[rcnute]

I should know this, but I don't. My Shimano 600 derailleur from the mid-80s is dying. I have a new-ish 105 ten-speed derailleur in the bin. The bike has a six-speed freewheel and the rear shifting can be indexed. Will the 105 work? Will it work with six-speed indexed shifting? Thanks!

 

[farva]

It should work as long as the derailleur cage is wide enough to accept a 6 speed chain without rubbing. Rear derailleurs have no indexing. The compatibility magic is between the shifters & cassette/cogs.

 

[PJ352]

I should know this, but I don't. My Shimano 600 derailleur from the mid-80s is dying. I have a new-ish 105 ten-speed derailleur in the bin. The bike has a six-speed freewheel and the rear shifting can be indexed. Will the 105 work? Will it work with six-speed indexed shifting? Thanks!

Wow, your 600 RD wore out already?

Your 105 RD will work fine with any of the variables you described. The shifter dictates travel, not the RD, but you'll obviously have to adjust the limit screws.

 

[rcnute]

Wow, your 600 RD wore out already?

Your 105 RD will work fine with any of the variables you described. The shifter dictates travel, not the RD, but you'll obviously have to adjust the limit screws.

Yeah, 25 years is unacceptable!

Will modern derailleurs usually fit wider six-speed chains or is it hit and miss?

 

[PJ352]

Yeah, 25 years is unacceptable!

Will modern derailleurs usually fit wider six-speed chains or is it hit and miss?

Generally speaking, yes. But since chains tend to be the lower priced component (and have less service life), I tend to think of it in opposite terms: is the chain compatible with the other drivetrain components.

Six speed chains are compatible with drivetrains up to 8 spd and measure about 7.1mm's in width. The 10 spd Shimano RD cages measure (approx.) 10mm's. That given, I think you've got much better odds of 'hitting' than 'missing'. BTW, FWIW there's only about a 1mm difference in chain width going from 6 spd to 10 spd - 7.1 to 6.2mm's.

Of course, if your chain is as old as your 600 RD, you may want to spring for a new one.