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Can anybody explain the zip tie thing? How does it work?

I used to very sceptical about it until I has rebuilding the Pantah 500. I just couldn't get pressure in the front brake and in desperation I zip tied the front brake lever, left it for a couple of days, and bugger me it worked! I thought this might be a temporary state of affairs surmising that perhaps under pressure the air dissolved in the fluid and would slowly appear again over the next day or so with the pressure released, but it didn't. The brake line remained firm and had no more problems.

So where did the air go? With the lever pulled back it can't get out as there is no path back to the reservoir. I can only assume that the air ends up at the top of the system and when the lever is released it is ejected through the bleed hole back to the reservoir and out. Can anyone offer a better explanation?

A couple of days ago I noticed that the front brake on my Scrambler had gone soft over the winter with the lever coming nearly to the bars. I tied it up overnight and the next day it was as good as always. But I still don't know how
What I know is that the "bubble" finds his way all the way up. I would also suggest to remove the reservoir cup while doing it. I did it many times succesfully with my previuos bikes
 

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Indeed, but there are often 'high' points in the system. For example the rear brake line on the Supersport goes from the master cylinder up to ABS unit between the cylinders then down to the caliper, the highest point being the ABS unit where you'd think the air would end up at the banjos.
The front brake line is from the master cylinder on the handle bar down to the Abs unit then back up to the steering head before going down again to the calipers. The bubble rising theory would have air trapped in the line at the steering head.
 

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Yeah, I've never owned a bike with ABS. So I get your point. OTOH, nothing to lose by tying the brake down and see if the bubbles squeeze out.
 

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On the front bubble can find its way from the master cylinder the reservoir. Reservoir is connected to the outside air as it needs to breath in air in order to compensate for the wearing brake pads. Air is only problem between the master cylinder and the calipers, in the reservoir it is natural occurance. Mushy brake lever is an air bubble compressing under pressure of braking between the master and the calipers.

In the front air in the master can escape upwards to the reservoir when the lever is depressed. In the rear really not, as the reservoir is behind a low bend after the master.
 

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In the front air in the master can escape upwards to the reservoir when the lever is depressed. In the rear really not, as the reservoir is behind a low bend after the master.
In a non-ABS set up that would be the case as there is a direct upward route from the front calipers to the master cylinder but that is not the case with the ABS. As you can see from the attached screenshot of the brake line set up.
 

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In a non-ABS set up that would be the case as there is a direct upward route from the front calipers to the master cylinder but that is not the case with the ABS. As you can see from the attached screenshot of the brake line set up.
I'm not suggesting that the whole system could be bled just by holding the lever down with a zip tie. Rather that it is possible for the air in the front master cylinder to escape to the reservoir in some cases. And I suppose my point was, the in the rear there isn't any hope with that method.

I would suggest curing soft brakes by replacing the brake fluid everytime. That not only fixes the issue, but also prevents it from happening again in the near future.
 

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You are right but I suppose I'm getting hung up on not understanding why zip tying works even on the ABS systems of the Supersport and Scrambler where there is no direct route upward for either front or rear brake. I guess the bottom line is - if it works, it works!
 

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I suppose, that just a small, single bubble is enough to mess with the feel of the brakes. And it doesn't need to be at the caliper, but anywhere between the lever and the caliper will cause the issue. A tiniest amount of gas anywhere will compress enough to make the lever feel bad. If that gas is at the very top of the system it just might escape to the reservoir when given the chance.

I guess if it works, it isn't silly

This might be interesting watch:

 

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@Jippo I'm well aware of how brake systems work but I'll watch that video anyway, I might just learn something.
Yes, it only needs a tiny bubble to affect the feel of the brakes (and hydraulic clutches). From my own experience air usually gets trapped at the master cylinder banjo and at the ABS unit banjos. Holding the brake lever with a tie wll compress the bubble which possibly encourages it to move when the pressure is released or, because it is smaller it may move to the top of the system more easily.

As a slight aside, while in the Dolomites 4 years ago with a group of Multistrada riders 4 of them had difficulties in finding although the bikes had been ok at lower altitudes. They obviously had air in the lie which hadn't been an issue until the reduced air pressure at altitude allowed the bubble to expand reducing the available lift. I bled the air at the master cylinders restoring the clutch action.
 

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I just got my SSS out of moth balls for 1st ride of the season Friday. (Wisconsin) No rear brake. Nothing. You could drag a stick and do more. I had the same thing last spring after having my motor rebuilt. (another story) The dealer bled out the air in the rear lines and it was fine for the rest of the season. Now absolutely nothing at the rear again after sitting all winter. Not a glazed pad issue. I called my Dealer. He said good news, Ducati has just issued a fix for all SS's. Ducati says that the installation of the rear lines were not crimped properly from the factory and some of the seals allow for air to get into the lines. Odd because I see no sign of any leaking. Ducati will replace all the rear brake lines. They did not say anything about a master replacement. Bad news is that one of the lines is on back order, so I'll be waiting a while. I might be doing a bleed myself. At least it isn't the front!
 

