Front and rear caliper removal for fluid replacement

[Linz]

I'm about to replace the ABS, linked brake fluids on my '02 RT. I have Jim von Baden's DVD, several .pdf files and the tools and mechanical ability.

 

What's confusing me is the need to remove the brake calipers. I see images of blocks of timber used to keep the pads separated when doing the job but is the pads are separated with the disk, and the Speed Bleeder is accessible from the top of the caliper, why do we need to remove them?

 

Can anyone techy tell me why please?

 

TIA.

 

Linz

[T__]

I'm about to replace the ABS, linked brake fluids on my '02 RT. I have Jim von Baden's DVD, several .pdf files and the tools and mechanical ability.

 

What's confusing me is the need to remove the brake calipers. I see images of blocks of timber used to keep the pads separated when doing the job but is the pads are separated with the disk, and the Speed Bleeder is accessible from the top of the caliper, why do we need to remove them?

 

Can anyone techy tell me why please?

 

TIA.

 

Linz

 

Linz, I never remove the calipers.. All I do is push the pistons back in their bores & insert some plastic wedges I made up to hold the pistons & pads back.. The idea is to decrease the dead fluid space in the calipers behind the pistons so the fresh fluid will force the old fluid out.. I do turn the front forks one way then the other as I flush fluid through the system..

 

Be sure to buy lots of fluid so you don’t try to skimp on fluid during the flushing process.. Once a container is open you might as well use it all as brake fluid doesn’t store well once the container is opened..

 

I flush & re-bleed every year or so so really don’t have an old skunky fluid issue..

 

I really don’t have a set mileage or time period to flush & bleed the brakes so just do it when I have the Tupperware or fuel tank off for other reasons..

 

 

Twisty

[smiller]

Linz, I never remove the calipers.. All I do is push the pistons back in their bores & insert some plastic wedges I made up to hold the pistons & pads back.

How do you push the pistons back in their bores without removing the calipers?

[jfremder]

Removing the calipers, and inserting the spacer blocks allows for a predictable amount of fluid remaining in the resevoir after bleeding. If the pads are well worn you will have a little less, brand new pads a little more.

 

Some people choose to just shim them in place.

[T__]

Linz, I never remove the calipers.. All I do is push the pistons back in their bores & insert some plastic wedges I made up to hold the pistons & pads back.

How do you push the pistons back in their bores without removing the calipers?

 

 

I use a special tool just for that job.. A screwdriver.. I just pry the pads back & that pushes the caliper pistons back in.. Once I get a little space between the pads & caliper I use the plastic wedge to push them back the remainder.. I usually drain the ABS controller down a little first so that doesn’t overflow as I push the pads back..

 

Twisty

[Lawman]

As Jeff discussed it seems to me like you should just shim them in place, assuming they do not need to be replaced, since forcing them all the way open will decrease the amount of fresh brake fluid in the system once it is flushed..

[Linz]

So, if I understand you replies correctly, leaving the calipers in place with the disc between the pads, isn't sufficient to remove the old fluid inside the calipers.

 

What you are saying is that, I have to force the pads (and pistons) back as far as they'll go to get the old fluid out.

 

This can be done in place with plastic shims.

 

Please understand that when I said "remove the calipers" I really meant, unbolt the calipers and let them hang free. I see this done everywhere in DVD and .pdf instructional information and then the user blocks the pads with timber to keep them from touching during the process.

 

I couldn't work out why, as the disks are preventing the pads touching whilst the calipers are in place and I can access the speed bleeder easily.

 

Sorry to be so dense. I'm still not positive from your replies why anything needs to be shimmed, unless the pistons have to be completely forced back as far as they can go to remove any trace of old fluid.

 

I don't "remove" the calipers from the bike when I change the fluid on my Triumph and am struggling with the concept for the Beemer.

 

Not arguing here, just failing to understand.

 

Linz

[John844]

Yes, they are trying to get you to fully compress the piston. This can be done either on the bike with thinner shims, or off the bike with thicker shims. Either way will work as long as you compress the piston all the way.

