Sticking front wheel

dodge1chevy2 · Jun 28, 2019

Success for caliper 2

Na Cl K9 said:
I think its time to get the brake disc out of the way. It sounds like the eccentric pin is being held in place by the tension between the frozen brake caliper piston with pads tight against the brake disc and the position of the eccentric pin in the bore of the caliper. Put the bike on its center stand using a 1 x 12 x12 or 2 x 12 x 12 under it to get a little more height at the front wheel and pull the front axle. Lower the wheel to the ground and roll it forward enough to extract the brake disc from between the pads. The wheel cant be completely removed until both calipers are loose and able to be rotated out of the way, You will or should be able to rotate the caliper in its mount and that should free up the eccentric so it can be pulled. The eccentric pins ride in brass bushings inside the mounting flanges on the sliders so it's not frozen in the mounts except in this case by trapped tension. Once the caliper is off the slider you can pull the wheel completely or put it back so you'll be able to roll the bike around your shop. No heating required. Just wiggle the caliper back and forth as you pull the eccentric down and out of its bore.

Following Johns advice and freeing the front wheel allowed me remove the right side caliper. Even with the wheel forward it required some pounding to remove the caliper pin. Now I have the two calipers with brake lines removed. I believe the next step is to use the compressor to free the pistons from the calipers. Unfortunately due my stroke from 6 years ago I have no short term memory. Please give me advice on which openings I should use for the air input. There is a significant amount of rust on the surface of the right piston so I’m what I will find on the inside.

I appreciate the advice.
Rick

20774 · Jun 28, 2019

Rick -

You should inject air into the same place that the brake fluid goes into, so the spot where you removed the bleed nipple. Be advised that the piston may shoot out of the caliper. I believe the best thing is to stick a thin piece of plywood or stuff in some rags to soften the pistons when they come out. Might want to wrap a towel over the whole affair just for good measure.

dodge1chevy2 · Jun 28, 2019

Confusion overwhelmed me

20774 said:
Rick -

You should inject air into the same place that the brake fluid goes into, so the spot where you removed the bleed nipple. Be advised that the piston may shoot out of the caliper. I believe the best thing is to stick a thin piece of plywood or stuff in some rags to soften the pistons when they come out. Might want to wrap a towel over the whole affair just for good measure.

First issue: I believe the bleed outlet and the fluid inlet provide two entry/exit points for brake fluid. Do I need to block one of these and provide the air to the other?

Second issue: Although the fluid inlet tube on the right caliber came out fairly easily, the inlet tube on the left caliper would not come loose with the caliper in my vise. It would appear that it has not been removed in quite a time.

Third issue: I assume that I should plan on replacing the pads. Particulary since I now cannot remember which pads are inner or outer and which came out of which caliper.

Fourth issue: Looking for pads on a couple of vendors websites, it appears that there may be a difference between English and German bikes. The bike that I purchased has a speedometer in kilometers. Does this indicate that the R90S is German? Does it make a difference for the brake pads?

By now everyone should have a true appreciation for my damaged mental state.

Rick

20774 · Jun 28, 2019

r65lsk75c said:
First issue: I believe the bleed outlet and the fluid inlet provide two entry/exit points for brake fluid. Do I need to block one of these and provide the air to the other?

Yes...plug one, air into the other. Usually the bleed port is left closed and air goes in the inlet port as one must disconnect the brake line from the caliper to get it off the bike.

Second issue: Although the fluid inlet tube on the right caliber came out fairly easily, the inlet tube on the left caliper would not come loose with the caliper in my vise. It would appear that it has not been removed in quite a time.

You'll need to use penetrants and time to loosen up the input port/nut. Be careful and proceed with a light touch as you might end up damaging the threads in the caliper and then you'll have another issue.

Third issue: I assume that I should plan on replacing the pads. Particulary since I now cannot remember which pads are inner or outer and which came out of which caliper.

Probably a good idea. Brakes are crucial on a motorcycle. Get the best so you have confidence when the bike is back on the road.

Fourth issue: Looking for pads on a couple of vendors websites, it appears that there may be a difference between English and German bikes. The bike that I purchased has a speedometer in kilometers. Does this indicate that the R90S is German? Does it make a difference for the brake pads?

Yes, the R90S is German...it's a BMW. Personally, I get my pads from a dealer. Other's will come along to give their recommendations for aftermarket pads. EBC?? Ferodo???

Anyname · Jun 28, 2019

r65lsk75c said:
Following Johns advice and freeing the front wheel allowed me remove the right side caliper. Even with the wheel forward it required some pounding to remove the caliper pin. Now I have the two calipers with brake lines removed. I believe the next step is to use the compressor to free the pistons from the calipers. Unfortunately due my stroke from 6 years ago I have no short term memory. Please give me advice on which openings I should use for the air input. There is a significant amount of rust on the surface of the right piston so I’m what I will find on the inside.

