you can also respace an 8 speed cassette using 9 speed spacers to give the right spacing, and use an extra spacer at the back of the cassette so that the 8 speed cogs are held tight when the lockring is tightened.
If I recall you have to cut parts of the splines on the plastic spacers to get them to fit, but I only did this once ages ago and I can't recall the exact detail. I did get it to work fine when I upgraded a bike from 8 to 9 speed when it first became available, and I kept the old wheels for a while.
you can also respace an 8 speed cassette using 9 speed spacers to give the right spacing, and use an extra spacer at the back of the cassette so that the 8 speed cogs are held tight when the lockring is tightened.
If I recall you have to cut parts of the splines on the plastic spacers to get them to fit, but I only did this once ages ago and I can't recall the exact detail. I did get it to work fine when I upgraded a bike from 8 to 9 speed when it first became available, and I kept the old wheels for a while.