Just replaced my cassette to an 11-28. I have always had to use 4 black spacers with the 12-25 but when using the 11-28, there is only 3. I would like to understand why just out of curiosity.
I assume you’re talking about the spacers in between the cogs, not the ones that go on the freewheel before installing the cassette? If it’s the spacers between the cogs, some of the cogs are permanently fixed together. On my 12-23 10sp, the 3 largest cogs 23-21-19 are all fixed together so there aren’t any loose spacers, the spacers are fixed with the cogs. I suspect with your change in cassettes there are different sets of cogs that are fixed together.
Just replaced my cassette to an 11-28. I have always had to use 4 black spacers with the 12-25 but when using the 11-28, there is only 3. I would like to understand why just out of curiosity.
The nice thing about SRAM Red XG 1090 cassettes is that there are zero spacers. The cassette is machined as one unit. And it’s light.