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Discussion Starter #1
I am having issues with rear brake and hoping somebody could chime in with ideas.
Here it goes.
Every so often air gets into the system. I bleed it and it's fine for some time but then happens again. This is my track bike and I only take it to track days twice a month. But even then I barely use them. How it lets the air in is beyond me. I checked everywhere for leaks, nothing.. everything is dry and clean.
On all the bikes I had owned this is the first time ever happened. If somebody told me before I would not believe it myself. Normally when pressure is lost there must be leak somewhere, but not this time.
Any ideas? What should I do, start rebuilding caliper, master cylinder?
 

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Same thing happens to mine. I usually wiggle the arm where the reservoir line connects to the MC while pressing on the peddle and the air comes out. I'm guessing it doesn't seal well and allows air in.
 

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Discussion Starter #3
Another thing I should probably mention is when I tie down the bike to the trailer one of the straps just about touch brake fluid reservoir. Could this be that vibration and potholes make the strap to shift reservoir so it lets the air in through the rubber hose?
 

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Discussion Starter #4
Same thing happens to mine. I usually wiggle the arm where the reservoir line connects to the MC while pressing on the peddle and the air comes out. I'm guessing it doesn't seal well and allows air in.
thanks. this may support my theory of tie down strap interfering with the reservoir.
 

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Another thing I should probably mention is when I tie down the bike to the trailer one of the straps just about touch brake fluid reservoir. Could this be that vibration and potholes make the strap to shift reservoir so it lets the air in through the rubber hose?
Probably. I have a reservoir delete that definitely vibrates a lot lol.

Like this one:
 

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I have the same issue with the front brakes on my RSV4. Still haven’t figured out what the problem is
 

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I’m surprised no one has posted this yet: “who uses the rear brake anyway!”:O
Ever heard of "brake dragging" into corners?

Also, people who commute with their bike, can stop on an incline and rear brake helps to get going again.
If there is a stoplight on the incline, i usually sit straight, let off the clip-ons, right foot on rear brake and left on road.
 

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Ever heard of "brake dragging" into corners?

Also, people who commute with their bike, can stop on an incline and rear brake helps to get going again.
If there is a stoplight on the incline, i usually sit straight, let off the clip-ons, right foot on rear brake and left on road.
I was just messing with you ....:BigGrin

I have also heard of track riders/racers intentionally introducing air into the rear brake to reduce power and prevent accidental lockup.
 

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Discussion Starter #10
Probably. I have a reservoir delete that definitely vibrates a lot lol.

Like this one:
I've seen this setup other guys have not their track bikes. now makes sense why. is this a kit or purely diy
 

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Ever heard of "brake dragging" into corners?

Also, people who commute with their bike, can stop on an incline and rear brake helps to get going again.
If there is a stoplight on the incline, i usually sit straight, let off the clip-ons, right foot on rear brake and left on road.


Sorry for the syntax anal retentiveness: It's called, "trail braking," which can be done at either end. Trail brake the front results in over steer - results in 1) running the cornering towards the outside of the turn; 2) compresses the front suspension. The latter is useful on corners with rippled tarmac, prevents the forks from cycling between over compression/rebound resulting in shock lock.

At the rear, trail braking results in under steer - resulting in 1) limited shock squat which can result in poor handling, esp. over rough tarmac; 2) creates in tightening the steering - which is very useful when/if the rider is running wide coming out of the apex of the corner. *Racer tip, this is the genesis for the term: late braking. Trail braking is ideal for braking @/past the apex which can allow a trailing rider to 'out brake a leading rider. This can be useful in coming under the lead rider - arriving faster to the corner, then scrubbing speed off with both brakes, and because of the under steering dynamics of the rear trail braking keeps the rider/bike from running wide at the corner exit.

There is a critical element to trail braking: 1) whenever trail braking the front wheel, if you are sensing impending lockup, smoothly release brake pressure immediately. Keep eyes up, and look only where you want to go. On the other hand, if the rider senses impending rear brake lock up do not release rear brake pressure rapidly! Keep eyes up, look where you want to go. The rear can sway as long as the rider points the rolling front tire where they need/want to go. There are lots of examples where a fast rider actually kicks out the rear end, by stomping on the rear brake and is 'steering with the rear end' whilst on the throttle.

These techniques ought be worked up to. There's a lot that can go wrong when things go tits up. Trail braking is a "feel" thing. This is a skill that is every bit as complex as 'stoppies' and/or 'wheelies.'



Goblin, yes the HRC kit is a DIY... as long as you have the skills/tools to bleed your rear brake. BTW, bleeding the rear is definitely much easier than doing the fronts. Also, how are your brake lines. And DO NOT reuse the crush washer at the brake line connections.

MrZ, and et al with the dangle-y nature of the HRC kit:
https://www.satoracing.com/universalbrackets.htm

Duc995, it would be safe to say the I use my rear brake:wink
 

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Sorry for the syntax anal retentiveness: It's called, "trail braking,"
You are right about that, not my native language and didn't even cross my mind, even though i know that term. Anyway you got the point.

MrZ, and et al with the dangle-y nature of the HRC kit:
https://www.satoracing.com/universalbrackets.htm
How would anyone use this kind of bracket to hold the brake tube? :dowhat
And why would anyone pay for something that can be done for free? It's DIY after all...

I used a piece of metal from an old pc case, bended it , drilled and spray painted.




And since the link you provided has examples of brackets for the front brake reservoir.
I wouldn't use an alloy braket to hold my front brake fluid res ever again.
I had to ride a two hour trip with the brake reservoir dangling around because the alloy failed due to vibration.
 

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Discussion Starter #18
Resurrecting this thread.
The update is this. I swapped brake fluid reservoir with a tube and thought that was it. It was not.
I am not going to any track days anymore this season so I winterized the bike and left it lifted on the stands. About a month passed and out of curiosity i decided to check rear brake. it was not there.
obviously the reservoir was not the problem to start with. now the only components left are MC and the caliper. The line can't be the problem as there is no leaks around banjo bolts.
what do folks think, is it MC or caliper?
 
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