Rear Brakes problem

[Trikindan]

Hey Guys, been out of touch with the group for a while, so many things going on in my life the Trike got placed somewhere on the back burner. I've only ridden it about 8 times in the past year and that's not normal for me by far.

To get to the heart of this post, I need HELP!!! The last couple rides I have noticed I half almost NO Brakes in the rear wheels when I back out of the garage and roll backwards down the drive (about 30') The front wheel will grab and slide but the rears do nothing. I pull to the top and roll back down pumping the brakes and they will slowly start to do a little braking. After I ride awhile they get a little better but could not stop the Trike without a lot of front assist. Brake fluid reservoirs are full and I see not leak streaks on the inter wheels. Not really sure how to bleed system and really not sure if this is the problem.

Your input and suggestions would be certainly appreciated.

Oh yeah These are DRUM Brakes...

[OldNick]

My 0.02 worth. All IME. Not a pro, just an older vehicle mucker-about.

Is the brake pedal soft/spongy at first application? Does it improve as braking improves with pumping?

If os I would have 2 main ideas: there is air in the fluid, or the escapement that keeps the shoes up to the drums is frozen form lack of use. It _may_ be that the brakes need manual adjustment, depending on where the brakes were sourced.

If it's air, the braking system will start softg then harden up as it compresses the air to a usable, if not iudeal pressure in the lines. If you do not brake for a while, the system allows the air to expand again and off we go again. If it's the brake adjustment, the system will slowly feed more fluid into the lines, pushing the drums onto the shoes at each pump. That hardens the brakes. But then the shoe springs bring the shoes back in again and the system gets soft.

If the brake system is pumped by hand and each pump makes the fluid level drop noticeably, I would be looking at shoe adjustment, whereas air in lines where it makes a huge softness tends to be in narrow tubing, so the actual volume of fluid needed to compress the air is smaller than the last idea....unless you have _really_ serious air in there.

If the pedal is hard at first application, but braking is poor, I would be thinking sticky wheel cylinders caused by gunk in there. Again, this could happen with long unused brakes. It would have to be bad to really cause brake loss as bad as you describe, but I recently rekitted my wheel cylinders and cleaned them and I could feel the difference, just not really major like yours. Here, I would expect some sticcking _on_ of the brakes once you have pumped them up, if the gunge is that bad.

Checking the need for manual adjustment is not that hard. Bleeding is not that hard, but you have to be careful. Let's know how the pedal feels and I or somebody can talk you through either.

Nick

[Jack Klarich]

If you have a hose to the rear brakes before the steel line, lightly but enough clamp force on the hose. If your pedal still sinks look at the master cylinder by passing that chamber. The fluil level may not go down but you will not build the right pressure. Do this after checking the adjystment of the rear shoes

[OldNick]

Yeah had not thought of that. (Even though I have had it happen ). Same could go for wheel cylinders....

In my case, the pedal stayed soft when there was bypass. Could it be improved by pumping in some cases, in a bypass situation?

Nick

[Trikindan]

Thanks Guys, good info. I have not had the time as I had planned to get serious on this but hopefully I will find time in the near future.

[OldNick]

Well if you work out what the trouble is, let's know and I at least () may have some ideas

Nick

[Jack Klarich]

Yeah had not thought of that. (Even though I have had it happen ). Same could go for wheel cylinders....

In my case, the pedal stayed soft when there was bypass. Could it be improved by pumping in some cases, in a bypass situation?

Nick

No, pumping will only cavitate and cause more air bubbles

You cannot comress the fluid with the air

1 or the other

The air willfloat over the fluid

this is why bleeders are always at the top of a cylinder be it a wheel cylinder or a caliper

Once a cup rolls over in a cylinder the air is trapped in the void

The fluid cannot move past theair

Pumping WILL make it worse

[Lee H. Mann]

Thanks Guys, good info. I have not had the time as I had planned to get serious on this but hopefully I will find time in the near future.

I stumbled upon this thread and thought my 2 cents might be worth hearing.....

I see that you have a GL1500 Motortrike with drum brakes.

You still have a linked system:

That is when applying the rear brake pedal it also applies the Left Front caliper as well.

I have converted an number of GL1500's over the years and I have noticed that the GL1500, either the two wheeled version or a three wheeled version, get an air pocket in the line going to the front wheel when the brake system is un-modified.

That line exits the mastercylinder and runs very close to the exhaust, and in some cases less than 1/4". All of the offending GL1500's had not recently (within the last 10 years) flushed their brake fluid. I suspect moisture had gotten into the line and boiled next to the exhaust creating an air pocket in the front line about 4" from the connection at the rear mastercylinder.

I have purged these systems and none have failed so far. Several customers said that prior to the purging they had a problem at the beginning of each riding season and they would only bleed the rear brakes. I did have to replace one mastercylinder on a 1989 GL1500 that wouldn't hold pressure unless you applied the brake quickly.

[BIG DENNY]

Hey Guys, been out of touch with the group for a while, so many things going on in my life the Trike got placed somewhere on the back burner. I've only ridden it about 8 times in the past year and that's not normal for me by far.

To get to the heart of this post, I need HELP!!! The last couple rides I have noticed I half almost NO Brakes in the rear wheels when I back out of the garage and roll backwards down the drive (about 30') The front wheel will grab and slide but the rears do nothing. I pull to the top and roll back down pumping the brakes and they will slowly start to do a little braking. After I ride awhile they get a little better but could not stop the Trike without a lot of front assist. Brake fluid reservoirs are full and I see not leak streaks on the inter wheels. Not really sure how to bleed system and really not sure if this is the problem.

Your input and suggestions would be certainly appreciated.

Oh yeah These are DRUM Brakes...

I would change out the old brake fuild and check for rust in dums.