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Brake issues 500x5 clevelands

B

BillFear

Well Known Member
During our conditional we decided to change our pads and discs on the 7a. Went with Rapco discs and used the pads we already had (not sure of brand). Put everything back together and now they drag like crazy. Checked the discs and they seem to identical to the old ones. Anyone have any idea of what could be causing this? Plane has about 800 hours.

any ideas would be appreciated.
 
Thicker pads cause this.

Bill, they usually find their own, new positions. You can use a vice grip pliers...the ones that look like a C-clamp, and push the pistons back into their recesses, to allow for the additional thickness of the new pads. If you have just bolted the calipers back on, the new, thicker pads will drag but it won't last long....they'll find their own new position...just go fly a time or two:)

Best,
 
If the pistons are flush with the caliper, then you have a problem Houston. The tires should rotate with no drag with new pads installed.
 
Haven't taxied around yet?

I'd taxi around and do the pad brake in procedure, then come back and check them.
With your pants off of course.
Just make sure no ones around when you get out :)
 
Last edited:
Thanks for the input

Walt, the pistons are all the way in. It is something else.

Tried alittle taxi but they get very hot very fast.

We have the Matco pedal cylinders with the internal springs, they seem to be retracting back fully.

We micd the new discs and they seem to be correct at .187". We have a new set of linings coming from Rapco to have a look at.

Any other ideas?
 
BillFear said:
Walt, the pistons are all the way in. It is something else.

Tried alittle taxi but they get very hot very fast.

We have the Matco pedal cylinders with the internal springs, they seem to be retracting back fully.

We micd the new discs and they seem to be correct at .187". We have a new set of linings coming from Rapco to have a look at.

Any other ideas?
Click to expand...

Look to see if you have a small lip on the front piston on the o-ring side. If so, you have a known issue with the piston.
 
drag

make sure the disc offset is is identical to the old discs, new parts may be slightly different,being in the auto trade for 40 years ive seen alot of stuff ups. wheel must turn freely otherwise its not right.
 
trifield said:
make sure the disc offset is is identical to the old discs, new parts may be slightly different,being in the auto trade for 40 years ive seen alot of stuff ups. wheel must turn freely otherwise its not right.
Click to expand...

The entire caliper floats on the anchor bolts that slide into the torque plate. Make sure the holes in the torque plate are clean and the anchor bolts (dowels) are clean and lube them with a dry lube like tri-flow. Install the pressure plate (with the pad riveted) and slide the caliper into the torque plate. It must not bind at all. Bolt down the back plate (with the pad riveted). If you can't turn the wheel, you have a problem with the pad thickness.

New pads are .186 to .188 thick. The pistons should push back in easily with your thumbs.
 
BillFear said:
During our conditional we decided to change our pads and discs on the 7a. Went with Rapco discs and used the pads we already had (not sure of brand). Put everything back together and now they drag like crazy. Checked the discs and they seem to identical to the old ones. Anyone have any idea of what could be causing this? Plane has about 800 hours.

any ideas would be appreciated.
Click to expand...
Exact same experience. Thought it would wear in but not so in over 10 hours. Never had this trouble in 800 hours with original brake rotors. If not for cold outside temps I would not taxi far.
 
Brake issue

Pumped fluid in from bottom brake bleeders. Do not believe there is any air in the system. No air bubbles in transparent lines, and do not believe this is the problem, but will pump more in and suction it out of the firewall reservoir to be sure. This is odd because This has never been an issue for me with this airplane in 800 hours nor on any other I have owed and maintained for over 4000 hours. Will post when I discover the cause. Bill, please post if you find the solution. Rapco rotors look good, and I expected new linings to wear in quickly, but there is noticeable drag when moving plane by hand---not noticeable when taxiing until you touch the rotors. Perhaps these linings are different as they do not seen to wear. Haven't really had time to study this and having cold temps outside when I have had to commute has helped, but it won't stay cold long.

Pistons in the calipers are easy to push in by hand to move the pads away from the rotors relieving the drag, but tapping the brake pedals positions the pads securely against the rotors and they do not loosen much. I have never needed external brake springs before. Obviously, others are using them for this same purpose. Guess I could try this, but fear it may just be masking the problem.
 
