Brake Pad replacement on 82 100RT Question

[asaint]

Hi all,

Tomorrow I'm going to replace the rear brake pads on my 82 100RT. This is the first time I've replaced brake pads on anything in my life, so keep your fingers crossed for me.

I've read over the Clymers procedure on this and I can't figure out WHY the following step is included.

"Partially withdraw the rear axle from the left hand side sufficiently to clear the rear caliper carrier" (Pg 639)

Now, per the picture attached, the rear axle pin doesn't come anywhere near the caliper carrier. What am I missing here?

peace
Asaint

[sumran]

The carrier they are refering to is the bulky aluminum plate that the axle goes through. When you remove the lower support arm that attaches to the plate and partially remove the axle as described, the entire plate and caliper assembly can be lifted out for easy access.

It is a good idea to change the fluid and bleed the system while you have it out. it is the only way you can properly bleed the rear disc brake. When it is installed the bleed valve is not the highest point and air gets trapped. I use two wood shingles inserted from opposite directions to maintain spacing and provide resistance against the pads for bleeding.

[asaint]

Sumran,

Just so I am clear, does the red arrow in my pic below point to the "bulky aluminum plate"? If so, I pull the axel bolt just far enough back so this this plate drops off?

peace,
Asaint

[sumran]

Sumran,

Just so I am clear, does the red arrow in my pic below point to the "bulky aluminum plate"? If so, I pull the axel bolt just far enough back so this this plate drops off?

peace,
Asaint

Yes. If you look on the underside of the muffler you will see a brace attached to the bottom of the same plate. You don't need to remove the brace, just the nut and bolt that attaches the brace to the plate.

[ccolwell]

Yes. If you look on the underside of the muffler you will see a brace attached to the bottom of the same plate. You don't need to remove the brace, just the nut and bolt that attaches the brace to the plate.

I don't think so. The arrow seems to be pointing to the disk carrier, which is bolted to the wheel. The caliper carrier is the piece that directly contacts the swingarm. Look at what the caliper is bolted to in order to figure this out.

[sumran]

I don't think so. The arrow seems to be pointing to the disk carrier, which is bolted to the wheel. The caliper carrier is the piece that directly contacts the swingarm. Look at what the caliper is bolted to in order to figure this out.

It is true that the tip of the arrow is on the disc carrier, but it is pointed at the mounting plate. If the angle brace is attached to the disc carrier he has other issues.;)

[AnnapolisAirhead]

Randy, is the part in the blue circle what you are talking about (for us exclusively plagued with rear drum slowing devices)? :scratch

I think I could see where this dropping down would make it easier to remove the caliper. I dunno, I'm just here for the show. :lurk

[asaint]

Thanks for all the advice and tips.

The good news is I was able to replace the brake pads.

The bad news is the rear brake is just as mushy as before.

I re-bled the rear brake with my Mighty-vac but it doesn't seem to do any good. Odd thing is when I loosen the rear bleed screw, it appears air is being drawn in around it's threads. I hear a slight sucking sound and lots of bubbles are in the fluid. When I slowly tighten it up, the bubble decrease and the sucking sound goes away.

Ideas?

peace,
Asaint

[AnnapolisAirhead]

You may want to try carefully wrapping the bleeder screw threads with teflon and re-bleed. I use speed bleeders and had the same problem on my front brakes. Teflon worked, doesn't take much.

Also, make sure the tube on your Mighty Vac is not too loose. From time to time, you might need to trim it a 1/4" or so.

Hope that helps.

[skiteach]

You should not have to loosen bleeder too much, probably no more than a turn and a half from seated.

[asaint]

Here's the latest,

I cut a 1/4" off from the Mighty Vac hose that connects to the bleeder screw. I wrapped a SINGLE wrap of teflon tape to the screw. I then re-bled the rear brake for about 5 minutes.

The sucking sound is greatly reduced but I can just barely hear it.

I turned the bleeder screw 1/4 turn and the screw is loosened at that point.

The rear brake is just as mushy as before.

Should I wrap a few more layers of teflon tape to the bleeder screw and try again?

peace,
Asaint

[AnnapolisAirhead]

Here's the latest,

I cut a 1/4" off from the Mighty Vac hose that connects to the bleeder screw. I wrapped a SINGLE wrap of teflon tape to the screw. I then re-bled the rear brake for about 5 minutes.

The sucking sound is greatly reduced but I can just barely hear it.

