Dragging Brake

[jrevens]

So Kitfox's instruction to use LPS-1 on those posts is not the best product?

I think it probably would be just fine Eddie. I wouldn't want to say that any particular product was the "best"... there are so many availabe now days. Like I said, there are probably many different lubricants that would be ok. The most important thing in my opinion is that the lube be something that is at least relatively dry and less likely to attract dirt. LPS-1 would meet that requirement. A good high temperature rating would also be desirable. Then, periodic cleaning - I like an aerosol no residue cleaner that I can spray in there and flush out any contaminants before applying new lube. Keep the lube off your discs and pads of course. I don't feel it's usually necessary to disassemble everything unless the linings/pads look like they're ready for replacement.

[Esser]

This may sound silly

Let the air back out of the tire. If this corrects the problem, then tighten the bolts that hold the wheel halves together.

Funny, this is one of the things I was thinking of. Thanks for the suggestions everyone. I meant to get at it this weekend but life got in the way again! (Septic tank issues that needed attention)

[PapuaPilot]

For lubing the brake caliper pins I would avoid using anything that stays wet as it attracts dirt. Grease or oil could also be the reason the brakes caught on fire.

Where I work we teach the new mechanics to clean the pins & bushings and use a spray dry graphite.

[Esser]

OK, I lifted up the plane and tried turning the tire by hand. I couldn't do it. So I removed the caliper this morning and as soon as I loosened the bolt holding the halves together a little bit, I could spin the wheel freely. I took the caliper and gave the pins a shot of LPS one and reassembled. As I was slowing tightening the bolts, I kept spinning the wheel. As I got to what I felt was tight it started getting stiff. I got the torque wrench out to give it the recommended 75in lbs. and discovered I was above that number. I backed it off and torqued it to the specified amount which doesn't feel like much. It turns by hand now but for sure doesn't spin. It's much easier to move the plane around now so I'll chock this up as a win. I think previously I had the caliper bolts over torqued.

[jrevens]

For lubing the brake caliper pins I would avoid using anything that stays wet as it attracts dirt. Grease or oil could also be the reason the brakes caught on fire.

Where I work we teach the new mechanics to clean the pins & bushings and use a spray dry graphite.

His pins were actually dry, Phil. That was probably a contributing factor. A plastic brake line melted or softened and came loose, and the fluid caught fire. That's one reason I like to use teflon-lines hoses in that area, and also the higher temperature-rated brake fluid.

[jrevens]

OK, I lifted up the plane and tried turning the tire by hand. I couldn't do it. So I removed the caliper this morning and as soon as I loosened the bolt holding the halves together a little bit, I could spin the wheel freely. I took the caliper and gave the pins a shot of LPS one and reassembled. As I was slowing tightening the bolts, I kept spinning the wheel. As I got to what I felt was tight it started getting stiff. I got the torque wrench out to give it the recommended 75in lbs. and discovered I was above that number. I backed it off and torqued it to the specified amount which doesn't feel like much. It turns by hand now but for sure doesn't spin. It's much easier to move the plane around now so I'll chock this up as a win. I think previously I had the caliper bolts over torqued.

It seems (to me anyway) that you still may have an issue that you should get to the bottom of, Josh. When those 2 bolts are tightened the parts come together metal to metal, and I think it's unlikely that any deformation could occur with overtightening, considering the design of those 2 parts. You'll over-stress the bolts, yes. Things should turn freely... there may be a very light rubbing of a pad against the rotor, but not enough to impeed rotation. Is the face of the piston on that brake cylinder pushed all the way in and at least flush with the surface of the assembly? If not, push it in. If it is cocked slightly and jambed that is a problem of course. There is probably a single o-ring seal on the piston, and some temporary lubricant applied at the factory. Once brake fluid is in the system, it provides lubrication. Is the unwanted friction relatively equal throughout a full rotation of the wheel, or is it greater in some spots than others? If it is, there may be some misalignment of the rotor - perhaps foreign material between the mounting surface and the wheel, or a deformed/bent rotor. Make sure you have torqued the wheel-half bolts evenly and properly also. Don't mess with them until you let the air out of the tires! Obviously, the axle nut needs to be properly tightened also.

[efwd]

I wondered when that axel nut was going to come in. I found it was incredibly easy to tighten it up barely too much and the free rotation was eliminated.

[Esser]

Hey John, thanks for your thorough comments. I did check all the faces and the pistons were flush. The wheel has the same resistance all the way around with. I spots that are worse. The only thing I didn't check of everything you mentioned was the axel nut. I guess I'll try and play with that to get it fully loose.

I didn't really think to play with that as the caliper seems like it is independent of where the rotor is as it is just sliding on those pins. My first thought was my rotor was too thick when I tightened the caliper and it bound.

[jrevens]

You're welcome, Josh. There is always a possibility that you got an incorrect part... that's not unheard of. I hope you find out what the problem is without too much more work. Good luck!

[Esser]

For anyone interested, I revisited this. I took the wheel off, sanded the paint off the “rotor” and then sanded some corrosion off the the pads. After that I reassembled. It spun freely better than the wheel that I didn’t have an issue with so I gave the other side the same treatment.