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Brake groan

LettersFromFlyoverCountry

LettersFromFlyoverCountry

Well Known Member
Anybody ever get a 'groan' out of one side of the plane when applying brakes. I've occasionally heard them on big jetliners, but I've had one almost from the start on the left side, even after replacing a brake pad last winter (the old one had iced up and broken off).

My pal, Brad, says he's heard it can be caused by some vibration of the brake line and the solution is to secure them more, but I've already got the three rings of electrical tape in there and before I go to the hassle of pulling farings off, I figure I can compare notes.

The thing is, i get it even when lightly apply the brake (tho' obviously not as loudly). Very weird.
 
LettersFromFlyoverCountry said:
Anybody ever get a 'groan' out of one side of the plane when applying brakes...
Click to expand...

I had this once after someone else worked on my airplane. The brake line was rubbing on a wheel fairing plate nut. Everything looked fine with the fairing off. The line didn't fail until I was checking it with my fingers. The finger pressure was the straw that broke the brake line, causing a hole while sitting in my hangar.
 
I don't know if it's the same noise you're hearing, but we had one that was the brake line vibrating due to the loop in the line not being aligned quite right and causing the trailing edge of the pad to drag on the rotor. The vibration eventually lead to a fatigue crack in the brake line and we had to replace it. Of course, the prudent thing to do would have been to fix it before it got to the point of failure:)

Hope this helps,
Regards,
Rob
N706DR
RV-7A
 
I have had the problem in the past. The brake line were not positioned correctly. They were putting some load on the brake caliper. Hitting the brake would stiffen up the brake line and create a groan. Taking the wheel pant off, reposition the brake line without loosening any fittings, and then trying the brake operation again. Once the brake line was in the correct position with no pre-load on the caliper, the noise was gone.
 
Try some CRC Disc Break Quiet...

Likely that you have some metal to metal chatter where the break piston contacts the back of the pad... try some CRC Disc Break Quiet. About 4 bucks at any car part place.

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Bob I heard yours in the AirVenture video

When I heard it I knew immediately what it was because I had the same exact agonizing noise that I asked about in this forum and received many good suggestions which I tried and seemed to improve but not correct the problem. I finally solved it myself.

I sitting in my kitchen at the computer and I haven't looked at the assembly for a while so please forgive me if I say something awkwardly general.

There is a small part that is secured to the axle with a bolt that passes through the axle. You have to remove everything on the axle to get to it but it is worth the effort. TIGHTEN THAT BOLT! Since I finally took it down to that level and did it I have not had the problem recur.

We traveled for years and I developed operational work arounds like tapping the breaks to minimize the duration of the squall but it was alway there.

Bob Axsom
 
Back if the pad...

Apply to the back of the pad where the piston mates... let it set up for 10+ minutes then instal.

Check the tighteness of the break assembly attachment as Bob A suggests as well.
 
Got it too

I am completing my first condition inspection and just installed a new set of pads (Grove Brakes).

Mine have moaned since new.

I have tired everything on the forum, bevels, aluminum backer plates, cleaning, lube pins, still there. I have not tried the new pads yet - I'll report back if they help. They told me at Oshkosh that the pad material has changed at some point so try the new pads...

I have braided lines and am going to try supporting them differently as some report the brake lines contribute to the problem.

Post back here if you find something that helps!
 
By way of an update: Checked the bolt that passes through the axle. It was plenty tight. Bought some Disc Brake Quiet and lathered it on the back of the pad plate. We'll see. the stuff doesn't set up very quickly in 97 degree heat.
 
I'm sure you are right but ...

LettersFromFlyoverCountry said:
By way of an update: Checked the bolt that passes through the axle. It was plenty tight. Bought some Disc Brake Quiet and lathered it on the back of the pad plate. We'll see. the stuff doesn't set up very quickly in 97 degree heat.
Click to expand...

On the bolt tightness I'm sure you are right but I hope you added a little torque when you checked it. I believed mine were plenty tight as well but the extra torque with almost no perceptible movement of the bolt stopped the noise that had persisted through all efforts to get rid of it for years and it sounded exactly like yours on the video. Thanks for checking and reporting, it would have bothered me not knowing.

Bob Axsom
 
I had the same issue on my -7A. My hangar neighbor recommended slightly beveling the leading edge of the brake pad. I was skeptical but it worked perfectly and resolved my issue.

Best,
Jamie
 
There contaminants on the brake pad- like grease or hydraulic oil will cause the brake pads to chatter very rapidly sounding like a groan. If you think you got oil or grease on the pads, the best solution is to replace them.

Dan
 
an automechanic friend helped me put new tires on my RV-6A snd he lubricated the brake holding pins that slide thru with dialectric grease. If it is in the instrictions, I missed it. I also used the red can product on back of the pads and the sound rarely occurs now.
 
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