SRAM S7 internally geared hub
Some notes and information on the SRAM S7 7-speed hub.
The series of hubs - also known as the earlier Sachs Super 7 - were produced in different versions from the nineties until the early 2010s. Unlike previous designs, the 7-speed hubs used concentric push-rods with a clickbox gear shifting system from the start of the production.
(Some notes regarding the above photo: This hub is the 2005 revision model that has the new type of mechanical design for the brake and the small driver ball ring was broken on this particular hub due to loose lock nuts, so it was replaced by loose bearing balls.)
Doing maintenance overhauls or repairs on the S7 is similar to the P5, with the biggest difference being the extra sun gear on the axle. It is easy to work on and shares some common spare parts with the P5, like the fixed axle cones, left ball ring, smaller driver ball ring, brake components, pawls etc.
Dimensions for wheel building:
Compared to the ubiquitous Shimano Nexus 7, the SRAM S7's conservative mechanical design with sliding blocks engaging with sun gears and clutches is a bit old fashioned. Gear shifts feel a bit clunky and not as smooth as the Shimano because spring-loaded components have to click axially into each other, instead of the purely radial/rotational system of the Nexus. But the S7 internal mechanism is very durable and due to the single-stage gearing design, the mechanical efficiency should be higher (meaning lower energy loss) than the two-stage design of the Nexus 7.
The Achilles' heel of the S7 (and P5) hub is its clickbox gear shifting system. Most often, problems with gears and gear shifting is not due to any mechanical failures inside the hub, but instead bent or seized pushrods, broken locating sleeves, water/moisture-damaged clickboxes, or incorrectly adjusted or installed gear cables.
The clickbox roll bar (officially called "Clickbox protection arm") as shown in the first photo on this page should be installed if you have it, to protect the external components of the gear shifting mechanism from damage if the bike falls over.
Some years after SRAM stopped producing and supplying spare parts for their internally geared hubs, SunRace Sturmey-Archer started offering compatible clickbox/shifter kits for the P5 and S7 hubs, enabling the hubs to keep running for many years to come. The EAN number for the S7 shifter kit is 4710944266603 and the corresponding pushrod set is 4710944268911.
Page last updated 2024-05-18 11:49. Some rights reserved (CC by 3.0)