The International Cessna 170 Association

New to me 170B with McCauley wheels and brakes. New non metallic Rapco pads and Rapco steel rotors put on during pre buy/ annual about 25 hours ago. From day one I’m hearing an occasional grinding noise from both sides. Not at the same time. We thought the wheel pants were rubbing somewhere but no joy so I am running with them off. Same noise. Removed the brakes and cleaned and lubed the pins and holes with anti seize. They were tight. Put it back together. After a few flights, same noise. I took them apart again and this time beveled the edges of the pads. Reassembled with some auto disc brake lube recommend by mechanic. After a few flights same noise. Took them apart again and cleaned cleaned and lubed again. After a few flights, same noise.

This noise stops as soon as light brake pressure is applied to whichever wheel is noisy. That wheel will stay quiet for a bit. If I lightly ride the brakes, no noise. This is NOT the classic squeak we hear from some brakes. I think the mechanic who installed them did the break in, but I wasn’t there. I have done it again a few time with no difference.

Any ideas?
Thanks
Rich

Rich,
I’d start out by getting rid of the stainless discs based on this Service Bulletin from Cleveland.

I installed stainless disks when I moved to the Mississippi gulf coast in 1990, thinking of corrosion resistance. I don’t recall ever having an issue with braking action, but by the time in left the area six years later, the disks were completely shot, with grooves probably 25% of the thickness worn in them. As far as I remember, the carbon steel steel disks I replaced the stainless ones with are the ones still on the airplane and in good shape.

Sorry guys. My mistake. Rotors are not stainless they are Rapco nickel platted steel. I’ll edit the first post.

Rich

I have a similar problem and have tried all sorts of fixes. What my issue is the RH wheel rotates in flight and the pads touch the disc now and then . After take off and at about 500 ft I give the brakes a application to stop rotation. But within about 5 mins this wheel starts rotating again. I have torqued my main wheels ,replaced bearings and seals , , greased the locating pins for the pads, beveled the edges on the pads even swapped wheels over from left to right . I get a small amount of “grinding noise but also a “clunking” sound as the wheel rotates. However I run felt bearing seals and was told yesterday that a “rubber” garlock type seal is now available for my size wheel . It has a tighter fit to the axle.

I have had good service from the Black Steel disks. They seem to be much better than chrome disks. I am on my second set of black disks.

170C wrote:I have had good service from the Black Steel disks. They seem to be much better than chrome disks. I am on my second set of black disks.

I’m surprised you even need brakes on that slow green thang.

Rich
Brake chatter could be being caused by one or two issues that I can think of. Do the brake pads pull away from the disc when you release brake (pedal) pressure? If so it can be being caused by two different issues.

The first is the Loc O seal in the master cylinder is not properly set allowing the piston in the brake caliper to be drawn away from the pad when the master cylinder is no longer having foot pressure applied. That is because the Master cylinder is drawing fluid back from the Brake on the wheel which it should not do. The loc-O seals function is to allow pressure to be applied below the piston when depressed thus applying pressure at the brake caliper. The second function of the Loc-O seal is two allow the master cylinder piston to retract and not draw fluid back into the master cylinder. The brake pads should always be in close contact with the disc and not be pulled away.

The second possibility is the brake line arrangement at the wheel. Do you have flex lines at the Caliper? A picture of the arrangement I describe is clearly seen at the wheel in his inflight picture of his green aircraft on page 31 of New member/new project posts. The early documentation for installing Cleveland wheels and brakes gave the option of using a hard line all the way to the caliper or using a flex line which allows the caliper to float more freely. My Cleveland wheel brakes were installed with a hard line all the way to the wheel. It caused complete one brake failure on a landing once because the brake line was keeping the pad away from the disc. And a full stroke of the master cylinder was not enough to take up the space at the wheel. Pumping the Brake pedal a couple of times would set the brake. But it is not something I wanted to be doing at landing. I installed the flex lines on both Main gear the next day. This is a picture of my 170A you can just see the Black flex lines at the bottom of the gear legs. This may not be the cause but it is a place to look. Regards,
Jim

Jim

Thank you very much for those suggestions. I do have flex lines to the calipers but I had not considered the MC issue you described. Makes sense. This airplane sat for 13 years. Anything is possible.

Rich.

Old flex lines can collapse inside and hold fluid pressurizing the cylinder. Don't ask how I know.
John

Yes, I know that from my 66 Corvette! I think these flex lines are new, but I have to check the paperwork. They look good on the outside but that doesn’t mean anything. I will check. Thanks for the reminder.

Rich

I believe my problem is solved. Although I have flex lines, they are short and therefore not that flexible. They were routed so they were putting a side load on the calipers not allowing the pins to slide no matter how much I lubed them. Re routed and all better. Thanks for all the suggestions.

Rich