mojopt

Tell if I'm thinking right. I'm starting a build. I have a Dura-Ace 8 speed cassette. Presuming the RD has the range of motion to accommodate an 8 speed cassette is it the spacing between the cogs that pretty much determines what indexed shifter will work?

If this is not correct please set me straight.

I'm just trying to think ahead for later upgrades.

Thanks,

Mike

DannoXYZ 

No, it's the shifter that determines which positions the RD will click into. You don't have to use Dura-ace shifters + RDs since 8-spd spacing was the same across the board. You can pretty much use any Shimano 8-spd shifter with any RD (Dura-ace exceptions apply).

Here's some links of interest:

https://www.sheldonbrown.com/dura-ace.html (Dura-ace compatibility with early/late 8-spd)

Al1943

All Shimano 8-speed cassettes have the same cog to cog spacing but if you plan to use a Dura-Ace 8-speed rear shifter you will need to use a Dura-Ace 8-speed rear derailleur. You could use any other Shimano 8-speed shifter with any other Shimano rear derailleur.
You can even use any Shimano 9-speed rear shifter with the Dura-Ace 8-speed rear derailleur with any Shimano 8-speed cassette.

Al

johnknappcc

There is the rare exception, that the RD will pull a different amount of cable (due to cable routing), especially true of older friction-only RD's. My Shimano Light Action was like this, but it was also from a 23 year old bike that was only ever intended to run friction.

If that's the case, RD's are cheap.