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Help! Suntour/sugino rd has no tension

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Help! Suntour/sugino rd has no tension

Old 06-17-21, 06:24 PM
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3dvvitch 
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Help! Suntour/sugino rd has no tension


HI folks, I just got this Sugino75 rd delivered, but having just now mounted it on a hanger it has no return tension (Velobase says that, mechanically, the Sugino75 rd is a mix between Superbe and Superbe Pro iirc).

How easy is it to replace the tension spring? Do I just need a spanner for those slots on either side of the mounting bolt? Will it be possible for me to find a replacement spring (assuming that's what it needs) - or should I try to initiate a return on this and find something else? Thanks!

EDIT: Now I'm confused- this diagram depicts the mounting bolt and not as not having any associated spring mechanism, just a washer. Am I crazy? Is that not supposed to be a sprung pivot point in this design?

Http://mauisvintage.blogspot.com/2010/08/suntour-superbe-pro-rear-derailleur.html?m=1

Last edited by 3dvvitch; 06-17-21 at 06:35 PM.
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Old 06-17-21, 06:34 PM
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Old 06-17-21, 06:35 PM
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I've no experience with Superbe or Superbe Pro, but no Suntour I've ever had my hands on has had a sprung upper pivot.

I had to go and look - that assembly looks exactly like my ~1977 Cyclone GT.
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Old 06-17-21, 06:38 PM
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Originally Posted by DiegoFrogs View Post
I've no experience with Superbe or Superbe Pro, but no Suntour I've ever had my hands on has had a sprung upper pivot.

I had to go and look - that assembly looks exactly like my ~1977 Cyclone GT.
Ohhhh, I'm still a newbie with a lot of this stuff. I've never encountered a derailleur that lacked a sprung upper pivot.
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Old 06-17-21, 06:47 PM
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The B-screw is screwed into the upper knuckle of the derailleur. Under normal circumstances, the chain tension pulls that screw's end against the derailleur hanger's notch - it's free-moving. Later (I think) Shimano designs incorporate a sprung pivot there to allow the guide pulley to better track the cogs a bit.

In a way it's nice, though. With the wheel removed it's easy to move it out of the way by hand. It also simplifies it, and that function doesn't add much value on a friction shifting bike, anyway.
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Old 06-17-21, 08:03 PM
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I'm in the group that thinks there is no upper pivot spring in that derailleur. You should be able to unscrew that locknut on the back of the bolt and verify this.

I do have some later SunTour derailleurs that have sprung upper pivots, but they look different....





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Old 06-18-21, 08:50 AM
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It may not be the case here, but I had a Suntour derailleur that was shifting horribly. Return tension was almost non existent. After taking it apart, I discovered super hard grease inside around the spring. A good cleaning and fresh grease, and it was back to normal.
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