to disassemble the crankset and insert spaces between the chainrings?
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Old 09-21-20, 05:02 PM
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Yes unless you plan on using an 11 speed chain.

Otherwise chain rub on the big ring is likely when you're using smaller cogs.

Wheels Manufacturing, Origin 8, and LeTour all make 0.5mm shims for one cog. AFAIK, Wheels Manufacturing has 1.0mm shims too.
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Old 09-21-20, 05:27 PM
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Use a 10 or 11 speed chain.
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Old 09-21-20, 05:43 PM
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Originally Posted by adlai View Post
I just received an 11 speed crankset in the mail and I noticed that the space between chainrings is very narrow. It is noticably more narrow than an 8 speed crankset.

The chainrings themselves look fairly thick, about the same if not larger than the 8 speed chainring.

If I am using the crankset on a 9 speed system, does it then make sense to disassemble the crankset and insert spaces between the chainrings?
No, you don't need any spacers between the chainrings. I just went through the process of upgrading my wife's 1991 Trek road bike from 7-speed to 9-speed. I don't have the links at hand anymore, but in the process of researching the project, I found a Lennard Zinn article where he explains that chainring spacing is not different enough to matter in this case. That prompted me to buy an FC-R7000 11-speed crankset for my wife's bike, and we paired that to a 9-speed cassette and 9/10-speed chain. The system works & shifts flawlessly with no chainrub in any gear combination.

For further clarity: the bike has 126mm spacing in the back. We bought a new Mavic Aksium wheel with an 8/9/10 speed freehub body with 130mm OLD spacing. We changed the non-drive side spacers from a single 10 mm spacer to a 6mm set, re-installed the locknuts, and trimmed a few mm off the axle. Everything went together like legos from there.

One addendum here: you might need to adjust the bottom bracket spacers on the drive side to put the driveline in the correct position. On my wife's bike, I made sure the center of the gap between the chainrings lined up with the middle cog on the 9-speed cassette. I think I used 2 x 1 mm spacers to get it right.

Last edited by BoraxKid; 09-21-20 at 05:46 PM.
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Old 09-22-20, 04:13 AM
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According to the Shimano Frame Fit specifications, the center to center distance between 11 speed double chainrings is 7.9mm and the center to center distance between 9 speed double chainrings is 7.7mm on current production road cranksets. To continue what would seem to be counterintuitive, the current production 8 speed doubles have a 7.6mm center to center distance between chainrings. So, the 11 speed crankset has more space between the chainrings than 8 or 9 speed.

Those numbers are for the majority of the cranksets in each category, but there are some that have distances that vary from that norm by up to .4mm, so Shimano doesn't seem to be too concerned with keeping that space consistent.
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Old 09-22-20, 07:20 AM
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The cranks will work fine.
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Old 09-22-20, 06:12 PM
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Originally Posted by BoraxKid View Post
No, you don't need any spacers between the chainrings.
When I attempted to use an FSA "9 and 10 speed compatible" compact crank with a 9 speed chain, I had chain rub in the 2-3 smallest and no overlapping range between rings.

Spacing it out to standard 9 speed dimensions it worked fine.
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Old 09-22-20, 06:14 PM
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Originally Posted by Drew Eckhardt View Post
When I attempted to use an FSA "9 and 10 speed compatible" compact crank with a 9 speed chain, I had chain rub in the 2-3 smallest and no overlapping range between rings.

Spacing it out to standard 9 speed dimensions it worked fine.
Interesting. That sounds like an FSA problem. I had no trouble with the Shimano setup as described earlier.
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