Topic: 77 550 caliper rebuild kit

[sniper1]

Does anyone know where to get a good front brake caliper rebuild kit for a '77 550K?

My brakes are squealing like pigs and I don't think the piston "retracts" enough after releasing the lever.

Does this make sense that a rebuild or replace is in order?

[benjamin550]

sniper,

im in the process of rebuilding my caliper/ master cylinder right now and have done a lot of searching on the forum for answers. There are several good threads that discuss exactly what your talking about. Here is what Ive found.

Several reasons reasons why your brake isnt retracting enough:
1. there are 2 holes in the bottom of the master cylinder. One has a small hole in the bottom of it and can very easily get clogged and cause this symptom of not letting fluid pass through on release. Take a small wire (guitar sting or wire brush wire) and pass it through to releave the debris.
2. bad seal in the brake cliper- there is a ring in the caliper thar goes around the piston. the piston pushes forward and the seal helps pull it back. If the seal is bad, or if there is rust/debris in the grove that the seal sits in, then it cannot properly bring the piston back.
3. pitted piston- if the piston is pitted from years or use, then it cannot form a complete seal on the seal i mentioned above in the claliper and because there is a lack of pressure, cannot be pulled back. It might be a combination of bad piston/ seal.

As far as "rebuild kits" for the caliper, i dont know that a complete kit exists, and even if it does, the OEM piston from honda is like 100 bucks. If you take your caliper apart and notice some rust pitting on the piston then order a new phenolic piston from forum member Kevin400f. Then, order that seal from honda (its 8 bucks of so) and maybe new brake pads if you need them. As far as I know, thats about all of the parts inside your caliper to replace, and you might not need to replace all of them.

you CAN however order a full rebuild kit for your master cylinder and redo that as well.

Before you start taking stuff apart, I might just try clearing the tiny hole in the bottom of the master cylinder.

[Kong]

I think I should point out to everyone that nothing retracts when you relieve pressure on the brake system.  The pads may be pushed back a few hundredths of a thousandths of an inch but that's about it, there is no mechanism to physically pull them back away from the disk, and so in fact it doesn't happen.  I don't know that his has been mentioned here, and it may not have any relevance at all, but on my Harley when the rear brake begins to squeal I can fix it by retorquing the rotor mounting bolts.  Might help on the Honda, might not - worse that can happen is you'll know your Rotor bolts are properly torqued.

[DavePhipps]

I think I should point out to everyone that nothing retracts when you relieve pressure on the brake system.  The pads may be pushed back a few hundredths of a thousandths of an inch but that's about it, there is no mechanism to physically pull them back away from the disk, and so in fact it doesn't happen.  I don't know that his has been mentioned here, and it may not have any relevance at all, but on my Harley when the rear brake begins to squeal I can fix it by retorquing the rotor mounting bolts.  Might help on the Honda, might not - worse that can happen is you'll know your Rotor bolts are properly torqued.

I do believe you're right about there not being a mechnism for retracting pads but the pistons in the caliper do retract.

[SohRon]

As mentioned in a previous post, the pad retraction "mechanism" is the oil seal located in a slot down in the bore of the caliper. It grips the piston and is deformed when the brakes are applied. When the brakes are released, the O-ring returns to its original position, dragging the piston with it.

[cameron]

http://www.z1enterprises.com/detail.aspx?ID=2652

[jimkalfakis]

Okay, forget the caliper rebuild kit. You don`t need it. Go to Bike Bandit and buy just the caliper piston seal (it`s different than just any o-ring) for under ten bucks. That`s all you need to fix your problem. I just did the same on my 550. If your mechanical then also buy the master rebuild kit for around 20 bucks. Just to play it safe and be done

[Fritz]

I think I should point out to everyone that nothing retracts when you relieve pressure on the brake system.

Well, that's not completely right.

As mentioned in a previous post, the pad retraction "mechanism" is the oil seal located in a slot down in the bore of the caliper. It grips the piston and is deformed when the brakes are applied. When the brakes are released, the O-ring returns to its original position, dragging the piston with it.

Exactly. The "Honda Common Service Manual" is a very good source for good understanding and maintenance of bikes in general. The following diagram is from the manual.

When replacing the seal it's groove in the caliper should be cleaned thoroughly.

[cameron]

Okay, forget the caliper rebuild kit. You don`t need it. Go to Bike Bandit and buy just the caliper piston seal (it`s different than just any o-ring) for under ten bucks. That`s all you need to fix your problem. I just did the same on my 550. If your mechanical then also buy the master rebuild kit for around 20 bucks. Just to play it safe and be done

Agreed 100%.

[CBDee]

But isnt it true that the pad isn't attatched to the piston, so when the piston retracts the pad is still free to contact the disk?

[OrganDonor]

That is true.  But with no pressure there's really no friction.  The caliper half containing the pad on the opposite side also requires an adjustment after any disassembly to keep it from either binding or allowing too much play in the brake handle.

[Kong]

That explanation, while it may be accurate, is preposterous.  That very most it could possibly retract the piston would be less than one fourth of the clearance between the piston and the brake cavity and I would suggest that that measurement would be something on the order of hundredths of a thousandth of an inch and for the purposes of this discussion (cause of squeaking brakes) have no relevance what so ever.  Brake squeal does not indicate that the caliper needs to be rebuilt nor does it have a thing in the world with the need to rebuild the master cylinder.

[OldSchool_IsCool]

But isnt it true that the pad isn't attatched to the piston, so when the piston retracts the pad is still free to contact the disk?

