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Rear brake fluid is empty


Wheeler

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Watching some videos on YouTube. Just wondering where to start. Assuming there is a leak somewhere. Then I'll replace seals and fill back up. Just curious if anyone has any tips for this process. Thank you for any and all input. 

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Wait....   so the brakes no longer operate?  Or is the fluid just not visible in the reservoir?

 

I would ASSUME you would see a mess of brake fluid all over the rear of your bike or under it's parking spot.

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On a non-linked brake 8th gen, there's only a small number of places it could be leaking.  Brake fluid doesn't readily evaporate so it is very likely you will see a leak if one exists.

 

Check entire rear master cylinder, banjo bolts at both ends of hose, and pistons behind the brake pads for fluid.

 

I would suspect the master cylinder is leaking, and needs a piston seal kit.  If your brakes work, this would explain why/where its leaking.  The fluid comes out behind the piston and doesn't affect the volume of fluid it pushes to the caliper, or the pressure it can generate.

 

The alternative is whoever serviced your brakes last time wasn't good at their job.  But my money is on a leaky master cylinder piston seal.

 

 

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I get zero braking power from the rear and don't see any in the Reservoir. I'll try to identify a leak so I know what I have to replace. 

 

I had a few inches of flood water in the winter and had the bike stored in my sunroom. Didn't see any leaks on the floor. 

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Are you a heavy rear brake user?  Have you looked at the rear caliper to see if your pads are thin and your caliper pistons are extended?  Have you tried filling and bleeding?

 

Like I said, a leak of that magnitude should be a mess.

 

 

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6 minutes ago, Wheeler said:

Yes I ride more on the rears than most people probably 40% on the rears. I'll fill and bleed today to see the outcome. 

 

Inspect your pads!

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Curious (rally) why you use the rear so much. 

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There is black soot shit around the rim of the rear. I honestly use more rear cause I love locking the rear on my old 500F. I don't do that on the vfr though. 

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Can't really tell from that angle...   but the pads look pretty thin.  I see mostly backing plate.  And your disc definitely shows "use".

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The volume behind the pads, even worn thin, isn't enough to deplete the reservoir.

 

Check the bottom of the master cylinder, where the rod from the lever pushes up into it.  Bet you will discover its wet there unless the system is completely dry.  The top of the cylinder (banjo bolt) looks dry in your photo.

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13 minutes ago, ShipFixer said:

The volume behind the pads, even worn thin, isn't enough to deplete the reservoir.

 

Check the bottom of the master cylinder, where the rod from the lever pushes up into it.  Bet you will discover its wet there unless the system is completely dry.  The top of the cylinder (banjo bolt) looks dry in your photo.

 

Yeah, I agree.  But that is assuming it was properly filled / maintained in the first place.  Improbable, but not impossible.

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Is the rear reservoir at that angle just for the photo? It should be horizontal.

 

With so much rear brake use, could you have actually boiled the old fluid? It's possibly absorbed some moisture over the years which wouldn't help!

 

The 8gen is a simple bike to flush brake and clutch fluid. Get into flushing brake and clutch system every 2 years Max. It's one of the most neglected yet important maintenance items on your bike. So many unnecessary brake/clutch problems are caused by fluid neglect

 

I sure hope in an emergency situation you are instinctively able to extract the maximum braking effect from Both front and rear brakes, it might just save your life!

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Okay so I'm not the brightest bulb in the pack. Opened the rear Reservoir, and there was fluid. It was just extremely clear. If I 100% the brake peddle I do get some braking power. It's just not like my previous bike were i could lock the rear. I'll take it to the shop when they calm down with all the spring business and have them slap new pads and rotors and tell them I don't get much stopping power and hopefully they can identify the issue. If it was the front brakes I would be a bit more comfortable tooling around with the issue. 

 

Thank you all for your input. This is a great community. 

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I don't understand. The braking nearly all happens from the fronts. Who cares if the rear works? I only use mine if I'm going downhill on a gravel road. 

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26 minutes ago, bmart said:

The braking nearly all happens from the fronts. I only use mine if I'm going downhill on a gravel road. 

 

Which is why I still use the fronts on (downhill) gravel.  But I have also been riding and racing in dirt my whole life.  It feels more controlled and safe for me...  even on my non ABS-LBS bikes.   The weight and avaliable traction are still up front on (downhill) gravel.  Just like I don't switch to rear brakes in the rain.  Just have to control it.

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I agree. But the greep, the greep! We also use the rears on the grass at track days...if we find ourselves in the grass. Not a suggestion!

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32 minutes ago, bmart said:

I agree. But the greep, the greep! We also use the rears on the grass at track days...if we find ourselves in the grass. Not a suggestion!

 

 Oh yeah, grass.  That is my exception.  It is the same as ice.  Butt puckering.

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1 hour ago, bmart said:

I agree. But the greep, the greep! We also use the rears on the grass at track days...if we find ourselves in the grass. Not a suggestion!

heh, heh... did that last weekend. Except it was dirt & sand. Switched to rears as I went off-roading! 🤣

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  • 3 weeks later...
On 4/16/2023 at 9:45 PM, Captain 80s said:

 

 Oh yeah, grass.  That is my exception.  It is the same as ice.  Butt puckering.

So you are saying don't use the fronts on grass and ice?

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10 minutes ago, Noles said:

So you are saying don't use the fronts on grass and ice?

 

No.  I'm saying that I change my technique accordingly depending on conditions and available feedback.

 

I'm never all rear unless I'm on a bike with no front (flat tracker).

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