rear brake not working

[Ed Brock]

This was a surprise and not a pleasant one. I was doing about 15mph, going down a slight hill and was only using the rear brake pedal. The bike pedal felt normal, the rear brakes have always work well, but now, the rear brakes barely applied. The front brakes work excellent. Tried pumping the rear brakes several time with no change. This is different then an empty master cylinder, the brakes do apply, just not enough to stop the bike even at 5mph. Again front brakes work excellent, no pulling so I'm guessing that both calipers are working together.
Has anyone experienced this before? The rear master cylinder has clean brake fluid in it, DOT 4. So far I have not check anything else yet. The bike has 30,000 miles on it. Has been serviced regularly all of it's life.
Thanks Ed

[MikeB]

I did experience this once, on my ST1100. The brake pedal felt like it was doing its job, it felt hard as I pressed it down but the rear brake was not applying properly. I got it figured out though. I inspected the pedal through its movement and found a small rock lodged between the pedal arm and the frame of the motorcycle. It was not brake related at all but a victim of asphalt chip sealing. One of the small rocks got kicked up by the front tire and lodged itself between the frame and brake pedal arm.

[minimac]

When did you check the pads last? Very worn pads will act like that. A rotor that is at or near minimum thickness, as well as a hose that it deteriorating from the inside will do that also. Did this happen only once, or gradually get worse? It's not all that uncommon for some debris to be kicked up and temporarily cause an issue with the pads or caliper also.

[Ed Brock]

minimac,
Thanks for your information. I last checked the brake pads (front/back) in December of 2019. I performed the bikes hibernation for winter storage and that included changing all fluids including brake and gear etc. At that time the rear brake pads showed about 60% pad life left. I did flush the front and rear brake lines and found no air in the complete system. After I was done with it's winterization the bike sat for 2-3 months. I took it out of hibernation and test rode it a few time (short rides), everything worked as it did before it's hibernation.
The bike has 30,000 miles on it, I have all of the shop service records and there is no mention of the rear caliper being replaced. I don't think at the 30,000 mile point the disc would need to be replaced.
This situation only happened once, as I have not taken the bike out since. I need to remove the left saddle bag and look into this situation before I riding it again. I did not like the concern factor that went with applying the brake. Once the saddle bag is off I will look at the brake lines. Weather or not I see a problem on the outside of the rubber brake line I will most likely replace it. I am thinking about buying SST lines.
I pumped the rear brakes up several times and then held it down for 1-2 minutes, then pumped it up again several more times. I did block the rear pedal in the applied position overnight and repeated the above process again. The bike has been sitting this way for 3-4 days now. I think today I will look at it.
Ed

[minimac]

I had a similar thing happen...just once. It was as though there was a 'phantom air bubble' or something. The rear brake petal went all the way, no resistance whatsoever,when I went to stop. I pumped the pedal a couple of times, it came back to where it should be, and it never happened again. I checked the fluid, the lines, pads, even the rotor thickness, and never found a thing wrong.

[Ed Brock]

To all,
I was able to MOVE the left side saddle bag enough without having to remove it. I'm not done checking yet, but I found the rear bleeder just a bit to loose. It was very snug, not tight, The rear rubber brake line is the interference point, the wrench hits it. That "snugness" could be enough to over time let some air in. Going to re-bleed all of the brakes.
It's almost like "minimac" describes. Only the problem never went away.

I wish to apologize to all for the astrects I used awhile ago in a post. I was not meaning any offensive language to anyone. Sorry, will not do that again. Very nice to see this site is well monitored.
Ed

[Ed Brock]

I believe that my problem is solved. Only time will tell. The only thing I found was a snug rear brake bleeder vs a tight rear brake bleeder.
Hope that's the end of problem. Thanks all for the help.
Ed

[pocketchange]

pump up the brake and hang a weight on the rear pedal lever.. overnight.. then bleed it in the morning,
if you are still having problems. pc

[Ed Brock]

Thanks. Have used that trick many times on trucks, cars and bikes. It just simply works. All is normal now. When I rebleed the brakes this time, I saw the smallest amount of air once the second time I pumped up the system and bleed it, after holding the pedal down over night. It was in the rear caliper. I will have to play the wait and see game.
Ed

[WingAdmin]

You can generally tell what is going on by how the pedal/brake lever reacts.

