Simplex RD Pull Ratio?

[HovR]

Does anyone know what pull ratio Simplex used for their rear dérailleurs in the mid to late 80's, and if it happens to match the pull ratio used by any modern shifters?

I'd quite like to upgrade my Peugeot to a modern set of indexed shifters, but if possible I'd like to keep the original rear dérailleur. It's marked SXG-10 if that helps anyone, and can be seen below!

Cheers!

 

[Smokin Joe]

You need to find out the spacing between the sprockets and see if any modern systems use the same or almost the same (Within a mm over the full range.

Alternatively you could see how easy it is to slot in a nine or ten speed wheel, it's a steel frame and in my experience the dropouts pull apart enough to do that with only light thumb pressure. You would need a new mech though, odds on the Simplex would not work with indexed shifters of any type.

 

[HovR]

You need to find out the spacing between the sprockets and see if any modern systems use the same or almost the same (Within a mm over the full range.

Alternatively you could see how easy it is to slot in a nine or ten speed wheel, it's a steel frame and in my experience the dropouts pull apart enough to do that with only light thumb pressure.

The frame has already been cold-set, and those are Fulcrum Racing 7 (10 speed) wheels with a spacer and Shimano 8 speed cassette. The only original bit of kit on there is the dérailleur (which I was hoping to keep, if possible) and the friction shifter.

You would need a new mech though, odds on the Simplex would not work with indexed shifters of any type.

That's what I figured. I was just wondering if by some slim chance it matched the pull ratio of a modern system, as if I stick with the original rear dérailleur I won't have to tap a thread in to the gear hanger. Plus I just quite like the originality of it.

 

[raleighnut]

You will have a lot of trouble trying to index that rear mech. The way Shimano got indexing to work was by allowing the top jockey wheel to float sideways by a mm or so to prevent the chain side plates from riding on top of the sprockets, maybe a new top jockey wheel would fit.

 

[andrew_s]

The CTC shimergo page has a table of how far various shifters pull the cable per click, and of sprocket spacing for different cassettes.
Fit an indexed rear shifter, and measure how far the Simplex moves over 4 or 5 of the middle clicks (end clicks are generally larger and rely on the limit screws). That will tell you how far the mech moves per mm of cable pull, and allow you to peruse the tables and see if there's any suitable combination. So long as there isn't more than about 1 mm of mismatch across half of the number of sprockets, a floating top jockey wheel should see something usable with a bit of fiddling.

 

[HovR]

The CTC shimergo page has a table of how far various shifters pull the cable per click, and of sprocket spacing for different cassettes.
Fit an indexed rear mech, and measure how far the Simplex moves over 4 or 5 of the middle clicks (end clicks are generally larger and rely on the limit screws). That will tell you how far the mech moves per mm of cable pull, and allow you to peruse the tables and see if there's any suitable combination. So long as there isn't more than about 1 mm of mismatch across half of the number of sprockets, a floating top jockey wheel should see something usable with a bit of fiddling.

Really useful resource! I'll look in to it, cheers!