Brake Bleeding - Chicagoland Sportbikes
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post #1 of 8 (permalink) Old 03-23-2007, 07:20 PM Thread Starter

 
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Brake Bleeding

Here is a great article I found on brake bleeding.

Here is the info:

Brembo-recommended brake bleeding procedures:
1. Fill the master cylinder reservoir with fresh, specified brake fluid from a sealed container. Operate the master cylinder lever SLOWLY several times to fill the brake circuits and begin to expel air from them.

2. Connect a transparent plastic tube (of appropriate bore for a leakproof fit) to the caliper bleed valve, placing the free end in a brake-fluid-proof container. Position the bleed tube so that it rises above the bleed valve for a few inches (to allow a fluid head above the bleed valve exit) before descending into the container.

3. Operate the brake lever 3 - 4 times, keeping it pulled in on the last stroke. Loosen the caliper bleed valve enough to allow fluid and purged air (seen as bubbles in the fluid) to enter the attached tube. Close the bleed valve. Repeat this operation several times while maintaining a sufficient fluid level in the master cylinder reservoir. With each cycle of bleeding, the lever should meet with more resistance, indicating that the air is being removed from the system (there should also be progressively fewer bubbles in the purged fluid in the tube). If conditions are ideal, satisfactory lever resistance should be attained at the point no more bubbles are observable in the purged fluid in the tube.

4. Occasionally, a system will still have "spongy" lever even though no more air can be found in the purged fluid. This indicates air is still trapped in some part or parts of the circuit, and must be removed. The following methods will help to free the trapped air and complete the bleeding process:

(a) Making sure the reservoir is filled and capped, lean the machine so the reservoir is positioned above the master cylinder outlet, then give the lever several short, quick strokes. This gives the residual air a less- interrupted upwards path towards the reservoir, and out of the line. Return the machine to the upright position, rap the calipers sharply with a plastic hammer or screwdriver handle, manipulate the flex lines and repeat. If this doesn't quite correct the problem, let the machine sit overnight and repeat the next day. In most cases, this should give an air-free final bleed. Be sure the reservoir is filled to the correct level after final bleeding.

(b) In the case of master cylinders mounted on clip-on bars with a steep angle, it may be difficult to lean the machine sufficiently to position the reservoir above the master cylinder outlet. In this case it will be necessary to bleed the fitting at the high point (i.e. the master cylinder outlet). If your machine is fitted with a bleed-type banjo bolt (see FD ), this is a simple process of fitting the plastic tube and bleeding in the normal manner. If not, this can still be accomplished by bleeding the standard fitting with some basic precautions: (1) Be sure the sealing washers for the fitting are fresh (2) Position an absorbent rag or towel around the fitting to prevent expelled brake fluid from contacting painted finishes (3) Pull the brembo master cylinder lever in fully and hold (4) Loosen the fitting just enough to allow fluid (containing any trapped air) to escape onto the rag (5) Retighten fitting, release lever, remove rag, check brake action (6) Recheck reservoir for correct level and fill if necessary.

(As many machines now use clip-on master-cylinder fitment, this procedure for bleeding the high point of the system can be useful in firming lever response on machines which seem to have had a "soft" lever from new. Although an initial system setup bleed may yield nothing but fluid at the calipers, unbled air at a high point outlet of a master cylinder is often overlooked if for no other reason than minute residual air bubbles will, with time and use, loosen and rise, coalescing at the high point into a large bubble that will defy any attempt to bleed it out at the calipers. Since fluid from the reservoir will simply flow underneath an air bubble at a high point during a bleeding process, a resultant "spongy" lever is often incorrectly blamed on the braking components rather than an incomplete bleeding procedure). (c) In particularly troublesome cases another method may be used in conjunction with method (b)- (1) Remove caliper from disc (2) Fit bleed tube, container and check reservoir level as in C1 & C2 (3) Open bleed valve (4) Slowly push the caliper pistons their fully retracted positions (5) Close the bleed valve (6) Refit caliper to disc (7) Operate master cylinder to extend pads to disc (8) Remove caliper from disc (9) Remove master cylinder reservoir cap (10) slowly push the caliper pistons to their fully retracted positions, taking care that the fluid in the master cylinder reservoir does not overflow onto a painted surface (11) Refit caliper to disc (12) bleed master cylinder high point as in method C4(b) (13) Check brake action, adjust reservoir level and recap. (If the wheel/disc assembly is removed to perform this method, be sure that a plate or shim of the same thickness of the disc is inserted in place of the disc into the caliper not being bled-this is necessary to prevent accidental loss of pistons and fluid during this process).

