I am looking for rear brake advise

BudRinPa

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I just replaced all pads, front and back less than 1000mls ago. Everything was fine until today. I went for a short ride and about 1/2 mile before home I went to use the rear brake and got nothing to little braking. The pedal just went all the way down to the stop. Unfortunately it was dusk when I got home and could not see much. What I did see is the reservoir was full and I could not see any sign of leakage along lines or the caliper. The front seems to still be working fine. Any ideas of where I should begin diagnosis? Thanks in advance fellow riders!
 

BaldKnob

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Heard reports of this in the past and it may be related to an ABS failure. How many miles on your machine?
 

gunslinger_006

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This is the same presentation as all the other failures (maybe a dozen ever?).

Its going to be your abs module. They cost at least $800 to replace which sucks.

The alternative solution is you can bypass the abs but you will have to custom make the brake lines to do it and then you lose rear abs and linked brakes.

If this happens to mine I intend to either trade it in to the dealer i bought it from, or replace the entire module.

The big issue is the modules can be hard to find these days.

I just found two on ebay and they are both used and both $1000. :-(

Here is how to confirm:

Do a full brake bleed as per the service manual.

Do not power on the bike, test your rear brake and verify it holds pressure.

Start the bike, ride until the abs light goes away and use your front brake.

Now the rear should be useless again.

If so, you confirmed air ingress via the abs pump internals. You need a new abs unit.


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gunslinger_006

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See:

Rear brake pedal frozen


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gunslinger_006

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What would cause this?
The abs unit fails internally and allows air into the unit, or it fails in such a way that locks pressure in the rear line which causes rear pedal lockup (not lockup of the brake, just a frozen pedal).

We have had threads on both failures here and iiuc they were almost always this issue.

Its tempting to bypass the abs for the rear as i would like a rear only abs disable like on the Africa Twin, but that would kill your resale by about $1000 most likely.


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gunslinger_006

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Op: If this is the abs unit PLEASE report this to the NTHSA and Yamaha corporate.

It hasn’t happened enough for a recall but with more reports you could help get this fixed for everyone.


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EricV

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Before jumping to conclusions about the ABS block, I have to ask if you pressed the brake pedal several times after replacing the pads and pumped it back up? You had to spread the caliper piston apart to install new pads. If you forgot to pump it back out after you got done, you'd have exactly what you described happen, pedal all the way to the stop w/o brakes because each stroke only moves the piston so far.

So, does the pedal pump up and apply brakes, feel normal at that point? Or if you pump it several times it stays the same, going all the way to the stop with no brake impact?

ABS modules do fail. Usually because no one changed the fluid or cycled the ABS for too long and corrosion sets in inside on the piston in the ABS block and it seizes.
 

Sierra1

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. . . . ABS modules do fail. Usually because no one changed the fluid or cycled the ABS for too long and corrosion sets in inside on the piston in the ABS block and it seizes.
That's where my little pea brain was going, but I didn't know. The RT had power servos on the brakes that were rumored to fail frequently, and at great expense. That being said, I never had a brake issue, and loved them. Freaked people out that were standing close by when you started cycling the brakes, and the bike started humming/buzzing.

I didn't suggest brake bleeding 'cuz, damn, isn't that a given?
 

EricV

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Good advice from eric. I assumed op had done the due diligence of checking the front and rear before riding a half mile.
You should have SEEN the look on my wife's face when I forgot to pump up the brake pedal after a tire swap one time! :eek: It happens to the best of us.

Considering the recent work done, I look forward to reading what the OP says about if the pedal pumps up. Even if it goes away again, that's a different set of symptoms than the ABS block, and then a flush/bleed might be the next step in the diagnostic process. Too high a level in the master cylinder can cause odd problems too.
 

RCinNC

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I'll go you one better on the brake faux pas: on a brake change a couple years ago, I put on the new pads, took it for a test ride, and heard an awful grinding from the rear wheel. Turned out that I somehow managed to get both pads on the same side of the rotor. And, with no pad on the opposite side, I managed to grind off some metal on the caliper as the caliper got pulled against the rotor. Tough to imagine the special level of stupid it took on my part to accomplish that task.
 

gunslinger_006

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I'll go you one better on the brake faux pas: on a brake change a couple years ago, I put on the new pads, took it for a test ride, and heard an awful grinding from the rear wheel. Turned out that I somehow managed to get both pads on the same side of the rotor. And, with no pad on the opposite side, I managed to grind off some metal on the caliper as the caliper got pulled against the rotor. Tough to imagine the special level of stupid it took on my part to accomplish that task.
I thought only i was capable of that level of mistake lolol. Glad to see its not just me.


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BudRinPa

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I have driven the bike (2013) at least 800 mls since pad replacement and had no issues until about 1/2 mile ago. I am going to try the bleed then test suggestion by Gunslinger and pray that it is something else. The bike has 23500 mls on it. I did hit the brakes hard earlier in the day and the anti-lock did engage briefly. Friggin Murphy's Law! I have round the country trip planned, leaving in about 2 weeks. Unfriggin believable! Well I will report back with my findings. You guys are much appreciated! Happy riding.
 
B

ballisticexchris

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I would recommend to re-bleed the brakes by back flushing from the caliper to make sure there is no air bubbles. Remove MC, zip tie plunger, get the line above caliper, and tap line. Leave overnight and enjoy rock solid brakes.
 

BudRinPa

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OK update. Just went out and pumped the pedal and it responded as though nothing ever happened, very firm first press. Started the engine and the same, no issue at all. Could this be an intermittent problem where as the module may be on the way out? I wonder. None the less I will be flushing/bleeding the system ASAP.
 

RCinNC

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Same here, Sierra. I don't know how I even managed it. At first I couldn't even believe what I was seeing; I wish I'd taken a photo.

We're in rare company, gunslinger, though I can say that I've never risen to the level of a neighbor I once had who, while trimming the branches on a tree with a chainsaw, managed to cut the one he was standing on and fell out of the tree.
 

EricV

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OK update. Just went out and pumped the pedal and it responded as though nothing ever happened, very firm first press. Started the engine and the same, no issue at all. Could this be an intermittent problem where as the module may be on the way out? I wonder. None the less I will be flushing/bleeding the system ASAP.
Ok, this is good info. Intermittent issues can be difficult to diagnose. Now, a common scenario for having no brake, then when it pumps up after a few pedal or lever actuations it acts normal is that the pads are being pushed out when the wheels are turning. You brake, it pushes the piston/pads back in, but takes a couple presses to get braking action, so first one is "oh sh*t" with nothing, then maybe you get a little the second and finally full normal braking the third press.

The three most common issues where the pads get pushed out are:

Axle spacer in the wrong position. (or binding tension arm on the rear caliper. Bolted to the side of the tab instead of centered on the tab)

Warped or damaged brake rotor, (you should be able to spin the wheel and see this.)

Bad wheel bearing allowing the wheel to move around. This is harder to visually see, but removing the wheel and spinning the bearing with your fingers should tell you if it's smooth or rough/notchy.

Put the bike on the center stand and spin the rear wheel by hand. Smooth or rough? Can you see any waver or in and out of the brake rotor when looked at strait on from behind? After spinning, does the brake pedal have less firm feel? And if you grab the wheel and try to wiggle it side to side, does it move? (this often won't happen unless the wheel bearing is really bad)
 
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WJBertrand

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Worst case there are a few outfits out there rebuilding ABS units.


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