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I apologize if this is a repeat of a previous thread. I checked and found nothing, but even so, I hate duplicative threads.

So here goes:

Caveat: While I welcome thoughts on what is/how to fix my problem, this thread is not for debating the merits of rear brake use. FYI, I use my rear brake regularly, so the fact that it is not trustworthy is bothersome. For 7000 miles, it has worked beautifully with absolutely no complaints.


I hauled the SS out of storage three days ago (after our interminably long 6 month winter, but who's complaining?) and discovered excessive rear brake lever travel. The lever traveled several inches before engaging the rear brake and even then it only engaged the brake a wee bit. I was a bit concerned but figured, "Who knows? I guess anything can happen over 6 months in freezing temps." I then adjusted the rear brake per the manual and it worked like a charm. I rode the beautiful beast for 140 miles and then took it out of the garage again this morning. I immediately noticed excessive rear brake travel again.

Since I have to take the SS in to the dealer for an unrelated issue (warranty mirror fix) soon, I resolved to not use the rear brake until I could have the issue addressed. This worked relatively well on my commute to work today until I slowed from 65 mph to make the final right hand turn to the road leading to my office. As soon as I let up on the throttle I felt significant braking (engine braking I initially believed) but far more engine braking than normal. After making the turn I engaged the throttle and felt very sluggish acceleration. Upon releasing the throttle again...massive braking power. Finally, the bike came to a complete stop at the side of the road. The engine was fine, but the bike wouldn't move. I downshifted to 1st gear and attempted to accelerate again. The bike didn't move, but simply squatted in the rear. At first I wondered if the chain wasn't rotating due to lack of lube, but soon realized the bike was somehow braking itself.

Finally I checked the rear brake lever and it wouldn't move at all. Zero freedom of movement. I pressed on the lever and after several seconds, the rear brake released and the lever returned to its previous state of excessive travel. I rode approximately 0.5 mile to work and parked the bike.

While it is possible that I tapped the rear brake pedal several times on my way to work (since I usually use the rear brake) I was definitely not touching the rear brake as I sat flat-footed on the pavement and attempted to accelerate.

In summary:
1. 6 mos. storage
2. Excessive rear brake lever travel
3. Brake lever adjusted
4. 140 miles of in-spec rear brake operation
5. Excessive rear brake lever travel
6. Auto-initiated rear brake lockup
7. Excessive rear brake lever travel

Any ideas out there? Dealer is closed today, of course.
 

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It could have been the piston not extending fully, brake adjusted taking up the slack. Then after riding and using the brake the piston fully released causing the brake to lock up because of the over adjustment. Then again the piston would not fully extend, in other words a sticky brake calliper. Just my thoughts, but you should get the dealer to check it over.
 

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Yes it sounds as DucColin has said. I think your piston had been sticky from the layoff and then an over adjustment with a sticky piston has resulted in it jamming. either way you or your Dealer will have to inspect the pads for glazing after it has locked up. the rear callipers are relatively easy to remove so you can remove the pads and check. I am wandering if road sault has caused your pistons to get stuck ? keep us informed.
 

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There should always be a little free play at the rod from the pedal to the master cylinder. If you adjust it too tight you will prevent the piston from fully returning, blocking off the return hole to the reservoir. This means that the system is closed and every time the brake is used the pads don't fully return so they touch the disc and build up heat, which causes the fluid to expand pushing the brake on harder until it is locked on. Bad enough on the rear but could be fatal on the front.
Get the brake checked out by your dealer and adjusted properly.
 
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O k so I spoke to a Suzuki Bike engineer today who had been at the Australian Superbikes on the weekend and had told me that one of the Suzuki's had to pull out after practice as the rear brake was coming on and pulling the bike up on its own. actually he said it was an ECU fault which was affecting the ABS system and they did not have a replacement computer so had to pull out of the race. ? So who Knows these days !!!
 

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I was on board with the piston thoughts until I read @Rhino 's ECU statement. That also has merit.

I still think it's the pistons, though. Let us know once it's been diagnosed.
 