I turned the bleeder screw 1/4 turn and the screw is loosened at that point.

The rear brake is just as mushy as before.

Should I wrap a few more layers of teflon tape to the bleeder screw and try again?

peace,
Asaint

Sounds like you are probably about there. It takes time to push the air out, each time you press the brake pedal, it only moves the fluid about 1/2-3/4 of an inch. So, just keep at it, it'll take a while and make sure that the rear master cylinder never runs out (or even gets close) while you are bleeding, otherwise, it'll just suck more air into the system and you'll be at it for months.

Speedbleeders you only need to unscrew about 1/4 turn. I can't vouch for the standard bleeders--but Skiteach surely knows.

Did the bubbles stop in the Mighty Vac? I pump mine up about 1/2 way, otherwise the tube walls start to collapse until they eeeek a little air past the threads or weakest point. So its not a time thing, its when you get all the bubbles to stop.

[manicmechanic]

What isn't obvious is that your rear brake line comes UP from the master cylinder and over the swing arm, then DOWN to the caliper. So you may have an air bubble in the hose. What is needed is to remove the caliper from the carrier and raise it ABOVE the hose, and then flush the system watching for the bubbles to come out. Then close the bleeder and you should get pressure once you've remounted the caliper.

One other option you can try is to use maybe a large flat screwdriver or tire iron to spread the pads apart. This will force fluid and bubbles back into the reservoir.

[asaint]

Guys,

I just re-bled the rear brake twice.

1st time: use the standard method of opening the screw, having my daughter push down on the brake pedal, close the screw, she released pedal. Did this for about 15 minutes. Made the rear brake worse!

2nd time: wrapped a 2nd teflon strip on the screw. Used the Mighty-vac for 30 minutes. The air never stopped coming out. I finally came to the opinion that the air is leaking around the teflon and stopped at that point.

Rear brake is still mushy.

Maniac - I can try your idea of removing the caliper from the carrier and raising it above the hose tomorrow morning.

peace,
Asaint

[sumran]

Randy, is the part in the blue circle what you are talking about (for us exclusively plagued with rear drum slowing devices)? :scratch

I think I could see where this dropping down would make it easier to remove the caliper. I dunno, I'm just here for the show. :lurk

Yes that is the part I was refering to. All of these glossy pictures with circles and arrows would remind me of Alice's restaurant if the circles and arrows were on the back. I need to figure out how to do that.

Good luck on your brakes asaint. Have you checked the thickness of the rotor? Any fluid leakage around the caliper? The master cylinder may need a rebuild, although it sounds more like air in the system.

[RecycledRS]

I had a similar experience while bleeding my 82 RS. I was able to get a good firm peddle after I removed the caliper and rotated it so the breed screw was at the highest spot (not easy and keep it on the disk) while bleeding it.

[asaint]

Ok,

I pulled the unit off, held the bleed screw up so any trapped air bubbles in the line leading to it would be flushed out. Bled an entire Mighty-vac container of brake fluid out of the lines.

No difference. Back brake now super mushy.

While I had the unit off and the bleed valve totally closed, I had my daughter push on the brake pedal. The brake pads just quivered and moved a hair closer together.

Any ideas on what to try next?

peace,
Asaint

[sumran]

You have to find out where air is getting introduced to the system. By your description it is getting worse as you bleed the system, even with the vac. Most of the time it will leak a little fluid at the point of the air leak, but not always. Check the hose and the fittings between the resevoir and the master cylinder. Since this portion of the system is gravity feed instead of pressured, an air leak here might not leak fluid. Then check the fittings on the hard line between the MC and the caliper. Any leak on the pressure side of the MC should leak fluid if it is not sealed. If you have a bad seal in the caliper it will allow air back in when you release the pedal. Again, I would expect a fluid leak if that were the case.

If the MC was bad, you might not generate enough force to push the air out, but it should not get progressively worse. It is possible to damage the seals in the MC while bleeding the system. When you open the valve It allows more pedal travel than normal. If a ridge has developed, pushing the seal past the ridge can damage them. At least, that is what I have been told by very experienced mechanics. I never actually seen one damaged this way. Again, you are getting a steady and increasing supply of air, which points to another problem.

If you can get an experienced local airhead to help out, it would be a great help to you. If nothing else, for the encouragement. I'm not sure where you are located, but we could try to get you hooked up with someone if you let us know.

