Bicycle Mechanics - Cassette spacers

I have a 9 cog cassette and Dura ace components. I purchased a 105 9 cog cassette and separate wheel to use when the bike is on a trainer.

When on the trainer with the new wheel, I hear a noise that seems to be coming from the casssette. When it gets to the two highest gears it sounds like the chain is rubbing against the links. . It is not the sound a chain makes when the derallieur is not shifting to the correct position. It is more like a low rumble that might be caused becase the cassette needs a wider space between cogs.

The thing that is confusing is that this cassette was working just fine at one time.

So, I guess I have two questions:

1 - has anyone run into this problem

2 - where can I purchase spacers to try and widen the gap between cogs if that is what I need to do.

THX -

Spacing should be the same on both. I would imagine you could get spacers at your LBS, but I never have. I know Harris Cyclery puts together custom cassettes, so they would definitely have them.

Is the cassette on tight enough? Perhaps it's loosened up. I'm sure someone else has a better idea!

The cassettes might be positioned slightly differently on the two wheels. You can test it by adjusting the cable and finding whether the noise disappears from next to largest cog. For the level of adjustment required, a spacer out of a pop can would do.

tellyho might be onto something, and it is absolutely worth checking first and foremost--your lockring may simply be too loose. There should be a torque spec right on the ring, and it's important to make sure it's good and tight.