Das 1x1 der Shimano Rollerbrake: Unterschied zwischen den Versionen

This article gathers information about Shimano Rollerbrakes, a type of drum brake which may optionally be installed on many models of Shimano Nexus internal-gear hubs as well as some Freehubs and front hubs. There are also articles on this site covering

A Rollerbrake is a kind of drum brake.

The images of several Rollerbrakes below are all at the same scale.

Because Rollerbrakes are grease-lubricated like coaster brakes, they add a bit of drag even when not applied. There are front Rollerbrakes available, but, in our opinion, a conventional cantilever brake is better for the front. We do not particularly recommend the Nexus front brake.

[Shimano has introduced improved Rollerbrakes since Sheldon first gave this advice; still, the demand on a front brake is greater than on a rear brake, and there is an issue with fork-blade loading, as with any front hub brake. An especially stout front fork should be used, and it must have a special brazed- or welded-on fitting. The Rollerbrake does not, however, tend to pull the wheel out of the fork as disc brakes do. Front Rollerbrakes typically include the infamous Shimano Power Modulator, which limits front braking. See Sheldon's article about braking and turning for advice on how to use a front brake for emergency stops-- John Allen]

A Rollerbrake has cylindrical rollers around a central, multi-faceted cam. The rollers press three brake shoes outward against the brake drum, for a more even distribution of outward force around the drum than with a conventional two-shoe drum brake.

Thanks go to Henry Cutler of Workcycles in Amsterdam for the photo below which shows the internals of a Rollerbrake -- from the middle outwards, the cam, six rollers (partially hidden under the retainer which positions them), three brake shoes and half of the external shell. The brake drum fits over the top of this assembly and around the brake shoes. The other half of the shell fits over the brake drum and holds the assembly together. In the photo, you can see a couple of tabs which have been pried up to open the shell and allow the brake drum to be lifted off.

A rear Rollerbrake's reaction arm attaches to the left chainstay using a clamp, or sometimes a brazed-on or welded-on fitting. The special fitting for a front Rollerbrake is shown in the photo below. It goes without saying that the cable to a front hub brake on a suspension fork must be run in housing, but the cable to a front hub brake with a rigid fork must also be run in housing, because flexing of the fork during braking can tighten the cable and lock the brake. We leave it to your imagination what will happen if you ignore this advice.

The image below shows the left side of a Shimano Nexus 8-speed internal-gear hub without Rollerbrake. There is a rubber cap, held in place by a nut and flanged washer:

Removing the nut, flanged washer and rubber cap reveals the Rollerbrake splines:

The Rollerbrake is installed in place of the rubber cap and flanged washer, and secured in position by the same nut. Splines on the brake drum engage the ones on the hub. Some Rollerbrake models require a spacing washer between the drum assembly and outer nut -- check which ones may apply to your combination of brake and axle. A link to technical documents is later in this article.

The reaction arm (at left in the photo below) must be securely attached to the left chainstay or fork blade. Leave the nut that holds the Rollerbrake only finger-tight, and leave the left axle end nut loose until you have installed the hub in the dropouts and secured the reaction arm to the chainstay. The nut which secures the Rollerbrake projects above the face of the shell, and can then be tightened with a 17 mm cone wrench. An easy mistake to make is to forget to tighten this nut, and only tighten the axle end nut (the one at the outside of the dropout) against this nut. Then the brake will be loose on the axle, and the shell can tilt and rub on the rotating brake drum assembly.

A locknut with a shoulder (red arrow in the photo below) holds the adjustment of the hub's left bearing cone and supports the Rollerbrake, or the flanged washer. If no Rollerbrake is installed, you can reduce the overlocknut dimension by leaving the cap and flanged washer off, but then you must replace the shoulder locknut with a nut which has a larger surface to press against the dropout. You could use the nut which held the cap and flanged washer in place, or a thinner locknut. The axle threading is 3/8 inch (9.5 mm) x 26 TPI. Some weather protection for the hub bearing is lost if the rubber cap or Rollerbrake is left off. Unscrewing the bearing cone to add grease is a good idea when making this modification. You might also install a different weather barrier, for example a rubber O-ring.

The Rollerbrake works with most common brake levers, other than levers intended for use with direct-pull brakes. The lever must be able to pull at least 14.5 mm of cable.

Again: the cable to a front hub brake must run down the fork blade inside a cable housing. Flexing of a fork blade due to braking can tension an open cable, locking the wheel.

You may search for technical documents for numerous Rollerbrake models at

Rollerbrake maintenance manual

A grease gun with a short nozzle will not do the job well, because it does not squirt the grease in far enough. You could use a needle which goes in as far as the Shimano tube does. Such needles are most commonly used to inject grease inside the rubber boots of automotive universal joints.

Aaron Goss, of Aaron's Bicycle Repair in Seattle, has sent the two photos below of Rollerbrakes, fully disassembled and cleaned. These photos may be helpful when rebuilding a brake. The photo below is of a small, front Rollerbrake.

Some higher-end Rollerbrakes have brake shoes with peaked (roof-shaped) braking surfaces. The brake must be disassembled further to get these brake shoes out, and these brakes are also more difficult to reassemble. The photo below is of an BR-IM70R rear brake, the same one shown in the image at the top of this page. This is a large Rollerbrake with peaked brake shoes.

There are links below to a Web page and a video about disassembly and reassembly of such a brake. The video's narration is in Russian but the procedure is clear enough from the images.

If a Rollerbrake is worn out, the entire main assembly must be replaced. Shimano doesn't offer spare parts. External parts -- nuts, bolts, adjusting barrels, clamps etc.-- are available for replacement.

   

Shimano tech Web site -- structure and function, troubleshooting charts etc.

Shimano Nexus lubricants

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