[musketeermail] Brake calipers / A&P question

[Rellihan]

I have not yet found any approved process/repair station for resurfacing piston aircraft brake rotors/disks.  I know of a couple of cases in which homebuilders bought used disks and attempted to have them resurfaced.  They were unable to locate an auto shop that could properly position them on their equipment.   My best guess is that you could eventually find a machine shop that could resurface them, either by jigging them or surface-grinding them using repetitive re-positioning, but I suspect that new disks would be far less expensive.  
 
The disks don't have to be perfectly smooth to be reusable.   Your A&P will make that call.  New pads take longer to properly seat and "break in" on worn rotors, and you have reduced braking capability while that is going on.  New pads will also wear out far faster on worn disks; it isn't unusual to have pads last only 25% as long on worn disks, versus when they are paired with new disks (especially chrome disks, for less-frequently flown planes).  
 
I have seen a few severely worn disks that were still in service, that had lost far too much metal to be safe.   Most of our disks are single-thickness, unlike common auto disks that have two heavy sides separated by ventilation-cooling "spokes" (or the single-layer disks that have cooling slots in them).  Any significant loss in thickness causes much faster heat build-up during serious braking, with less mass to both absorb and carry away the heat.  More of it therefore goes into the brake pads, calipers, and fluid.
 

----- Original Message -----
From: Al ODonnell (sundowner6699x@yahoo.com)
To: musketeermail@yahoogroups.com (musketeermail@yahoogroups.com)
Sent: Tuesday, July 12, 2005 4:24 PM
Subject: [musketeermail] Brake calipers / A&P question


Just had my annual and the brakes are good but will need replacing by
next time. The A&P said the rotors were waring and indeed if you drag
your finger across them you feel smooth bumps. Can these be turned
like you do on auto rotors or do they have to be replaced. The A&P had
never heard of anyone turning them but was not for sure. Does anyone
know the answer?

Thanks

Al

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[jerry at tr4.tr2.com]

Mike Rellihan wrote:
>
> I have not yet found any approved process/repair station for resurfacing =
> piston aircraft brake rotors/disks.

*** Fortunately, brake disks are one of the few reasonably priced items that
we deal with. AFAIK, there are two vendors: Cleveland & Rapco. Rapco is
cheaper than Cleveland. Both are FAA/PMA. No need to do anything heroic
with the old ones.

- Jerry Kaidor ( jerry@tr2.com )
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