[asaint]

Sumran,

I looked over the lines briefly but nothing caught my eye. Any techniques for finding a place where air might be getting in?

I'm far NW Chicago Burbs, Elgin, IL.

peace,
Asaint

[sumran]

I would look and listen very carefully at any potential air leak points while working the pedal. You will need good lighting and a quiet garage. If you don't have line issues, that leaves the master cylinder and the caliper. At some point, I would just rebuild them.

You mentioned in an early post that this was the first time you had done this. It would be good if you could get someone alongside that has done it successfully many times. I understand that may not be possible or you may want to beat this on your own. But I have benefitted a great deal from the help of other airheads. There are lot af first-rate wrenches in your area. Hopefully some of the Chicago folks will see your post and get in touch.

[26667]

Hey, Asaint. My bike has a similar set-up and based on the age alone I'd guess MC. That was the problem w my front at any rate. Once we bled the brake lines, we could never get pressure again. There was a leak at the little plunger which I believe can be purchased separately. Perhaps the rear is the same.
There's an airhead out near you...sort of ...named Ed Dybala. Reall y knows his stuff. I don't have any contact info for him, but you might find him or someone like him thru Al Sloan, the IL Airmarshal out that way. He's 815.286.7374 according to the airmail mag I have on my desk.
You might try also Seymour Goldberg's indep shop at addison and Elston in Chicago. Walk to the Blue Line. if you can ride w front brake only. Great guy. Chi Tech Committee. 773. 617. 8061. He's in his shop by seven am.
Good luck and lemme know if I can try to help.
773 343 3359

[asaint]

Hey guys,

I really appreciate the help and advice. I also appreciate the names of some contacts.

I should note at this point that I'm having a ball working on the bike. One of the reasons I purchased this bike was to learn to do my own maintenance and repairs. Each niggle is a chance to learn something new and have some fun.

Ok, that's out of the way.

I ordered up the caliper rebuild kit form Bob's BMW (real nice folks). The kit includes (4) seals (2 for each piston). I also ordered up a new bleed screw as the current one just doesn't seem right (although I can't put my finger on why).

If that doesn't do it, then I'll take your suggestion, 2227, and learn how to rebuild the rear MC.

Now, question - when I remove the rear caliper unit to put in the new seals, I need to detach the brake line. Will the brake fluid all leak out? Should I drain the entire rear brake before disconnecting it?

peace,
Asaint

[AnnapolisAirhead]

I ordered up the caliper rebuild kit form Bob's BMW (real nice folks). The kit includes (4) seals (2 for each piston). I also ordered up a new bleed screw as the current one just doesn't seem right (although I can't put my finger on why).

If these are Brembo calipers (and I think they are) the kit does not include 4 seals, it will contain 2 seals. Each piston requires only a single seal. The caliper comes apart with 2 large Allen head bolts (which should be included in the kit as well as wavy washers for each). It should also include a small o-ring that goes between the two caliper halves where the fluid passes between them. They do not sell that washer separately and it is NOT a nitrile compound like the carb o-rings (e.g. no substitute). With the help of a forum user, I bought a pack of 50 o-rings made of the proper compound to resist brake fluid for about $4.80 from an automotive source. Guess I am set for life.


Now, question - when I remove the rear caliper unit to put in the new seals, I need to detach the brake line. Will the brake fluid all leak out? Should I drain the entire rear brake before disconnecting it?
Yes, a little bit will probably ooze out, so protect all painted surfaces like the frame, etc. Also, wear rubber gloves because you don't want brake fluid or brake cleaner to get into your bloodstream.

Before you remove the Allen bolts to split the halves, it makes life much easier to use a small amount of compressed air into the threaded hole where the hard brake line was. this will pop the pistons out of their cylinder. Then remove the Allen head bolts to split the halves--carefully notice where the small o-ring goes.

The seals are actually in the cylinder walls where the pistons live but not in the piston (like the engine cylinders). I used a pair of plastic pliers and was careful not to scratch the cylinder walls. Then, if you have a small dental mirror and a plastic or wooden pick, carefully inspect the seal seat for aluminum corrosion...you can slide the pick in there to remove it. This will allow the new seal to seat properly.

I also replace the pins and spring (in the kit too I believe otherwise you can order it (cheap), as mine were very rusty and would cause the brakes to lock up. On Brembo calipers, there is no adjustment or retraction mechanism, effectively the pads gently ride on the rotor, so the pins need to be clean.