No brakes, cannot pump up brakes: air in brake lines and/or empty reservoir
Spongy brakes with too much travel (or requires pumping up to obtain sufficient pressure): air in brake lines
Firm brakes with too much travel (or requires pumping up to obtain sufficient pressure): Stuck piston or excessive rotor runout
Brakes operate, but may require pumping to obtain sufficient pressure, and pedal sinks slowly after pressure applied: brake fluid leak or worn seal in master cylinder
Brakes firm and seem to work normally, but little or no braking actually occurs: oil or brake fluid contamination on rotor and/or pads

[Ed Brock]

Wingadmin,
So true. Good information. You can tell a lot by what the pedals do. Also just looking at the fluid will tell you a bunch as well. In my case, before winter storage all worked as it was suppose to. After winter maintenance and storage, then on the 2nd ride, well, I had a surprise. I'm glad I was using a lot of cation. Now I'm in a wait and see mode. I do hope the snug breeder, not a tight bleeder is the cause. I have seen others with dirty fluid have issues in heat, but not in the spring in 50-60 degrees.
Ed

[CrystalPistol]

Again front brakes work excellent, no pulling so I'm guessing that both calipers are working together.

I'm sorry, had to smile. It's just one front wheel, even with just one brake it ain't gonna pull left or right.

On your GL1500 bike, the right front caliper is the only one operated by the handlebar brake lever, the left front caliper is operated along with the rear caliper by the foot pedal rear master cylinder anyway. You may have a failing rear foot operated master cylinder or a leak under pressure like that "not tight" bleeder. If you bleed them, bleed the left front caliper first, then the rear caliper, repeat as needed.

Just tonight I visited a buddy who had the soft rear pedal on his '96 GL1500, it's sat unused a lot last couple years as he's had other irons to tend. Last year he complained about the brakes and even bought a rebuild kit … I told him several times to try the tie down brake pedal trick, even leaving it so. Today I asked if he'd done it, he said yes and that he forgot to check it in last week or two, so I went over and saw the pedal was tied all the way down with bungie strap. I undid it, let the pedal up, he has a great pedal now, he was speechless. I told him we should get together & change brake fluids & bleed them all soon, but now his carbs leak. Well crap.

[Ed Brock]

CrystalPistol,
Glad to make you laugh. I was tiring to say that both front caliper are working together. Apposed to one side working the other not working (there by the "pull"). Boy, choice of words can get one into so much trouble.
Thanks.
Ed

[Solo So Long]

The only way to tell if both sets of front calipers are working equally is to use a crush gauge. If you are getting ANY effect from the rear brake pedal to the front brake, it will look the same as one that is applying full force.

[Ed Brock]

Solo So Long,
I have never heard of a "crush gauge". What is that? Is it like a line pressure gauge? Thanks for the infofmation.
Looking forward to learning about the gauge.
Ed

[soumilinon]

front right brake is connected to rear brake lever,may have to bleed front caliper

[Ed Brock]

soumilinon,
Thanks for your input. I have rebleed the brakes. As I mentioned I did find the rear caliper bleeder was "just" snug, not tight. So far, no more issues. I still like my rear brake pedal height block I built. It just simply works for me.
Ed

[bellboy40]

front right brake is connected to rear brake lever,may have to bleed front caliper

That is true for your GL1200 but the 1500 is the opposite. Left front caliper is linked to the rear brake.

[Ed Brock]

well now, I guess my dyslexia got in the way again. I read soumililion comment as left front. I see now that he states right front. Thanks folks. I did not know Honda made a change from left to right. I'm guessing everybody's left means when you are "sitting" on the bike, versus "standing in front" of the bike. If I'm wrong about body placement, to determine left from right, please correct me.

Why did Honda make a change in sides from the 1200 to the 1500? Is the 1800 the same as a 1500? Advantage of the change is what?

Thanks Ed

[CrystalPistol]

well now, I guess my dyslexia got in the way again. I read soumililion comment as left front. I see now that he states right front. Thanks folks. I did not know Honda made a change from left to right. I'm guessing everybody's left means when you are "sitting" on the bike, versus "standing in front" of the bike. If I'm wrong about body placement, to determine left from right, please correct me.

Why did Honda make a change in sides from the 1200 to the 1500? Is the 1800 the same as a 1500? Advantage of the change is what?

Thanks Ed

Just guessing from the 1200 vs 1500, moving the lines on the 1500 so right front is handlebar controlled (vs left front on the 1200) saved a little line on each unit as no crossing over the front forks, maybe just a few pennies per bike, easier, etc. The 1800s have a different set up, I think their front calipers have 6 or 8 pistons each and some of the pistons are activated by brake pedal, the remainder by the handlebar when needed, so in effect, both front calipers get some power from rear pedal, and rotors wear more evenly left vs right.

Yeah, left of the bike is your left as you sit on it.

My Norton & Triumphs had timing side (right) and drive side (left) for many items "location" … but then left side brake & right side shift.

[Ed Brock]

Darn bean counters any way. Thanks for the information, I forgot about the 1800's 6 piston calipers. I have heard of someone trying to convert a 1500 to the 1800 calipers. I never heard what his results were however. Difficult swap I'm sure. A lot of people talk about left and right side as they are looking at an object, I just like to make sure of which side people are referring to. You know, never "assume" anything, works well for me.
Happy 4th.
Ed