New Brake Pad Burn-in

Another thread got me to wondering.... but, I didn't find anything in the archives directly about this topic, although I vaguely recall something being there...

I have long thought that the manufacturer's recommendation to "burn in" new pads was insane. I've never done it, and have gotten around 400 hours from each set of pads.

What have others found?

Same hear, although I do one panic stop right after I replace pads. Fast taxi (20-25 MPH) then complete stop. Basically done while taxing to the run up area.

I had to replace just one side on a plane and it made no differencve in braking after one fast taxi to a complete stop, using the brakes hard. After that it stops straight as an arrow.

Hi Alex,

I never burn them in either, Just use them normal and after one or two landings they are working great. My Rapco pads and my dads Rapco pads squeak like you described, even when just rolling the airplane around, this is obviously normal for these so no worries, they do seem to be lasting better and stopping better then the Cleveland pads, we are also using the Rapco rotors.

Russ

Geico266 said:

Same here, although I do one panic stop right after I replace pads. Fast taxi (20-25 MPH) then complete stop. Basically done while taxing to the run up area.

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Although a good way to do your break-in, you may not want to try an immediate take-off right after this due to the risks of not having brakes, or of having a brake fire in the event of an aborted take-off. Let them cool off awhile.

I installed Redline Brakes on my friend's N3N. We did not burn them in. When we first started flying with the new brakes, they would barely hold the airplane during run up. The N3N doesn't have a steerable tailwheel. Sometimes you do need the brakes while taxiing. After several flights, the brake effectiveness improved pretty dramatically.

My RV-6 is not a heavey airplane with an R-985 in the nose, and I haven't noticed that issue when I change brake pads. On the first flight after changing the pads, I steer with the brakes on the way to the runway.

I thot burn-in, run-in, whatever you want to call it had nothing to do with longevity, but everything to do with the need to have *good* breaking with *new* brakes.

Brakes will glaze over if they aren't tempered correctly. Also, pads are porous and will collect brake dust in the areas that don't have rotor contact.

I think most of the time, the pads are changed without smooth grinding the rotors and you need to run-in the pads so that the rotor to pad surface areas are *matched* and maximum pad area is applied to the rotor when the pistons outpresses.

I also suspect that the speeds at which you land an RV are less than you'd land something with higher wingloading and a faster approach speed and as such poor rotor to pad contact isn't as noticeable during break-in time if you allow it to happen without a formal break-in period.

Just a guess, but I suspect that is the reasoning behind the request, suggestion, whatever you want to call it.

Chicken Soup

AlexPeterson said:

...I have long thought that the manufacturer's recommendation to "burn in" new pads was insane... What have others found?

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I think of the break in procedure as being like taking chicken soup for a cold...it can't hurt.

Since burning in the pads is so easy to do, why not do it? Just maybe the manufacturer knows something we don't. It takes just fifteen or twenty minutes, most of which is spent sitting at idle while the brakes cool down between taxi runs. It's not as though the manufacturer has us doing this just for grins, or because we'll wear out the brakes sooner. So maybe, just maybe, you'll avoid whatever potential disaster may have caused the manufacturer to recommend this in the first place. It's your choice but as for me, I follow the suggested guideline.

Chris

Chris is probably right and I should revise what I said, I don?t go out of my way to break them in but I suppose they do get broke in, I?m on a 3000 foot runway and have plenty of 3 and 4k? runways to use, I do use the brakes to slow the airplane the first couple of landings and they do improve through the first couple of landings, after that they are as good as there going to get. So if you need to make your first landings on say 1500 too 2000 feet over an obstacle needing brakes then you best get them seated before leaving the ground! I guess it just depends on what you need from your brakes on landing that can determine how you should handle seating them, I am also used to never needing brakes for landing on 3000 feet of asphalt as well as flying champs back in the 90s that never had working brakes so it does not bother me to fly with little to no brakes depending where I?m planning to go.

Russ

More for Safety than longevity

I just got my plane out of annual, where the pads were replaced (I didn't build my RV9A so don't do the maintenance). It was my first experience with new pads. The A&P cautioned me about the "break-in" period and reduced breaking, although his concern seemed to be more that he got all the air out of the system when he bled them.

Anyhow, while the brake peddle felt very very solid, the initial breaking was terrible! I thought that he may have accidentally gotten some oil or grease on the pads. I was really glad he'd warned me or I might have found myself in some real trouble. In fact after one taxi down the runway, I had to exit the plane and pull it around to turn onto the taxiway, after the braking on one side was too poor to do an effective turn. I had braking but it was probably only 30% as effective as the old brake pads were. He was about to take the wheel pants off and check things again when the braking started to improve, a little bit each time I applied them. I finally had brakes that were good enough that I dared to do a flight. That was about 1 hour of flight time and 6 or 8 take-offs and landings ago and they keep on improving. I think they're almost up to the point of where my old brake shoes were before they were replaced.

Based on my experience, I'm also inclined to think the break-in is more about safety than longevity. Also, I found it interesting that before he pulled the wheel pants off again, he stuck his head down and he could smell the hot pads, so he knew they were pinching. They just weren't grabbing.

Rick Luck
N109RV
RV9A

chrispratt said:

I think of the break in procedure as being like taking chicken soup for a cold...it can't hurt.

SNIP

Chris

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Well... there have been fires when people have done the burn in, perhaps reported on this list. The post about the friction coefficient changing is indeed interesting. I have never noticed any difference in braking power when changing from old to new pads.

I guess a prudent thing is to do the burn in with the pants off, with someone watching from the outside. Taxiing with some brakes applied is very hard to control from a brake temperature point of view. Putting 20 horsepower or so for a few seconds into brake disks that only weight a couple pounds will tend to warm things up.