Dragging Brake

[Esser]

I just pulled my kitfox out of the garage and noticed it's left brake is dragging bad enough that I needed a second person to help pull it back in. My brake lines aren't hooked up so I'm surprised it's dragging. All I have done is put about 10 psi in the tires. Anybody have any ideas on how to loosen this up? The right side is fine.

[jiott]

Take the bolts out of the caliper and pull off brake pads to see what's going on.

[HighWing]

My thought would be that when installing and tightening the bolts there was a slight misalignment between disk, pad and caliper. Then when tightening, it resulted in an inadvertent friction lock. Loosening the bolts, seating the caliper piston then re-tightening, I suspect would correct it.

[Floog]

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.

[mr bill]

Sounds like a brake puck may be stuck.

[N981MS]

I have had a similar issue for years on mine. Maybe since new.

If I brake to a complete stop and get out to push they drag. I can roll it but it is difficult.

If I let it coast a bit before the stop no drag.

My impression is that if they jiggle a bit while coasting in it seems to help.

If there is a known way to fix this I would be interested. But it is not really much of a problem in that I have adjusted to it.

[DesertFox4]

My right brake will do this same thing at random times. Makes it feel like I'm pushing a Cessna 206 back into the hangar. I've wondered if I had air trapped somewhere in the right brake loop although I can not see any. It heats up after moderate brake use and expands and puts pressure on the puck. Not a hydraulic engineer so just a musing.:confused:
Would love to solve this little issue also.
P.S. --- Cleveland wheels and brakes.

[jrevens]

These "Cleveland style" brake assemblies (Grove, Matco, etc. are basically the same design), with 2 guide posts attached to a cylinder assembly, can exhibit this type of issue. I'm not saying it's the issue here, but there's a long-known potential problem with the plate that runs on those posts and has one of the linings/pads riveted to it, and also where they run through a couple of bosses on the mounting plate that attaches the assembly to the axle. A problem like what you describe can be caused if everything doesn't move along those posts nice and smoothly, with no binding, as they may get slightly cocked or dirty. You want to make sure that the brake lines, or anything else, is not pulling on the "floating" assemblies and causing them to misalign and bind. There are several schools of thought regarding lubricating those moving/sliding assemblies... everything from just keeping them dry and clean to using heavy grease on them. I'm of the opinion that a light lube of the proper kind is good. What I like to do during my annual inspections at least, is clean those sliding components with a spray cleaner that leaves no residue, and then apply a few drops of "Lock-Eze", which is a graphite containing light oil. It wicks into the contact areas, and the oil mostly evaporates leaving a relatively dry film. There are many different lubricants that would work well in a similar fashion. I used a spray-on bonded dry lubricant on the posts before assembly for awhile. I can honestly say that I've never had a binding brake problem.

Quite a few years ago, a friend had one brake that would "catch" and drag periodically. He just ignored it because it would usually go away if he just tapped on the brake pedals a little. He was taxiing from his hangar to the run-up area one day and didn't notice, or ignored that it was dragging, and in that relatively short distance the brake got so hot that a fire started and traveled right up the brake line and gear leg to the fuselage. By the time he got out with his fire extinguisher a lot of damage had been done - it could have been worse. It was a valuable lesson for me.

[DesertFox4]

Thanks for the info John. :)
I will investigate to see if my brake line is causing interferance with proper movement then disassemble and clean then apply
Lock-eze to the posts.

[efwd]

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

[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.