 

The purpose is to allow you to flush as much of the old fluid out as possible.

 

I think it is more critical on a bike with ABS. I don't know the exact reasons, but I bet someone else on here will.

[Linz]

OK, it's penetrated the thick cranium now. Thanks.

 

I'll now attempt to find the right shimming material and keep it handy for this task.

 

I appreciate your reply.

 

Linz

[russell_bynum]

Yes, they are trying to get you to fully compress the piston. This can be done either on the bike with thinner shims, or off the bike with thicker shims. Either way will work as long as you compress the piston all the way.

 

The purpose is to allow you to flush as much of the old fluid out as possible.

 

I think it is more critical on a bike with ABS. I don't know the exact reasons, but I bet someone else on here will.

 

Just a note on that:

 

When you take your car (with ABS) to have the brakes flushed, they don't push the pistons back into the calipers.

 

When you take your non-servo ABS BMW to the dealership to have the brakes flushed, they don't push the pistons back into the calipers.

 

There's no question that doing so causes more of the old fluid to be expelled, but is it necessary? I'm going to say "no". If it was necessary, then it would be necessary on all brake system flushes.

 

It's not a bad idea and it's definitely going to get more of the old fluid out. Potentially...if your pads are all really worn so the pistons are pushed way out, it could be a pretty large amount of fluid.

 

Personally, the only time I push the pistons back into the caliper (or slave in the case of a hydraulic clutch) is if I've sucked air into the system...like when I'm replacing the lines or one of the components.

[russell_bynum]

I'll now attempt to find the right shimming material and keep it handy for this task.

 

I've got a bunch of plastic wedge-shaped shims for shimming doors and stuff that I got at Home Depot. Those would work just fine.

[T__]

So, if I understand you replies correctly, leaving the calipers in place with the disc between the pads, isn't sufficient to remove the old fluid inside the calipers.

 

What you are saying is that, I have to force the pads (and pistons) back as far as they'll go to get the old fluid out.

 

This can be done in place with plastic shims.

 

Please understand that when I said "remove the calipers" I really meant, unbolt the calipers and let them hang free. I see this done everywhere in DVD and .pdf instructional information and then the user blocks the pads with timber to keep them from touching during the process.

 

I couldn't work out why, as the disks are preventing the pads touching whilst the calipers are in place and I can access the speed bleeder easily.

 

Sorry to be so dense. I'm still not positive from your replies why anything needs to be shimmed, unless the pistons have to be completely forced back as far as they can go to remove any trace of old fluid.

 

I don't "remove" the calipers from the bike when I change the fluid on my Triumph and am struggling with the concept for the Beemer.

 

Not arguing here, just failing to understand.

 

Linz

 

Linz, if you look at a calipers you will see the path from the fluid brake line entering the caliper to the bleeder screw does not go through the depth of the piston bores.. It think the reasoning for pulling the calipers & blocking the pistons back in the bores is to tilt them up so the ALL the old fluid exits with the flushing process.. Probably to be real anal that would be the correct way but even then I doubt ALL the old fluid exits the calipers..

 

My reasoning for just pushing the pistons back in their bores then wedging there with plastic wedges is; that eliminates MOST of the pocketing in the piston bores & most of the old brake fluid then exits with the flush & bleeding process..

 

I haven’t ever seen signs of contaminated brake fluid & it comes out clean looking every time I do a seasonal flush & bleed..

 

I guess if you feel like pulling the calipers then do so.. If you don’t then don’t pull them (I haven’t felt the need)..

 

Just remember to check & set the brake fluid level in the ABS controller reservoirs after you pump the pistons & brake pads back in contact with the rotors (you need to do that whether or not you pull the calipers off)..

 

Twisty

[T__]

I'll now attempt to find the right shimming material and keep it handy for this task.

