Bleeding/Servicing your Brakes - the BEST way. (Edited July 4, 2019)

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Bleeding/Servicing your Brakes - the BEST way. (Edited July 4, 2019)

Post by CycleRob »

EDITED: 7-4-19 to change the photo provider AWAY FROM PhotoBucket to my faster, much less intrusive Postimage.org account and add numerous modifications throughout.


This post is NOT written for novices with little wrenching experience or lacking quality tools because there is too high a probability they will screw up (expensive) things. It is written for semi to very experienced owners capable of working on their bike with enough confidence and a history that has proven that they will NOT screw things up. :lol: I will just show quicker/better ways to brake service all F800 series bikes that are home serviced and Boxer motor ABS/Non-ABS bikes after the ABS unit has been fully bled clean, using what you know about keeping the ABS reservoir filled and the ignition key On or Off. For F800 series ABS bikes its owner friendly ABS system makes it much easier, essentially using the regular brake bleeding procedures at the calipers to bleed the entire ABS system. This outline can also apply to all non-BMW bikes with disc brakes because their systems are very similar, differing in the number of caliper pistons and if the Rear/Front brakes have floating or fixed calipers. If you bleed your brakes when you should OR at anytime before the DOT-4 fluid gets darker than beer, you need only perform this more involved brake servicing at "every other" brake bleed. The procedure to be outlined is the next best thing to taking EVERYTHING all apart for cleaning. The latter will be necessary for very neglected older bikes to replace old, hardened piston seals or ones where the brakes are either not working normally or are staying partially ON after releasing the lever/pedal, causing brake rotors to run HOT, even though the brakes were used very little. My decades of experience has been that few if any bike shop service departments will go the extra steps to do ALL of the following:
--Remove most ALL the very dark old, trapped in the piston bores DOT-4 fluid at brake bleed time.
--Correctly deciding when the DOT-4 fluid is bad enough that (photo documented) taking everything apart is the only good solution.
--Do NOT push in dirty caliper pistons at pad change time.
--Clean and re-grease both of the floating caliper carrier's locator posts and their mating rubber bushings.

Here is what I mean about taking EVERYTHING apart, as performed on my R1150R (gone since June 2009) due to the years and mileage it had attained. Because of the way I bled the brakes (to be described here), I was pleasantly surprised at how shiny clean the piston bores were when I took the pistons out for inspection and cleaning, as shown in the 4th front caliper pic below. The odometer readings stated in the pics reminded me the front and rear tear-downs were about 1 year apart, initiated by the color of the reservoir fluids. On older bikes with gummy, gelled DOT4 in the reservoir, this level of take apart is what will be required to make things right again. For experienced mechanics, besides making things good-as-new, it is an easy job that can provide many future rides with a lasting, therapeutic satisfaction. The 50R front master cylinder was also completely disassembled, still mounted in place, as its' very difficult removal from the handlebar was not necessary. On MY 2002 model R1150R the square locator tab on the front master cylinder's retaining snap ring OD surface (seen protruding at the seven O'Clock position in the 1st pic linked to below) made it's re-assembly frustratingly difficult, even for an experienced, patient man soon to be fully aware of it's apparently tight tolerance and need for absolute proper alignment. The difficulty was in compressing the very stiff snap ring held in perfect rotational/axial alignment against the firm spring tension of the piston assembly . . . . all at the same time. Here are the other parts, broken down for cleaning. Note the "as found" sparkling cleanliness of the high mileage caliper piston bores in pic 4, showing the absolute proof this pump-out-push-back-push-out bleeding technique really works:
*** for fullsize photo (IF it is available), click on thumbnail, click on pic displayed, then right click to save fullsize pic ***
Image Image Image Image