Where you get the caliper back on the bike...they should be torqued. I seem to recall it was 46 ft. lbs. but DOUBLE check.

Hope this helps. I just got finished rebuilding both my front Brembos. If you don't have Brembos, er, sorry. I guess I just used up all my words for the day. :doh

[asaint]

The rear Brembo brake saga continues.

I successfully installed the brake caliper rebuild kit. The hardest part was getting the seized allen bolts (that hold the 2 halves of the caliper unit together) off. Ended up with a socket wrench, allen bolt adapter and a hammer. Good thing the caliper kit came with new allen bolts.

Bad new is the infinite air leak problem continues.

I closely inspected the rear brake fluid container and the hose that leads from it down to the master brake cylinder. I noticed the first top inch of the flexible hose is stained a darker color. In fact, it was just barely moist to the touch.

Should I replace this brake hose and see if it does the trick? If so, is this a hose I can get at NAPA? Is there a spec on this hose.

peace,
Asaint

[AnnapolisAirhead]

The rear Brembo brake saga continues.

I successfully installed the brake caliper rebuild kit. The hardest part was getting the seized allen bolts (that hold the 2 halves of the caliper unit together) off. Ended up with a torque wrench, allen bolt adapter and a hammer. Good thing the caliper kit came with new allen bolts.
Yikes, torque wrench and hammer should never be in the same sentence! It's a precision tool and *should* only tighten...so, not sure how you used itt o loosen the Allen bolts.

I used Kroil (gun oil) and PB Blaster over night as penetrating fluids. Check the Clymer's for specs, but when you put caliper back on, it should be torqued--something like 46 ft. lbs on the front. I have a drum brake (er, slowing device) on my rear wheel so I'm not sure what the torque value is--probably less than 46 ft. lbs, but check).


Bad new is the infinite air leak problem continues.

I closely inspected the rear brake fluid container and the hose that leads from it down to the master brake cylinder. I noticed the first top inch of the flexible hose is stained a darker color. In fact, it was just barely moist to the touch.

Should I replace this brake hose and see if it does the trick? If so, is this a hose I can get at NAPA? Is there a spec on this hose.

You know, I thought about that being a possible leak, but have been away from my PC for a while. I'm not sure if NAPA has them or not, but it sounds like the culprit (or at least something that should be replaced as a preventative measure). I'd bite the bullet on this one and order from a dealer--and probably braided stainless steel line, not rubber.

[asaint]

Annapolis,

Funny thing is the line running from the brake fluid container to the master cylinder is identical to the fuel line running to the carb. It's a black cloth woven hose. Is that what it should look like?

Yes, I got a little caveman'ish on those allen bolts. Had the caliper unit wrapped in towels so it wouldn't get hurt.

I see your recommendations for torque in foot-lbs. As a beginner wrencher, I'm guessing this is some sort of spec on how hard to tighten something. I use craftsman wrench set and am guessing I need some sort of tool to measure torque?

Oooops - noticed in my last post I put "torque wrench". I have no idea why I wrote that, I meant socket wrench. I'm typing between trips to the garage with the bike.

peace,
Asaint

[AnnapolisAirhead]

If the brake line is the same cloth covered material as the fuel line, that is extremely dangerous (especially on front brake where most of the braking takes place). Fuel line is nitrile and can not withstand the chemical make-up of brake fluid. If that is indeed fuel line, and old fuel line then I would suggest that you have found your leak. I'd recommend getting a dealer supplied brake line (braided stainless if you can).

If you have a Clymer's manual, all the specifications (most of them) are in there, including torque values. A torque value is specific method of tightening something based on the strength of the fastener, the material being fastened, mating surfaces, exerted force, etc. These bikes are pretty specific about torque and you can do more harm than good by ovetighening, so if you aren't sure, look it up or ask.

You can pick up a decent torque wrench from Sears, etc. Be sure is registers in "foot pounds" and newtons. I thin I paid about $30 for mine. Looks like a large ratchet, but only tightens. The handle usually has a dial although there are other styles.

