Rear brake with reduced stopping power

4166 Views 18 Replies 12 Participants Last post by noscharger, 2 mo ago

Salt Cured

Discussion Starter · 4 mo ago

I'm currently on a trip and noticed an issue with my rear brake the other day. Whereas I have locked up the rear wheel in the recent past (e.g., approaching a tope I didn't see until the last minute), I noticed I had lost braking power in the rear and was no longer able to lock up that wheel even with quite a bit of downward force on the lever.

I changed out my rear pads and fluid but the issue remains--I have some braking power but not full. I did notice 1) the old pads were still thicker than my new ones (EBC FA174HH) and 2) I didn't have the pad brackets on my bike.

I am thinking the previous owner used thicker pads because the brackets had gotten lost at some point. I am wondering if, without the brackets, the new thinner pads aren't able to close as firmly on the rotor? What else I can check that might be causing this issue?

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PeteW

· #2 · 4 mo ago

Try changing the fluid before you panic, flush and bleed the system. Air bubbles in the line will cause that as well.

In my experience dealer mechanics usually toss those thermal shims if they do a pad change anyway. They would be of use if I did track days on a DL, I don't so there isn't much change. They reduce the amount of heat that gets into the brake fluid and retain heat in the pads so they work better on hard repeated stops. Normal use there's no difference.

Reactions: 1

Dark Angel

· #3 · 4 mo ago

If you push the lever too far down it pulls air into the system which will have to be bled out.
Start by replacing the missing parts, then make sure the piston isn't sticking in the caliper. After that, fully bleed the system to remove any trapped air, making sure to NOT fully depress the brake lever. I have found best results by pushing the pistons fully back into the caliper to force any air back into the reservoir before flushing with new fluid.

Reactions: 1

Salt Cured

Discussion Starter · #4 · 4 mo ago

Thanks. I did flush the fluid when I changed the pads but it was my first time doing that job so maybe the best next step is to have it done by a professional.

Marmora

· #5 · 4 mo ago

What does your rotor look like?Glazed,brown?Maybeclean ‘er up with some brake cleaner,light scuff up with fine emery cloth.Then brake clean again.No need to take parts off to do this.

Reactions: 3

STCorndog

· #6 · 4 mo ago

The missing hardware isn’t the issue. I would try bleeding the rear brake of potential air a few times.

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StretchNM

· #7 · 4 mo ago

I would try bleeding again before going to a professional. Bleeding the brakes is not a complicated procedure.

Reactions: 2

Motorpsychology

· #8 · 4 mo ago

Marmora said:
What does your rotor look like?Glazed,brown?Maybeclean ‘er up with some brake cleaner,light scuff up with fine emery cloth.Then brake clean again.No need to take parts off to do this.

STCorndog said:
The missing hardware isn’t the issue. I would try bleeding the rear brake of potential air a few times.

10-4. Make sure the disc and pads are clean. Unlikely, but you may have a little chain lube or rear shock oil that has gotten onto the discs.

Reactions: 2

Solarguy

· #9 · 4 mo ago

I also would try another round of bleeding the rear brake system. Easier with two, but very doable with one.

When the bleeding nut is open, you cannot let off the brake pedal even a tiny bit, or that sucks air back into the circuit.

That's why it's easier with two people.

Another alternative that makes it easier for one person, is to get a small jar and put a hose on the bleeder bolt. Clear vinyl tubing works great so you can see the color of the brake fluid and also the presence or absence of bubbles. One end on the bleeder bolt, and the other end in a small clear jar. The end of the hose in the jar needs to be immersed in brake fluid by the middle/end of the bleeding procedure. That way, if you let off the brake pedal a bit prematurely, it can't suck air back up into the cylinder/line. Once you're set up, a fast/enthusiastic/hard squeeze is more likely to flush the bubbles out.

There's also commercial kits that make this easier. There's also "reverse" bleeding and other tricks. Feel free to ask for additional help if you have any doubts about the bleeding process.

Good luck! Let us know how it turns out.

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Reactions: 5

NVDucati

· #10 · 4 mo ago

Salt Cured said:
I'm currently on a trip and noticed an issue with my rear brake the other day.

You mention that you are currently on a trip. Are you near any of us that could give you a hand?
I'm in the San Fran Bay Area.

Reactions: 3

dravnx

· #11 · 4 mo ago

Is the pedal soft or hard? If soft, you probably have air in the brake system. If the pedal is hard then you have to look at the pads or rotor. As others have stated, you may have contaminated the pads. Bleeding the rear brakes is a pretty straight forward operation and can be easily done by one person. Doing the front left is easier with 2 people.

Reactions: 3

Salt Cured

Discussion Starter · #12 · 4 mo ago

NVDucati said:
You mention that you are currently on a trip. Are you near any of us that could give you a hand?
I'm in the San Fran Bay Area.

Thank you! But I'm in western Guatemala at the moment...

I will try cleaning the rotors. When I bled the rear brake line, I did use a hose and tried to be careful, but it's possible (more) air got into the system. The peddle doesn't feel very soft/spongy, but for me it's harder to tell with the rear brake than the front.

Worse comes to worse, there is a Suzuki shop here in town. It can't be too expensive to have them bled the line.

Reactions: 4

Marmora

· #13 · 4 mo ago

Make sure you have some “free play” in the rear master cylinder push rod.And that it is returning to that relaxed state.

Reactions: 1

Fox

· #14 · 4 mo ago

dravnx said:
Is the pedal soft or hard? If soft, you probably have air in the brake system. If the pedal is hard then you have to look at the pads or rotor. As others have stated, you may have contaminated the pads. Bleeding the rear brakes is a pretty straight forward operation and can be easily done by one person. Doing the front left is easier with 2 people.

If it's 'hard', it could also be possible the brake lever pivot itself is frozen or partially frozen from dirt/corrosion and lack of grease. This can limit the travel to where the brake doesn't apply fully, but the way I experienced it I could stand on it and get very abrupt full braking force. I would suspect this more strongly if rear braking seemed like an all-or-nothing thing lately.

If this is the culprit, it's pretty straightforward to remove the whole assembly with a hex bit to clean and add grease.

Reactions: 2

Marmora

· #15 · 4 mo ago

I meant push rod adjustment😀

Reactions: 1

dravnx

· #16 · 4 mo ago

Any mechanic, car or motorcycle, can bleed the brake for you. It's as simple as a rock.

Reactions: 1

noscharger

· #17 · 2 mo ago

Marmora said:
Make sure you have some “free play” in the rear master cylinder push rod.And that it is returning to that relaxed state.

How much should push rod move? When I disconnect from the brake lever I can't move mine by hand?

Marmora

· #18 · 2 mo ago

I’d guess 1/4” is plenty.l don’t have a manual.The important thing is to have free play,.Again check linkage and pedal are clean and lightly oiled,greased(your preference).l give them a shot of chain lube when l lube chain.

Reactions: 1

noscharger

· #19 · 2 mo ago

My issue with hard brake pedal wasn't pivot point it was loose as a goose after disconnecting from the master cylinder. I took advice from another post finally went out on a gravel road and stood on the brake pedal forcing the wheel to lock up and ABS to activate it seems after a few panic stops the lever got back a normal feel and ABS is correctly pulsating now on the rear.

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