It's a No-Brainer that you should bleed your bikes brakes every 12,000 miles or 2 years, whichever occurs first. BMW and other bike manufacturer's maintenance schedules all say so. Too many riders, because their brakes are working fine, overlook even doing that, thinking it doesn't really need it. Some time later they notice the transparent brake fluid reservoirs (or clear plastic check window) show a dark colored fluid that looks like Colombian Coffee. Ooops. I guess it's past time for a brake fluid bleed job. By then, some damage has already occurred. That dark colored fluid tells the savvy observer the rider is neglecting his/her bike, at their own peril. As the DOT-4 fluid gets darker in color, it is visually telling you that it has and is absorbing water. Absorbed water that if left to stagnate in the master cylinders and brake calipers will slowly etch and corrode critical and very smooth Aluminum casting piston sealing surfaces, spoiling your ride and sooner or later taking big painful bites out of your credit card and disposable income. By then you may have brakes that weep fluid after the seals got chewed up and/or more likely than not that brake will stay ON after you release the pedal/lever. I know of 2 customer's Hondas, occurring years apart, both ridden by the rider knowing that recently the brakes were not releasing because of a front brake rotor that was getting hot enough to "feel the heat without touching them" or "smell hot". Anxious to get to the destination, he said he had to keep adding more cruising speed throttle on his 1100 Honda Magna until seconds later the front wheel locked solid at speed, causing a very nasty low side spinning bike accident. What happened? The caliper got hot enough to boil the water entrapped fluid, quickly flashing it to very high pressure steam, immediately putting the front brakes on HARD, able to lock the front wheel at speed (!!) even with severely overheat faded front brake pads! The brake pressure held because the master cylinder's tiny bleed back hole was (or quickly got) plugged with very old contaminated brake fluid gunk.

Now for a better way to service your brakes and greatly extend their lifespan. If you are unable to do this very specific servicing, please ask for the help of someone with the patience, experience and tools to do the job as you watch, help and learn. I always bleed the brakes at a time period away from the scheduled service day, which turns out to be anytime when the light beer tint of the DOT-4 reservoir fluid tells me it's time for a change. I just did my F800ST 2 weeks ago at about 21K miles and after reading all the recurring problems too many riders are having with their brakes and bleeding them, decided to use it for this post. On the plus side, doing it away from the scheduled service time shortens every future scheduled 12K/24K service. It gives you something good to do to your bike besides clean it, at a time and clear sunny day chosen mainly because of it's low humidity, to minimize any DOT-4 water absorption. Because of the extra parts disassembly required, it also takes a lot longer than just bleeding the brakes, so if included in that 12K service (trust me) it would end up being more than just 1 "free time" session day in your garage.

- - - Finally, getting to the point ! - - -
Now for the most important paragraph here. Around every 12K service I perform what can be functionally described as a Caliper Piston Push-Back-Push-Out Purge-N-Replace Procedure. That's where you (think logically now) first bleed the calipers alternating 3 times between them sequentially to get clean fluid past any Y fittings all the way TO each caliper. Then, without compressing any caliper pistons;
1) Remove the brake pads of only 1 caliper.
2) Remove the mount bolts then remove that same caliper.
3) Pump the new DOT-4 fluid to equally extend the pistons against a tool used as a spacer so you can thoroughly clean off the dirty piston's now exposed circumferential surfaces. DO NOT use Brake clean sprays as they will age/harden the long lasting rubber seals. If you need a cleaning fluid, use new DOT4 fluid on a rolled/folded paper towel section to "shoe shine clean" the hidden portions of the pistons.

After cleaning off those extended pistons, with the lever/pedal mechanically held slightly depressed to prevent push-back back-flow of the old fluid into the master cylinder and with the bleeder screw loosened, creatively rotate standard tools to SLOWLY push ALL of that caliper's pistons fully IN (bottomed-out) to pump nearly all the old fluid out the open bleeder's attached hose. On any caliper with more than 1 piston you may have to prevent the other pistons from being blown out of the caliper if you inadvertently rapidly push back just the starting piston, especially if the bleeder is barely opened enough (like just a quarter turn) to accommodate the faster flow rate. Finally, bleeder closed, lever/pedal pump out the pistons against your travel limiting spacer tool again. Then, lever/pedal slightly depressed, open the bleeder, push all the pistons back in to purge out old fluid again. With each purge cycle repetition, the expelled DOT4 fluid will get cleaner each time the pistons are all bottomed-out. Keep repeating the pump-out-push-in-purge cycle until you are comfortable that the expelled fluid is just like the new DOT4, usually from 2 to 4 complete fill/purge cycles. If you do this every 12K miles, there will be NO gummy deposits on any of the internal surfaces.

