The International Cessna 170 Association

I just put new tires on my 170b, and once I got it back from the shop my left brake begun sticking.

It rubs quite aggressively, and my plane pulls to the left on taxi. Immediately after taking off, the wheel stops spinning too.

The caliper also doesn't 'float' when I move it by hand as it should—the piston is extended and pushing the pads onto the rotor causing it to rub aggressively.

What could be causing this?

I brought it back to the shop, and my mechanic took the brake apart, cleaned it, greased it, then re-bled the system. This fixed it for just a day, then the next flight the pads were pushed up against the rotor again rubbing.

Suggestions?

Is there a new seal or rebuild kit for these calipers?

Notes*
1. The brake feels good, no squishiness, just rubbing a lot
2. My rotors are worn significantly—they have a small lip at the outer edge (time for replacement soon)
- the mechanic said he believes worn out rotors can cause pistons to push too far out and get stuck in the ON position, though I'm not sure about the validity of this
3. Still lots of pad life left

Cheers from rainy Vancouver, Canada

The pistons don’t actually “retract” after brake release….. they just don’t apply pressure against the pads. If your caliper doesn’t “float” …I believe that may be at least part of your problem. Are the pins bent? Dirty? Scored?
Are the bores clean and smooth and round? (When I do brakes one of the things I do is run a rifle-bore brush thru them, then lubricate them with dry aerosol lube.)


Meanwhile you might turn your discs to true them up if they’re not too thin already. If you know the part numbers I can look up the minimum for you.

GAHorn wrote:The pistons don’t actually “retract” after brake release….. they just don’t apply pressure against the pads. If your caliper doesn’t “float” …I believe that may be at least part of your problem. Are the pins bent? Dirty? Scored?
Are the bores clean and smooth and round? (When I do brakes one of the things I do is run a rifle-bore brush thru them, then lubricate them with dry aerosol lube.)


Meanwhile you might turn your discs to true them up if they’re not too thin already. If you know the part numbers I can look up the minimum for you.

Pins — you mean the bolts which hold the caliper onto the wheel, correct?

Maybe they damaged them when they removed the wheels to change the tires and this could be causing the problem

Reece , here I’ve illustrated the PIN which slides thru the BORE and allows the CALIPER to “float”.

Your mechanic could be right. Your disks may be to thin. It may be time to remove, flush and clean the caliper of dirt and grime that might be causing the piston to jam. While you are at it polish the pins with Scotchbrite and slide the brake pad over it to make sure it slides easily on the pins and also the caliper slides easily in the bracket. Loosen the hose and reposition it so all this movement happens. Often tension from the hose will make a calper cock of and not slide in the bores as it should.

Easy to measure the disk with a micrometer and look in the Cleveland service limits table in Appendix A. Don't know what disk you might have? Look in the Parker Hannifin (Cleveland) product catalog. Of course the disk you have should be recorded in your logs either with a 337 field approval or using an STC

Sidewall contact ?

If your airplane is equipped with Cleveland Wheel and Brake STC for the 170 the kit number will be199-46 the disc for that kit is 164-02601, the minimum thickness for that brake disc is 0.205/5.207 = Inches/millimeters. Unless it has been modified by some other means which I have found to be true of some airplanes I have looked at being re imported back to the United States.
Regards,
Jim

c170b53 wrote:Sidewall contact ?

Those were my thoughts also, especially when it just started after the tire change. Different tire brands have different profiles. Are they 800's? When I went from 700's to 800's I had to make a spacer disc to go between the brake disc and the inner wheel half to keep the caliper from rubbing on the tire...

Joe
4518C

Also check that the brake line is not side loading the caliper which impedes the caliper from floating freely. I had this exact problem on my new to me 170. Brakes were not dragging enough to stop the wheels but they would make a scrapping sound. I took them apart three times to lube them. That lasted one day each time. The local mechanic fixed it by moving the lines so they parallel the gear legs rather than having the loop you show. He said he see that a lot on 172’s.

Richgj3 wrote:Also check that the brake line is not side loading the caliper which impedes the caliper from floating freely. I had this exact problem on my new to me 170. Brakes were not dragging enough to stop the wheels but they would make a scrapping sound. I took them apart three times to lube them. That lasted one day each time. The local mechanic fixed it by moving the lines so they parallel the gear legs rather than having the loop you show. He said he see that a lot on 172’s.

Thanks for this. Sounds like it's likely the culprit. I'll adjust the brake line so there's no tension on it impeding proper caliper movement and go from there.

Cheers!

Subscribed. I have a squeaky brake after installing new pads.

Likely any side load from the brake line is due to the flex lines, no longer flexing. It looks like the normal black color flex lines are whiteish in the pic, a sure sign that they are somewhat due for replacement.

Turns out the pistons were seized inside the caliper. Re-bored the caliper and replaced some seals, fixed the problem.

Brake line is the flexi fabric one, so not the issue causing the jam.

I brought it back to the shop, and my mechanic took the brake apart, cleaned it, greased it, then re-bled the system.

Re-bored ? or just Re-cleaned with Scotch-brite ?

c170b53 wrote:

I brought it back to the shop, and my mechanic took the brake apart, cleaned it, greased it, then re-bled the system.

Re-bored ? or just Re-cleaned with Scotch-brite ?

Re-bored!