When the piston is properly retracted due to seal rebound, the pad will keep it's distance from the disk due to Ekman Flow.  Same reason that the read head in your hard drive doesn't physically contact the platter despite the freedom to do exactly that.

EDIT: Changed Bernoulli Effect to Ekman Flow.  It's tough to keep those 18th century mathematicians straight!  Bernoulli Effect is how the venturi inside a collaborator works.

[CBDee]

Thanks for that, whatever that Bernoulli Affect is, i guess it works! I'm wondering if the OP didn't forget to put that little rubber o ring i between the pad and piston? I know my brakes squealed like a banshee when i forgot mine!

[bryanj]

The "resiliance" or "Twist" in the seal is all that retracts pistons in any disc brake and it only has to be a fraction of a thou to stop the pad making contact BUT to work properly the pad has to be free to move in its housing whatever type that is

[Fritz]

That explanation, while it may be accurate, is preposterous.

If so, I don't know why Honda took the time to explain it in their service manual. And furthermore why has cleaning the seal groove and properly lubing the back and sides of the pads stopped my brake's squeling?

benjamin550 wrote a good summary of what is to be checked. I just have two additions: Use brake lube (Down Corning silicone grease was proposed in different threads) on the back and the sides of the plate that the pad is glued to and check and grease the bushings of the caliper bracket.

[Kong]

Actually I don't know what fixed your brake squeel, but it could have been something that you changed by simply taking them apart and reassembling them.  I'm not saying that bad seals might not be part of the cause, but consider this.  When a car's disk brakes squeel no one changes the caliper seals to fix it, they put in new pads, maybe turn the rotors (maybe not) and good mechanics always use a sealer between the piston and the pad to make sure they don't squeel in the future.  I've not known of very many brake jobs on cars that ever involve replacing seals.  So why dose it have to be seals on our bikes but not on the millions of automobiles out there on the road.

I think you have to start by asking yourself, 'what's vibrating to make that sound'?  Well, there's basically only a few possible culprets.  It could be the rotor.  That makes sense because its a great big bell of a thing sitting right out there in the air where it could make all sorts of noises.  So how could it vibrate?  Well, if the surface was irregular or if the mounting was lose it might contribute to the squeel, so start by tightening the bolts and just feel the surface - is it marred with the groves of age?  If so get it resurfaced and see if that helps.  If not the rotor then it must be the pads, right?  Well, are they free to vibrate or have they been bedded in silicon, is the plastic spacer that's supposed to be behind the pushing puck still there or did someone lose it on an earlier brake job?  These would be things to look at.  Next there is the piston, is it a good tight fit in the caliper or has it or the bore it fits into corroded over the years enough to allow vibration?  If so replace them.  And the last thing I'd look at is if the caliper itself is firmly bolted to the lower leg.

I'd think if you'd look at those things - oh and maybe replace that $10 seal somewhere along the line - it will take care of the problem without resort to esoteric discussion of the movement of fluids - by the way the Bernoulli  effect is what allow both your soda blaster to work and airplanes to fly, it is one of the most elementary basics of fluid dynamics.  In short what it says pressure and the velocity of a fluid's flow are inversely related.

[bryanj]

Not saying changing the seal will stop the squeal, just that it is the seal that retracts the piston, albeit by a tiny fraction, and if the groove is full of corrosion and/or the seal old and hard it dont do its job properly.

Also over here in UK where copious amounts of rock salt are used on the roads every winter its common to do caliper rebuilds to stop the pulling to one side problem on cars

[Kong]

Interesting comment on the salt.  They use tons of it here too, but I rarely ride the bike on roads that have been salt treated, it being wintertime and all.

I noticed that the OP is from Virginia Beach, and indeed salt will be his enemy if that's his home.  Add salt to the problem of a plated piston in an aluminum caliper and the galvanic issues must be intriguing.  He's fortunate in being from that area though because its a real industrial powerhouse of an area (the entire Hampton Roads area is dominated by the presence of the US Navy) where any sort of machine work, and more importantly materials and supplies to include obscure "O-Rings".  He shouldn't have any problem finding anything he needs.

Along the same line, and this is just for inspiration, I found that some seals are more common than we might imagine.  I have a boat that has hydraulic steering and an auto pilot, it requires replacement seals frequently.  The seals for the slave cylinder on the thing were costing me about $50 a set.  There was also a seal (square O-Ring similar to the one in the Honda brakes, but smaller) in the steering head that failed about once a year at $15 a pop.  So I was back home and riding past a hydraulics shop one day and I just pulled over and walked in.  I had the old dead seals in my truck and I showed them to the guy and asked if they might be available locally.  He went over to a bin and came back about a minute later with the two seals for the cylinder unit and the seal for the steering unit, total cost was $3.00, a buck each.  I have one of the Honda caliper seals laying out on the bench and while the shop I was going to has gone out of business (I hope not from selling seals to cheap) there are others around and if I can find a really cheap replacement I'll let you all know.

[sniper1]

1. there are 2 holes in the bottom of the master cylinder. One has a small hole in the bottom of it and can very easily get clogged and cause this symptom of not letting fluid pass through on release. Take a small wire (guitar sting or wire brush wire) and pass it through to releave the debris.


Before you start taking stuff apart, I might just try clearing the tiny hole in the bottom of the master cylinder.
[/quote]

Thanks for the advice. There are two small holes towards the rear of the reservior (towards the rider). One is open and the other (closest to the headlight) appears to be plugged. Is it supposed to plugged? Or should I try to clean it out? With the cap off and I pull on the brake lever a stream of brake fluid comes squirting out. Is that normal??