 

Linz

 

 

Linz, you can use most anything.. I made mine on the mill using Delron.. I would imagine you could use plastic door stops cut down,, or plastic ice scrapers,, or cedar shingle shims,, or bondo squeegees with strips of wood between them or even strips of wood or plastic..

 

Twisty

[Ken H.]

I've got to vote the other way. Of all the fluid in the system, the fluid behind the position gets the most punishment because its exposed to the most heat. When doing a flush I want as much as possible of that cooked fluid out. So pushing the pistons all the way in is critical to a thorough job in my opinion.

[smiller]

I've got to vote the other way. Of all the fluid in the system, the fluid behind the position gets the most punishment because its exposed to the most heat. When doing a flush I want as much as possible of that cooked fluid out. So pushing the pistons all the way in is critical to a thorough job in my opinion.

Generally brake fluid is replaced because of its hygroscopic (water absorbing) qualities, not because of heat damage.

[Flyer5]

I've got to vote the other way. Of all the fluid in the system, the fluid behind the position gets the most punishment because its exposed to the most heat. When doing a flush I want as much as possible of that cooked fluid out. So pushing the pistons all the way in is critical to a thorough job in my opinion.

Generally brake fluid is replaced because of its hygroscopic (water absorbing) qualities, not because of heat damage.

Sorry, I cant agree fully with that.Its also replaced because of the ash residue left behind from cooking, ABS is prone to damage from this ash mostly . So when changing the fluid dont compress the caliper with the bleeder closed it just pushes that ash up into the system ,if not opened before. Dave

[russell_bynum]

I've got to vote the other way. Of all the fluid in the system, the fluid behind the position gets the most punishment because its exposed to the most heat. When doing a flush I want as much as possible of that cooked fluid out. So pushing the pistons all the way in is critical to a thorough job in my opinion.

Generally brake fluid is replaced because of its hygroscopic (water absorbing) qualities, not because of heat damage.

Sorry, I cant agree fully with that.Its also replaced because of the ash residue left behind from cooking, ABS is prone to damage from this ash mostly . So when changing the fluid dont compress the caliper with the bleeder closed it just pushes that ash up into the system ,if not opened before. Dave

 

Why would this be any different for an ABS braking system vs. a conventional one?

 

How hot does brake fluid have to get before it starts "cooking"?

[Flyer5]

Sorry, I cant agree fully with that.Its also replaced because of the ash residue left behind from cooking, ABS is prone to damage from this ash mostly . So when changing the fluid dont compress the caliper with the bleeder closed it just pushes that ash up into the system ,if not opened before. Dave

 

Why would this be any different for an ABS braking system vs. a conventional one?

 

How hot does brake fluid have to get before it starts "cooking"?

 

Depends on the type of fluid . ABS is more prone to damage from the ash because of all the valving with small orifices and tight clearances .The ash is not good for the rest of the system either but rebuilding a caliper is a lot cheaper than replacing a ABS unit . The black stuff floating in the fluid is the ash .Another thing not good to do is pushing the master cyls all the way in when bleeding . just go about half to 3/4 of the way . Dave

[smiller]

The black stuff floating in the fluid is the ash .

The black stuff floating in the fluid is dissolved rubber from components in the brake system. With regard to 'ash', I have never heard of this contaminant being associated with brake fluid, nor have I been able to find a single reference to this in an Internet search. Do you have any links?

[Flyer5]

The black stuff floating in the fluid is the ash .

The black stuff floating in the fluid is dissolved rubber from components in the brake system. With regard to 'ash', I have never heard of this contaminant being associated with brake fluid, nor have I been able to find a single reference to this in an Internet search. Do you have any links?

 

Thats the first I have heard about the dissolved rubber parts. I was told about the ash at a ABS class when I was working at a GM dealership long long time ago . Actually about 1989 . Dave

[ianboydsnr]

Brake fluid would never get hot enough, to produce ash, in fact the whole reason for changing, is to prevent the fluid from boiling, which is worse the more water contamination in the fluid,If the fluid boils, you have no brakes, the only reason for pushing the pistons back, is to remove more of the contaminated fluid.