I appreciate the advice.
Rick

Some people consider compressed air to be potentially risky. These folks suggest using a grease gun. While I have never tried it myself, it does make sense since grease guns actually generate a lot more pressure and grease is non-compressible so that a exciting sudden release can't happen. Or so they say...

pglaves · Jun 28, 2019

Anyname said:
Some people consider compressed air to be potentially risky. These folks suggest using a grease gun. While I have never tried it myself, it does make sense since grease guns actually generate a lot more pressure and grease is non-compressible so that a exciting sudden release can't happen. Or so they say...

I would NOT do this. The seals designed to contain DOT 4 brake fluid are certainly damaged by petroleum products. This is a good way to require all new seals and a new total rebuild.

ccolwell · Jun 29, 2019

Compressed air works well to get the pistons out. But. Place a piece of wood to prevent the piston from completely exiting the caliper. At the very least you will be startled when it pops out with considerable force. Worse, major mechanical surgery will be required to remove the piston from what it ends up embedded in. Worst, real surgery if it becomes embedded in flesh. DAMHIK

ccolwell · Jun 29, 2019

Also, get some red grease to reinstall the pistons. This stuff http://www.redrubbergrease.com/
Somebody used to sell small amounts on ebay. I got one of those tins, did four or five caliper rebuilds and still have most of it left.

Na Cl K9 · Jun 29, 2019

I haven’t tried a grease gun before simply because air pressure works so well. Seat one bleed valve and introduce high pressure air through the remaining open hole. Either hole works. Wood is referenced but not completely explained- I use a wood house paint stirring stick cut in half to double the thickness and then placed against the stationary pad supports opposite the caliper piston to act as a backstop. When the piston exits its bore it does so with a loud pop and hits the stirring sticks hard enough to crack them. The piston will be tight against the wood so work one of the two stirring stick halves loose. The other stick falls away and the piston can then be fully extracted using pliers to grasp the piston pad backing flange. Wiggle, turn and pull till it comes free. If there are any rust pits present on the piston it has become a souvenir. I perform this operation with the caliper held in a vice - don’t damage the nylon buttons by clamping across them. Soft jaw covers, gloves and eye protection advised. More later...

The "red grease" or 'caliper assembly paste' as Brembo refers to it works fine but only use a very small amount of the stuff. The first time I loaded a piston into a caliper using the product I used too much of the stuff and created a "soft lever" where the brake lever feels soft and spongy. Mostly I use brake fluid coating the caliper bore and the piston with new seal. Holding the caliper in a vice again, I use a 'c' clamp to slowly press the new piston into the bore of the caliper. There is a pin on the back of each pad. One pin, on the pad that moves with the piston has an O' ring and that pin seats tightly in a receptacle in the piston pad backing flange. Don't load the piston so far in that you can't get the pin to seat in the receptacle - once the pad is attached, you can use hand pressure to push the piston the rest of the way seating it against the caliper body. A spring clip holds the stationary pad to the supports opposite the piston.

Notes: Your master cylinder is most likely 'bad'. that is the bore has become pitted and the seals are leaking and the fluid return hole is probably plugged up. You can spot this by simply looking at the paint on the frame below the brake fluid reservoir. I will have evidence of damage from brake fluid or, if not, there will be fluid at the rear of the master cylinder around the piston plunger pin. If the master cylinder is working properly there will be a jet of fluid present inside the reservoir as the brake lever is released plus of course, no leaks. Be careful and cover the reservoir when bleeding the freshly overhauled brakes as the jet of brake fluid will shoot out and damage painted surfaces. Cover the fluid reservoir with a shop cloth while bleeding.

Mark Frappier (and others) restores ATE master cylinders, He sleeves the piston bore using stainless steel. He makes them to fit the exact size of your new piston which you must send along to him with the body of the master cylinder. The fluid reservoir has an O'ring between the tank body and the master cylinder. Replace that too. Clean the threads and seating surfaces of the metallic brake pipes to get the best seal. Replace them if they are kinked. Replace rubber bushings between the rubber brake hose and pipe at the hose support bracket bolted to the slider. Use new BMW rubber hoses. Use only Dot 3 or 4 fluid.