I would get the wheel off the ground, get my face right in there, and find the reason for the friction. You say you have okay clearance with the piston retracted, but once brakes have been applied you get drag? Possibilities are: 1) torque plate is warped and bushings are no longer parallel. This causes binding. With the outer pad removed does the cylinder (caliper) assembly slide freely on the guide pins? I've seen where they will slide okay when slightly crooked, but will bind when centered by the 2 linings because it is warped. 2) Do you have solid (tubing) brake lines and are they exerting any kind of pressure on the brake cylinders making them bind? 3) When cylinder is assembled on the rotor are the guide pins bottomed out with the cylinder right up against the torque plate bushings? This may be if the rotor/torque plate are not correct for each other or torque plates installed backwards on axle. Possible to adjust with washers under torque plate bolts which moves torque plate outboard, although not correct. 4) Uneven drag (drag/no drag) would be a warped or crooked rotor. Rotors will warp quickly if driven around with draggy brakes. One trip up and down the taxiway can do it. 5) Air in the brake cylinder. Heat from brake application will immediately heat the cylinder expanding the air and pushing the piston out. 6) Check the inside of the brake cylinder for marks indicating that the OUTER EDGE of the rotor is rubbing (as if the rotor diameter was too large). 7) If all these check out you could try paper shims. Make them by tracing the pattern on the outer brake lining carrier (about 1/2" wide, curved with 2 bolt holes). Make them out of card stock or something. The shims are bona fide parts on some Cleveland brakes and are sometimes used with new linings and then removed later as the linings wear. Caution, too thick shims can allow the piston to pop out when linings get worn out. I can't think of anything else right now, probably will as soon as I walk away.
 
I knew I'd think of another one. Rotors don't always warp "wavy". Often they will "cone". In other words, if you lay the rotor on a flat surface it will rest on it's outer edge with a gap at the inner diameter, thus "coned". This makes the rotor surface stand "tipped" between the linings requiring a larger gap. A rotor like this will drag evenly withou the stop/go of a wavy rotor.
 
Shims sandwich between outer lining holder and brake cylinder (caliper). The two 1/4" bolts pass through the shims. You should be able to wiggle the brake while assembled and make the piston retract enough to roll freely. That's normal. If you can't, then either your torque plate is dicked, your rotor is coned, or your linings are too fat (needing shims). Lastly, if the brake pedals aren't fully retracted (open fluid passage), you will get expansion pushing on the piston which will only push harder as fluid temperature increases due to heat conducting through the brake.
 
update

We received new Rapco linings and they did not help at all, same thickness. The caliper is sliding fine in the torque plate and everything seems straight. As soon as we put them together (with the piston fully back and no fluid in the system) and tighten them up the inside pad gets pushed against the rotor and you can barely turn the tire. Also, at this point the caliper is not fully seated into the pressure plate. We built a small shim .067" and inserted that to free up the pads. Tires now roll freely, we will test brakes tomorrow when we refill the fluid and bleed them. Our only conclusion is there is something different about the Rapco rotors. Rapco tech support told me to use the shim.

Will update tomorrow after further testing.
 
When Rapco first started making linings we had to shim a bunch of brakes. I suspected yours might need shims, but wanted to eliminate everything "wrong" first. A Cleveland rep once told me that overtorque on the 1/4" bolts over time can actually crush the cylinder bringing the linings closer together. Objectively, I can't imagine losing more than a smidge that way although I have seen a tiny ridge around the cylinder rim from crushing.
 
update 2

After a very complete replacement of the fluid (bottom up) and working the brakes and then bleeding all air out, they now seem to be working great with the .067" shims. After testing them and making a few landings the pistons appear to be out about 1/16" from fully seated position. The plan is to monitor them and when we get alittle wear in the system we will remove the shims.

Our shims are made out of stainless steel and follow the pattern of the outside pad mount.

Very happy with the quality and performance of the Rapco parts and the support we got from Mike at Rapco.
 
Upgraded Caliper Piston/Pucks - Parker-Cleveland

The upgraded caliper pistons (aka pucks) have been machined and are now available for the single piston brake calipers. (like used in my RV-7A Kit). I have pics of what happens to Parker OEM design pistons. Email me if you're interested in more info. :)
 
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