Rear brakes

Rear Brake Systems - Blue Fox

The rear brakes on the US CX and GL models are functionally the same. Some European models use a hydraulic piston/rotor assembly, but the US models both use an expanding shoe arrangement, actuated by a arm connected to the foot lever. We will only examine the expanding shoe type here. The rear hub contains a pair of half-circular shoes (#5) to which a friction material has been bonded to the outside. These are held slightly ajar of the wheel drum and are fastened to the drum plate (#3) on one end. The other ends are held in contact with a rod (#7) with a elongated cross section that when rotated force the shoes apart with a cam action and into contact with the drum.

Altho the rear brakes only account for a small portion of the stopping power, their operation is essential to the safety of the bike. For those who have not experienced a front wheel slide from application of the front brake on less than ideal surfaces, try using the rear brake for low speed braking in gravel lots. The rear brake acts like dragging an anchor, and won't tip you over as easily as the front. In fact, I like to use the rear for many low speed maneuvers.

 There is little maintenance required on this system. The main problem area is the shaft #7 above that is inserted thru the hub. This sometimes will become difficult to turn due to rust on the shaft. Removal is straight forward and the shaft cleaned and re-lubed. Honda Moly 60 paste works well here as you also need some for the wheel splines later. I have personally encountered a bike that I was purchasing that needed a few hammer blows to the actuating arm to be able to even push the bike. A small dab of grease on the cam contacts at the shoe and some light oil in the shoe axles and they should be good.

The shoes themselves need to be checked for thickness and contamination with grease or oil. If the lining thickness is 2.0 mm or less, the shoes should be replaced. A note here in that if you purchase new shoes from Honda, you need to order 2, as they are sold singly. Other vendors may be different, so check before you purchase. Shoes contaminated with oil or grease can be partially cleaned with lacquer thinner, but the better alternative is to replace them with new.

These brakes also incorporate a wear indicator #8, that is visible outside the hub. If this indicator points to the reference mark on the hub under full application, the brakes need service. A difference between the CX models and the GL's is that the actuating rod and arm are over the top of the axle on the GL due to the Pro Link shock arrangement. The CX's rod follow below the axle to the hub.

The most common problem is that the rear brakes squeal, squeak, and make noise. This is almost always due to the friction characteristics between the shoes and the wheel drum. A glazed hard surface on the shoes against the smooth shinny drum sets up a resonant vibration not dissimilar to fingernails against a chalkboard. The remedy is to change one of the surfaces. Fingernails on cardboard are no problem. So either sand, abrade, scrape or roughen one of the surfaces. The shoes are the easiest and safest to do. Just don't overdo it and use up too much of your friction material. This may have to be repeated depending on the age and composition of your shoes.

Some steps to take if your rear brake is noisy

From the viewfindpostp232392 forum - Interstater

1. Clean the cam that operates the shoes, and the pivot pin on the other end of the shoes too. Dried grease and brake dust on the cam and pin, or excessive wear on either, can cause the shoes to not seat properly on them, making the shoes more likely sit unevenly and to resonate. I clean them, and then lightly coat them with brake grease, the same stuff used on caliper pins. Another thought… also make sure the shaft of the cam is not so loose in the bore that it rides in that it wobbles. Looseness in an assembly can change the natural frequency of it, letting resonance happen.

2. Use adhesive to temporarily line the brake drum with sandpaper, then mount the wheel and spin it by hand while lightly applying the brakes. Then take the wheel back off and look at the brake shoes to see how large the contact patch is. It is probably pretty small, and may be off to one side or the other a little bit. Clean any debris then remount the wheel and continue to spin by hand while applying the brakes, to make the contact patch larger. Do this multiple times. It can take some time, but get the contact patch as large as you reasonably can without sacrificing too much of the pad on the shoes, since new shoes are not cheap and you do want a decent life from them. When you take the sandpaper back off make sure you clean the drum really well to remove all traces of adhesive. I was taught this years ago by a Honda service manager when a customer complained about squeeky brakes on a new bike. Maybe it just ages the shoes prematurely, but it seems to help.

3. Make sure the springs installed on the shoes are up to snuff, as proper tension can help control resonance. Some shoes come with new springs, some don’t. If you put non-Honda springs on because they came with your shoes, and your new brakes squeak, try putting your old springs back on. If your springs are old and have not been replaced yet, try some new ones.

4. When reinstalling the wheel the final time make sure you do the ‘Swedish’ trick, I think they call it. Doing this is good practice anyway if you want good drive spline life. Loosen the nuts that connect the drive shaft housing to the rear drive, fully install and tighten the wheel and axel, then as the final step re-tighten the nuts on the drive shaft housing. It probably doesn't help brake noise, but maybe it evens out or changes the tension the spacer puts on the brake shoe mounting plate, changing the resonance?

5. I can’t really explain it, but I have found improvement if I reduce the amount of free play of the brake pedal. By tightening the nut on the rear rod so the free play is less, the total travel needed by the cam to actuate the shoes is less, meaning the shoes are maybe less likely to get out of alignment? Maybe it is just that more spring tension on the rod allows less vibration or resonance. I don’t really know why, but it seems to help on my GL’s.

6. Keep the assembly clean. This means that once or twice a season you should probably be dropping the wheel to remove brake dust and clean/lube the cam and pins. It’s a good time to lube the drive splines anyway.

Doing the above I have had, I think, pretty good success keeping the brakes on my GL’s quiet. I can’t guarantee the above will solve all the noise on yours, or that the noise won’t come back sooner or later and you have to redo some or all of it, but none of it is really expensive or difficult so it probably wouldn’t hurt to try.