Most owners freak out about disconnecting the brake lines and loosing reservoir fluid, getting air in the system and then not having enough brake fluid or time to bleed their way back to a "solid pedal" (normality). That's because you are not doing it right! You DO NOT need a vacuum tool like a MityVac, even if the master cylinder reservoir and it's piston bore is totally empty and/or you are installing new brake lines. Think. Think like an air bubble. It is very hard to push air bubbles DOWN and out the bleeder. It is VERY easy to push air up-n-out through the master cylinder reservoir fluid. Here's how. BEFORE taking the components above the old brake lines apart, fully bleed the calipers with about 3 piston pump-out-push-back-bleed-out sessions. Use the caliper(s) as clean brake fluid injectors to purge the empty brake lines of air by pushing it Up-N-Out the master cylinder's tiny bleed-back hole with their pistons 3/4 fully extended by clean DOT4 fluid. If the master cylinder is fluid filled have the lever/pedal partially depressed to stop banjo boss outflow anytime before the lines are disconnected. Only a small amount of upstream fluid will weep out when the brake line banjo bolt is removed. Then you just hook up the empty lines and 1/4 filled either the dry new -or- the existing master cylinder (lever released) and SLOWLY push all the externally cleaned off pistons fluid filled bores back in to bottoming out. I say SLOWLY because there is a certainty that if done quickly the DOT4 stream will hit your ceiling! You should orient the caliper, without bend stressing brake lines, so the banjo bolt is at the very top to help expel trapped air in the nearby bleeder passageways. It works better on the center stand with the steering turned slightly left so the air goes upward as it travels thru the now tilted up master cylinder bore, then up-n-out, bubbling thru the partially filled reservoir fluid. On each caliper, push the pistons back slowly, watching for when the air bubble stream turns into a liquid stream, then STOP. Go to the other caliper and do the same thing. Give the front brake lever a dozen small 1/2 inch travel squeezes, just beyond clicking the brake micro-switches. With the steering turned left, watch as a few very tiny bubbles come up-n-out the tiny bleed-back hole. It is quite entertaining as the air bubble stream slowly gets smaller and less populated, until it is only liquid. Next, push all the caliper pistons in all the way, watching that the reservoir does not overfill. Since the air has been removed from the system, you now have an almost completely bled brake system, needing only the tiny bleeder passageway bled with just one lever squeeze. Done properly on a system with clean/new fluid will need no additional bleeding at all. Remember that procedure the next time you change to new brake lines. It is also much quicker than any other method while using less than a 12oz bottle of DOT-4 fluid. After installing the brake pads in their former locations and remounting the calipers, you'll need several slow, full travel lever pumps to seat the brake pads against the rotor. Then a hard lever squeeze will tell you if or not another pump-out-push-back or conventional bleeding is needed.

