brake pad wear

[dougknight]

In the middle of annual condition inspection. 101.4 hrs RV-9A, cleavland mains. I went ahead and replaced brake pads because I had them on hand.

I miked the new vs the old and there was .030"-.035" wear on the old.

Was it time? or should I have tried to get more out of them?

thanks
doug

[Mel]

Your brake pads should have a notch at each end. When the pads are worn down to the bottom of the notch, you're getting close to the rivets. That's the time to change.

[dougknight]

Mel:
The originals did not have the notch, nor did the replacements I got from Vans (groves).

Maybe I should ask "how deep is the notch"?

thanks

doug
N625DK

[mrreddick]

The last set I received from Van's had no notch (wear indicator?). I ordered a set from Grove when I ordered my new nosewheel and the Grove set have no notch either.
There IS a chamfered edge which is much harder to see. The depth of the chamfered edge is about the same depth as the notch from an older set of pads I checked.

[Mel]

I've always used Rapco. I thought they all had the notches.
I get them from Aircraft Spruce, $22.85/set of 4.

[Bob Axsom]

I have had two brake incidents on my RV-6A. The first was my fault I tried to stretch usage to the maximum and they wore too thin on the right side (the side that gets the most wear because of the natural action to apply the right brake with the right takeoff rudder)so the fluid was able to leak out around the piston O-ring. I won't go into the details but I can vouch for the plane's ability to turn tight circles with one brake applied. The brakes are so important on an "A" model and you only see them once a year that I find it safer just to replace them. Their cost is microscopic for the work they do on these tens of thousands of dollar airplanes. Replacing them is a mandatory line item on my condition inspection checklist. Your flight operations are unique so your wear per hour and hour per year numbers may justify some other maintenance schedule but you should develop a check/replacement schedule and stick to it.

Oh the second incident ...well that was a broken tube flare during landing at Prescott, AZ on a trip to California. The linings were not a factor.



Bob Axsom

[terrykohler]

Bob:
they wore too thin on the right side (the side that gets the most wear because of the natural action to apply the right brake with the right takeoff rudder)so the fluid was able to leak out around the piston O-ring.

How did brake pad wear lead to seal failure. This may be important to those of us that like to see 200-300 hours on a set of pads. I'd rather replace the pads early than risk brake failure.
Terry, CFI
RV9A, N323TP

[kevinh]

Originally Posted by terrykohler

Bob:
they wore too thin on the right side (the side that gets the most wear because of the natural action to apply the right brake with the right takeoff rudder)so the fluid was able to leak out around the piston O-ring.

How did brake pad wear lead to seal failure. This may be important to those of us that like to see 200-300 hours on a set of pads. I'd rather replace the pads early than risk brake failure.
Terry, CFI
RV9A, N323TP

If the pad gets too thin, the o-ring can pop out and lose all the pressure.

That said, I was careful to have a slight forward bias on my rudder pedal angles. I just replaced my pads with 225 hrs on my first set of pads - there was still a lot of wear left (I forget how much - but definitely well under the Cleveland limits), but I figured this was the right annual. Every six months I'd check them and be surprised they were still holding up. I do lots of short flights even...

Definitely not good to push pad life, but if you are careful to not ride the brakes there is no reason to think an A model RV will go through lots of pads.

[N941WR]

This is one of the few things I didn't photograph during my condition inspection.

With the taildragger -9 at 190 hours and 302 landings in the first year the brakes looked almost brand new. Heck, even the tires still had the part lines on the center. (Yes, I did rotate the tires and brake pads.)

I attribute this to the tail wheel steering and the low landing speeds of the -9 rather than pilot skill or some such BS.

All that said, there is nothing wrong with replacing the brakes early, you did the right thing. Save the set you removed and when you order a new pair for next year's annual, compare them. What you don't want to do is expose the rivets, they can damage the rotors, if the pads wear down enough.

[RV8Squaz]

A quick check of the online Cleveland Wheels & Brakes maintenance manual shows that 0.100" is the minimum lining thickness.

Jerry
RV-8 N84JE 290 hours and a ton of landings on the original pads.