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blocked brakes


Juliet Golf

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You should lube the caliper guide pins. I clean with CRC carb spray cleaner and then use a smidgen (Arkansas term :rolleyes: ) of the synthetic Mobile One grease on them. Lets those pins move without binding.

Matco would prefer you don't use any grease. I specifically asked. I suppose it accumulates dirt.
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MFG"s are always right. Why do you think there are so many LOA's in the LSA market and FAA required fixes for other aircraft over the many years.

I think Matco worries about grease getting to the pads. Just use a thin film. They may even be worried about dirt accumulation, but that happens any way. Metal on metal there doesn't move as smooth dry and no grease allows more water oxidation and corrosion. Its served me well for 10 years and on many planes.

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MFG"s are always right. Why do you think there are so many LOA's in the LSA market and FAA required fixes for other aircraft over the many years.

I think Matco worries about grease getting to the pads. Just use a thin film. They may even be worried about dirt accumulation, but that happens any way. Metal on metal there doesn't move as smooth dry and no grease allows more water oxidation and corrosion. Its served me well for 10 years and on many planes.

 

They may not be always right, but they are more often than not.

 

I have been working on airplanes for 35 years, I know I'm a young pup. I have seen where the application of lubricant has transferred the wear from the sacrificial part to the part they intended to last. This happens over a longer period of time than 10 years and a thousand or so hours.

 

I have replaced brake assemblies on older aircraft because of this, but the most notable was a set of control wheel shafts.

 

The owner decided to lube the control shafts with silicone grease, instead of a simple cleaning every once in a while. The grease made them move really smooth. When I replaced them they had worn almost all the way though the 1/8" wall thickness of the shaft. I replaced the bushing that the shaft slid through at the same time I replaced the shaft. The bushing which is supposed to wear had almost no wear, where the shaft had worn to the point it was no longer serviceable. In this case the grease caused two $1,000 parts to be worn out instead of the $20 bushing.

 

Once the grease was applied the first time there was no going back, at least not without major disassembly. Because of this the grease was continually applied until the shafts were replaced.

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I haven't seen any issues over the last 10 years. If you glob it on it could get to the pads. A little common sense here goes along way. The guide pins still get cleaned, just lubed again. Aircraft brakes don't get near the use that auto brakes so parts should wear slower. Water is a big influence on aircraft brakes. Corrosion can happen in and around the piston and cause pitting and sticking. I have never had a guide pin issue on any of my customers. A thin film means just that. The Marc brake disc would bind up all the time. I would take my trusty Dremel with a sanding drum and just touch and open the holes on the disc where the guide pins went through. (Terrible design) Made the disc move freely and not bind. When I say just a touch that's all I mean. No excessive enlarging of that hole. That said I hate Marc brakes. The Italian Marc brake MFG is either cheap or a few decades behind or maybe both.:)

 

To lube or not to lube(guide pins), that is the question.

Sounds like one of those personal choice items. Both seem to work so toss the coin and go either way.

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Roger, the point I was trying to make is the application of the grease might change the wear point from where it is intended to wear. It might be a situation where instead of the easily replaceable and inexpensive part wearing out a more expensive harder to replace part might wear out instead. You may not see a problem at 10 years or even 20 years, but it can show up over time. The control shafts I spoke of were on a airplane that was almost 40 years old and 9,000 hours.

 

Now, will you see a problem from applying a little bit of grease to the pins in the short term likely not. Even at 10 years you report no issues. Over time however it may cause wear where wear was not intended. For instance the torque plate might wear out instead of the easily replaceable pins that were intended to be the part to wear.

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I've apparently been using the wrong terminology for about 50 years.

 

As in, "I let my pads wear down to the backing plates and it scored my rotors".

 

Learn something every day!

 

I still say the same thing too. But, when we talk about servicing the liners, we really have to draw the line so we know which component we are referring to :-D

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                                                                                               :giggle-3307:

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That's why you're supposed to clean and put new grease in.

 

Although having gaiters on the matco pins might not be a bad idea!

On the one hand, without lube my rotor pins got quite corroded, even though my Sky Arrow was hangared almost all of the time.

 

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Caused the rotors to bind. Now I clean and then lightly lube the pins periodically, and so far, so good.

 

On the other hand, it is true that the pins that most auto brake calipers slide on are protected from dirt and moisture by rubber boots, and when they do have issues it's usually because those boots have been compromised.

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