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MATCO brake discs

B

benjam

Active Member
Hi All,

Can anyone offer advice on the tool to remove the bolts from this MATCO discs?

Torx drive, but T27 is too small, and (next size up) T30 too big?

What would you replace them with if you accidentally flogged it out trying to tighten it up? The black bolt on the right is high tensile but a different drive head.

asking for a friend…😳😳

any advice out there please?
IMG_9592.jpeg
IMG_9591.jpeg
 
I had those internal-caliper Matcos for many years on my -6 and the rotors were retained by Allen button heads (like your black one). Just be sure to get new Nord-Lock washers.
 
I’m looking for a standard milspec for this button head cap screw. Can anyone tell me what it is? Matco part is MSC.25-20X.75BHCS but ordering through them will take too long (I’m in Germany). Who can say what this size and thread is - or give standard AN or mil reference?
 
The secret decoder ring --

MSC - Mil Std/Spec, CAD
.25 == 1/4"
-20 == 20 TPI
.75 == 3/4"
BH == Button Head
CS == Cap Screw -- Either TORX T25 or ALLEN Hex.
 
A note on Torx Plus... you can undo a torx screw with a torx plus bit, but you can't undo a trox plus screw with a torx bit. I installed the torx plus per Matco's latest recommendation. I later switched back because I was afraid one day I would get caught somewhere and not be able to get them off. If I recall, the impetus is be able to apply greater torque (which is not needed - see below) and less wear of the screw head.

Another BIG caution on Matco inboard wheel halves... do not over torque the brake disk screws. The threaded aluminum wears after years and the threads get a little sloppy. Always use new Nordlock washers and a little medium Locktite. I had two screws strip out and depart while in flight and the remaining screw let go on landing. Great fun when your rudders are ineffective below 20 kts and you don't have any flaps. I ended up replacing the inboard wheel halves of both mains when I took a closer look at the conditions of the threads. I'm pretty careful about torquing correctly... but you never know about the previous owner or shop who may have worked on the plane.

MTCW
 
Just like Don's story above; I've had the new design screws back out in flight also. I chose to toss out the convenience of not having to deal with safety wire and reinstalled the old style bolts. I just don't trust them.
 
benjam said:
Hi All,

Can anyone offer advice on the tool to remove the bolts from this MATCO discs?

Torx drive, but T27 is too small, and (next size up) T30 too big?

What would you replace them with if you accidentally flogged it out trying to tighten it up? The black bolt on the right is high tensile but a different drive head.

asking for a friend…😳😳

any advice out there please?
View attachment 61938
View attachment 61937
Click to expand...

bjdecker said:
The secret decoder ring --

MSC - Mil Std/Spec, CAD
.25 == 1/4"
-20 == 20 TPI
.75 == 3/4"
BH == Button Head
CS == Cap Screw -- Either TORX T25 or ALLEN Hex.
Click to expand...



To add some definitive info to this thread, the Matco rotor bolts are in fact Torx Plus. The "BHCS" in the secret decoder ring seemingly isn't accurate in this case because these fasteners use T27IP Torx Plus. Here's the fastener on Matco's site. I've confirmed myself they are T27IP. T25IP is too small for these.

Matco sell both a 25IP and 27IP Torx Plus bit, so other rotors or Mtaco components might use 25IP.

This Torx Plus bit socket set is made in Taiwan and appears to be of good quality. Torx Plus is not a common fastener (in my experience) but who doesn't want more tools?
 
Last edited:
FWIW... after I almost lost my second brake disk using torx and nordlock washers (new at every removal) and a little bit of blue locktite, I changed to drilled allen head bolts and safety wire. I have no confidence in the Matco design, but its too expensive to change at this point. Inspect frequently.
 
Ezburton said:
FWIW... after I almost lost my second brake disk using torx and nordlock washers (new at every removal) and a little bit of blue locktite, I changed to drilled allen head bolts and safety wire. I have no confidence in the Matco design, but its too expensive to change at this point. Inspect frequently.
Click to expand...

Curious how you've got them safety wired.

Any pics?
 
Dad's RV-10 said:
Curious how you've got them safety wired.

Any pics?
Click to expand...
I don't have any pics. The screws I got sat low in the disk's counter bore and the safety wire holes were too low to get the wire through. For my plane I have the thick disks and the bore may be deeper. I added a split washer to raise them up. The location of the safety wire hole in the disk is inconvenient.

Having Cleveland brakes on my previous plane, the disks are bolted through the wheel half bolts (if I recall correctly). I think the big problem with Matco is the steel bolt going into an aluminum wheel. The torque is low (100 or 120 in-lbs I think) and I'm scared I'll over torque it and strip the threads. I replaced the inner wheel halves because they aluminum threads were worn, but still had the screws back out, even with the blue Loctite. Another weird fact is the screws with the Nordlock washers only loosen up on the right wheel and not the left. I think they need to add threaded steel inserts to the wheel design so you can torque them up correctly.

I had a long term problem with dragging brakes as well. After replacing all the components, no lube / graphite / nickel grease, rebuilding the master cylinders, checking geometry, etc. I still had dragging brakes. I thought the fit was too sloppy and measured the caliper pin (bushing) holes in the torque plate and they seemed too small compared to the OD of the bushings. After pistol whipping the tech rep, he finally told me ID of the torque plate and I found the fit I had was twice as sloppy. Replaced the torque plates and the dragging went away. Matco also changed the torque plate design from my originals and I think it has a better bushing than the old.

I'm finally happy that I have solved all the braking problems.
 
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