Bicycle Mechanics - Shimano 600 8 speed with 6 speed freewheel - how to make it work?

Hello there, I've just bought a nice road bike but the previous owner had Shimano 600 8 speed derailleur installed working with 6-speed freewheel. As a result the shifting is not perfect - 2 times the chain gets in between the cogs on in the freewheel - is there any way to fix it other than changing the rear wheel that is? Shiftmate? Fancy cable routing? Any ideas please?

Does it have 8 speed "indexed" shifters that click into each gear ? Downtube shifters or integrated with the brake levers ?

As a good (but not unbeatable) rule, Shimano derailers are usually cross-compatible across the range. Shifters and cassettes OTOH are usually not. So start by telling us what kind of shifter it is that you're using, and then maybe we can help figuring out how to fix your problem.

As a good (but not unbeatable) rule, Shimano derailers are usually cross-compatible across the range. Shifters and cassettes OTOH are usually not. So start by telling us what kind of shifter it is that you're using, and then maybe we can help figuring out how to fix your problem.

Best advice I've heard so far. The 8 sp derailleur should work perfectly with a 6 sp freewheel. That is if it has 6 sp shifters. We need more information.

The shifters are shimano 600 levers with indexing - the same line as derailleur. I was doing some research on line and apparently I could just swap the 6 speed freewheel for 7 or 8 freewheel. I would like to solve it without changing the freewheel though, if it possible. If not, the I was thinking of getting the 7 speed shimano mountain bike freewheel which has got the same cog spacing as 8 speed but is much easier to get.

and obviously the levers are way to sweet to touch them either...;)

If they are downtube shifters, those levers will work with any number of speeds on the rear wheel in friction mode- your easiest solution if the number of speeds and number of index clicks are not the same. Turn the D-ring on the right side shifter from SIS to Friction and you are done. If we are talking about a brake/shift lever combination (often called a brifter) then the number of indexed clicks and freewheel speeds need to match.

7 speeds will not give you any performance improvement, all things being equal. However, if your current freewheel is a corncob(like 12-18) and you need more range, then a 14-28 or 13-26 6 or 7 speed will work with those shifters and derailleur- again, if the number of index clicks are the same at both ends, in index mode, otherwise in friction mode. If the 8 speed RD is a 600 tricolor/640X series, then 28 is probably the largest rear cog that will wrap.

Stay away from 8 speed freewheels- they are notorious for bearing failure.

Stay away from 8 speed freewheels- they are notorious for bearing failure.
True and an 8-speed freewheel probably won't work on the OP's current hub without adding a spacer under the drive side locknut and recentering the axle to make up for its greater width.

Also, the fact the chain can slip between the cogs tells me it's an 8-speed chain being used with a standard spaced 6-speed freewheel and friction shifting won't prevent that.

Does it have 8 speed "indexed" shifters that click into each gear ? Downtube shifters or integrated with the brake levers ?


As a good (but not unbeatable) rule, Shimano derailers are usually cross-compatible across the range. Shifters and cassettes OTOH are usually not. So start by telling us what kind of shifter it is that you're using, and then maybe we can help figuring out how to fix your problem.


Best advice I've heard so far. The 8 sp derailleur should work perfectly with a 6 sp freewheel. That is if it has 6 sp shifters. We need more information.

Pictures can be helpful too