Brake lining failure

[drill_and_buck]

Last year I replaced my brake pads on my RV-8. I usually get 3-4 years of use on a set of brake pads. During this year's condition inspection I found pieces of my right wheel brake linings had broken off. What I found curious is that they broke off on both the inboard and outboard pads at the same location.

I've never seen this before. I'm stumped as to the cause. These are WHLM66-106 linings. Note the cracks radiating from the rivet holes.

Rivets were installed using a threaded screw action tool.

Thoughts on potential causes? (email sent to Matco tech support)

 

[280FX]

From my neighbor with an RV-10 -

Just changed the brakes on my RV-10 and found the exact same issue. Haven't reached out to Matco yet, but plan to. My linings have pieces broken off and many cracks along the linings.

 

[9GT]

Probably resulted from over squashed rivets.

 

[280FX]

Probably resulted from over squashed rivets.

Reply from neighbor -

Possibly, but mine were done at the factory.

 

[AlexPeterson]

I have a small crack in one of the pads also (Matco) - nothing has completely fractured yet, but I will be replacing them this month. About 140 hours on them.

 

[lr172]

Last year I replaced my brake pads on my RV-8. I usually get 3-4 years of use on a set of brake pads. During this year's condition inspection I found pieces of my right wheel brake linings had broken off. What I found curious is that they broke off on both the inboard and outboard pads at the same location.

I've never seen this before. I'm stumped as to the cause. These are WHLM66-106 linings. Note the cracks radiating from the rivet holes.

Rivets were installed using a threaded screw action tool.

Thoughts on potential causes? (email sent to Matco tech support)

View attachment 87225View attachment 87226View attachment 87227

This would appear to be caused by cracking the pads by applying too much force on the rivets. Never used a screw tool, but suspect it provides more leverage and therefore easy to over do it. Yhe nice thing about the hammer type tools is it progesses slowly and the sound changes once it gets tight. You tap a couple times and check. I usually lighten up on the tapping force once close to avoid going too far. The pads are quite brittle and not designed for that kind of force. Also. the area where the rivet applies its force is very thin.

 

[lr172]

Reply from neighbor -

Possibly, but mine were done at the factory.

Your pic shows cracks that do not start at a rivet, so evidence that over tight rivets may not be the cause. Could have been a defective pad or possibly subjected to the UPS "Lets drive over this thing and see what happens" entertainment phase of shipping. Could have been a piece of debris got stuvk between pad and plate.

 

[larrynew]

Based on advice I got on VAF many years ago, I run a file over the brake pad backing plate every pad change to make sure the pad sits flat. Don’t know if that’s the reason I’ve had good luck with RV brake pads for the last 2000 hours but I’m going to keep doing it. Only adds a minute or two to a pad change.

 

[danny]

Based on advice I got on VAF many years ago, I run a file over the brake pad backing plate every pad change to make sure the pad sits flat. Don’t know if that’s the reason I’ve had good luck with RV brake pads for the last 2000 hours but I’m going to keep doing it. Only adds a minute or two to a pad change.

Me too. I think the backing plate "pluckers" a little bit during rivet removal. And I think installing the rivets is more of what you're used to doing. I've been using the screw type squeezer (that word doesn't look right) for 40+ years and can't recall ever seeing that issue.
danny

 

[280FX]

Your pic shows cracks that do not start at a rivet, so evidence that over tight rivets may not be the cause. Could have been a defective pad or possibly subjected to the UPS "Lets drive over this thing and see what happens" entertainment phase of shipping. Could have been a piece of debris got stuvk between pad and plate.

Reply from neighbor -

I also have pieces of lining material that have broken off starting around the rivets. The linings are the originals that were installed by Matco at the factory and were part of the brake and wheel assembly - so it wasn’t a shipping issue. As to debris - both sides exhibited the same missing pieces and cracks. I think it’s defective linings and/or incorrect assembly at the factory.

 

[RV-9erA]

Last year I replaced my brake pads on my RV-8. I usually get 3-4 years of use on a set of brake pads. During this year's condition inspection I found pieces of my right wheel brake linings had broken off. What I found curious is that they broke off on both the inboard and outboard pads at the same location.

I've never seen this before. I'm stumped as to the cause. These are WHLM66-106 linings. Note the cracks radiating from the rivet holes.

Rivets were installed using a threaded screw action tool.

Thoughts on potential causes? (email sent to Matco tech support)

View attachment 87225View attachment 87226View attachment 87227

Are these metalized brake pads or the older fiber style pad? If not metalized, I would start using metalized brake pads. I have Cleveland main wheels on my RV-9A and have always used Van's metalized brake pads (over 20-years now) and have never had a problem and also get long brake pad life. On other airplane's I've owned in the past, I have seen excessive wear and cracking on the older fiber style brake pads.

Matco Brake Reline Kit 5:00x5 Pads for 1 and 2 Place RVs

Replacement Brake Pad Set

store.vansaircraft.com

 

[CDN]

I also had similar failure with Matco linings on my RV-10. Last summer I replaced the brake pads with swiftline (factory lined) pads. After about 50 hours of use, I had one of the linings break away from the pad on landing roll out due to cracking at the rivets. Fortunately, the Matco RV-10 brakes have 2 linings per pad and that was enough to get me back to the hangar, albeit with a little bit of grinding noise whenever I had to apply braking to turn on the taxiway. I just replaced all 8 linings with Rapco and intend to monitor them carefully through their service life to see if these are better.

 

[drill_and_buck]

Are these metalized brake pads or the older fiber style pad? If not metalized, I would start using metalized brake pads. I have Cleveland main wheels on my RV-9A and have always used Van's metalized brake pads (over 20-years now) and have never had a problem and also get long brake pad life. On other airplane's I've owned in the past, I have seen excessive wear and cracking on the older fiber style brake pads.

Matco Brake Reline Kit 5:00x5 Pads for 1 and 2 Place RVs

Replacement Brake Pad Set

store.vansaircraft.com

Matco doesn't specify whether their brake linings are metal or organic. The ones sold by Vans aren't qualified either.

 

[RV-9erA]

Matco doesn't specify whether their brake linings are metal or organic. The ones sold by Vans aren't qualified either.

Unless they've just changed recently, I've been using Van's Aircraft brake pads (the three rivet style) on my RV-9A for many years (over 20-years), and they have always been metalized pads (i.e. brass partials embedded into the pad fiber material itself), and it's easy to tell by observation. And, they last much longer and hold together extremely well in my experience! This video clearly shows the brass metal on the old and new pads.

 

[Norman CYYJ]

Is it possible that maybe these pads at sometime in their life got over heated and caused them to become more brittle thus eventually braking?

 

[drill_and_buck]

Is it possible that maybe these pads at sometime in their life got over heated and caused them to become more brittle thus eventually braking?

That is a possibility I’m looking into. Matco also thought the linings showed heat checking from high temperatures.