I have 3 different type of spreader tools, 2 of which are useable to easily/quickly rotate or compress those extended pistons, but you can creatively use ordinary tools. If you are without the tool to rotate those pistons, folded long strips of WD-40 sprayed cloth can clean them completely . . . with a lot of patience and caution that the attached brake lines are not traumatized by tight radius bending. You must resist the temptation to use pliers' jaw teeth to grab onto the very edge of the pistons to rotate them for easier cleaning. That will leave sharp burrs that will chew away on the hidden "dust seal" in the caliper. In a pinch, I have used a pair of dykes (wire cutters) with the cutting head forcefully held "open" inside the hollow ID of the caliper pistons, to grab on and rotate them for easier cleaning access. For good tool angular access doing it that way you need to have the opposing pistons still left bottomed out. I use the closed Dykes to compress the extended pistons by rotating their narrow head's thickness between the pistons until the wider width has them separated enough to use a bigger tool. Spreader tools like the 2 on the right below are hard to come by now. The orange handled one, which works the best of all, was cut off and ground down 90 degree snap ring plier tool that came from Harbor Freight, but they no longer carry it in-store or on-line.
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To further clarify, when you just bleed your brakes, that does absolutely nothing to change the fluid stagnating for years in the fluid pocket formed by the partially extended caliper piston(s). Look at how close the bleeder screw is to the brake line Banjo Bolt. That is the path of the new brake fluid when you bleed them the normal way. From the brake line hose, to going right out the bleeder, a very short and useless 1-inch-or-less ride. The crappy liquid in the partially extended piston bores just stays there, for 4, 8, 10 years until brake pad replacement time. Then, because almost anybody able to remove the old pads can replace them, the naive "mechanic" pushes in (with difficulty) the dirt coated pistons to install the fat new brake pads, impressed with the cash he/she just saved. Some of that pushed in piston grit WILL get slid past the stationary caliper piston dust and pressure seals, scratching the smooth rubber sealing surfaces and getting embedded into the flat surface of those pressure seals only to cause a future weep or a binding piston. Like sand in your bathing suit, the is NO long term tolerable/acceptable level of this contamination! It is always a bad thing. Also, if the brake lever/pedal was not partially depressed during that piston push-back to prevent the very contaminated old fluid from pushing back into the master cylinder bore, instead of out the bleeder, they have naively done more harm than good. That was all the historic bad stuff routinely possible that most people never even think about . . . and here is how to prevent it.

- - - In The Beginning - - -
You should have at least 2 of these on hand, for about $4 each in the "Wally-Mart" store. Looking at the pic below, that single ice pick punched perimeter hole at the 9 O'Clock position from the full display of the main label facing you greatly simplifies the speed and accuracy of the repetitive right-hand grab-lift squeeze-n-pour out the left side of the bottle routine. It also minimizes water vapor entry and prevents a huge disaster if the bottle falls over or is dropped. That's not anal or an OCD, it's just smart planning for good mechanics working efficiently while on the clock!

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--- Rear Brake System ---
First you need to remove the F800 rear master cylinder mount bolt, then move it out of the way as shown, unscrew the cover and tip out the old fluid. For the R1150 models, just slip the reservoir sideways out of it's springy holder strap to a position where you can dump out the contents. Likewise, with required changes for other bike brands.

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On the F800 S/ST you need to remove the muffler, rear wheel, speed sensor and caliper before removing the brake pads. The rear belt pulley totally gets in the way of removing the brake pad retaining pin. Care should be taken to NOT compress the dirty caliper pistons at all as you lift the rear caliper straight up and OFF the rotor. On OilHeads, have the rear brake applied as you tap out the brake pad retainer pin first, before loosening the caliper mount bolts. That prevents the drift pin tapping on the pad retainer pin from compressing the 2 dirty outboard pistons. Unlike the front pads, no pad location ID inscription is needed as the rear pads on both bikes are different (mirror image) parts. IMPORTANT! Before you take anything apart, take a close look and note how the pads are in full contact with the piston on one side and the forked caliper housing on the other -AND- see how the square end of both brake pad end lugs fit fully into their steel wear insert in the square home socket. If you do not duplicate and MAINTAIN these exact, full contact positions on reassembly, there will be a very frustrating installation problem! It is very easy for the pads to fall out of position as you are trying to re-install the assembled caliper so work s-l-o-w-l-y and be ready for them to slip out of place.

