SunTour Vx derailleur

itboffin

I have one of these beauties on my Mercian



Problem is i've just changed the down tube shifters to SIS friction and the spec on the derailleur says index compatibility is friction, will I still be able to use it or is an upgrade in order?

If the later does anyone know of a similar style 7 speed derailleur, most of the models I found are nasty cheap looking things.

http://www.disraeligears.co.uk/Site/Sun ... (2nd_style).html

itboffin

Don't all rush at once :P

ride_whenever

If you've got friction shifters they will work. They should also work with indexed 7spd ones assuming the pull ratio is the same...

If you get some that are changable from friction to indexed (fair few) then they should work.

itboffin

ride_whenever wrote:

If you've got friction shifters they will work. They should also work with indexed 7spd ones assuming the pull ratio is the same...

If you get some that are changable from friction to indexed (fair few) then they should work.

Ta i'll give it ago

itboffin

It sort of works, I can shift up and down which is a good start with hardly any noise but its not reliable sometimes it's shift up and down two or three and sometimes not down at all.

I have no idea how to begin indexing down tube shifters.

GarethPJ

It's not just the pull ratio that needs to be the same, the spacing on the block/cassette needs to be the same too. So if you're using Shimano shifters you will need a Shimano SIS compatible block or cassette as well. And that's assuming the pull ratio is the same.

Bear in mind that Suntour had the patent on the slant parallelogram rear mech until 1984 so they had the lead over the competition. However when the patent expired the competition started using similar designs and adding their own improvements that they had developed to try to catch up with Suntour since the sixties. As such this meant that the competition leapt ahead. Suntour on the other hand didn't adopt those refinements and so stagnated. Shimano in particular developed indexing and added it to their cheaper ranges. This means that within a few years a cheap Shimano mech would be better than a much more expensive Suntour mech. Which is why Suntour disappeared up their own bumhole.

If you want to retain that mech, rather than trying to get indexing working try a pair of Suntour Powershift levers. They are not indexed as such but they have ratchet action so you do get a much more positive shift. And obviously they are more historically accurate as and accompaniment to your mech.

itboffin

GarethPJ wrote:

It's not just the pull ratio that needs to be the same, the spacing on the block/cassette needs to be the same too. So if you're using Shimano shifters you will need a Shimano SIS compatible block or cassette as well. And that's assuming the pull ratio is the same.

Bear in mind that Suntour had the patent on the slant parallelogram rear mech until 1984 so they had the lead over the competition. However when the patent expired the competition started using similar designs and adding their own improvements that they had developed to try to catch up with Suntour since the sixties. As such this meant that the competition leapt ahead. Suntour on the other hand didn't adopt those refinements and so stagnated. Shimano in particular developed indexing and added it to their cheaper ranges. This means that within a few years a cheap Shimano mech would be better than a much more expensive Suntour mech. Which is why Suntour disappeared up their own bumhole.

If you want to retain that mech, rather than trying to get indexing working try a pair of Suntour Powershift levers. They are not indexed as such but they have ratchet action so you do get a much more positive shift. And obviously they are more historically accurate as and accompaniment to your mech.

Thanks very useful information.

itboffin

For anyone who might find this thread in the future a SunTour Vx rear derailleur works perfectly with 5,6,7 speed friction or indexed shifters.

now if I could just find some replacement jockey wheels to fit

Earblown

itboffin wrote:

For anyone who might find this thread in the future a SunTour Vx rear derailleur works perfectly with 5,6,7 speed friction or indexed shifters.

now if I could just find some replacement jockey wheels to fit

I think "perfectly" might be a slight exaggeration; the SunTour Vx S I own seems to have neither a Shimano-style "cable saver" (or "pre-select") spring in the cable-housing stop nor a Shimano-Centeron-style sideways-floating guide pulley to put downshift-now-and-let-the-derailleur-catch-up action or index-misalignment forgiveness in the derailleur, but perhaps Hyperglide-style smooth-shifting features (ramps, shaped teeth, neighboring-sprocket tooth alignment) in modern sprocket clusters let one ignore the absence of a derailleur feature.
Perhaps someone needing replacement pulleys can find a dealer at velo-orange.com and get some Velo Orange Grand Cru Jockey Wheels.