Where'd my rear brake go?

So today it dawned on me that the rear brake is no longer doing anything. The pedal goes down really far now too. I always put the brakes on together and for that reason didn't really notice anything wrong with the back. I was stopped on a downhill and tried using the rear brake by itself and to my surprise I rolled as though I hadn't applied the brake at all. It's definitely gone.
Is it the pads? The fluid is at the halfway mark on the reservoir...

could have got some air in there. try flipping the caliper and bleeding it.

What do you mean by "flipping" the caliper?

I went through a rear brake problem on my '13 Strada. Bought the bike used at 19K miles. Dealer had it priced too high, so it sat for about 4 months with NO activity. When I test rode it ... it had NO rear brake.

The dealer said it "just needed bleeding"! We negotiated a deal. I brought the bike in to have the rear brake bled. But repeated bleeding did not solve the problem. They had no solution at that time.

They ended up installing a whole new Master cylinder. There is more to this as the apprentice mechanic screwed up the install causing further delays/complications. (did not cost me anything)

My theory (and of the master mechanic at the dealer) is that this bike does not like to sit around unused ... and in doing so, somehow the rear brake system either gets AIR in it ... or somehow things get screwed up.

On my bike now, it takes some HEAT and USE to get the rear brake working right ... and feeling right.

IMO, some serious design deficiencies here. After all, my system is ALL NEW, yet it still does not behave properly if the bike has sat for a couple weeks unused. With everyday use ... it's FINE.

Any ideas or theories on this? How can this be PERMANENTLY corrected?

Do check the pads. The caliper has a little ledge built into it to keep from pushing the pad backing plate into the rotors when the pads are almost fully used up.

Others have posted that if you bleed the brakes without following the factory procedure of removing the caliper and positioning it so the bleed nipple is at the top you'll never get it bled properly. When it was time for a fluid flush I took the extra time to do it right and it was fine after bleeding. Maybe the techs working on it weren't following the correct procedure.

pacaver said:

Others have posted that if you bleed the brakes without following the factory procedure of removing the caliper and positioning it so the bleed nipple is at the top you'll never get it bled properly. When it was time for a fluid flush I took the extra time to do it right and it was fine after bleeding. Maybe the techs working on it weren't following the correct procedure.

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Thanks much for that tip! I will remind them of this next time in. I know the Master Mechanic knows correct method, but the other mechs? Maybe not.

So I just need to bleed the brake?

I don't understand a brake ceasing to work because the bike has sat for a few weeks. How did they f**k up so badly to make this possible? It's 2017 and we've had hydraulic disc brakes on motorcycles since 1969 and Ducati managed to screw this up? How is that even possible?

My car sits for months at a time unused and its brakes don't stop working....
Same for my Suzuki...

philthymike said:

So I just need to bleed the brake?

I don't understand a brake ceasing to work because the bike has sat for a few weeks. How did they f**k up so badly to make this possible? It's 2017 and we've had hydraulic disc brakes on motorcycles since 1969 and Ducati managed to screw this up? How is that even possible?

My car sits for months at a time unused and its brakes don't stop working....
Same for my Suzuki...

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Your car brakes done get nearly as hot as the bikes. I have had to replace master cylinders and caliper due to moisture getting into the brake fluid and oxidizing the inner piston surfaces. I have had success with just rebuilding master and caller as well but if it has corroded the cylinder wall then it won't last. It will chew up the new seals and you will be back to square 1. One thing i dont understand fully is the inner working of the ABS unit. That might be the issue too. I assume that it allows pressure to build but once one wheel spins different than the other the pump alters the pressure. Maby the pump is stuck in the position of not allowing pressure, I don't know, that is a guess.

If you look into the piston cylinder wall on this one you will see corrosion caused by moisture and sitting. Ine of my Beringer ($500 piece of junk in my opinion) master cylinder that had the same issue.

Araitim said:

Your car brakes done get nearly as hot as the bikes. I have had to replace master cylinders and caliper due to moisture getting into the brake fluid and oxidizing the inner piston surfaces. I have had success with just rebuilding master and caller as well but if it has corroded the cylinder wall then it won't last. It will chew up the new seals and you will be back to square 1. One thing i dont understand fully is the inner working of the ABS unit. That might be the issue too. I assume that it allows pressure to build but once one wheel spins different than the other the pump alters the pressure. Maby the pump is stuck in the position of not allowing pressure, I don't know, that is a guess.