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O k so I spoke to a Suzuki Bike engineer today who had been at the Australian Superbikes on the weekend and had told me that one of the Suzuki's had to pull out after practice as the rear brake was coming on and pulling the bike up on its own. actually he said it was an ECU fault which was affecting the ABS system and they did not have a replacement computer so had to pull out of the race. ? So who Knows these days !!!
Bloody hêll. Computers that can apply the brakes sounds like a dodgy game :eek:
 

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Bloody hêll. Computers that can apply the brakes sounds like a dodgy game :eek:
he asked if I had my bike back yet and I told him that they are waiting for a replacement ECU. I told him that I had an incident where my bike had done some strange things while riding, i.e. DQS dropping gear, extreme engine braking, then full throttle :surprise: and he then told me about the Suzuki team problem and said its not just Ducati they have a hand in operating everything these days.
 

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he asked if I had my bike back yet and I told him that they are waiting for a replacement ECU. I told him that I had an incident where my bike had done some strange things while riding, i.e. DQS dropping gear, extreme engine braking, then full throttle :surprise: and he then told me about the Suzuki team problem and said its not just Ducati they have a hand in operating everything these days.
Yes, it's rather worrying sometimes. We now have computers controlling the throttle (ride by wire, cruise control and quick shift gear change), the brakes (ABS, active cruise control, traction control and stability systems) and the suspension (active and semi-active systems). These are great aids when they are working but the potential for disaster is enormous if they go wrong. We can only hope that the designers have taken every possible failure factor into consideration.
 

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he asked if I had my bike back yet and I told him that they are waiting for a replacement ECU. I told him that I had an incident where my bike had done some strange things while riding, i.e. DQS dropping gear, extreme engine braking, then full throttle :surprise: and he then told me about the Suzuki team problem and said its not just Ducati they have a hand in operating everything these days.
Our DQS and ABS are computed by the black box. THe throttling is done through the ECU. I think you have a balls up in both boxes. THat's a disaster waiting to happen. Seriously that spider bite may have saved your life.
 

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Yes, because our lives depend on it...literally. Scary to think about, actually...:|
That’s exactly what I was thinking as I was reading down the page. Have we perhaps gone too far?
 

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Beautiful day ruined, I just experienced what the @fishoutofh20 described. Coming out of corner and just over the hill I let off the gas and I feel excessive engine braking. Hmm, give it a little gas, let off the throttle again and the bike is hauled down from about 50 to a complete stop without me touching the brakes. Rear brake is completely locked, the pedal is completely in the up position and frozen. The rear master cylinder is so hot it burnt my finger. Stuck in the middle of the road over the crest of a hill and I can't move the bike, perfect! After about 10 mins... while anxiously watching the crest of the hill while pondering my predicament... even if my wife brought my trailer how would I get loaded... the rear brake magically freed up and allowed me to get home. Some background... my bike rarely sits for more than a a few days and my rear brake has been weak for a while. It takes a lot of pedal travel to get it to engage but when it does it works. I had adjusted it to remove some of the travel about a month ago, still a lot left before it appears to engage, but perhaps not enough free play as @Derek points out. That's the first place to look and would be the simplest cause, Occam's Razor thing, but to be honest, this seemed very weird. When I let off the gas the second time, it felt like the brake pressure was increasing w/o touching the brake rather than just dragging. Outside of @fishoutofh20, has anyone else experienced this?
 

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Beautiful day ruined, I just experienced what the @fishoutofh20 described. Coming out of corner and just over the hill I let off the gas and I feel excessive engine braking. Hmm, give it a little gas, let off the throttle again and the bike is hauled down from about 50 to a complete stop without me touching the brakes. Rear brake is completely locked, the pedal is completely in the up position and frozen. The rear master cylinder is so hot it burnt my finger. Stuck in the middle of the road over the crest of a hill and I can't move the bike, perfect! After about 10 mins... while anxiously watching the crest of the hill while pondering my predicament... even if my wife brought my trailer how would I get loaded... the rear brake magically freed up and allowed me to get home. Some background... my bike rarely sits for more than a a few days and my rear brake has been weak for a while. It takes a lot of pedal travel to get it to engage but when it does it works. I had adjusted it to remove some of the travel about a month ago, still a lot left before it appears to engage, but perhaps not enough free play as @Derek points out. That's the first place to look and would be the simplest cause, Occam's Razor thing, but to be honest, this seemed very weird. When I let off the gas the second time, it felt like the brake pressure was increasing w/o touching the brake rather than just dragging. Outside of @fishoutofh20, has anyone else experienced this?
I've had the same thing. As you say, not enough freeplay. Did you adjust using the stop on the pedal, the pushrod between the pedal and master cylinder, or both? I've loctited a half nut on the push rod to make it easier to adjust if it sticks through expansion again.
 

