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Old 01-12-19, 12:01 AM
  #9  
dddd
Ride, Wrench, Swap, Race
 
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Join Date: Jan 2010
Location: Northern California
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Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.

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Huret made a relatively small number of true retrofriction levers with a level of friction that adjusted itself based on the cable tension. It worked by anchoring the cable head to the end of the spring instead of to the lever itself. I consider these the most sophisticated "friction" levers ever, with the most linear effort force curve across the lever's range of motion and better able to accomodate a wider range of weird old derailers without slipping. Perfect for the Gran Turismo with it's heavy return spring!

Shimano Unishift DT levers (also found as headset-mounted on certain Schwinns), and Shimano M700 "stag's head" Unishift thumb levers all have a true clutched release.

Campagnolo offered Doppler retrofriction levers.

I'll cast another vote for the micro-ratcheted Suntour Sprint levers as seeming to be functionally the equal of most retrofriction levers.

If a retrofriction lever is loosening, either one of two possibilities exists.
Either the screw is self-loosening because of the anti-rotation plate, washer or mount having some back-and-forth freeplay, or the spring clutch is seized or unlubricated, forcing the screw to serve as a tensioning adjuster (it is supposed to be tight, with the inner sleeve/bushing not turning as the lever is moved).
Perhaps lubricating the lever internals thoroughly will free up the clutch wrap spring, allowing the mounting screw to hold the bushing stationary and thus remain tight.
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