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SkyrangerRich

Dragging Brakes

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Hi,

Am slowly getting to grips with my (new to me) 2006 CTSW. 

The wheel brakes are excellent, quiet, balanced and very powerful, but they do seem to be very draggy - the aircraft won't freewheel down a gentle slope and feels like it requires a lot of revs to taxi. The brake lever runs out of movement after less than 50% of the available travel. 

The previous owner says it's always been like this, even with new pads and cleaned up calipers etc. 

Feels like there's too much pressure in the system to me and it's holding the pads on the disks slightly. Is there some adjustment at the master cylinder?

 

Thanks. 

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Are these Marc or Matco brakes?  It doesn't seem normal; my airplane at idle (~1800rpm) will taxi itself on flat ground to about 20-25 knots.  I have to add brake to keep from taxiing too fast most of the time.

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It's normal. The brake lever never goes all the way back and if it did it would be broke. Giving it some throttle to roll is also normal. Don't over think your aircraft. Just go have fun, but never ever be afraid to ask questions here. That's how we all learn.

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They're the Marc brakes. I've just cleaned up the sliding pins for the floating disks, might have helped a bit. 

Still feels draggy, but if it's normal I'll ignore it!

 

Thanks

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13 hours ago, Tom Baker said:

Lift the wheels off the ground and check to see how much resistance there is. The Marc wheels and brakes should spin fairly freely.

Did this yesterday. The wheels definitely drag - they require a fairly decent shove to get them to turn. 

I've freed off the sliding pins for the floating disc, but it's not helped. 

They're both equally bad, which makes me think it's a problem at the master cylinder. Is there a way to adjust it to remove any pressure when the brake isn't engaged?

10 hours ago, ct9000 said:

It may not be the brakes dragging. It could also be wheel alignment, a common fault on SW's.

The brakes are definitely dragging, but I'll look into this as well. Thanks. 

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Are you sure it's the brakes and not the wheels too tight on the axles?  It's very easy to overtighten the big castle nuts that hold the wheel on and make the wheels bind. 

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Good point Andy. Too many times I see Matco wheel nuts either way too loose or too tight. Matco's do drag more than Marc's because of the type of bearing difference. The Marc's are a standard round ball bearing and axle nut torque makes no difference, but the Matco's use a tapered roller bearing and do a a specific torque and because of this they do have some drag over the Marc's which is normal.

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Fairly sure mine are the Marc brakes (picture attached). 

If so, from the posts above I guess it can't be the torque of the main wheel nut?

Is there adjustment on the master cylinder to reduce the pressure in the system when the brakes aren't engaged?

1724DE1B-DC36-4ACC-8A38-884D532EC8D6.jpeg

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The next step is to pull the break pins, and check the rotation of the wheel. This will tell if the bearings are good. As you get to the last 2 pins for removal set  the parking brake to hold the disk in place. I balance tires on the Marc wheels this way.

One other thing I am noticing from your picture is the color of the brake line. At least here in the USA we use the standard red aviation hydraulic fluid for our brakes. This makes the color of the line slightly pink in color, yours seems to be clear. If someone put the wrong fluid in the brake system it could cause seals to swell causing dragging brakes. Also not CT related, but I have had fluid get old and king of congeal causing dragging brakes before, but the airplane was much older than your CT would be now.

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46 minutes ago, Tom Baker said:

The next step is to pull the break pins, and check the rotation of the wheel. This will tell if the bearings are good. As you get to the last 2 pins for removal set  the parking brake to hold the disk in place.

That's a great idea. Wish I'd thought of it when I had the pins off to clean and lube them!

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Brake pins out and the wheel spins beautifully, so it looks like it's the brakes. 

Looking into the caliper, the pad springs seem to still be in there, but the pads aren't able to slide clear of the rotors. 

I assume I can't push the pistons back into the calipers without releasing some fluid out of the system?

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The caliper piston keeps the pads right up near the disc. Those springs which you usually don't find in other brakes keep the pads up against the disc so the disc (because it can move back and forth) won't push them away. When this starts to happen you will have to start pumping the brakes to get them to work. This is one reason a huge majority of us went to Matco's. The Marc's have heat fade and many of us had to pump the brakes up to get them to work. The Matco MC puts out almost twice the volume and pressure. The other issue is those Italian's made the disc float and the caliper solid which is ass backwards from what most do with a floating caliper and a solid disc.

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Thanks for the replies all. 

Spent a few hours on it this afternoon. WHAT A TERRIBLE BRAKE CALIPER DESIGN!

The pins the pads slide on are threaded. It feels like the pads get hung up on the threads which doesn't help them move back off the disk. Those little springs between the pads that push the pads off the disk are odd, they're never going to be powerful enough to retract the piston...

Anyway, I've cleaned it all up. Smoothed the threads on the pins a little and neatened the holes in the pads so they can slide a bit more easily. Feels like it's rolling better, but low cloud prevented a circuit to test. 

The brakes feel plenty powerful to me, we've got a 4% slope on our runway, brakes have been man enough to stop me when landing downhill. 

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2 hours ago, SkyrangerRich said:

The brakes feel plenty powerful to me, we've got a 4% slope on our runway, brakes have been man enough to stop me when landing downhill. 

mine have been trouble free for almost 13 years.  except for the need to pump at times they have worked fine.

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On 3/1/2019 at 9:08 AM, Roger Lee said:

 The Matco MC puts out almost twice the volume and pressure. 

Is the brake lever to MC mounting different on the Matcos? Pressure and Volume are inversely related properties in a hydraulic system. Unless the amount of work input into the system increases, this is physically impossible.

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