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Both the pushrod and the stop. But you give me confidence that it’s a simple fix. Brake pads might be toast but I’m going to get a flush ASAP, will replace them. All’s well, I managed to salvage some of the glorious weather we have today, just took the 748 out for a burn😎
 

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I've had the same problem on my used SS. The rear brake was always "weak" and needed a full travel to start to bite, a little. But after winter, the rear brake was not working at all. With the pedal depressed all the way to what felt like a hard mechanical stop, I could still move the bike and it would roll down a slight incline. I noticed the disk surface showed very little recent wear (not shiny, but with rust/grim) compared to the nice shiny front ones. Being cautious, I added 1.5 turn to the adjustor, so it bit a little, but it was still weak and required nearly maximum pedal travel to bite. I intended to adjust it gradually by steps. I went for a trial ride to check for disk heat build-up in case it is warped. The rear brake seized, could not budge the bike. It took a huge amount of engine power to crawl the bike to the side of the road, and stalled it quite a few time in the process. The heat from the rear disk could be felt from quite a few inches away. The pedal had no more free play and hardly any travel possible (it certainly had a lot after the adjustment and before the test ride). It freed-up after cooling down, so I could crawl it home. I took out a quite few turns from the brake adjuster, made gradual short test rides at increasing speed, always checking the disk temperature. Disk is warm, but not hot. And now the brake behaves like a normal rear brake, possibly for the first time since I've had the bike. I can feel the free play and hydraulic resistance, which was not the case before.

So on that test ride, the brake went from barely working to seizing, the pedal from excessive travel and free play to none of either. Something happened! But what? It seems to have "fixed" itself...

I'll have the brake checked as soon as Covid restrictions allow me to get to the dealer and keep watching it closely.

With the brake finally behaving normally, my immediate concern is that the rear brake disk get warm even when not using the rear brake. It is not hot, it can be touched. The front one does not get warm, unless just used. I suspect this is not the first time the rear brake seized on that bike, as the rear disk already had discoloration on the tangs between the outer friction surface and the inner wheel mounting surface. So I am wondering if this warmth of the rear disk could be caused by the disk having warped due to overheating? And is it a serious concern?

Thank you,

Yves46
 

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I think your brake fluid is toasted and there is air in the system. Mechanical adjustment reduces freeplay, that will help the bad fluid transfer enough pressure to operate the brake. But you are dragging your brakes and risking a complete seizure of the rear by doing so.

SS has the tendency to boil the rear brake fluid. If you loose the pedal feel, first step IMHO should always be bleeding the system. Getting the air out will temporarily cure the problem. But it can dealt with completely by switching to very high boiling point fluid, or byt getting rid of the catalysator that dumps heat into the fluid.

Please check the fluid, and then check that your rear brake has enough free play.
 

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Thanks Jippo!

Free play is now more than required, for added safety margin, until I can have this positively sorted out. And I'll be checking it often. I'll have the brake fluid professionally changed and upgraded to very high temperature grade when I can have the issue looked at by the dealer.

I doubt that in this case the catalyzer was an issue, as it was a short test ride in April in Canada! Just short of wearing a heated jacket! In any case, I am pretty sure I'd be illegal without it around here. :-(

Thank you so much!

Yves
 

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@Yves46 Welcome! Very glad you joined us!

If you haven’t already, you might also check with your dealer to see if your bike had the rear brake TSB (Technical Service Bulletin) done. Check this thread starting at post #13. (This TSB is valid in the US, but seems to not always be valid for all countries, however.)
 
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