Are 7&8 speed freewheels interchangeable?

[UpWrong]

If they are both Shimano splined? Same widths?

And I am asking about freewheels, not cassettes.

[Barrowman]

Going 8 to 7 should be fine. 7 to 8 will inevitably be wider , and you might find the smallest cog catches on the frame.
If this is happening, you might have to space the axle a little to prevent it happening. If you take the freewheel off you will see there's a spacer on the freewheel side of the hub/axle.
There might be a spacer behind the freewheel too. You can lose this but it puts the freewheel closer to the spokes so you have to be happy that the rear Mech is adjusted properly and isn't going to mash the spokes.
This hadn't used to be a problem with solid Axles, however quick release Axles don't give you much leeway . If there is a spacer on the axle in the opposite side to the block you can take it out ( feasibly) and put it back on the other side.
Depends just how much room you have.
Also probably have to re dish the rear wheel for optimum performance if you do this .
And if the spacer makes the axle wider between the locknuts ( the 'OLD' : Over Lock Nut Distance) you might have to spring the frame slightly ( assuming a steel frame here) .
Not as simple as you might have thought ...

[UpWrong]

Thanks. Yes wondering if I might go from 7 to 8. It would be a solid axle, so maybe.

[gregoryoftours]

Do you mean Shimano splined as in the splines for removal tool? When you say interchangeable do you mean you want to be able to use the same indexed gear levers with the new freewheel or just that you can fit the new one on the same hub without having to change axle/spacers?

It might be possible, but It is unlikely to be a straightforward swap from 7 to 8 speed. If the spacing between cogs is different you may need different shifters. Your axle may need re spacing and wheel dishing, you may have chain clearance issues with the stays in small sprocket, depending on your rear derailleur you might have difficulty getting the full range of side to side movement over 8 gears.

[UpWrong]

Regular freewheels don't have splines (unless you mean the splined fitting for the removal tool) so that's a little confusing, are you sure you don't mean freehub/cassette? and I don't know of any Shimano 8 speed freewheel either. When you say interchangeable do you mean you want to be able to use the same indexed gear levers or just that you can fit them on the same hub without having to change axle/spacers?

Yes, screw on Shimano std freewheel rather than Campag. 8-speed freewheels are apparently wider than 7-speed freewheels (at 39mm) so it depends on the hub whether there is room or not.

[gregoryoftours]

Regular freewheels don't have splines (unless you mean the splined fitting for the removal tool) so that's a little confusing, are you sure you don't mean freehub/cassette? and I don't know of any Shimano 8 speed freewheel either. When you say interchangeable do you mean you want to be able to use the same indexed gear levers or just that you can fit them on the same hub without having to change axle/spacers?

Yes, screw on Shimano std freewheel rather than Campag. 8-speed freewheels are apparently wider than 7-speed freewheels (at 39mm) so it depends on the hub whether there is room or not.

Ah I don't know, you'd need to find out the spacing of the sprockets on the 8 speed freewheel, and other variables with hub and frame, derailleur etc. It's probably going to have to be something you'll have to try physically to see if you can get it working or not. I edited my last reply so that's changed!

[simonineaston]

Are 7&8 speed freewheels interchangeable?

I'm currently examining combinations of 5, 6, or 7 speed freewheels from SunTour. I read that one of the criteria dictating which you choose is the cycle's over-locknut distance, described here by the ever-excellent Sheldon. The same will be true of Shimano 7 and 8.

[simonineaston]

...and as an earlier respondent noted, I had to move the axle a bit in order to prevent the chain rubbing on the frame when in top gear - in my case 12t.

[rjb]

Give some thought to fitting an outrigger bearing if you go to 8 speed. May save your axle breaking.
viewtopic.php?p=1502644&hilit=outrigger ... b#p1502644