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I just got my SSS out of moth balls for 1st ride of the season Friday. (Wisconsin) No rear brake. Nothing. You could drag a stick and do more. I had the same thing last spring after having my motor rebuilt. (another story) The dealer bled out the air in the rear lines and it was fine for the rest of the season. Now absolutely nothing at the rear again after sitting all winter. Not a glazed pad issue. I called my Dealer. He said good news, Ducati has just issued a fix for all SS's. Ducati says that the installation of the rear lines were not crimped properly from the factory and some of the seals allow for air to get into the lines. Odd because I see no sign of any leaking. Ducati will replace all the rear brake lines. They did not say anything about a master replacement. Bad news is that one of the lines is on back order, so I'll be waiting a while. I might be doing a bleed myself. At least it isn't the front!
Thank you for the post. @Gempeler

Would you please ask the dealer if there's a TSB (Service Bulletin) for replacing the rear brake line...
 

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Ed, I will ask my dealer if there has been an official TSB yet and post it if there is. I did find this complaint on the NHTSA website that talks about the rear brake line being routed to close to the catalytic converter that might contribute to this:

https://www.nhtsa.gov/vehicle/2018/DUCATI/SUPERSPORT

TL* THE CONTACT OWNS A 2018 DUCATI SUPERSPORT. THE CONTACT STATED THAT HE HAD TO BLEED THE REAR BRAKES THREE TIMES WITHIN THE PAST YEAR. THE CONTACT RESEARCHED THE FAILURE ONLINE AND FOUND THAT THE BRAKE LINE RAN TOO CLOSE TO THE CATALYTIC CONVERTER. THE CONTACT STATED THAT THE REAR BRAKE CABLE HAD HYDRAULIC FLUID IN IT, WHICH BECAME HOT AND CAUSED AIR TO ENTER. THE FAILURE CAUSED THE REAR BRAKES TO MALFUNCTION. AZ MOTORCYCLES (15500 NORTH HAYDEN ROAD, SCOTTSDALE, AZ 85260, (480) 609-1800) SERVICED THE BRAKES, BUT THE FAILURE RECURRED. THE MANUFACTURER STATED THAT THERE WAS NO FAILURE AND SUGGESTED THAT THE CONTACT CONTINUE TO BRING THE VEHICLE IN FOR SERVICE. THE FAILURE MILEAGE WAS 1,386.
 

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Thank you @Gempeler

Interesting, took a quick look at the bike and although the brake line is fairly close to the engine, it does not appear to be near CAT. Maybe better visible though diagrams.

Also interesting that it seems like quite a few cases reported on this Forum related to these types of rear brake issues after winter storage...
 

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To me it does sound very reasonable assumption.

I believe that the brake line goes in between the swing arm and the top of the cat. It's a very hot spot, especially if the bike is not moving and there is no airflow. To me, it is very plausible that the fluid boils in that spot. Running engine warm in the garage might actually heat the cat quite a bit. Running 20 minutes around a track at full throttle and coming into pits definately will heat up the cat enough. I believe that cooked my fairly new fluid once, as I really don't use the rear brake that much. In fact, that (and the bloody flap & servo thingy) prompted me to get rid of the cat altogether. I haven't had problems with the brakes boiling after going with the Termignoni. There is loads more air under the bike, nevermind the fact that the cat runs hotter in the first place.

Problem with boiling can be managed with a very high boiling point fluid in the rear or by removing the cat.
 

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Took a closer look, and yes, the brake line is quite close to the CAT. About the same distance as the CAT is from the tire.

I’ve also observed that at the closest point between the CAT and tire, the CAT heats up the tire quite a bit after a long warmer season ride when the bike sits for a while.
 

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The master cylinder being so close to the cat is likely to be a contributing factor but my experience is that I have my bike serviced the end of every year (this was when I bought it) and at the same time I moan about the rear brake not working. The dealer will bleed it each time, tell me there is no fix and I will ride home with it working great.
3 months later when I get the bike out of winter hibernation, without fail the rear brake will go straight to the end of its travel.


The brake fittings not being crimped correctly is a theory that would fit this issue, has there been an official recall or anyone had new brake lines and found it corrected the issue?


Matt
 

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Incorrectly crimped brake fittings would surely leak fluid as well as allow air to enter. There will be a fair bit of pressure in them when you push your foot down on the pedal. The leakage would be evident and the fluid level in the reservoir would go down. That theory just doesn't wash with me.
 

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Incorrectly crimped brake fittings would surely leak fluid as well as allow air to enter. There will be a fair bit of pressure in them when you push your foot down on the pedal. The leakage would be evident and the fluid level in the reservoir would go down. That theory just doesn't wash with me.
Yup, I agree with this as well. That theory doesn’t hold fluid for me (see what I did there?).

Pulled mine out last weekend from storage expecting no rear brake, but it was/is just fine. Weird.
 
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