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That's a good point about the ABS. The HS is the 1st vehicle I've owned that had it. I imagine any number of things can go wrong with it. Maybe I should disable it and see if my brake starts working again....

My hyper rear brake has not failed completely, but it is odd. I have to press it pretty far before it engages. There is not enough adjustment range to get a normal pedal.

That said, my ktms always lost rear brake after sitting a long tim. Can't explain it.

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I'm pulling this one up, as I've had the same problem. The front requires one or two pumps before they're at full pressure, and the back is mush until the very bottom. This is after multiple bleedings. The pads are good, so I'm not sure what else it could be.

For the front, that's kinda common with the stock master cylinder. Having moved to an SP with a radial cylinder I can vouch for a much better braking experience. As for the rear, dunno, I recall reading something about needing to remove the master cylinder in order to be able to position it properly to bleed and let air bubbles escape but I never had a problem with mine on my 2015 hyper.

Here's a system that works. I think the problem is air/moisture/old fluid in the ABS system and you can't bleed it out just through a normal bleed. ( I have speed bleeders that make this a lot easier.)

Pull the calipers and get something the thickness appx. of the calipers to shim between the pads.

After they're pulled open the bleed valve on one and push the calipers apart. Close valve, put the shims in (on both sides!) and squeeze them while feeding fluid into the master cylinder. When tight on the shim bleed until no bubbles. Do this on the other side.

Now you have clean fresh fluid in the calipers.

Now, push the pads on one caliper apart and suck fluid out of the master cylinder.

You just forced fresh clean fluid through the ABS system. If you just pry the calipers apart without first bleeding them as described in the first part, you're just forcing crap through the ABS circuit.

Fill and bleed - do it on the other caliper.

Bolt calipers on again.

FYI: Getting the calipers apart during this process takes some force. A spreader or a screw driver on old pads will do the trick. Front and rear you use nearly one small bottle of fluid.

The results are solid - though after 2 months the rear seem a little weaker - could be my imagination. Fronts are the best they've ever been..

Whoa, whoa. Before attempting bleed job, you can adjust the throw. I had to do that pretty early into my ownership.

I also had to bleed my rear eventually. And, I, like many on this site, wanted to put .50 cal slugs through it after days of bloody knuckles trying to get the damn thing right.

Please search. Extensive rear brake servicing thread.

AJsarge said:

I'm pulling this one up, as I've had the same problem. The front requires one or two pumps before they're at full pressure, and the back is mush until the very bottom. This is after multiple bleedings. The pads are good, so I'm not sure what else it could be.

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For the rear brake, you need to remove the caliper and position it so the bleed nipple is at the top to do the job properly. If you did that and you're still having a problem, something else is going on.

Another thing is the link line between the two front calipers. In order to properly bleed the front you need to dangle them just so to get any air bubbles out of that piece.

My bike (and other bikes with ABS I've ridden) sometimes need a double or 1.5 pump in front to get a really firm lever. A downside of having so much volume and distance of brake lines. The rear brake has always been solid from day 1, so definitely check into that caliper bleeding by flipping it upside down.

kuksul08 said:

Another thing is the link line between the two front calipers. In order to properly bleed the front you need to dangle them just so to get any air bubbles out of that piece.

My bike (and other bikes with ABS I've ridden) sometimes need a double or 1.5 pump in front to get a really firm lever. A downside of having so much volume and distance of brake lines. The rear brake has always been solid from day 1, so definitely check into that caliper bleeding by flipping it upside down.

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this makes a lot of sense to me now. My Hyper is my first experience with an ABS bike and I was comparing it to my older monster as far as brake feel. I upgraded the front pads this weekend and bled the hell out of the front brakes and was scratching my head why it still took a couple of pumps to get a firm lever. my conclusion was because of the ABS. thanks for confirming

The procedure I outlined is similar to that in the ducati manual with the caveat of first filling the calipers with fresh air free fluid. It doesn't take long and uses about 3.5 oz of fluid.

I did it over the winter, the bike sat for 2 months and I've been riding it for about a month - no double pump and a nicely firm lever. If this changes I'll update, but it's the best bleed I've gotten yet.