I have an old (10 years) Scott bike that I'm slowly refurbishing. The original set up was a 7 speed freewheel and I have put on a new wheel with a 8/9 cassette hub. I have put on exactly the same 11-34 cassette as I had freewheel but with a spacer that I was sold with the new cassette. The problem is I am getting a rubbing/grinding on every cog as if the chain is either not lined up correctly or is too wide for the cogs. This only happens when I'm riding so i can't find exactly where it is rubbing. Do I need to change the rear derailleur or do I need a different chain?