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Old 05-18-07, 09:51 AM   #1
bobchmara
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Rear Derailleur gear span question

I have an 86 Miyata Seven Ten on which I replaced the stock Suntour six speed 13-26 freewheel with a Shimano seven speed 11-28 freewheel. The seven speed freewheel is a bit wider than the six speed, but there is sufficient clearance for the freewheel to fit and for the chain to engage the 11t sprocket without having to mess with spacers/redishing, etc.

The stock Suntour Cyclone rear der can readily span the seven cogs, but does not have sufficient capacity for the 28t rear cog. So I purchased a Suntour VGT rear der to replace the Cyclone. The VGT accommodates the 28t cog just fine, but will not engage the 11t cog even with the high gear limit screw fully backed out.

So I made a shim to fit between the rear der and the hanger, and the VGT now spans all seven cogs just fine. But the B tension adjuster screw only barely engages the flange on the hanger. Is there a shim I can buy that addresses this problem, or am I better off just buying a newer rear der?

Thanks,
Bob Chmara
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Old 05-18-07, 12:32 PM   #2
Gonzo Bob
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The Cyclone doesn't run on the 28T? I had a Cyclone equipped Fuji back in the mid-80s and I thought it had a 13-28 FW. You might be able to get the Cyclone to work with a hanger spacer - space it a little more outboard and the parallelogram will drop the guide pulley just a little more by the time it gets to the 28.

So the B-tension screw of the VGT is only partially on the tab of the hanger? If you think it might slide off to the side then you need to fix it, but it might work as is.
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Old 05-18-07, 12:39 PM   #3
Sheldon Brown
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Quote:
Originally Posted by bobchmara
I have an 86 Miyata Seven Ten on which I replaced the stock Suntour six speed 13-26 freewheel with a Shimano seven speed 11-28 freewheel. The seven speed freewheel is a bit wider than the six speed, but there is sufficient clearance for the freewheel to fit and for the chain to engage the 11t sprocket without having to mess with spacers/redishing, etc.

The stock Suntour Cyclone rear der can readily span the seven cogs, but does not have sufficient capacity for the 28t rear cog. So I purchased a Suntour VGT rear der to replace the Cyclone. The VGT accommodates the 28t cog just fine, but will not engage the 11t cog even with the high gear limit screw fully backed out.

So I made a shim to fit between the rear der and the hanger, and the VGT now spans all seven cogs just fine. But the B tension adjuster screw only barely engages the flange on the hanger. Is there a shim I can buy that addresses this problem, or am I better off just buying a newer rear der?
The VGT was hot stuff in 1974 when I bought my first one, but technology has left it far behind.

Even a $20 Shimano Tourney Megarange would be a MAJOR upgrade from that relic. There has been a LOT of improvement in derailer design over the last three decades.

Sheldon "Old Frames, New Parts" Brown
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Old 05-18-07, 12:49 PM   #4
bobchmara
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Thanks Sheldon, I expected that was the answer, but I had to ask the question!

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