[sumran]

The hose looks like the fuel line, but is a different item. There is no pressure on this line; it is a gravity feed from the resevoir to the master cylinder. The stock hose looks like the one you describe. It should not have fluid leaking out. If fluid is leaking out, air is likely getting in. That is the hose I was refering to in my earlier post. It sounds like you may have found an entry point for air in the system. Hopefully, it is the only one. Pictures and part numbers are at this link. You want items 16 and 17. Less than 7 bucks for the hose and both clamps.

http://www.maxbmwmotorcycles.com/fiche/MainDiagrams.asp?mospid=47888

[asaint]

Annapolis,

Thanks for the explanation. I'll pop over to Sears tomorrow ("Hey kids, it's Sunday - let's go to sears" ":} ) and pickup the torque wrench. Sounds like something I'll need to use constantly moving forward.

Sumran,

I'll order up the brake line today and it should be here by about Tuesday. A bit of a bummer as I havn't been riding the bike without the rear brake. I'm pushing into 2 weeks without a ride <snif>.

peace,
Asaint

[AnnapolisAirhead]

I think this is he exploded view of the parts Randy was referring to in his post.

Line is part number: 34321236259 $4.27 at MaxBMW. Quantity 1. Indeed DOES look like fuel line, go figure my bad.

Clamp part nubmer: 16121116458 $0.95 at MaxBMW, quantity 2. You have to replace these, they are one-time use only. I think a small stainless band clamp would work too though.

Also, this link does a much better job at explaining a torque wrench (http://en.wikipedia.org/wiki/Torque_wrench#.22No-hub.22_wrench) than I did. I'd get the dialable 'click' type not a 'beam' wrench. There are also digital ones, but I'd stick with the clicker. Works everytime, anyplace. Be sure to 'unload' is when you store it, that is undial it to zero foot pounds during storage.

Good luck at Sears. I'm going riding/camping with a group of good ole crusty airheads. :dance

[keelerb]

Bungee or cable tie the brake lever depressed (i.e., in the "brake on" position) overnight. Works wonders.

[asaint]

Annapolis,

I have the new brake line and 2 clamps. Clymers doesn't cover how to remove the old clamps nor install the new ones.

I *assume* you crimp these clamps into place. I don't really like that and would prefer to install new hose clamps (with the little screw) instead. Any reason I shouldn't?

Also, how the heck do I get the old clamps off?

peace,
asaint

[asaint]

Ok,

A bit of an update on this brake problem.

I replaced the hose running from the brake fluid container to the master cylinder, this did not fix the problem. I put on standard hose clamps (and glad I did ).

Ok, I rebuilt the rear MC. Very long job in getting this done. Had no idea what I was getting in for here. Rebuild takes like 10 minutes - removal and reinstall took 4 hours - yes you read that right. Many things I learned along the way here. Say the 30 minutes I looked for "pin"that connects the yoke arm to the brake pedal - you know - the "PIN" Clymers DOESN'T show! I finally went to the BMW schematics to figure that one out.

Ok, very long story short, MC is reinstalled. Problem still remains. I've narrowed it down to this as the specific symptoms;

1. I removed the steel brake line from the MC. I pushed down on the brake pedal and then when I would let up, would put my finger over the hole. No fluid would come out no matter how long I did this.

2. Rethreading the steel brake line back onto the MC gave me problems. I can't figure out why. Possible I misthreaded at some point. I put some teflon tape on it. screwed it back down. HOWEVER, now when I push down on the pedal, air bubbles come out around the thread and inside the screw where the steel brake line emerges.

I'm open to ideas.. kinda hitting the wall here.

peace,
Asaint

[sumran]

If you the MC isn't pushing fluid you have no way to make progress. If you don't have a perfect seal between the MC and the line fittings, you can't make it work. To get the air out you can only allow fluid to move in one direction. Air will rise to the higest point. Leaving the handle clamped overnight, as suggested in an earlier post, may allow air to escape through the master cylinder and resevoir. the rest has to be pushed out through the bleed valve. But you can't do that unless the MC is pushing fluid.

[asaint]

Randy,

Yes, it appears I need a new MC as the rebuild did not take.

Anyone know if a reconditioned one can be purchased. Bob's quotes $165 for a brand new one.

peace,
asaint

[asaint]

Well, ok, I stand corrected.

After leaving the bike sit with the brake pedal tied down, I get sorta new results.

When I push down the on pedal, brake fluid squirts out from the inside of the bolt that attaches the steel line to the end of the MC.

So you can picture this, the brake line runs through this bolt and the bolt holds the brake line to the MC.

It appears the MC is working, but I need a new steel brake line with the bolt on the end. Well, that is unless there's a way to remove that bolt from the brake line.

I'll post a pic tomorrow.

peace,
Asaint