I haven't looked to see if complete master cylinders with reservoirs are still available in a while preferring to rebuild them since re-sleeving works so well. I believe the caps are all gone though so treat yours carefully. Buying a used master cylinder can be an exercise in replacing junk with more junk. Your goal is to make your bike stop at least as well as it did when it left the factory.

dodge1chevy2 · Jul 1, 2019

Indeed have not experienced success

Na Cl K9 said:
I haven’t tried a grease gun before simply because air pressure works so well. Seat one bleed valve and introduce high pressure air through the remaining open hole. Either hole works. Wood is referenced but not completely explained- I use a wood house paint stirring stick cut in half to double the thickness and then placed against the stationary pad supports opposite the caliper piston to act as a backstop. When the piston exits its bore it does so with a loud pop and hits the stirring sticks hard enough to crack them. The piston will be tight against the wood so work one of the two stirring stick halves loose. The other stick falls away and the piston can then be fully extracted using pliers to grasp the piston pad backing flange. Wiggle, turn and pull till it comes free. If there are any rust pits present on the piston it has become a souvenir. I perform this operation with the caliper held in a vice - don’t damage the nylon buttons by clamping across them. Soft jaw covers, gloves and eye protection advised. More later...

The "red grease" or 'caliper assembly paste' as Brembo refers to it works fine but only use a very small amount of the stuff. The first time I loaded a piston into a caliper using the product I used too much of the stuff and created a "soft lever" where the brake lever feels soft and spongy. Mostly I use brake fluid coating the caliper bore and the piston with new seal. Holding the caliper in a vice again, I use a 'c' clamp to slowly press the new piston into the bore of the caliper. There is a pin on the back of each pad. One pin, on the pad that moves with the piston has an O' ring and that pin seats tightly in a receptacle in the piston pad backing flange. Don't load the piston so far in that you can't get the pin to seat in the receptacle - once the pad is attached, you can use hand pressure to push the piston the rest of the way seating it against the caliper body. A spring clip holds the stationary pad to the supports opposite the piston.

Notes: Your master cylinder is most likely 'bad'. that is the bore has become pitted and the seals are leaking and the fluid return hole is probably plugged up. You can spot this by simply looking at the paint on the frame below the brake fluid reservoir. I will have evidence of damage from brake fluid or, if not, there will be fluid at the rear of the master cylinder around the piston plunger pin. If the master cylinder is working properly there will be a jet of fluid present inside the reservoir as the brake lever is released plus of course, no leaks. Be careful and cover the reservoir when bleeding the freshly overhauled brakes as the jet of brake fluid will shoot out and damage painted surfaces. Cover the fluid reservoir with a shop cloth while bleeding.

Mark Frappier (and others) restores ATE master cylinders, He sleeves the piston bore using stainless steel. He makes them to fit the exact size of your new piston which you must send along to him with the body of the master cylinder. The fluid reservoir has an O'ring between the tank body and the master cylinder. Replace that too. Clean the threads and seating surfaces of the metallic brake pipes to get the best seal. Replace them if they are kinked. Replace rubber bushings between the rubber brake hose and pipe at the hose support bracket bolted to the slider. Use new BMW rubber hoses. Use only Dot 3 or 4 fluid.

I haven't looked to see if complete master cylinders with reservoirs are still available in a while preferring to rebuild them since re-sleeving works so well. I believe the caps are all gone though so treat yours carefully. Buying a used master cylinder can be an exercise in replacing junk with more junk. Your goal is to make your bike stop at least as well as it did when it left the factory.

I will give the MC a more careful inspection. Upon the first look there was no visible leakage and the paint below did not show damage. In terms of how things have gone so far, I would not be surprised to find yet another issue. Speaking of another issue, my initial attempt to free the piston from the caliper with air pressure was a rousing failure. I removed the safety tip from the end of the compressor line and attempted to inject air through the fluid inlet. Of course it resulted in the expected spray of residual brake fluid. Turning my regulator to 80 psi did not yield success. So, do I need a better connection between the caliper and the end of the compressor hose? I had the caliper loosely mounted in my vise with a lot of padding hoping for the piston ejection. I ordered new pads - hoping for a chance to install them.

rickt

Na Cl K9 · Jul 5, 2019

You need a $5.00 air blowgun with a rubber tip. One of the two ports must be closed off by reinstalling the bleed valve and tightening it to ensure high pressure air introduced in the other port acts on the piston. 80 psi is more than enough pressure. Did you understand what the wood backstop is doing? Properly positioned it prevents the piston from damaging the opposite caliper pad support structure as it is pneumatically driven from its bore. If your master cylinder is bad it will show up when everything is back together and you start the bleeding process. Otherwise you could remove the plunger to check the bore and seals.

