Matco Brake Chatter

[BigJohn]

Hello All, Happy Independence Day! I changed out my brake pads and now I have a rather severe chatter of the brake caliper on one side. All speeds, slow taxi to takeoff. Goes away with brake appliction. Anyone else seen this, and (hopefully) found a solution?

[mcgaughy]

I'm not familiar with the RV12 set up....with that said, I would pull brakes off again and look for loose rivets, cocking / sticking of the brake pins first. Also look for any obscure cracks in any of the supporting brackets. I use an LPS spray product (can't recall the number right now, but it is not the normal 1,2,3 that we all use liberally) on the brake pins and back side of the plates. It drys to a dark grayish green color and is a high temp, dry lube. This particular lube was specified in my Grumman Tiger Maintenance Manual....and as I recall, one can cost almost $100! I'm hoping one can will last me almost a life time..... I've used high temp antiseize on the pins in the past with good success, but it has the potential to give other problems as opposed to a dry lube. Check too, while you are at it, that the master brake cylinder is coming back fully unloaded when you take your foot off the brake. Some brakes will drag when the pedal sticks not allowing the master cylinder to fully unload. If all this is fine, then I'm thinking the next level of check is the piston in the caliper. Sometimes it can get cocked or have a bit of debris causing sticking....I have seen this happen once and in my case, I simply pressed the piston more fully back into the caliper (watch doing this because the fluid level will rise in the reservoir.)

Hope this helps .... at least a little maybe.

Ellis
RV7a Finish Kit, A&P/IA

[vic syracuse]

I just had an RV that had severe groan/chatter on the right brake side. Upon inspection, the rivets were installed backwards and the pads were loose. Make sure those rivest are set tight and correctly.

Vic

[Vlad]

Since Grove is close to Matco design I have a question to the experts. Do pressure plates (11) and torque pins (4) wear out?

[DHeal]

I occasionally get some brief minor brake chatter when moving my RV-12 in and out of the hangar. No big deal. I use either a dry lubricant or silicone fluid (sparingly!) on the brake caliper sliding pins -- make sure they are clean and slide reasonably well. An old automotive trick I use is to take a file and chamfer the leading edge of new brake linings during their installation -- not sure if that does any good, but I usually have quiet brakes. Also, when working on the wheel/brake assemblies, make sure the brake disc is securely fastened to the inner wheel half.

[BigJohn]

Thanks to all for suggestions.

Vic, Yes the pads are securely riveted - they came straight from Matco under their exchange program.

Vlad, I have the same question, as mine seem a bit sloppy. I'm going to call Matco tomorrow with that question.

Dave, I think I will try the chamfer trick, as well as using some lubricant, even though that's not specified in the Matco literature. BTW, it is a beautiful day at Peck's Lake.

John

[snopercod]

When I have changed brake pads, several times the brake assembly has gotten "cocked" when I reassembled it. I just pry on it a little to free it up so it slides easily on those "torque pins". I have never used any kind of lube on the pins.

[Azjulian]

A friend of mine had this problem with his RV12 - I went through the entire caliper on that side looking for the issue. I then closely inspected the pads and saw a slight crack in them around the rivet making the pad materiel loose in the pad. I swapped out that pad and the shudder disappeared
.

[DHeal]

On a "brake caliper"-related note, be sure that there is no physical interference between the aft end of the inboard wheel pant attachment bracket and the aft-inboard corner of the brake caliper. If there is such interference, the brake caliper/linings may not wear evenly.

[BigJohn]

I always like to see some closure on threads like this so here is mine. I removed and disassembled both wheel and brake assemblies. I chamfered the edges of the pads as suggested. I found and removed a burr on one of the disc surfaces that I had not previously noticed that was cutting a slight groove in fhe matching pad. I added a very tiny film of grease to the bushings that the calipers slide on. When I reinstalled the wheels I was religious about following exactly the Matco instructions for axle nut torque. Then went to the runway and "conditioned" again the pads as per instuctions. Dont know exactly which remedy worked, but the chatter is gone and I have good braking. Thanks for the suggestions all.