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Old 07-17-21, 11:21 AM
Join Date: Jan 2018
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8 speed cassette spacing

I picked up a used Shimano Hyperglide XTR CS-900 12-28 cassette. I plan to put on road bike with Dura Ace RD-7403.
According to Sheldon Brown table, should be 1.8mm thick, 3mm spacing, and 4.8mm ctc spacing.

The 4 biggest cogs (18-28) are on a spider, and match the table dimensions. They have stamp Q R. Same for first loose cog (16T) and spacer.

But three smallest cogs (12,13, 14T) do not match. They are 2mm thick.
The 12T has expected 3mm integrated spacer.
The 13T has ~3.2mm integrated spacer.
These 3 have Q stamp.
These 3 dont line up exactly with any of the Shimano dimensions in Sheldon table, 7 or 8 speed, so not sure what to make of it.

Do the smallest cogs sometimes have different dimensions, or should all cog in cassette be same?
I am wondering are the three smallest cogs original from the cassette, or a mash-up pulled from another cassette?
Will these work on 8 speed or cause shift problems?

Thanks in advance for any insight.

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