MrCjolsen

Shimano SY20-A

Sunrace 7 speed clamp on downtube shifters

The bike is a 1986 Miyata One-Ten that has been extensively upgraded with Campy rims, Dura Ace and Ultegra 7-Speed drivetrain, a Brooks Saddle, etc. (I had a neighbor who was changing hobbies from cycling to woodworking and needed to clear space in his garage and gave me a big box of really nice old parts. If I was buying all that stuff, I sure would have put it on a nicer frame)

Anyway, the bike presently has Shimano clamp on downtube friction shifters. They work OK, but I'd like the rear to be indexed. I tried taking them apart, and putting Dura Ace indexed shifters on but it was off when using the big ring.

Now, it says the Sunrace shifters don't work with Dura Ace. Why is that? I held a non-DA freewheel up the DA freewheel, and the laterally, the cogs lined up perfectly.

And if the Sunrace shifters don't work, will the Shimano one's work OK? Or should I just stay with the non-indexed shifters?

badamsjr

I do not have experience with these specific shifters, but have found (through trial and ERROR) that not all shifters will work with all derailleurs. It has to do with the amount of cable pull the manufacturer builds into their components. My issue was with MTB front der. and road brifters not quite cooperating. Switching to bar end shifters fixed it. You might get lucky, but you might have less hassle using the friction shifters that already work. Just my opinion, and your mileage may vary.

MrCjolsen

So it's the derailleur, and not the cogset? If that's the case, then I have a Suntour cyclone, and an Ultegra RD that would work.

badamsjr

As long as the cable pull matches, it should work. I say try it--at worst, you may find it does not work, but might also get lucky and have it be just what you are looking for!

Zef

Shimano did some funky stuff with certain years of dura-ace that made it only compatable with other dura-ace components.

As for your last question about it being the derialleur and not the cogset...

...The derailleur, cogset, and shift lever specs all play an integral role in getting your shifting to work smooth.
The amount of cable pull at the shift lever must jive with how much movement that will cause at the derailleur which inturn must jive with the spacing of the cogset.

As has been pointed out...you can mix and match and get things to work well but it is usually based on a lot of trial and error. You may also never get things to work optimally.

For the most part you can mix and match components with good effect below Dura-Ace with each other as long as you stay shimano, but if you mix dura-ace with other shimano stuff you need to research the models years that had compatability issues.

I have a bike that has campy chorus 8spd ergo with an old shimano 600 front derailleur, an athena rear derailleur and an old 600 crankset that was designed for a 6spd bike. The rear cassette is campy as well. It works great but the rear drive train components (derailleur, cassette, shiftlever) are all campy and compatible with each other.


YMMV,
-j

-j