Internal Hub Transmissions
This article will discuss the adjustment of internal geared hubs. These include SRAM® Dual Drive hubs, and Shimano® 3-speed hubs. Consult the manufacturer for further information. Internal overhaul and service is not covered.
The SRAM® system uses a derailleur and a cassette gear stack. The hub has three internal gears, which "replace" the three chainrings of other bikes. The hub uses a rod that is pulled outward by a lever in the housing. The housing includes a button to move the lever, allowing to slip over the axle. The lever is actuated again, which locks the housing to the axle.
Shift the lever to the "neutral" or 2nd position. There are two dots on the lever indicating this position.
Use the barrel adjuster when the lever is in second and view the window in the housing. There are two lines in the window. Adjust the bright orange indicator so it is between these two lines.
Shimano® 3-speed Hubs
The Shimano® system uses a lever on the handlebar that pulls a cable. The cable activates a lever arm, which pushes a rod into the hub. The rod shifts the internal gears, giving the bike effectively three different gear ratios. Like other internal speed hubs, one gear is "neutral", as if the bike were a one-speed. The gearing is determined by the size of the front sprocket and the rear sprocket. The internal gears reduce this ratio for a lower gear ("1st"), and can also increase the ratio for a higher gear ("3rd").
To change the wheel, begin by shifting the lever to 3rd, which relaxes the cable. Unthread small lockring holding the shift cable adjusting barrel.
Unthread adjusting barrel completely from housing lever. Loosen locknut on housing, and unthread housing.
Replace wheel after tire or wheel service. Adjust chain tension as normal and secure axle locknuts. Thread on housing locknut, and install rod. Thread on housing fully. It may be necessary to back up in order to have lever arm point at adjusting barrel of cable.
Thread adjusting barrel onto lever stud. Place shift lever in "2nd".
Use adjusting barrel to tension cable. View housing at axle and look for a red letter "N" and a red line. The "N" represents neutral, which is considered the 2nd gear. Adjust until "N" appears squarely in the opening, and the red line is seen in the slot.
These hubs require occasional lubrication. Lubricate two times per year for light riding, or every other month for more consistent riding. Use a bicycle gear oil, if available, or a light weight automotive motor oil. Only a few drops are required at a time, do not over oil, as excess lubrication will end up on the spokes and then the rim braking surface.