[T__]

Us flatlanders will probably never get the BMW R-RT brake fluid hot enough to boil it.. Even with a fair amount of moisture in it (depends on the fluid brand/type/moisture content).. I ride fast in very fast traffic patterns so may need to make repeated high G stops from better than 90 mph.. Never experienced a soft brake or boiling brake fluid.. I sure hope I don’t as fluid aeration on an ABS system can be down right scary if you ever get it to enter ABS mode..

 

Unless racing or doing track days motorcycle riders seldom make numerous high speed stops without some cooling between the stops.. Plus the brakes are large (especially rotors) for the weight being deceled & the rotors are in good air flow (out in the open & unshrouded by deep dished wheels)

 

Now the riders up in the high mountains do have an issue if the brake fluid has moisture in it.. Water boils at a lower temperature at altitude.. I have had some of my test vehicles boil the brake fluid at the top of Pikes Peak with just very light braking (going up the mountain).. Coming down the mountain with a test truck with trailer can be down right scary if ANY moisture in the brake fluid.. One of the best brake fluids we have found for high altitude testing is the standard FoMoCo dot 3.. The company I work for used to maintain a high altitude test facility on pikes peak mainly for brake testing & high altitude emission testing & drivability.. Some of our engine/transmission on road testing is still done pulling Baker Grade but most brake altitude testing is now done on brake dynos in altitude chambers..

 

As far as ash forming in the fluid from heated brakes? That is a new one to me & I used to test brake performance as part of my vehicle development duties.. The 2 biggies on brake fluid performance are moisture & viscosity.. Moisture for boiling,, freezing,, corrosion issues (oh yes, that moisture can also freeze if you operate in a cold enough climate).. Viscosity can also be a factor on ABS systems as the viscosity can change the system response times & that is part of the ABS programming.. Viscosity is the main reason you don’t find DOT 5 in most ABS systems.. DOT 5 also doesn’t handle moisture very well as unlike DOT 3/4 the moisture doesn’t get absorbed IN the brake fluid but tends to just migrate to the low spots in the brake system a sit there doing what water does best..

 

Brake fluid is like old meat.. When-in-doubt-throw-it-out..

 

Twisty

[Jim VonBaden]

Yes, they are trying to get you to fully compress the piston. This can be done either on the bike with thinner shims, or off the bike with thicker shims. Either way will work as long as you compress the piston all the way.

 

The purpose is to allow you to flush as much of the old fluid out as possible.

 

I think it is more critical on a bike with ABS. I don't know the exact reasons, but I bet someone else on here will.

 

Just a note on that:

 

When you take your car (with ABS) to have the brakes flushed, they don't push the pistons back into the calipers.

 

When you take your non-servo ABS BMW to the dealership to have the brakes flushed, they don't push the pistons back into the calipers.

 

There's no question that doing so causes more of the old fluid to be expelled, but is it necessary? I'm going to say "no". If it was necessary, then it would be necessary on all brake system flushes.

 

It's not a bad idea and it's definitely going to get more of the old fluid out. Potentially...if your pads are all really worn so the pistons are pushed way out, it could be a pretty large amount of fluid.

 

Personally, the only time I push the pistons back into the caliper (or slave in the case of a hydraulic clutch) is if I've sucked air into the system...like when I'm replacing the lines or one of the components.

 

I have to disagree with that idea. BMW protocol IS to push the pistons back, there is a special tool to do it in place, with the calipers bolted to the bike.

 

 

Twisty does it on with a screwdriver, and I do it taking it off. I am much more certain to get them pushed back with the caliper off, but either way is probably fine. I use plastic shims now, not in the video, and totally believe that you should get the fluid at the calipers out as much as possible. I do believe that fluid is the most damaged from excessive heat, and that heat draws in moisture as the calipers cool.

 

Jim

 

PS The rear is done with the same tool, but caliper off the bike.