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Old 12-12-06, 12:11 PM   #1
koine2002
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Shimano Shifters/Suntour Rear Derailleur?

I did a search, but couldn't seem to find any answers. I've got a 1988 Schwinn Premis that was donated to me, and I've been doing some work on it. Someone respaced the dropouts to 130 and I'd like to put a 7 Speed (13-24) freewheel on it (it's got a 14-26 six on it right now). It presently has a Suntour Cyclone 7000 drivetrain. I do know that there are cog spacing issues between Shimano and Suntour (found that on the search). I'm not willing to shell out $90 for a freewheel (yellowjersey) and want to do this as low cost as possible. I can get shimano DT shifters and a freewheel for around $25 from my source. However, with Shimano shifters, would I have to replace the rear derailleur too, or is pull ratio not an issue in this case when it comes to indexing? Of course, I could always go friction as well.
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Old 12-12-06, 12:26 PM   #2
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I know I'm going to start sounding annoying with this line, but:

Why bother?

Is the addition of one cog to the rear going to make enough difference to bother changing over what's probably an already working setup? I'm already running five, six, seven and nine speed rears, and have never really seen what difference going up one cog in the rear is going to make. Five speed to nine, yeah. Six speed to nine, yeah a discernable difference, but not as much. Seven to nine is starting to be a wash, so I can't see where going up one additional cog can make all that much of a difference.

Of course, if you're talking going from a 14-28 six speed to a 14-34 seven, with a 28 as the next to the largest cog, then I can see the addition. If we're talking the same general range however, I get the feeling you're about to spend a fair bit of money, and take a lot of time and trouble for something that's going to make virtually no difference when you're out on the road.
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Old 12-12-06, 12:59 PM   #3
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Quote:
Originally Posted by koine2002
I've got a 1988 Schwinn Premis...and I'd like to put a 7 Speed (13-24) freewheel on it (it's got a 14-26 six on it right now). It presently has a Suntour Cyclone 7000 drivetrain.

I can get shimano DT shifters and a freewheel for around $25 from my source. However, with Shimano shifters, would I have to replace the rear derailleur too, or is pull ratio not an issue in this case when it comes to indexing? Of course, I could always go friction as well.
You're in luck! There's a serendipitous combination that will work for you:

Replace the Sun Tour derailer with a Shimano one, any model, even a $20 Tourney.

As explained at http://harriscyclery.com/freewheels:

"Mixed Sun Tour/Shimano Indexing

"Sun Tour indexed shifters pull less cable per shift than Shimano systems use. Thus, generally, you need to match Sun Tour indexed shifters with Sun Tour rear derailers.
However, it turns out that Sun Tour 6-speed shifters index pretty well with 7-speed clusters if you replace the old Sun Tour rear derailer with a Shimano unit!

"The mismatch in cable travel cancels out the mismatch between 6 and 7 speeds. There won't be a "click" for the lowest gear, but the derailer's low-gear limit stop will provide the "indexing" for that gear."

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Old 12-12-06, 01:48 PM   #4
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An alternate solution if you've already got the Shimano DT shifters (I'm assuming 7 speed) and a Shimano spaced freewheel is to add a Shimano derailler, almost any Shimano derailler designed for indexing. You should be able to do that for about $20 extra.
As you point out, you also have the option of friction.
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Old 12-12-06, 06:52 PM   #5
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Thanks all for the thoughts. A solution presented itself. I went to my main parts suppliers (30 miles away) and he's a haven of NOS (I don't think he's thrown anything away, ever!) to check out entry level MTB's for a friend of mine. I picked up a NOS 13-24 7 speed Suntour freewheel for $15. I've got a Suntour set of shifters that are multi-speed compatible (off a Nishiki International I'm restoring for a friend--I can use whatever parts off of there he said) and I'll put those on mine and put the white cyclone shifters off of mine on his (they're a better color match anyway). I'll take the 6 speed freewheel off of mine and put on his since his is shot (it freely spins in both directions). I just killed several birds with one stone.
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Old 12-13-06, 01:37 PM   #6
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First check your shifters. Some of the Suntour indexed shifters have 3 modes - 6-speed, 7-speed, and friction - selectable by loosening the D-ring and turning the housing on the shifter body. I put Suntour GPX on my frameset in 1989 and it has the 3-mode shifter.

While the spacing of Suntour and Shimano freewheels is not identical, usually there's enough play in an indexed system that you can mix and still get good shifting. I've used Suntour 6- and 7- and Shimano 6- and 7-speed freewheels in my bike and they all have worked fine.
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Old 12-13-06, 02:08 PM   #7
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Mine have all three of those options--6, 7 and friction.
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Old 12-16-06, 03:09 AM   #8
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so theoretically i shouldn't be able to use my 105 indexed downtube shifters with my xc pro rear mech?
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Old 12-16-06, 10:59 AM   #9
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Quote:
Originally Posted by dooley
so theoretically i shouldn't be able to use my 105 indexed downtube shifters with my xc pro rear mech?
Probably not, but it depends on how many speeds you're talking about for both the shifters and the cluster.

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Old 12-17-06, 04:12 AM   #10
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the shifters are 7 speed, the freewheel is a shimano 7
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Old 12-17-06, 10:47 AM   #11
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Quote:
Originally Posted by dooley
the shifters are 7 speed, the freewheel is a shimano 7
That's not likely to work with a Sun Tour derailer, unless you manage to jigger up something similar to the Shimano "Alternate Cable Routing" http://sheldonbrown.com/alternate

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Old 12-18-06, 04:42 PM   #12
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someone forgot to tell my rear mech
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