Things to remember when bleeding brakes:
Air tends to rise through brake fluid and lodge at high points in the brake system. Anything that can be done to ease the upward travel of air to the fluid reservoir in a hydraulic system will make a complete bleeding of the brakes that much easier.

Avoid overfilling the master cylinder reservoir. Too much fluid will result in brake drag or even brake lock.

Glycol-based brake fluids are highly damaging to painted surfaces and certain plastics. Extreme care should be taken to avoid spillage of brake fluid when working on a brake system. Any spills should be blotted up immediately flushed with large amounts of water, blotted again, and flushed again.

Used brake fluid (even clean, fresh fluid pumped through a new system to bring it up) should NEVER be reused.

MAKE SURE the master cylinder lever has at least 0.1mm freeplay between the lever cam or pushrod and the piston, i.e. - be positive that the piston is FULLY returned when the lever is released. EVEN SLIGHT ENGAGEMENT OF THE PISTON CAN RESULT IN BRAKE DRAG AND/OR LOCKUP!!!


D. At every brake pad change we recommend checking the thickness of your brembo brake rotor against the minimum thickness found stamped on the edge or mounting flange-this will let you know how close the disc is to the end of its service life and allow you to take steps to maintain your system in top order. Operating any brake disc below its minimum thickness can result in total brake system failure. Be sure to perform this vital inspection no matter whose brake system you are using. Brake pads themselves should never be used with friction material less than 0.8mm in thickness for the same reason.

Here is the original source:

http://www.tawvehicle.com/brembo_tech_info.htm

Greg K.
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post #2 of 8 (permalink) Old 03-24-2007, 07:16 AM
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There are easier and faster ways then that. The above saids like it asumses you have an empty brake system.

Good now the less, but I prefer faster methods and you don't need a mity vac either.

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post #3 of 8 (permalink) Old 03-25-2007, 06:05 PM
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Quote:
Originally Posted by JRSMAIL View Post
There are easier and faster ways then that. The above saids like it asumses you have an empty brake system.

Good now the less, but I prefer faster methods and you don't need a mity vac either.
So you're telling us you have a better method just so you can feel good about yourself? Or....you could post your magical brake bleeding method so the rest of us can be enlightened by your geniusness (is that a word?).

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post #4 of 8 (permalink) Old 03-25-2007, 06:53 PM
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Should have been at the tech day at Wink's and you would have learned young grasshopper.

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post #5 of 8 (permalink) Old 03-25-2007, 06:55 PM
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Just buy a mity vac




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post #6 of 8 (permalink) Old 03-26-2007, 01:07 PM Thread Starter

 
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Quote:
Originally Posted by JRSMAIL View Post
Should have been at the tech day at Wink's and you would have learned young grasshopper.
That about sums it up. Bring it to Winks. Roll it up on the table under the brake service tent. Go get a brat. Come back 10 minutes later.

My brakes are the best they've ever been! Big Big thanks to the Lockharts! they are the brake bleeding masters!

Greg K.
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post #7 of 8 (permalink) Old 03-26-2007, 01:23 PM
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brake bleeding is easy, but its also easy to mess up. Just take your time, watch what your doing and make sure everything is tight when your done
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post #8 of 8 (permalink) Old 03-26-2007, 01:45 PM
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Quote:
Originally Posted by gkotlin View Post
That about sums it up. Bring it to Winks. Roll it up on the table under the brake service tent. Go get a brat. Come back 10 minutes later.

My brakes are the best they've ever been! Big Big thanks to the Lockharts! they are the brake bleeding masters!

Thanks Greg. Happy to be of service.
A few observations:

Many of the bleeders were very tight.

Snug them up, don't crank them down. You do not want to damage the "seat" area or stretch the threads. If the threads get too loose, air can leak back around the threads. Teflon pipe tape can be used if this is a problem. (not recomended)

Crush washers really should be a 1X use part.

I like the soft aluminium ones. You can buy a assortment for a few $ from JC whitney.
If you have to reuse them, you can resurface them by rubbing them over sandpaper on a flat surface.

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