FelixScout

Hey all,

I have an old Bianchi Advantage of early 90's vintage that has a Sun Tour XCM derailleur and X-Press accushift plus shifter set. And long story short I snapped off one of the shifter levers last weekend and find myself needing a replacement real derailleur shifter. Aside from trawling Ebay for old stock and replacing the shifter with a friction shifter are there any modern options that are compatible?

Andrew R Stewart 

No, not that I know of. I would suggest you go current Shimano compatible cog set, der and shifter. Once the SunTour freewheel wears out you'll be revisiting this lack of compatibility. Andy

Unca_Sam

What cassette are you using? If it's an accushift cassette (on a suntour hub) and you don't want to replace or relace your wheels, your best bet for indexing will be Suntour old stock. They used a wider spacing on the higher gears, which the shifters compensate for.
Apparently the floating guide pulley on Shimano derailleurs will make acceptable shifting using a more common Shimano shifter.

Unca_Sam

Hm. Looking at Ebay prices now, I stole my X press shifters...

Best to price it out both ways. New drivetrain (maybe add a cog or two) or NOS/used shifters.

70sSanO

I guess it is 7 speed. If so, you could use Suntour accushift thumb shifters, but the sources are the same.

This is kind of the long and short. The only long term solution, other than friction, is to convert the shifters, derailleurs, and freewheel to Shimano compatible. The only real issue is whether you have a freewheel or a Suntour cassette.

If it is a freewheel you can just buy a cheap Shimano compatible freewheel that will last for a while, or get lucky with an old expensive Sachs Aris freewheel. If it is a Suntour cassette, then things escalate pretty quickly, unless you can re-space it to Shimano cassette spacing. I’ve never re-spaced Suntour so I don’t know the spacer diameters. If you can’t re-space, then a new hub/wheel.

If you are going to go that far, you need to re-consider staying with 7 speeds.

John

FelixScout

Hmmm, well I'm feeling a bit dumb. Since I swapped the very worn Suntour freewheel with a Shimano one and wondered about why my shifting was odd, not horrible but odd. Now I know.

So I should just be able to get a Shimano shifter and be fine since it will pull appropriately for a Shimano freewheel (FW 723 14-34)? Or get old gear, or just get a friction shifter.

FelixScout

It is a freewheel and I already pulled a dumb and swapped the old worn Suntour freewheel with a Shimano one (FW 723 14-34) and wondered about the odd shifting. Now I know better.

So would a Shimano rear shifter work in this case since the freewheel is already Shimano? Or should I just follow that course to the end and swap the shifter and rear derailleur?

The friction shifters are sounding tempting...

Unca_Sam

70sSanO already mentioned that. You're golden since you have a freewheel hub. Yes, the derailleur moves as much as the cable pull, so any appropriate width derailleur with enough chain wrap will work. Yes, a 7 speed Shimano shifter should index alright.

Swapping out a worn freewheel from a defunct manufacturer isn't a dumb, especially since Suntour had to stand out with variable cog spacing.

70sSanO

You will need to swap out the rear derailleur from Suntour to Shimano if you want to use Shimano index shifters.

The way it works is the shifter pulls a certain amount of cable length that moves the derailleur just the right amount to push the chain onto the next cog. The rear derailleur has a ratio that it will move a 1mm for every 1mm of cable pull to 1.7mm for every 1mm of cable pull depending on the mfg.

I think you can see where this is going. The Shimano shifter will pull a certain amount of cable to move a Shimano derailleur and move the chain from one cog to another. Because Suntour uses a different ratio than Shimano so it will move the chain some other anount. Putting a Shimano freewheel on the hub, doesn’t make the derailleur move the correct distance.

You’ll need Shimano front and rear derailleurs to use Shimano shifters; along with the freewheel you bought.

John