Converting index shifting

[Derosid]

I have an older steel bike that came with Shimano 105 in the early ’90’s. It has index shifting on the downtube, and I’d like to convert it to shifting on the brake levers. I know I have to match pull on the lever to the derailleur, but I don’t know much about the 105 group.

The back of the rear derailleur is stamped “RD-1051”. Is there a compatible brake shifter for this version of the 105?

This is a great project where we are passing on my wife’s old Giordana to my daughter, who is very excited about starting cycling on this bike.

[rccardr]

That RD was originally intended for 6/7 speed indexing.
Shimano used the same cable pull for a long time so they will also index with 8-9-10 speed shifters but then you've got to change the chain, cassette, etc. to match.
7 speed brake/shifter units made by Shimano (Sora) and LT Woo are out there.
Used ones too, but since they are 25 years old they will likely not be as reliable as new units.

[Mark McM]

Originally Posted by rccardr

That RD was originally intended for 6/7 speed indexing.
Shimano used the same cable pull for a long time so they will also index with 8-9-10 speed shifters but then you've got to change the chain, cassette, etc. to match.
7 speed brake/shifter units made by Shimano (Sora) and LT Woo are out there.
Used ones too, but since they are 25 years old they will likely not be as reliable as new units.

For 6/7/8spd, Shimano had only 2 cable pull ratios - one for Dura-Ace, and one for everything else (including MTB). For 9spd, Shimano unified the cable pull ratio, so Shimano 9spd shifters/derailleurs are essentially all inter-compatible. After that, Shimano indexing started to diverge again.

From the photo, it appears that there are 7 sprockets. 7spd cassette/freewheel systems were essentially universal - the same spacing was used by Shimano, SRAM (Sachs) and Campagnolo (and while Suntour wasn't exactly the same, it was close enough).

So, long story short, just about any Shimano 7spd indexed shifters will work with the 105 RD-1051 derailleurs. This includes road downtube or dual control handlebar shifters, and MTB thumb or Rapidfire shifters.