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Here is why that rear caliper pad retaining pin is so hard to remove on F800/R1150 bikes. It has a very stiff steel expanding "C" collar that has an interference fit into the caliper pin hole:

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At this stage of disassembly it is a must to remove the brake carrier assembly from the caliper casting so you can clean out and re-grease the bellows interior sliding surface and polished exterior of the sliding caliper carrier studs, also called "pins". The factory grease can dry out and be gummy or be washed away if the bellows are cracked or get knocked or pulled out of position. The re-greasing ensures that the caliper "floats" freely on the carrier so both brake pads get equal pressure against the rotor and more importantly, that a binding carrier stud will not hold the inboard brake pad ON against the rotor when you release the brake pedal. THAT condition (a binding or dry bellows interior sliding surface) is exactly why those inboard pads wear out faster!!
Gently separate the carrier and caliper assemblies until the bellows' accordion folds almost get stretched out straight and flat at near full extension, then pry off their single attachment points on each assembly at both ends of the caliper casting. If you just pull it apart to pop off the bellows, there is a danger that a 7+ year old bellows will tear apart instead. To help with what part of the rubber bellows to pry off, the F800 rear pin bellows stays with the piston casting, the front pin rubber bellows stays with the caliper mounting carrier. The R1150R is structurally very similar.

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Here is an easy way to keep the rear brake pedal depressed when you need to prevent the brake fluid from going back into the master cylinder as you depress the caliper pistons to push the old fluid out the bleeder hose. Any similar socket will do, but this one was used for wheel removal and right at hand:

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Because of what I have recently read in brake related posts on our sites, I purposely tried those descriptions, shown in this group of pics to show what TO do and what NOT To do.

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Here is an easy way to neatly get Moly grease "worms" wrapped around a small screwdriver shaft to insert the grease deep into the small rubber bellows openings. Just guide the grease worm fully into the opening and crank it around the inner circumference as you are retracting it. Sorry about using Macro Focus at too great a focal distance and not noticing the resulting blurry pic on the camera's 2.5" LCD screen :-X until after it was ALL put back together. #-o My bad.

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After you insert the carrier posts into their respective rubber bellows you need to ensure the excess air and excess grease is expelled -and- confirm that both bellows are fully attached to their expanded mounting ridges at the open end. Notice the firm, hard, compressive hand squeeze:

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--- Front Brake System ---
First of all you'll need a plastic sheet, cardboard sections and/or several layers of cloth to protect the painted area parts from brake fluid contact damage. Like the rear brake system just covered, it's the same order of procedures, just the parts look and are different. The main thing is that the front calipers on both bikes are fixed and with opposed pistons. On the R1150R they also have very short brake lines, making it difficult to maneuver the calipers for cleaning without stress damaging the brake lines -until- you disconnect the line restraining mounting bolts from both fork tubes. Then the lines will allow a lot more wiggle room.
Tip out draining of the F800 front brake master cylinder reservoir after 2 bolt removals is harder than it was on the rear brake. It's easier to suction out the old fluid. Use a home sourced, home made compressible brake bleeder bottle as shown held in my hand above to suction out the F800 plastic cup or the Boxer's hard fixed Aluminum reservoir. Be careful and mindful of when and how much you squeeze the bottle so no accidental squirt shots happen. The last remaining fluid can be wiped out with a paper towel, steered around with a screwdriver tip to get into the sharp and on the R1150R, hard to access corners.

To remove the F800 bike's reservoir cap you MUST compress the hidden, opposing, cap locking tangs. I have done it alone with difficulty using 2 strong fingernails of one hand (thumb and middle finger) to release both tangs and the other hand to loosen the cap. Or with 2 people, 1 person compressing both opposing tangs with 2 screwdrivers while the other person holds the reservoir and unscrews the the usually very tight cap. If you are working alone, had some spare time earlier and are capable, you can make a special tool out of scrap "metal":

