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Disk brake bleeding question


stewie911
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I need to bleed my xt brakes, but I see there are two methods.

1. Syringe connected at bleed nipple and inject oil through the system

2. Open bleed nipple and top-up reservoir with mineral oil

 

Can any one of these methods be used?

 

I did method 2 yesterday, but didn't seem to work all that great.

 

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Top up or bleed?

 

Bleed doing 1 and top up doing 2 but dont open the bleed nipple (it takes a bit longer and you need to keep squeezing the lever and you will see bubbles coming out of your system).

 

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Method two will also work but is messy and takes to much time . Method one also gives better results with no air in system .dirt-rider2010-05-17 05:43:08

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Johan, ek sou, maar my fiets sit in centurion. Bietjie ver van jou af.

 

Ek wil na een van jou kursusse ook kom, as ek net 'n naweek bietjie af het.

 

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Method 2 works fine, but you must get your sequence right and setup properly. I have done it a few times, sorted! Its the traditional way one bleeds car and bike brakes.

Best done with a small ring spanner on the bleed nipple, open it, pull lever in, close before releasing, the lever will suck more juice from the reservoir, which you need to keep topping up. If you bike is in stand, brace with bars against the frame with string or masking tape so they dont swing about and make a mess with the oil. From the nipple a small transparent plastic pipe into a hole made in used 300ml plastic bottle which is also held in place against the frame with masking tape. ?

When done bleeding top up the resevoir until overrunning and roll the diaphragm ?from from the back side to ensure no air trapped upderneath.

Check out the Hope website, Mr Yorkshire Pudding has a few informative videos up on this topic.

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I always used to use the pump system i.e, method 1.

 

However, I now bleed everything from the bottom up. Bikes, cars....still looking for a plane to bleed.

 

I recently even bled a motorbike with a newly-installed ABS, all the way from the bottom to the top. It takes a few minutes and doesn't require acrobatics or a willing girlfriend.

 

I find the method so agreeable and hasslefree that I bled all three our cars in the same morning.

 

The method is like this for a bike with Shimano brakes.

 

1) Put the bike in a rigid stand and restrain the steering. Make sure the calliper is below the handlebars.

 

2) Loosen the brake lever clamp and level out the reservoir so that the fluid in there will not run out when you go onto the next step which is

 

3) Remove the reservoir lid and note the fluid lever. Important to note the level.

 

4) Have two syringes ready. One is charged with brake oil, the other empty. On the charged one, fit a piece of fish tank pipe that fits both the brake nipple and syringe tip. Secure it with a small cable tie onto the syringe if the fit is loose.

 

4 a) Now suck the reservoir dry with another syringe you have handy for emptying the reservoir and removing the old black fluid.

 

5) Fit the ring spanner over the nipple and stick the charged syringe's ppe over the nipple. If it is all fitted correctly, the pipe will fit inside the ringspanner that's now over the bleed nipple.

 

6) open the nipple a 1/4 turn or so. The syring will want to rotate with the spanner. Allow it to do so.

 

8) Gently inject some oil into the system, holding the syring downwards so that any bubbles in it is at the top against the plunger and wont go into the system.

 

9) Take a breather by closing the nipple and leave the bottom syringe hanging there. Go to the reservoir and suck it dry again.

 

10) Keep on repeating the process until fresh pink oil fills the reservoir and your helper (I lied about this being a one-man job) tells you she doesn't see any more of those tiny champagne bubbles coming out the hole in the reservoir.

 

11) Now suck out the excess fluid so that the reservoir is filled to the level it was initially in point 3. If it is too full at this stage you wont be able to fit new pads when those wear down. New pads push the fluid up into the reservoir and you thus need some space in there.

 

12) remove all your paraphernalia, clean the floor, fit the cap, re-angle the brake lever and tighten it.

 

13) Go ride.

 

The other method requires you to pump the brake lever and attempt to force the bubbles downstream and out the bottom. It works, but it requires long arms and patience. I don't like it. Like Kosmo says, you have to get your sequence right. One missed beat and you are back to square one.

 

But...there is more than one way to skin a cat.

 

 
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Thanks guys. I did what Johan suggested earlier this afternoon.

 

I did it alone, as no-one was home. One hand to pump fluid and the other to suck oil at the reservoir.

 

I removed all the bubbles this way, however my brakes are still soft.

 

I can pull them onto the handlebar, but they were that way from the day I bought them. They still brake when they're supposed to, so that's fine.
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Maybe adjust the bite point with that black nob so they sit farther from the bar and dont come so close before biting ?

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I think you should add more oil into the system this way they will be a bit harder. Just practise and you will get the hang of it.

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I think you should add more oil into the system this way they will be a bit harder. Just practise and you will get the hang of it.

 

This is a common misunderstanding of hydraulic systems and of course, not true.

 

The reservoir level has nothing to do with the point of engagement. Also, the reservoir level should never be topped up during normal operation. The oil cannot go anywhere and is not consumed by anything.

 

Stewie, see if there isn't still some air left. Leave the brakes for 20 minutes or so. Now focus and observe as you pull the lever. Note where it takes. Quickly pump it a few times and see if the take-point rises. If it does, there is air in.

 

Otherwise, do as WW says, adjust the bite point....I don't know what brakes those are so perhaps they don't even have an adjuster.

 

These adjusters are simply a screw that determines when the lever contacts the master cyclinder plunger.

 
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Yip they have the screw. I can adjust it, but then my initial reach for the lever would be too big.  But the brakes work fine this way, so I'll try a complete re-bleed one day when I feel like working on the bike again.

 

Thanks for all the info guys. Much appreciated.

 

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