Mounting a 7-Speed Cassette on an 8/9 speed hub I asked an earlier question regarding putting modern road wheels on my old steel frame.

After clarifying a few things the main issue to me is the number of gears on the freehub. (The freehub I'm considering takes an 8/9 speed and has a Shimano fitting). My bicycle is currently a 7-speed and uses a freewheel rather than a freehub.

So I think I have 2 options:


Put an 8-speed cassette on the new wheel and increase the number of gears on my bike. Issues: I assume an 8-speed uses a narrower chain; will my front chainring work with it?
Put on this 7-speed cassette which says it can work on an 8/9-speed hub with a set of spacer rings. Questions: how do I use the spacer rings? Do I need only one of each for the whole cassette of one for each sprocket? Will this allow the slightly wider chain I currently use on the 7-speed.


Which option would be the better choice?

A few points to consider:


Shifters are friction, so no need to consider indexing but I am unsure whether they have the range for an 8-speed (but with a narrower chain maybe the range is the same, just with smaller movements between gears)
My deraileur is actually a modern Shimano 8/9 speed already (as the old one broke). I have adjusted it to suit my 7-speed with the limiter screws.
Since you have friction shifters and an 8/9 speed derailleur, you should be able to pop a 9 speed cassette on the back and use the full range.  You'll have to re-adjust your limit screws of course. Worst case, if that doesn't work, you may be able to remove one of the small cogs and space it out to use only 8 speeds. 

The font chainrings will also likely be fine, usually you can go up/down one size without issue for front chainrings. Since your front chainring is designed for 8-speed, it will probably work fine with a 9-speed chain. I regularly use a 9-speed chainring in front with an otherwise all 10-speed setup without issues.