dodge1chevy2 · Jul 7, 2019

Pistons have been removed

Following advice from Na Cl K9 I purchased a new nossel and removed the pistons. I'm not certain that I really wanted to see the inside of the calibers. Both pistons appear to be in decent condition. The calipers not so much. I've taken a couple of pics but I'm afraid I do not know how to include pics with my post. I'm wondering if the calipers can be cleaned out with a gentle honing. A quick survey of a couple of BMW parts vendors indicate a price of $400+ for new calipers. This is well outside of my current budget. I welcome any advice. This motorcycle has a gorgeous paint job and I have a set of new stainless exhaust pipes in the basement. I've just begun to realize why the selling price seemed so reasonable.

rickt

Omega Man · Jul 7, 2019

This page may help you with picture posting-

https://forums.bmwmoa.org/showthread.php?2021-How-do-I-post-a-picture/page53

Good luck.

Gary

20774 · Jul 7, 2019

r65lsk75c said:
I've taken a couple of pics but I'm afraid I do not know how to include pics with my post.

To upload a picture, check out post #15 here:

https://forums.bmwmoa.org/showthrea...he-MOA-Forum&p=1159528&viewfull=1#post1159528

Na Cl K9 · Jul 8, 2019

Check the pistons with a magnet to see if they are stainless steel. Pistons must be free of rust pitting. I hope that what you see in the caliper bore is simply debris and not oxidation. I’ve never considered boring a caliper to restore the surface simply because there are no over-sized pistons available. Try ‘brake parts cleaner’ and see what happens.

dodge1chevy2 · Jul 8, 2019

Apparently not stainless

Na Cl K9 said:
Check the pistons with a magnet to see if they are stainless steel. Pistons must be free of rust pitting. I hope that what you see in the caliper bore is simply debris and not oxidation. I’ve never considered boring a caliper to restore the surface simply because there are no over-sized pistons available. Try ‘brake parts cleaner’ and see what happens.

Hi John. The pistons are not stainless. Both have just a couple of tiny spots of rust. In my humble opinion, they are useable. Of more concern is the calipers. More searching gave me only used items. I'm thinking that I need to salvage the current calipers. Is it acceptable to work on the inside with very fine 2000 wet/dry grade emery paper or steel wool? I also noted that the seals are rather expensive. On one of the calipers the seal is still partially retained. The calibers contained a fair amount of insoluble gung. I now need to look more closely at the MC given the current state of the downstream brake system. Please let me know your thoughts on cleaning the inside of the calipers.

Thanks
Rick T

pglaves · Jul 8, 2019

Attempting to clean the caliper bores is worth the try. Reusing a seal because a new one is "expensive" is not even worth thinking about. Your health, safety, and life depend on those brakes.

Na Cl K9 · Jul 8, 2019

PGlaves said:
Attempting to clean the caliper bores is worth the try. Reusing a seal because a new one is "expensive" is not even worth thinking about. Your health, safety, and life depend on those brakes.

What Paul said.

You could use progressively ‘hotter’ solvents till you find something that cuts the gunk. As a last resort 0000 steel wool would be the limit of what I would ever use to restore a caliper bore surface finish. To some extent the caliper doesn’t need to be perfect but the piston does. Run your fingernail across those rust pits and you’ll feel the rough spot and even leave a little nail behind. That's the issue - the rust pits eat the seals. Here’s the deal - replace the rusted piston(s), install new seals and dust covers, new pads, new hoses, DOT 3 or 4 fluid. Replace the O’ring under the master cylinder reservoir and then bleed the system once a year. Done right it should last 30 years or more and that makes your investment seem insignificant compared to the return. Done cheaply and it’s like you place a rather small value on your life. By the way, this is only the first chapter in the book of ATE. Are you familiar with Snowbum’s web site? Lots of info there. “RUZNEB” and “BEEMERUSS” nailed it at the beginning of this thread by the way. See where this is going?

ccolwell · Jul 9, 2019

There are plenty of tools designed to hone calipers out there. But. You're already on a bike with skinny tires and mediocre brakes compared to modern traffic. If it's just crud, clean it and rebuild it with new seals. If it's rust, then replace. And this is why changing brake fluid every year on bikes and every two on cars is good insurance.

dodge1chevy2 · Jul 9, 2019

Confusion is beginning to overwhelm me

After removing the residue from the piston seal/dust cover (not sure which it is) I encountered what appears to be a thin type of rubber? coating on the inside of the caliper wall. This was a bit of a surprise as I have not seen this on any R90S parts fiche. Am I imagining things or is this a normal part of the caliper? So, I really don't know where to go from here. I have ordered 2 "Protection Caps" and 2 other caliper parts. I am at a loss as far as attempting to clean the caliper bores. I have not been able to find new pistons on any of the vendors part fiche. Can anyone rescue me?

rickt

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