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Vintage low-end der shoot-out...

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Vintage low-end der shoot-out...

Old 05-31-19, 08:36 PM
  #26  
dddd
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What the old suntour GT design excelled at was handling a wide-range freewheel with a modest-ranging spread of chainring size.

Looking at the slant-parallelogram and snail-shaped cage pivoting in the single sprung body, the chain gap was well-controlled, and a convenient B-tension adjuster was also present.

But Shimano, Simplex and Huret both also knew how to maintain consistent chain gap, by using additional pivots.

Where one of these designs might perform more consistently though all of a bike's usable gears than a Suntour mech is when the chainring size difference is larger, since these designs could accomodate more chain uptake without having to use a spiroid cage plate that moves closer or further from the freewheel when a different-sized chainring is selected.

Looking back to the VGT era, most of the bikes with these had wide-range freewheels with narrow-ranging double (half-step in many cases), which was the perfect setup for that particular derailer.
Using the VGT with a modern "compact" chainring arrangement, expect some late-shifting shifting laziness when the bike is in the large chainring, especially when any kind of modern chain is used. At the extreme, one might find that the derailer frequently shifts across two cogs when only a single-cog shift is called for, but adjusting the axle position in the dropouts can usually help with this.

Shimano's and Simplex's arrangements were nearly identical to each other, but for the lack of tension adjustment in either of the Shimano's sprung pivots. So with the friction-shift era Shimano derailers one has to more carefully select a best chain length for any given size of freewheel, so as to keep the chain gap at a practical minimum.

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Old 06-01-19, 12:40 AM
  #27  
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@dddd, that's the best explanation ever. I always wanted to know that stuff, and no one has ever explained it (that I saw). Thank you.
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Old 06-01-19, 06:33 AM
  #28  
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Originally Posted by dddd View Post
What the old suntour GT design excelled at was handling a wide-range freewheel with a modest-ranging spread of chainring size.

Looking at the slant-parallelogram and snail-shaped cage pivoting in the single sprung body, the chain gap was well-controlled, and a convenient B-tension adjuster was also present.

But Shimano, Simplex and Huret both also knew how to maintain consistent chain gap, by using additional pivots.

Where one of these designs might perform more consistently though all of a bike's usable gears than a Suntour mech is when the chainring size difference is larger, since these designs could accomodate more chain uptake without having to use a spiroid cage plate that moves closer or further from the freewheel when a different-sized chainring is selected.

Looking back to the VGT era, most of the bikes with these had wide-range freewheels with narrow-ranging double (half-step in many cases), which was the perfect setup for that particular derailer.
Using the VGT with a modern "compact" chainring arrangement, expect some late-shifting shifting laziness when the bike is in the large chainring, especially when any kind of modern chain is used. At the extreme, one might find that the derailer frequently shifts across two cogs when only a single-cog shift is called for, but adjusting the axle position in the dropouts can usually help with this.

Shimano's and Simplex's arrangements were nearly identical to each other, but for the lack of tension adjustment in either of the Shimano's sprung pivots. So with the friction-shift era Shimano derailers one has to more carefully select a best chain length for any given size of freewheel, so as to keep the chain gap at a practical minimum.
Good explanation of the SunTour, but one may theorize all one wants about the Shimano early 600 (1984 6208), their performance was nowhere near that of my brother's SunTour, a much older design.
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Old 06-01-19, 09:00 AM
  #29  
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The other thing about the old Suntour stuff is it all works well. Suntour 7, Honor, or whatever, all work. The low end ones are just heavier, lots of steel parts, etc.

Open cage design was great. Sad to see that gone.
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