Weird Brake behaviour

[llamaloui]

Hello,

Today I was on the Kwinana Freeway and everything was fine until my rear brake lost all pressure. I could rest my foot on the rear brake lever and it would go all the way down. I believe I may have had air in my system causing pressure loss(?).
I promptly pulled off at the next exit but shortly after my rear brake was back to normal. It worked fine and was very responsive.

The bike is 2nd hand but the previous owner changed new brake pads.

What is the problem? I've read I may need to 'bleed' my brake system?

Also, If the brake went back to normal after, should I still worry about it?

Any advice what I should do?

Cheers

[Lord Augastus]

I only have one burning question, how does one find out he has an issue with a rear brake on a freeway?

[yaabaa]

My educated guess is that he was applying pressure to it in order to assist with slowing down while in traffic...

I wish I never had to brake on a freeway.

[Speed Dealer]

I only have one burning question, how does one find out he has an issue with a rear brake on a freeway?

Peak hour traffic?

[BlackFZR]

Hello,

Today I was on the Kwinana Freeway and everything was fine until my rear brake lost all pressure. I could rest my foot on the rear brake lever and it would go all the way down. I believe I may have had air in my system causing pressure loss(?).
I promptly pulled off at the next exit but shortly after my rear brake was back to normal. It worked fine and was very responsive.

The bike is 2nd hand but the previous owner changed new brake pads.

What is the problem? I've read I may need to 'bleed' my brake system?

Also, If the brake went back to normal after, should I still worry about it?

Any advice what I should do?

Cheers

If you loose pressure in the system, you need to bleed the rear brake. If the brake goes back to normal after it cools down a little, you need to bleed the rear brake.

Also double check its adjustment to see that the rear brake isn't dragging (partially engaged at all times). You may find that with the lever in its current position you are accidently touching it slightly all the time which will exacerbate the problem. Ensure to adjust the brake lever and gear selector to a position that suits you.

[wogalucci]

If you apply the rear brake more than once does the pressure come back?

[Graelin]

When I bought my bike the pressure in the rear brake would initially work and slow the bike and then lose all pressure. The dealer told me it was because I was not used to anti lock brakes. Yes I am so old I can't tell if the brakes do not work apparently.
After showing them fluid on the back wheel I was told I had ridden through a sprinkler.
Then they jumped hard on the brake and the rear hose broke away.

Took four visits of being fobbed off, then they fixed it with new disc and pads thrown in free.

So look for any signs of leaks or tell tale spots on the back wheel.

[TurboR1]

Wow Graelin lucky you stayed on it.

If you trigger ABS, trust me you'll know about it.

Also depending on the type of bike and how the brake lever is attached to the master cylinder, there is a retaining nut which can rattle loose. when this happens the lever retains full motion (often more) with no energy transfer to the master cylinder. Happen to my race bike in the past, went to do a skid in the pit lane and instead of lovely squeal and black line with some smoke I simply coasted past the tower in silence.

Found a picture on line... The bottom nut that he is about to destroy as he is on both nuts, should be hard up on the fitting underneath. If that unwinds rather than pushing the rod up into the master cylinder, the fitting simply slides up along the thread and does nothing.

[shan]

I tend to agree with [MENTION=6799]BlackFZR[/MENTION] here,
a little air or moistiour in the system and if the pads are dragged , air / moistiour gets hot, expands.
suddenly the system is pushing air and not fluid.
cool down and back to normal .
bleed with new fluid dude.

[llamaloui]

Hello all,

Thanks for the replies and advice.

I only have one burning question, how does one find out he has an issue with a rear brake on a freeway?

Yes I was applying brakes to slow down in peak hour traffic. Didn't do much filtering or lane splitting as I'm still new to riding.

If you apply the rear brake more than once does the pressure come back?

What happened is, pressure was lost while on the freeway. I cant tell if it was gradual or sudden since I was using the rear brake a lot. After ~10 minutes of continuous but light rear brake use, it lost pressure.
I freaked out and pulled off at the next exit. Traffic wasn't so bad then and I didn't use the rear at all. I tried it anyway after giving it a "rest" and it was fine (on a quiet stretch of road).

Also depending on the type of bike and how the brake lever is attached to the master cylinder, there is a retaining nut which can rattle loose

I'm riding a Yamaha WR dirtbike at the moment. Is the 'loose nut' a common issue in these types?
And theres no ABS on the bike either.


Edit: I went out for a ride and when I got back I checked the brake discs. Front one was OK. Rear one was extremely hot. I can hear a sliding noise coming from the rear when I roll the bike back and forth. Is this brake drag? Is there a way to loosen the brake pads slightly so they don't drag on the disc while the lever is not in use? I have only had the bike for 2-3 weeks and when I bought it, brake pads were new the whole calliper system had been checked. Perhaps there was over tightening of some screws somewhere?


Cheers

[biscuits1986]

This is the brake pedal adjustment they were talking about. Lift the rear wheel on a stand and spin it. My bet is the rear brake I dragging. If it isn't. Make sure your foot isn't sitting on it while riding. (Dumber things have happened) adjust your pushrod from your pedal to the brake master cylinder.

[Kristy]

sounds like brake pads in contact with the rotor if it's hot when you stop. Could mean warped rotor or brake mechanism needs some attention.
I was riding peak hour traffic up to the northern burbs after work one day - I was in a rush and was splitting everything but don't usually go fwy north so it was a bit of an unknown and was a bit tense and was hovering over the back brake all the way (which I do when splitting anyway but was a longer split than I normally need to do in my travels)... after the freeway jaunt I noticed it seemed to depress easily without much pressure, and didn't seem to have much bite. I was also aware my ankle was a bit sore from hovering in the same position for at least 15-20 mins. Given both of those things I wondered if I had sat on the rear slightly the whole way. After I got to my destination and got back on, the rear brake was fine and never had an issue after that.

[kennyboy]

My cbr had a damaged master cylinder on the rear, would push the lever all the way down and not return until left for a while.
Bike was in an accident and damaged the inner bore of the master cylinder, the internal shuttle would stay in the upper position causing the rear calliper to have pressure in it all the time. After stopping the rear disc would be extremely hot and difficult to move the bike around.
You issue sounds similar, has the right side of the bike seen the ground at any point?

[Phildo]

I only have one burning question, how does one find out he has an issue with a rear brake on a freeway?

How else do you bring the front wheel back down when you wheelie too far?

[agrid]

You're not riding along with your foot resting on the brake causing things to heat up are you?