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After I easily took the cap off with the homemade tool, I thought about grinding off those pesky plastic locking tang protrusions, but decided they gave good cap security and free tamper-proof insurance. Plus, I have the removal tool!
On the OilHeads you need a really good quality Phillips screwdriver to remove the front master cylinder cover. Put that driver's Phillips head into the cleaned out screw head, maintain perpendicular axiality, and lightly tap on the screwdriver handle end 4 times with a very small hammer to set the bit deep in place. It also shocks the Steel/Aluminum dissimilar metals junction between the screw threads and the threaded Aluminum casting, making it easier to remove. Taking these screws out without damaging the Phillips :oops: or snapping them off below the surface :shock: is the most common area where time consuming costly mistakes are most often made and usually someone else (like me) has to fix it. It is made much worse by previous wrenchers over-tightening those screws! Cheap-o screwdrivers, the screwdriver tilted off of axiality, not pressing down hard enough and not tapping the screwdriver into the heads to loosen them will lessen the chances you complete step one . . . getting the cover off.

Now for the front brake calipers. The job is to fill and refill the reservoir while alternating between both calipers, bleeding them until the fluid runs clean. Then you need to remove the brake pads of just one caliper BEFORE you remove that caliper to prevent dirty pistons from pushing dirt into the internal seal area. To control which pistons get pumped out you MUST progress from start to finish on just ONE caliper at a time until all the pistons of one caliper are extended, cleaned, push-back push-out purged (twice) and then reinstalled on the fork leg, it's brake pads in place with the retainer pin partially inserted just enough to hold the pads. Then pump the pads tightly to the rotor.

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Then remove the other caliper and do the same sequence of operations, start to finish. Easier said than done!

This Caliper Piston Push-Back-Push-Out Purge-N-Replace Procedure was copied from no one. It came about as I ate my boxed lunch on the raised motorcycle lift in my Washington NJ business' motorcycle service department about year 1995, 10 years before I fully retired my final career -and- from working at all. Back then I was looking for faster, better, more efficient ways to replace new brake lines, get rid of trapped dirty brake fluid that very few people are aware of and to find an easy procedure to prevent pad wear dirtied extended pistons from pushing their filthy deposits inside the piston bore at pad replacement time. Avoiding costly special tools was also a priority if it was ever going to be adopted. There is no magic. It's all sequential problem solving common sense logic with actually no other practical solution. The facts that it uses less than a 12oz bottle of DOT4 while either filling/bleeding an empty/disassembled system -or- purging/cleaning a "service due" system while best cleansing internals in the least amount of time and fluid usage is what makes it the one at the very top of my BMW posting list. There was also extensive thought and wording provided to warn/prevent expensive or messy damage by the bold and the brave.

Finally, after you have done everything in the right sequence and did not loose your patience (absolutely mandatory for ANY good mechanic!!!), you will have brakes that work as good as new and a pic like this to show for your time:

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Here are additional R150R pics, in order, taken Oct 12, 2001 with my (retired) Sony Mavica 1.3 MP camera that saved the pics to a 3.5" computer floppy disk!

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Last edited by CycleRob on Thu Jul 04, 2019 6:42 pm, edited 6 times in total.
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Re: Bleeding your brakes - the best way

Post by CycleRob »

Today I came across this MotorCyclist OnLine Magazine video on replacing brakepads and bleeding your brakes . . . from people you would think are the experts on such things. I watched Ari Henning not only push back dirty pistons (!!!) past the seals, he also, instead of pushing the dirty fluid out the bleeder (with the lever/pedal held in) he pushed that crappy fluid back up into the master cylinder and reservoir! This is why, when people tell you to not believe everything you see on the internet, you should believe them. See for yourself:

http://www.motorcyclistonline.com/tech- ... ake-system

Granted, instructing people to push pistons out to clean the exposed surfaces or remove them entirely for a total system cleaning is not only tediously too long for a simple How-To Video, it is beyond the capability of most reader/owners. It also opens the magazine up to liability concerns that nobody wants, so you will get the dumb-dumb simple solution shown in that video that is very wrong for anyone wanting to do things the best way on the bike they plan on keeping for a while. That's also why we have Make/Model dedicated chat boards like this one to get the whole story.
`09 F800ST

Member since Sept 10, 2001

"Talent, On Loan, From God" --Rush Limbaugh--
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