Does my rear brake need rebuilding?

[jcpeden]

My rear brake is a bit crap. I know the rear is a drum brake but with it pulled all the way in (to the handlebar) I can still shuffle the bike forward/backwards.

I can feel the brake acting and I remember something about drum brakes being more effective once the bike was in motion but I believe the rear lever should also engage the front brakes (which work very well).

Possible just need to adjust the cable?

[gn2]

Would be worth inspecting the shoes to check for excessive wear.
Which means taking the rear wheel out.

[montliz44]

JC, try adjusting your rear brake cable first. It's easy to do and there are adjusters on both ends of the cable. The brake lever shouldn't be loose enough to touch the handlebar. After you've adjusted the cable, put the scooter on the centerstand and spin the rear wheel. If the brake shoes are worn out you'll hear a metal-to-metal sound which is obviously not healthy and you may even still be able to spin the wheel with the brake applied. (Unlike disc brakes, drum brakes don't give an audible signal unless they're applied.)

As far as I can tell, there's no link between the two brakes. That would be hard to do, since one is mechanical and the other is hydraulic, and I don't see any such connection.

Johnny

[gn2]

Unless you visually inspect the shoes you cannot know the condition of the brakes.
Doing the adjuster up may improve the braking, but you will not know the condition of the brake.
Its a five year old scooter so the shoes could be fucked.

[zanggerk]

Once you adjusted the cable you can also get an indication about the wear of the brake shoes by looking at how close the little mark and arrow are at the rear brake when you pull the handlebar all the way. That's described in the manual on page 110.
Anyway, after 5 years of riding you might well have to replace the brake shoes. Takes just about 30 min or so- I did mine last weekend.

[honkerman]

Woah, slow down, back up the truck.

How many miles are on the scooter? Brake Drum shoes don't wear out terribly fast. Before you do anything crazy, adjust the Freeplay.

So, I made a quick video. One thing I don't mention on the video is that the lever freeplay is only supposed to be 10-20mm. That's not a bunch. I don't have my own set that tight, it feels too jumpy to me, so adjust to where you feel comfortable.


Sorry for the wind noise

[honkerman]

If you do take the rear drum apart, the manual doesn't specify what the shoes should measure, though if the leading edge is worn down too much, they should be replaced. The internal diameter of the drum has a service limit of 131 mm.

[gn2]

As well as the issue of wear, you can't tell if the shoes are glazed or contaminated unless you look at them.

[honkerman]

As well as the issue of wear, you can't tell if the shoes are glazed or contaminated unless you look at them.

That is so; however, we have no info as to how many miles are on the scoot. It's unlikely that brake shoes will be glazed after only a few thousand miles. The shoes on my kymco's drum brake lasted 20,000+ miles. So it's possible, but unlikely. His issue, with what little info he's given, sounds like it should be as simple as a freeplay adjustment.

By all means, if he wants to take the wheel off and inspect the shoes and drum, it's his time to spend; however, we don't even take a drum off to inspect it here in PA if it has a wear meter on it, which the PCX apparently lacks, which is annoying. Just the same, no need to shoot the horse if it throws a shoe. Best to start small and work your way up.

[gn2]

Best to start small and work your way up.

There's a very filthy joke hiding in there...

[jcpeden]

Scooter has only done around 12,000 miles, I was playing with the rear brake at the lights today and I believe it just needs to be adjusted for a few reasons:

1) The rear brake stops the bike effectively albeit with the lever pulled most of the way in

2) There is no audible noise when using the rear brake e.g. squeaking or grinding metal

3) The lever doesn't actually reach the handlebar. I'd like it to be a lot sharper as there is still too much travel but it cannot be pulled all the way in.

I had thought the PCX used Honda's combined braking system, in spite of only the front being a hydraulic disc brake:

http://world.honda.com/tech-views/motor/cbs/PCX/

[gn2]

The PCX rear brake is combined with the front but the rear drum goes out of adjustment over time.
Its really easy to adjust, you just turn the nut on the threaded rod.

[honkerman]

Scooter has only done around 12,000 miles, I was playing with the rear brake at the lights today and I believe it just needs to be adjusted for a few reasons:

1) The rear brake stops the bike effectively albeit with the lever pulled most of the way in

2) There is no audible noise when using the rear brake e.g. squeaking or grinding metal

3) The lever doesn't actually reach the handlebar. I'd like it to be a lot sharper as there is still too much travel but it cannot be pulled all the way in.

I had thought the PCX used Honda's combined braking system, in spite of only the front being a hydraulic disc brake:

http://world.honda.com/tech-views/motor/cbs/PCX/

As in my little video, and as GN2 said, the adjustment is simple. The system is combined, yes, but the left lever only actuates one of the front pistons. The front brake caliper has a total of three Pistons, two operated by the right lever, and one operated in conjunction with the rear brake.

[montliz44]

Oops -- Looks like I was wrong about the combined braking system. Sorry about that, and thanks for the Link, JC. That's a very interesting article, but it still didn't explain how the thing works. Enquiring minds want to know -- could there be a separate master cylinder hidden up under the plastic somewhere??

And the answer is YES! According to the Honda service manual, there's a small master cylinder, which Honda calls the CBS (combined braking system) master cylinder, hidden up in the front panel next to the ignition and seat/gas cap switches. I still haven't figured out how this one is actuated, but I'll save that for another day.

Anyway, sorry again about not believing in the CBS, and thanks for setting me straight.

Ya learn something every day

Johnny

[montliz44]

P.S. : Thanks for the video, Paul. Plus I stuck around for your history of the scooter vid -- well done and great fun. Thanks for that one too.

Johnny

[Robbie]

And the answer is YES! According to the Honda service manual, there's a small master cylinder, which Honda calls the CBS (combined braking system) master cylinder, hidden up in the front panel next to the ignition and seat/gas cap switches. I still haven't figured out how this one is actuated, but I'll save that for another day.

Rear brake cable pulls on a 2nd lever in front of the steering bearings (behind the headlight). This 2nd lever then operates the secondary front master cylinder (with the small reservoir you found) and also pulls another cable to the rear wheel.

There are therefore 2 separate brake cables between the handlebars and the rear wheel. There is also an adjustment to available to the back brake behind the headlight, but it's a pain to get to.

[montliz44]

Thanks, Robbie !

That one really had me scratching my head (needless to say, I've been too lazy to pull off the paneling to see what all was in there). So those photos the service manual has are of the adjustor for the lever from the cable to the CBS master cylinder. Neat trick. Got it. Now just waiting for for a good excuse to go in there and have a look.

Much appreciated,

Johnny